Author name code: liu-wei
ADS astronomy entries on 2022-09-14
author:"Liu, Wei"
------------------------------------------------------------------------
Title: Research on the On-orbit Background of the Hard X-Ray Imager
Onboard ASO-S
Authors: Liu, Wei; Chen, Deng-Yi; Jiang, Xian-Kai; Wu, Jian; Zhang,
Zhe; Hu, Yi-Ming; Su, Yang; Chen, Wei; Ma, Tao
Bibcode: 2022RAA....22i5011L
Altcode:
The space environment background of various particle fluxes of
the Hard X-ray Imager (HXI), one of the payloads of the Advanced
Space-based Solar Observatory (ASO-S) spacecraft, is investigated
and presented. Different approaches are used to obtain the input
information on various space environment particles (protons, alpha
particles, electrons, positrons, neutrons, and photons). Some special
regions (SAA and radiation belt) are also taken into account. The
findings indicate that electrons are the primary background source
in the radiation belt. Due to the large background flux generated by
electrons, HXI cannot effectively observe solar flares in the radiation
belt. Outside the radiation belt, primary protons and albedo photons
are the main sources of background at low and high magnetic latitudes
respectively. The statistical analysis of the flare and background
spectra shows that the errors of the flare energy spectrum observation
are mainly concentrated in the high energy band, and the detector still
has a certain spectrum observation capability for flares of C-class and
below in the low energy band of the non-radiation belt. The imaging
observation of flares of C-class and below is significantly affected
by the accuracy of background subtraction. The energy band with the
best signal-to-noise ratio is from 10 to 50 keV, which can be used to
monitor the formation and class of flares.
Title: Directly tracing cool filamentary accretion over >100 kpc
into the interstellar medium of a quasar host at z=1
Authors: Johnson, Sean D.; Schaye, Joop; Walth, Gregory L.; Li,
Jennifer I-Hsiu; Rudie, Gwen C.; Chen, Hsiao-Wen; Chen, Mandy C.;
Epinat, Benoît; Gaspari, Massimo; Cantalupo, Sebastiano; Kollatschny,
Wolfram; Zhuoqi; Liu; Muzahid, Sowgat
Bibcode: 2022arXiv220904245J
Altcode:
We report the discovery of giant (50-100 kpc) [O II] emitting nebulae
with the Multi-Unit Spectroscopic Explorer (MUSE) in the field of TXS
0206-048, a luminous quasar at z=1.13. An archival, down-the-barrel UV
spectrum of the quasar shows absorption at velocities coincident with
those of the extended nebulae, enabling new insights into inflows and
outflows around the quasar host. One nebula exhibits a filamentary
morphology extending over 120 kpc from the halo toward the quasar
and intersecting with another nebula surrounding the quasar host
with a radius of 50 kpc. The filamentary nebula has line-of-sight
velocities >300 km/s from nearby galaxies but matches that of the
nebula surrounding the quasar host where they intersect, consistent
with filamentary accretion of cool inter- or circum-galactic medium
or cooling hot halo gas. The kinematics of the nebulae surrounding
the quasar host are unusual and complex, with one redshifted
and one blue-shifted spiral-like structure. The nebular emission
velocities at 5-10 kpc from the quasar match those of inflowing
absorbing gas observed in a UV spectrum of the quasar. Together,
the extended nebulae and associated redshifted absorption represent a
compelling case of cool, filamentary gas accretion from halo scales
into the extended interstellar medium and toward the nucleus of a
massive quasar host galaxy at intermediate redshift. The inflow rate
implied by the combination of emission and absorption constraints
is orders-of-magnitude below levels required to sustain the quasar's
radiative luminosity, indicating highly anisotropic or highly variable
accretion.
Title: Galactic cosmic ray propagation: sub-PeV diffuse gamma-ray
and neutrino emission
Authors: Qiao, Bing-Qiang; Liu, Wei; Zhao, Meng-Jie; Bi, Xiao-Jun;
Guo, Yi-Qing
Bibcode: 2022FrPhy..1744501Q
Altcode: 2021arXiv210403729Q
The Tibet ASγ experiment just reported their measurement of sub-PeV
diffuse gamma-ray emission from the Galactic disk, with the highest
energy up to 957 TeV. These diffuse gamma rays are most likely the
hadronic origin by cosmic ray (CR) interaction with interstellar
gas in the galaxy. This measurement provides direct evidence to the
hypothesis that the Galactic Cosmic Rays (GCRs) can be accelerated
beyond PeV energies. In this work, we try to explain the sub-PeV
diffuse gamma-ray spectrum with different CR propagation models. We
find that there is a tension between the sub-PeV diffuse gamma-ray
and the local CR spectrum. To describe the sub-PeV diffuse gamma-ray
flux, it generally requires larger local CR flux than measurement
in the knee region. We further calculate the PeV neutrino flux from
the CR propagation model. Even all of these sub-PeV diffuse gamma
rays originate from the propagation, the Galactic Neutrinos (GNs)
only account for less than ∼ 15% of observed flux, most of which
are still from extragalactic sources.
Title: Construction and Validation of a Geometry-based Mathematical
Model for Hard X-ray Imager
Authors: Jiang, Xian-Kai; Wu, Jian; Chen, Deng-Yi; Hu, Yi-Ming; Wang,
Hao-Xiang; Liu, Wei; Zhang, Zhe
Bibcode: 2022arXiv220705390J
Altcode:
Quantitative and analytical analysis of modulation process of the
collimator is a great challenge, and is also of great value to the
design and development of Fourier transform imaging telescopes. The
Hard X-ray Imager (HXI), as one of the three payloads onboard
the Advanced Space-based Solar Observatory(ASO-S) mission, adopts
modulating Fourier-Transformation imaging technique and will be used
to explore mechanism of energy release and transmission in solar flare
activities. In this paper, a mathematical model is developed to analyze
the modulation function under a simplified condition first. Then its
behavior under six degrees of freedom is calculated after adding the
rotation matrix and translation change to the model. In addition,
unparalleled light and extended sources also are considered so that
our model can be used to analyze the X-ray beam experiment. Next,
applied to the practical HXI conditions, the model has been
confirmed not only by Geant4 simulations but also by some verification
experiments. Furthermore, how this model will help to improve the image
reconstruction process after the launch of ASO-S is also presented.
Title: Multiwavelength observations of Swift J0243.6+6124 from 2017
to 2022
Authors: Liu, Wei; Yan, Jingzhi; Reig, Pablo; Wang, Xiaofeng; Xiao,
Guangcheng; Lin, Han; Zhang, Xinhan; Sai, Hanna; Chen, Zhihao; Yan,
Shengyu; Liu, Qingzhong
Bibcode: 2022arXiv220800151L
Altcode:
We have obtained optical spectroscopy and photometry data during
four years after the event. The long-term photometric light-curve and
the equivalent widths of the Halpha and He I 6678 lines were used to
monitor the state of the Be star disk. The Halpha line profiles show
evidence for V/R variability that was accounted for by fitting the
Halpha spectral line profile with two Gaussian functions. We divided our
data into three phases according to the intensity of the X-ray, optical,
and infrared emission. Phase I covers the rise and decay of the giant
X-ray outburst that took place in October to November 2017. We interpret
phase II as the dissipation of the Be star equatorial disk and phase III
as its recovery. The timescale of a complete formation and dissipation
process is about 1250 days. The epoch when the dissipation process
stopped and the reformation period began is estimated to be around MJD
58530. We find a delay of about 100 to 200 days between the minimum
of the optical or infrared intensity and the strength of the Halpha
line after the X-ray outburst, which may indicate that the dissipation
of the disk begins from the inner parts. The motion of the density
perturbation inside the disk is prograde, with a V/R quasi-period of
about four years. The source shows a positive correlation in the (B-V)
color index versus V-band magnitude diagram, which implies that the
system is seen at a small or moderate inclination angle.
Title: Flux Variations of Cosmic Ray Air Showers Detected by
LHAASO-KM2A During a Thunderstorm on 10 June 2021
Authors: LHAASO Collaboration; Aharonian, F.; An, Q.; Axikegu; Bai,
L. X.; Bai, Y. X.; Bao, Y. W.; Bastieri, D.; Bi, X. J.; Bi, Y. J.; Cai,
J. T.; Cao, Zhe; Cao, Zhen; Chang, J.; Chang, J. F.; Chen, E. S.; Chen,
Liang; Chen, Liang; Chen, Long; Chen, M. J.; Chen, M. L.; Chen, S. H.;
Chen, S. Z.; Chen, T. L.; Chen, X. J.; Chen, Y.; Cheng, H. L.; Cheng,
N.; Cheng, Y. D.; Cui, S. W.; Cui, X. H.; Cui, Y. D.; Dai, B. Z.; Dai,
H. L.; Dai, Z. G.; Danzengluobu; della Volpe, D.; Duan, K. K.; Fan,
J. H.; Fan, Y. Z.; Fan, Z. X.; Fang, J.; Fang, K.; Feng, C. F.; Feng,
L.; Feng, S. H.; Feng, X. T.; Feng, Y. L.; Gao, B.; Gao, C. D.; Gao,
L. Q.; Gao, Q.; Gao, W.; Gao, W. K.; Ge, M. M.; Geng, L. S.; Gong,
G. H.; Gou, Q. B.; Gu, M. H.; Gu, F. L.; Guo, J. G.; Guo, X. L.; Guo,
Y. Q.; Guo, Y. Y.; Han, Y. A.; He, H. H.; He, H. N.; He, S. L.; He,
X. B.; He, Y.; Heller, M.; Hor, Y. K.; Hou, C.; Hou, X.; Hu, H. B.;
Hu, Q.; Hu, S.; Hu, S. C.; Hu, X. J.; Huang, D. H.; Huang, W. H.;
Huang, X. T.; Huang, X. Y.; Huang, Y.; Huang, Z. C.; Ji, X. L.; Jia,
H. Y.; Jia, K.; Jiang, K.; Jiang, Z. J.; Jin, M.; Kang, M. M.; Ke,
T.; Kuleshov, D.; Li, B. B.; Li, Cheng; Li, Cong; Li, F.; Li, H. B.;
Li, H. C.; Li, H. Y.; Li, J.; Li, Jian; Li, Jie; Li, K.; Li, W. L.;
Li, X. R.; Li, Xin; Li, Xin; Li, Y. Z.; Li, Zhe; Li, Zhuo; Liang,
E. W.; Liang, Y. F.; Lin, S. J.; Liu, B.; Liu, C.; Liu, D.; Liu, H.;
Liu, H. D.; Liu, J.; Liu, J. L.; Liu, J. S.; Liu, J. Y.; Liu, M. Y.;
Liu, R. Y.; Liu, S. M.; Liu, W.; Liu, Y.; Liu, Y. N.; Long, W. J.;
Lu, R.; Luo, Q.; Lv, H. K.; Ma, B. Q.; Ma, L. L.; Ma, X. H.; Mao,
J. R.; Masood, A.; Min, Z.; Mitthumsiri, W.; Nan, Y. C.; Ou, Z. W.;
Pang, B. Y.; Pattarakijwanich, P.; Pei, Z. Y.; Qi, M. Y.; Qi, Y. Q.;
Qiao, B. Q.; Qin, J. J.; Ruffolo, D.; Sáiz, A.; Shao, C. Y.; Shao,
L.; Shchegolev, O.; Sheng, X. D.; Shi, J. Y.; Song, H. C.; Stenkin,
Yu. V.; Stepanov, V.; Su, Y.; Sun, Q. N.; Sun, X. N.; Sun, Z. B.;
Tam, P. H. T.; Tang, Z. B.; Tian, W. W.; Wang, B. D.; Wang, C.; Wang,
H.; Wang, H. G.; Wang, J. C.; Wang, J. S.; Wang, L. P.; Wang, L. Y.;
Wang, R.; Wang, R. N.; Wang, W.; Wang, X. G.; Wang, X. Y.; Wang, Y.;
Wang, Y. D.; Wang, Y. J.; Wang, Y. P.; Wang, Z. H. Wang. Z. X.; Wang,
Zhen; Wang, Zheng; Wei, D. M.; Wei, J. J.; Wei, Y. J.; Wen, T.; Wu,
C. Y.; Wu, H. R.; Wu, S.; Wu, X. F.; W, Y. S.; Xi, S. Q.; Xia, J.;
Xia, J. J.; Xiang, G. M.; Xiao, D. X.; Xiao, G.; Xin, G. G.; Xin,
Y. L.; Xing, Y.; Xiong, Z.; Xu, D. L.; Xu, R. X.; Xue, L.; Yan, D. H.;
Yan, J. Z.; Yang, C. W.; Yang, F. F.; Yang, H. W.; Yang, J. Y.; Yang,
L. L.; Yang, M. J.; Yang, R. Z.; Yang, S. B.; Yao, Y. H.; Yao, Z. G.;
Ye, Y. M.; Yin, L. Q.; Yin, N.; You, X. H.; You, Z. Y.; Yu, Y. H.;
Yuan, Q.; Yue, H.; Zeng, H. D.; Zeng, T. X.; Zeng, W.; Zeng, Z. K.;
Zha, M.; Zhai, X. X.; Zhang, B. B.; Zhang, F.; Zhang, H. M.; Zhang,
H. Y.; Zhang, J. L.; Zhang, L. X.; Zhang, Li; Zhang, Lu; Zhang, P. F.;
Zhang, P. P.; Zhang, R.; Zhang, S. B.; Zhang, S. R.; Zhang, S. S.;
Zhang, X.; Zhang, X. P.; Zhang, Y. F.; Zhang, Y. L.; Zhang, Yi; Zhang,
Yong; Zhao, B.; Zhao, J.; Zhao, L.; Zhao, L. Z.; Zhao, S. P.; Zheng,
F.; Zheng, Y.; Zhou, B.; Zhou, H.; Zhou, J. N.; Zhou, P.; Zhou, R.;
Zhou, X. X.; Zhu, C. G.; Zhu, F. R.; Zhu, H.; Zhu, K. J.; Zuo, X.
Bibcode: 2022arXiv220712601L
Altcode:
The Large High Altitude Air Shower Observatory (LHAASO) has three
sub-arrays, KM2A, WCDA and WFCTA. The flux variations of cosmic ray air
showers were studied by analyzing the KM2A data during the thunderstorm
on 10 June 2021. The number of shower events that meet the trigger
conditions increases significantly in atmospheric electric fields,
with maximum fractional increase of 20%. The variations of trigger
rates (increases or decreases) are found to be strongly dependent on
the primary zenith angle. The flux of secondary particles increases
significantly, following a similar trend with that of the shower
events. To better understand the observed behavior, Monte Carlo
simulations are performed with CORSIKA and G4KM2A (a code based on
GEANT4). We find that the experimental data (in saturated negative
fields) are in good agreement with simulations, assuming the presence
of a uniform upward electric field of 700 V/cm with a thickness
of 1500 m in the atmosphere above the observation level. Due to
the acceleration/deceleration and deflection by the atmospheric
electric field, the number of secondary particles with energy above
the detector threshold is modified, resulting in the changes in shower
detection rate.
Title: Probing massive neutrinos with the Minkowski functionals of
large-scale structure
Authors: Liu, Wei; Jiang, Aoxiang; Fang, Wenjuan
Bibcode: 2022JCAP...07..045L
Altcode: 2022arXiv220402945L
Massive neutrinos suppress the growth of structure under their
free-streaming scales. The effect is most prominent on small scales
where the widely-used two-point statistics can no longer capture
the full information. In this work, we study the signatures massive
neutrinos leave on large-scale structure (LSS) as revealed by its
morphological properties, which are fully described by 4 Minkowski
functionals (MFs), and quantify the constraints on the summed
neutrino mass Mν from the MFs, by using publicly available
N-body simulations. We find the MFs provide important complementary
information, and give tighter constraints on Mν than the
power spectrum. Specifically, depending on whether massive neutrinos are
included in the density field (the 'm' field) or not (the 'cb' field),
we find the constraint on Mν from the MFs with a smoothing
scale of RG = 5h -1Mpc is 48 or 4 times better
than that from the power spectrum. When the MFs are combined with the
power spectrum, they can improve the constraint on Mν
from the latter by a factor of 63 for the 'm' field and 5 for the
'cb' field. Notably, when the 'm' field is used, the constraint on
Mν from the MFs can reach 0.0177eV with a volume of 1(
-1Gpc)3, while the combination of the MFs and
power spectrum can tighten this constraint to be 0.0133eV, a 4.5σ
significance on detecting the minimum sum of the neutrino masses. For
the 'm' field, we also find the σ 8 and Mν
degeneracy is broken with the MFs, leading to stronger constraints
on all 6 cosmological parameters considered in this work than the
power spectrum.
Title: First Estimates of Hydrothermal Helium Fluxes in Continental
Collision Settings: Insights From the Southeast Tibetan Plateau Margin
Authors: Zhang, Maoliang; Liu, Wei; Guan, Lufeng; Takahata, Naoto;
Sano, Yuji; Li, Ying; Zhou, Xiaocheng; Chen, Zhi; Cao, Chunhui; Zhang,
Lihong; Lang, Yun-Chao; Liu, Cong-Qiang; Xu, Sheng
Bibcode: 2022GeoRL..4998228Z
Altcode:
Continental regions are essential for the outgassing of deeply-sourced
helium in response to volcanic and tectonic processes. However,
the helium fluxes remain largely unknown for continental collision
settings such as the Tibetan Plateau. Here, we focus on hydrothermal
helium degassing from the Simao block, Southeast Tibetan Plateau
margin, and report flux estimates of (0.03 - 32) × 105
atoms m−2 s−1 for 3He and (3.2
- 32) × 1010 atoms m−2 s−1
for 4He, with mantle fractions of helium fluxes
up to 2−3 orders of magnitude greater than those of stable
continents. Geologically recent magma recharge beneath Quaternary
volcanoes is proposed to account for the high mantle helium fluxes and
3He/4He up to 7.24 Ra. Active tectonics driven
by the India-Asia continental collision possibly maintained efficient
release of crustal helium over geological timescales. These findings
present the first flux estimates for hydrothermal helium degassing
controlled by volcanic and tectonic processes in continental collision
settings.
Title: Evolution of Fractal Pore Structure in Sedimentary Rocks
Authors: Zhou, Nengwu; Wang, Min; Lu, Shuangfang; Dodd, Thomas J. H.;
Liu, Wei; Guan, Ying
Bibcode: 2022E&SS....902167Z
Altcode:
Geological processes alter pore spaces over time, and their analysis
can shed light on the dynamic fractal structure and fluid flow of rocks
over time. This study presents experimental evidence to illustrate
that the pore fractal structure evolves with sedimentation, carbonate
cementation, clay growth, and dissolution. It examines, describes and
characterizes a suite of core samples from the Gaotaizi oil layer of
the second and third members of the Qingshankou Formation, Songliao
Basin, China. The effects of mechanical compaction and other diagenesis
effects on fractal pore structure on sedimentary rocks are discussed. A
schematic diagram is proposed that describes the impacts of these
diagenetic processes on fractal pore structure at the microscopic
scale in sedimentary rocks. This work links the state of diagenetic
alteration and fractal pore structure, which can guide practical
applications such as predicting the permeability of sedimentary rocks.
Title: Measurement of the Gamma-Ray Energy Spectrum beyond 100 TeV
from the HESS J1843-033 Region
Authors: Amenomori, M.; Asano, S.; Bao, Y. W.; Bi, X. J.; Chen, D.;
Chen, T. L.; Chen, W. Y.; Chen, Xu; Chen, Y.; Cirennima; Cui, S. W.;
Danzengluobu; Ding, L. K.; Fang, J. H.; Fang, K.; Feng, C. F.; Feng,
Zhaoyang; Feng, Z. Y.; Gao, Qi; Gomi, A.; Gou, Q. B.; Guo, Y. Q.; Guo,
Y. Y.; He, H. H.; He, Z. T.; Hibino, K.; Hotta, N.; Hu, Haibing; Hu,
H. B.; Hu, K. Y.; Huang, J.; Jia, H. Y.; Jiang, L.; Jiang, P.; Jin,
H. B.; Kasahara, K.; Katayose, Y.; Kato, C.; Kato, S.; Kawashima,
T.; Kawata, K.; Kozai, M.; Kurashige, D.; Labaciren; Le, G. M.; Li,
A. F.; Li, H. J.; Li, W. J.; Li, Y.; Lin, Y. H.; Liu, B.; Liu, C.;
Liu, J. S.; Liu, L. Y.; Liu, M. Y.; Liu, W.; Liu, X. L.; Lou, Y. -Q.;
Lu, H.; Meng, X. R.; Meng, Y.; Munakata, K.; Nagaya, K.; Nakamura,
Y.; Nakazawa, Y.; Nanjo, H.; Ning, C. C.; Nishizawa, M.; Ohnishi, M.;
Okukawa, S.; Ozawa, S.; Qian, L.; Qian, X.; Qian, X. L.; Qu, X. B.;
Saito, T.; Sakakibara, Y.; Sakata, M.; Sako, T.; Sako, T. K.; Shao,
J.; Shibata, M.; Shiomi, A.; Sugimoto, H.; Takano, W.; Takita, M.; Tan,
Y. H.; Tateyama, N.; Torii, S.; Tsuchiya, H.; Udo, S.; Wang, H.; Wang,
Y. P.; Wangdui; Wu, H. R.; Wu, Q.; Xu, J. L.; Xue, L.; Yang, Z.; Yao,
Y. Q.; Yin, J.; Yokoe, Y.; Yu, N. P.; Yuan, A. F.; Zhai, L. M.; Zhang,
C. P.; Zhang, H. M.; Zhang, J. L.; Zhang, X.; Zhang, X. Y.; Zhang,
Y.; Zhang, Yi; Zhang, Ying; Zhao, S. P.; Zhaxisangzhu; Zhou, X. X.
Bibcode: 2022ApJ...932..120A
Altcode:
HESS J1843-033 is a very high energy gamma-ray source whose origin
remains unidentified. This work presents, for the first time, the
energy spectrum of gamma rays beyond 100 TeV from the HESS J1843-033
region using the data recorded by the Tibet air shower array and its
underground muon detector array. A gamma-ray source with an extension
of 0.°34 ± 0.°12 is successfully detected above 25 TeV at (α,
δ) = (281.°09 ± 0.°10, -3.°76 ± 0.°09) near HESS J1843-033
with a statistical significance of 6.2σ, and the source is named
TASG J1844-038. The position of TASG J1844-038 is consistent with
those of HESS J1843-033, eHWC J1842-035, and LHAASO J1843-0338. The
measured gamma-ray energy spectrum in 25 TeV < E < 130 TeV
is described with ${dN}/{dE}=(9.70\pm 1.89)\times {10}^{-16}$
(E/40 TeV)-3.26±0.30 TeV-1 cm-2
s-1, and the spectral fit to the combined spectra of HESS
J1843-033, LHAASO J1843-0338, and TASG J1844-038 implies the existence
of a cutoff at 49.5 ± 9.0 TeV. Associations of TASG J1844-038 with
SNR G28.6-0.1 and PSR J1844-0346 are also discussed in detail for the
first time.
Title: Ultraviolet Photooxidation of Smectite-Bound Fe(II) and
Implications for the Origin of Martian Nontronites
Authors: Rivera Banuchi, V. B.; Liu, W.; Yee, N.; Legett, C.; Glotch,
T. D.; Chemtob, S. M.
Bibcode: 2022JGRE..12707150R
Altcode:
Clay minerals detected with orbital and in situ instruments in ancient
Martian terrains constrain Mars' climate and aqueous alteration
history. Early in its history, Mars experienced an atmospheric redox
change and iron-bearing clay minerals may preserve the effects of
that transition. Ferrous smectites, the thermodynamically predicted
product of chemical weathering of basalts under anoxic conditions,
may have undergone oxidation by exposure to chemical oxidants in the
atmosphere or regolith, or by direct photooxidation at the surface. To
assess these potential oxidation pathways, ferrous trioctahedral
smectites of varying initial iron content were synthesized and
subjected to oxidation by ultraviolet (UV) irradiation. Experimental
UV irradiation under an anoxic atmosphere equivalent to approximately
7 years of flux on the Martian surface caused partial oxidation
of smectite-bound Fe (Fe3+/ΣFe = 16-18%) and octahedral
sheet contraction. Metal-OH vibrational bands in visible/near infrared
(VNIR) reflectance spectra of oxidized smectites changed in band depth
and asymmetry with higher iron content. X-ray diffraction patterns
of UV irradiated samples indicate the formation of a mixed di- and
trioctahedral smectite or a secondary nontronite phase, possibly on
the surfaces of higher iron content smectites. These experiments
suggest that UV irradiation is able to oxidize structurally
bound iron in smectites without the presence of other chemical
oxidants. Photooxidation may have influenced the mineralogy, both
syndepositionally and postdepositionally, of Martian alteration
assemblages formed near the surface and this process needs not be
limited to one part of their formation history.
Title: Study on the variation of orbital period, quasi-periodic
oscillations and negative superhumps in V729 Sgr
Authors: Sun, Qi-Bin; Qian, Sheng-Bang; Dong, Ai-Jun; Zhi, Qi-Jun;
Han, Zhong-Tao; Liu, Wei; Chang, Xin; Liu, Chang; Xiang, Hong-Bin;
Peng, Xue-Bing; Zhang, Bin; Zhang, Xu-Dong; Fernández Lajús, E.
Bibcode: 2022NewA...9301751S
Altcode:
Based on K2 and our observations of V729 Sgr, the study of the variation
of orbital period, quasi-periodic oscillations (QPOs) and negative
superhumps are presented. Using all available mid-eclipse times during
quiescence, we find that V729 Sgr has a cyclic variation of the orbital
period, with periods and amplitudes of ∼ 9 . 64 years and ∼ 442 . 37
s, respectively. Based on the interpret of light travel-time effect,
the mass of third body is derived as M3 sini' = 0
. 24(± 0 . 016) M⊙ . When the third body is coplanar with
the central body system, the third body may be a low-mass star. Using
the Weighted Wavelet Z-transform (WWZ) method, we find for the first
time that V729 Sgr has QPOs with the period of ∼1030-3370 s. Using
WWZ method, we find that V729 Sgr also has negative superhumps in
the first quiescence, indicating that the negative superhumps may be
permanent in the quiescence of V729 Sgr.
Title: Statistical Study of the Optimal Local Sources for Cosmic
Ray Nuclei and Electrons
Authors: Luo, Qing; Qiao, Bing-qiang; Liu, Wei; Cui, Shu-wang;
Guo, Yi-qing
Bibcode: 2022ApJ...930...82L
Altcode: 2021arXiv211000501L
Local sources, such as the Geminga supernova remnant (SNR), may
have played an important role in the anomaly of protons, electrons,
and anisotropy in past works. In fact, there exist 12 SNRs around
the solar system within 1 kpc. One question is whether other SNRs
also possibly contribute to the spectra of nuclei and electrons,
and explain the special structure of the anisotropy. In this work,
under spatial-dependent propagation, we systematically study the
contribution of all local SNRs, within 1 kpc around the solar system,
to the spectra of nuclei and electrons, as well as the energy dependence
of the anisotropy. As a result, only the Geminga, the Monogem, and the
Vela SNRs have quantitative contributions to the nuclei and electron
spectra, and the anisotropy. Here, the Geminga SNR is the sole optimal
candidate and the Monogem SNR is controversial due to the tension of the
anisotropy between the model calculation and the observations. The Vela
SNR contributes to a new spectral structure beyond TeV energy, hinted
by the HESS, the VERITAS, the DAMPE, and the CALET measurements. More
interestingly, the electron anisotropy satisfies the Fermi-LAT limit
below TeV energy, but rises greatly and reaches 10% at several TeV. This
novel structure will shed new light on verifying our model. We hope
that the new structure of the electron spectrum and anisotropy can be
observed by the spaceborne DAMPE and HERD, and the ground-based HAWC
and LHAASO experiments in the near future.
Title: Analogue cosmological particle creation in an ultracold
quantum fluid of light
Authors: Steinhauer, Jeff; Abuzarli, Murad; Aladjidi, Tangui;
Bienaimé, Tom; Piekarski, Clara; Liu, Wei; Giacobino, Elisabeth;
Bramati, Alberto; Glorieux, Quentin
Bibcode: 2022NatCo..13.2890S
Altcode: 2021arXiv210208279S
The rapid expansion of the early universe resulted in the spontaneous
production of cosmological particles from vacuum fluctuations, some
of which are observable today in the cosmic microwave background
anisotropy. The analogue of cosmological particle creation in a quantum
fluid was proposed, but the quantum, spontaneous effect due to vacuum
fluctuations has not yet been observed. Here we report the spontaneous
creation of analogue cosmological particles in the laboratory, using a
quenched 3-dimensional quantum fluid of light. We observe acoustic peaks
in the density power spectrum, in close quantitative agreement with the
quantum-field theoretical prediction. We find that the long-wavelength
particles provide a window to early times. This work introduces the
quantum fluid of light, as cold as an atomic Bose-Einstein condensate.
Title: Effects of peculiar velocities on the morphological properties
of large-scale structure
Authors: Jiang, Aoxiang; Liu, Wei; Fang, Wenjuan; Zhao, Wen
Bibcode: 2022PhRvD.105j3028J
Altcode: 2021arXiv210803851J
It is known that the large-scale structure mapped by a galaxy
redshift survey is subject to distortions by galaxies' peculiar
velocities. Besides the signatures generated in common N -point
statistics, such as the anisotropy in the galaxy two-point correlation
function, the peculiar velocities also induce distinct features in
large-scale structures morphological properties, which are fully
described by four Minkowski functionals (MFs), i.e., the volume,
surface area, integrated mean curvature, and Euler characteristic (or
genus). In this work, by using large suite of N -body simulations, we
present and analyze these important features in the MFs of large-scale
structure on both (quasi)linear and nonlinear scales, with a focus on
the latter. We also find the MFs can give competitive constraints on
cosmological parameters compared to the power spectrum, probably due
to the nonlinear information contained. For a galaxy number density
similar to the DESI BGS galaxies, the constraint on σ8 from
the MFs with one smoothing scale can be better by ∼50 % than from
the power spectrum. These findings are important for the cosmological
applications of MFs of large-scale structure, and probably open up a
new avenue for studying the peculiar velocity field itself.
Title: Deciphering the Migration of the Intertropical Convergence
Zone During the Last Deglaciation
Authors: Li, Shouwei; Liu, Wei
Bibcode: 2022GeoRL..4998806L
Altcode:
Proxy evidences suggest abrupt southward displacements of the
intertropical convergence zone (ITCZ) during Heinrich Stadial 1 (HS1)
and Younger Dryas (YD) against a long-term trend of northward ITCZ
migration from Last Glacial Maximum to modern climate. Climate model
simulations reveal that the abrupt ITCZ changes in HS1 and YD are mainly
driven by ice-sheet-induced meltwater while the long-term ITCZ trend
primarily results from orbital variations, rising atmospheric greenhouse
gases and ice-sheet retreats during the last deglaciation. Atmospheric
energetics analysis elucidates two important processes driven by
meltwater—less net radiation entering the top-of-atmosphere (TOA)
in the Northern Hemisphere than the Southern Hemisphere and a reduced
global cross-equatorial oceanic heat transport from the compensation
between Atlantic and Indo-Pacific heat transports—induce the southward
ITCZ shift during HS1. Ice sheet extent changes also create a large
interhemispheric TOA radiation asymmetry during HS1, which, however,
is not via the surface albedo feedback.
Title: Experimental study of chromium (III) coprecipitation with
calcium carbonate
Authors: Fang, Ziyao; Liu, Wei; Yao, Tao; Zhou, Gentao; Wei, Shiqiang;
Qin, Liping
Bibcode: 2022GeCoA.322...94F
Altcode:
Chromium (Cr) isotope compositions of marine carbonates have widely
been used to trace the evolution of oxygen levels in the atmosphere
and ocean during geological history. Recent studies have indicated
that Cr found in natural carbonates is dominated by trivalent Cr,
also known as Cr(III). However, the incorporation behavior of Cr(III)
into carbonates remains undefined. Here, we conducted coprecipitation
experiments for Cr(III) with calcium carbonate to constrain the
behavior of Cr(III) in carbonate deposition environments. Extended
X-ray absorption fine structure (EXAFS) results suggest that Cr(III)
is incompatible with the calcite crystal lattice. There are likely
to be several Cr species in the coprecipitation samples. Most Cr is
adsorbed on the crystal surface of calcite or exists as amorphous Cr
hydroxide [Cr(OH)3]. A small fraction of Cr can reside in
the calcite crystal, but Cr3+ cannot directly substitute
for Ca2+. It may exist in interstitial voids in crystals
or occupy the position of Ca2+ in the form of divalent
Cr hydroxide cation [Cr(OH)2+], leading to a distorted
structure. Moreover, we find that Cr(III) can stimulate polymorph
selection of vaterite [a metastable polymorph of calcium carbonate
(CaCO3)] during CaCO3 precipitation, likely due
to the formation of Cr hydroxide on the surface of vaterite crystals,
hindering its transformation to calcite. Because Cr(III) is incompatible
with the carbonate crystal lattice, we suggest that most Cr in natural
carbonates is adsorbed on the crystal surface and may be acquired at
water-sediment interfaces after carbonate precipitation. Therefore,
Cr isotope compositions of carbonates may easily be affected by
post-depositional diagenetic processes, and Cr isotope variations in
sedimentary carbonates should not exclusively correspond to changes
in oxygen levels in the atmosphere and ocean. Paleoenvironment
reconstruction based on Cr isotope compositions of carbonates should
take post-depositional processes into consideration.
Title: The Forward Physics Facility at the High-Luminosity LHC
Authors: Feng, Jonathan L.; Kling, Felix; Hall Reno, Mary; Rojo, Juan;
Soldin, Dennis; Anchordoqui, Luis A.; Boyd, Jamie; Ismail, Ahmed;
Harland-Lang, Lucian; Kelly, Kevin J.; Pandey, Vishvas; Trojanowski,
Sebastian; Tsai, Yu-Dai; Alameddine, Jean-Marco; Araki, Takeshi;
Ariga, Akitaka; Ariga, Tomoko; Asai, Kento; Bacchetta, Alessandro;
Balazs, Kincso; Barr, Alan J.; Battistin, Michele; Bian, Jianming;
Bertone, Caterina; Bai, Weidong; Bakhti, Pouya; Baha Balantekin,
A.; Barman, Basabendu; Batell, Brian; Bauer, Martin; Bauer, Brian;
Becker, Mathias; Berlin, Asher; Bertuzzo, Enrico; Bhattacharya, Atri;
Bonvini, Marco; Boogert, Stewart T.; Boyarsky, Alexey; Bramante,
Joseph; Brdar, Vedran; Carmona, Adrian; Casper, David W.; Celiberto,
Francesco Giovanni; Cerutti, Francesco; Chachamis, Grigorios; Chauhan,
Garv; Citron, Matthew; Copello, Emanuele; Corso, Jean-Pierre; Darmé,
Luc; Tito D'Agnolo, Raffaele; Darvishi, Neda; Das, Arindam; De Lellis,
Giovanni; De Roeck, Albert; de Vries, Jordy; Dembinski, Hans P.;
Demidov, Sergey; deNiverville, Patrick; Denton, Peter B.; Deppisch,
Frank F.; Bhupal Dev, P. S.; Di Crescenzo, Antonia; Dienes, Keith
R.; Diwan, Milind V.; Dreiner, Herbi K.; Du, Yong; Dutta, Bhaskar;
Duwentäster, Pit; Elie, Lucie; Ellis, Sebastian A. R.; Enberg, Rikard;
Farzan, Yasaman; Fieg, Max; Foguel, Ana Luisa; Foldenauer, Patrick;
Foroughi-Abari, Saeid; Fortin, Jean-François; Friedland, Alexander;
Fuchs, Elina; Fucilla, Michael; Gallmeister, Kai; Garcia, Alfonso;
García Canal, Carlos A.; Vittoria Garzelli, Maria; Gauld, Rhorry;
Ghosh, Sumit; Ghoshal, Anish; Gibson, Stephen; Giuli, Francesco;
Gonçalves, Victor P.; Gorbunov, Dmitry; Goswami, Srubabati; Grau,
Silvia; Günther, Julian Y.; Guzzi, Marco; Haas, Andrew; Hakulinen,
Timo; Harris, Steven P.; Harz, Julia; Helo Herrera, Juan Carlos;
Hill, Christopher S.; Hirsch, Martin; Hobbs, Timothy J.; Höche,
Stefan; Hryczuk, Andrzej; Huang, Fei; Inada, Tomohiro; Infantino,
Angelo; Ismail, Ameen; Jacobsson, Richard; Jana, Sudip; Jeong, Yu
Seon; Ježo, Tomas; Jho, Yongsoo; Jodłowski, Krzysztof; Kalashnikov,
Dmitry; Kärkkäinen, Timo J.; Keppel, Cynthia; Kim, Jongkuk; Klasen,
Michael; Klein, Spencer R.; Ko, Pyungwon; Köhler, Dominik; Komatsu,
Masahiro; Kovařík, Karol; Kulkarni, Suchita; Kumar, Jason; Kumar,
Karan; Kuo, Jui-Lin; Krauss, Frank; Kusina, Aleksander; Laletin,
Maxim; Le Roux, Chiara; Lee, Seung J.; Lee, Hye-Sung; Lefebvre,
Helena; Li, Jinmian; Li, Shuailong; Li, Yichen; Liu, Wei; Liu, Zhen;
Lonjon, Mickael; Lyu, Kun-Feng; Maciula, Rafal; Mammen Abraham,
Roshan; Masouminia, Mohammad R.; McFayden, Josh; Mikulenko, Oleksii;
Mohammed, Mohammed M. A.; Mohan, Kirtimaan A.; Morfín, Jorge G.;
Mosel, Ulrich; Mosny, Martin; Muzakka, Khoirul F.; Nadolsky, Pavel;
Nakano, Toshiyuki; Nangia, Saurabh; Navascues Cornago, Angel; Nevay,
Laurence J.; Ninin, Pierre; Nocera, Emanuele R.; Nomura, Takaaki;
Nunes, Rui; Okada, Nobuchika; Olness, Fred; Osborne, John; Otono,
Hidetoshi; Ovchynnikov, Maksym; Papa, Alessandro; Pei, Junle; Peon,
Guillermo; Perez, Gilad; Pickering, Luke; Plätzer, Simon; Plestid,
Ryan; Poddar, Tanmay Kumar; Rai, Mudit; Rajaee, Meshkat; Raut, Digesh;
Reimitz, Peter; Resnati, Filippo; Rhode, Wolfgang; Richardson, Peter;
Ritz, Adam; Rokujo, Hiroki; Roszkowski, Leszek; Ruhe, Tim; Ruiz,
Richard; Sabate-Gilarte, Marta; Sandrock, Alexander; Sarcevic, Ina;
Sarkar, Subir; Sato, Osamu; Scherb, Christiane; Schienbein, Ingo;
Schulz, Holger; Schwaller, Pedro; Sciutto, Sergio J.; Sengupta,
Dipan; Shchutska, Lesya; Shimomura, Takashi; Silvetti, Federico;
Sinha, Kuver; Sjöstrand, Torbjörn; Sobczyk, Jan T.; Song, Huayang;
Soriano, Jorge F.; Soreq, Yotam; Stasto, Anna; Stuart, David; Su,
Shufang; Su, Wei; Szczurek, Antoni; Tabrizi, Zahra; Takubo, Yosuke;
Taoso, Marco; Thomas, Brooks; Thonet, Pierre; Tuckler, Douglas; Sabio
Vera, Agustin; Vincke, Heinz; Vishnudath, K. N.; Wang, Zeren Simon;
Winkler, Martin W.; Wu, Wenjie; Xie, Keping; Xu, Xun-Jie; You, Tevong;
Yu, Ji-Young; Yu, Jiang-Hao; Zapp, Korinna; Zhang, Yongchao; Zhang,
Yue; Zhou, Guanghui; Zukanovich Funchal, Renata
Bibcode: 2022arXiv220305090F
Altcode:
High energy collisions at the High-Luminosity Large Hadron Collider
(LHC) produce a large number of particles along the beam collision axis,
outside of the acceptance of existing LHC experiments. The proposed
Forward Physics Facility (FPF), to be located several hundred meters
from the ATLAS interaction point and shielded by concrete and rock,
will host a suite of experiments to probe Standard Model (SM) processes
and search for physics beyond the Standard Model (BSM). In this report,
we review the status of the civil engineering plans and the experiments
to explore the diverse physics signals that can be uniquely probed
in the forward region. FPF experiments will be sensitive to a broad
range of BSM physics through searches for new particle scattering or
decay signatures and deviations from SM expectations in high statistics
analyses with TeV neutrinos in this low-background environment. High
statistics neutrino detection will also provide valuable data for
fundamental topics in perturbative and non-perturbative QCD and in
weak interactions. Experiments at the FPF will enable synergies between
forward particle production at the LHC and astroparticle physics to be
exploited. We report here on these physics topics, on infrastructure,
detector, and simulation studies, and on future directions to realize
the FPF's physics potential.
Title: Surface Solvation of Martian Salt Analogues at Low Relative
Humidities
Authors: Kong, X. R.; Zhu, S. Y.; Shavorskiy, A.; Li, J.; Liu, W. Y.;
Corral Arroyo, P.; Signorell, R.; Wang, S.; Pettersson, J. B. C.
Bibcode: 2022LPICo2678.1878K
Altcode:
The synchrotron-based approach is used to characterize the surface
of martian analogues, as well as their responses to varying relative
humidity.
Title: Search for very high energy gamma-ray emission from GRB
190829A with LHASSO-WCDA triggerless data
Authors: Yao, Y.; Liu, W.; Qiao, B.; Guo, Y.; Hu, H.; Yang, C.; Yao,
Z.; Lhaaso Collaboration
Bibcode: 2022icrc.confE.853Y
Altcode: 2022PoS...395E.853Y
No abstract at ADS
Title: Adaboost-DSNN: an adaptive boosting algorithm based on deep
self normalized neural network for pulsar identification
Authors: Tariq, Irfan; Meng, Qiao; Yao, Shunyu; Liu, Wei; Zhou,
Chenye; Ahmed, Adnan; Spanakis-Misirlis, Apostolos
Bibcode: 2022MNRAS.511..683T
Altcode: 2022MNRAS.tmp..188T
A modern pulsar survey generates a large number of pulsar
candidates. Filtering these pulsar candidates in a large astronomical
data set is an important step towards discovering new pulsars. In
this paper, a novel adaptive boosting algorithm based on deep self
normalized neural network (Adaboost-DSNN) is proposed to accurately
classify pulsar and non-pulsar signals. To train the proposed
method on a highly imbalanced data set, the Synthetic Minority
Oversampling TEchnique (SMOTE) was initially employed for balancing
the data set. Then, a deep ensemble network combined with a deep
self-normalized neural network and adaptive boosting was developed to
train and learn the processed pulsar data. The design of the proposed
Adaboost-DSNN method significantly reduced the computational time
when dealing with large astronomical data sets, while also improving
the classification performance. The scaled exponential liner units
activation function was used to normalize the data. Considering their
neighbour information and the special dropout technique (α-dropout),
Adaboost-DSNN displayed good pulsar classification performance, while
preserving the data properties across subsequent layers. The proposed
Adaboost-DSNN method was tested on the High Time Resolution Universe
Survey data sets (HTRU-1 and HTRU-2). According to experimental results,
Adaboost-DSNN outperform other state-of-the-art methods with respect
to training time and F1-score. The training time of the Adaboost-DSNN
model is 10x times faster compared to other models of this kind.
Title: The Spectral Features of Potential Life Markers on Mars by
Multiple Spectral Detection
Authors: Liu, W.; Wu, Z. C.; Chen, W. X.; Jin, G. B.; Li, Z.
Bibcode: 2022LPICo2678.1387L
Altcode:
The spectral features of potential life markers on Mars by multiple
spectral detection.
Title: Geminga SNR: Possible Candidate of the Local Cosmic-Ray Factory
Authors: Zhao, Bing; Liu, Wei; Yuan, Qiang; Hu, Hong-Bo; Bi, Xiao-Jun;
Wu, Han-Rong; Zhou, Xun-Xiu; Guo, Yi-Qing
Bibcode: 2022ApJ...926...41Z
Altcode: 2021arXiv210407321Z
The precise measurements of energy spectra and anisotropy could
help us uncover the local cosmic-ray accelerators. Our recent works
have shown that spectral hardening above 200 GeV in the energy
spectra and transition of large-scale anisotropy at ~100 TeV are of
local source origin. Less than 100 TeV, both spectral hardening and
anisotropy explicitly indicate the dominant contribution from nearby
sources. In this work, we further investigate the parameter space of
sources allowed by the observational energy spectra and anisotropy
amplitude. To obtain the best-fit source parameters, a numerical
package to compute the parameter posterior distributions based on
Bayesian inference, which is applied to perform an elaborate scan
of parameter space. We find that by combining the energy spectra and
anisotropy data, the permissible range of location and age of the local
source is considerably reduced. When comparing with the current local
supernova remnant (SNR) catalog, only Geminga SNR could be the proper
candidate of the local cosmic-ray source.
Title: Exploring Lorentz Invariance Violation from Ultrahigh-Energy
γ Rays Observed by LHAASO
Authors: Cao, Zhen; Aharonian, F.; An, Q.; Axikegu, Bai, L. X.; Bai,
Y. X.; Bao, Y. W.; Bastieri, D.; Bi, X. J.; Bi, Y. J.; Cai, H.; Cai,
J. T.; Cao, Zhe; Chang, J.; Chang, J. F.; Chen, B. M.; Chen, E. S.;
Chen, J.; Chen, Liang; Chen, Liang; Chen, Long; Chen, M. J.; Chen,
M. L.; Chen, Q. H.; Chen, S. H.; Chen, S. Z.; Chen, T. L.; Chen,
X. L.; Chen, Y.; Cheng, N.; Cheng, Y. D.; Cui, S. W.; Cui, X. H.; Cui,
Y. D.; Piazzoli, B. D'ettorre; Dai, B. Z.; Dai, H. L.; Dai, Z. G.;
Danzengluobu, Della Volpe, D.; Dong, X. J.; Duan, K. K.; Fan, J. H.;
Fan, Y. Z.; Fan, Z. X.; Fang, J.; Fang, K.; Feng, C. F.; Feng, L.;
Feng, S. H.; Feng, Y. L.; Gao, B.; Gao, C. D.; Gao, L. Q.; Gao, Q.;
Gao, W.; Ge, M. M.; Geng, L. S.; Gong, G. H.; Gou, Q. B.; Gu, M. H.;
Guo, F. L.; Guo, J. G.; Guo, X. L.; Guo, Y. Q.; Guo, Y. Y.; Han,
Y. A.; He, H. H.; He, H. N.; He, J. C.; He, S. L.; He, X. B.; He,
Y.; Heller, M.; Hor, Y. K.; Hou, C.; Hou, X.; Hu, H. B.; Hu, S.; Hu,
S. C.; Hu, X. J.; Huang, D. H.; Huang, Q. L.; Huang, W. H.; Huang,
X. T.; Huang, X. Y.; Huang, Z. C.; Ji, F.; Ji, X. L.; Jia, H. Y.;
Jiang, K.; Jiang, Z. J.; Jin, C.; Ke, T.; Kuleshov, D.; Levochkin,
K.; Li, B. B.; Li, Cheng; Li, Cong; Li, F.; Li, H. B.; Li, H. C.;
Li, H. Y.; Li, Jian; Li, Jie; Li, K.; Li, W. L.; Li, X. R.; Li, Xin;
Li, Xin; Li, Y.; Li, Y. Z.; Li, Zhe; Li, Zhuo; Liang, E. W.; Liang,
Y. F.; Lin, S. J.; Liu, B.; Liu, C.; Liu, D.; Liu, H.; Liu, H. D.;
Liu, J.; Liu, J. L.; Liu, J. S.; Liu, J. Y.; Liu, M. Y.; Liu, R. Y.;
Liu, S. M.; Liu, W.; Liu, Y.; Liu, Y. N.; Liu, Z. X.; Long, W. J.; Lu,
R.; Lv, H. K.; Ma, B. Q.; Ma, L. L.; Ma, X. H.; Mao, J. R.; Masood,
A.; Min, Z.; Mitthumsiri, W.; Montaruli, T.; Nan, Y. C.; Pang, B. Y.;
Pattarakijwanich, P.; Pei, Z. Y.; Qi, M. Y.; Qi, Y. Q.; Qiao, B. Q.;
Qin, J. J.; Ruffolo, D.; Rulev, V.; Sáiz, A.; Shao, L.; Shchegolev,
O.; Sheng, X. D.; Shi, J. R.; Song, H. C.; Stenkin, Yu. V.; Stepanov,
V.; Su, Y.; Sun, Q. N.; Sun, X. N.; Sun, Z. B.; Tam, P. H. T.; Tang,
Z. B.; Tian, W. W.; Wang, B. D.; Wang, C.; Wang, H.; Wang, H. G.;
Wang, J. C.; Wang, J. S.; Wang, L. P.; Wang, L. Y.; Wang, R. N.;
Wang, W.; Wang, W.; Wang, X. G.; Wang, X. J.; Wang, X. Y.; Wang,
Y.; Wang, Y. D.; Wang, Y. J.; Wang, Y. P.; Wang, Z. H.; Wang, Z. X.;
Wang, Zhen; Wang, Zheng; Wei, D. M.; Wei, J. J.; Wei, Y. J.; Wen, T.;
Wu, C. Y.; Wu, H. R.; Wu, S.; Wu, W. X.; Wu, X. F.; Xi, S. Q.; Xia,
J.; Xia, J. J.; Xiang, G. M.; Xiao, D. X.; Xiao, G.; Xiao, H. B.;
Xin, G. G.; Xin, Y. L.; Xing, Y.; Xu, D. L.; Xu, R. X.; Xue, L.;
Yan, D. H.; Yan, J. Z.; Yang, C. W.; Yang, F. F.; Yang, J. Y.; Yang,
L. L.; Yang, M. J.; Yang, R. Z.; Yang, S. B.; Yao, Y. H.; Yao, Z. G.;
Ye, Y. M.; Yin, L. Q.; Yin, N.; You, X. H.; You, Z. Y.; Yu, Y. H.;
Yuan, Q.; Zeng, H. D.; Zeng, T. X.; Zeng, W.; Zeng, Z. K.; Zha, M.;
Zhai, X. X.; Zhang, B. B.; Zhang, H. M.; Zhang, H. Y.; Zhang, J. L.;
Zhang, J. W.; Zhang, L. X.; Zhang, Li; Zhang, Lu; Zhang, P. F.; Zhang,
P. P.; Zhang, R.; Zhang, S. R.; Zhang, S. S.; Zhang, X.; Zhang, X. P.;
Zhang, Y. F.; Zhang, Y. L.; Zhang, Yi; Zhang, Yong; Zhao, B.; Zhao,
J.; Zhao, L.; Zhao, L. Z.; Zhao, S. P.; Zheng, F.; Zheng, Y.; Zhou,
B.; Zhou, H.; Zhou, J. N.; Zhou, P.; Zhou, R.; Zhou, X. X.; Zhu,
C. G.; Zhu, F. R.; Zhu, H.; Zhu, K. J.; Zuo, X.; Lhaaso Collaboration
Bibcode: 2022PhRvL.128e1102C
Altcode:
Recently, the LHAASO Collaboration published the detection of 12
ultrahigh-energy γ -ray sources above 100 TeV, with the highest
energy photon reaching 1.4 PeV. The first detection of PeV γ rays
from astrophysical sources may provide a very sensitive probe of the
effect of the Lorentz invariance violation (LIV), which results in
decay of high-energy γ rays in the superluminal scenario and hence
a sharp cutoff of the energy spectrum. Two highest energy sources
are studied in this work. No signature of the existence of the LIV
is found in their energy spectra, and the lower limits on the LIV
energy scale are derived. Our results show that the first-order LIV
energy scale should be higher than about 105 times the
Planck scale MPl and that the second-order LIV scale is
>10-3MPl . Both limits improve by at least
one order of magnitude the previous results.
Title: Identification of new M 31 star cluster candidates from PAndAS
images using convolutional neural networks
Authors: Wang, Shoucheng; Chen, Bingqiu; Ma, Jun; Long, Qian; Yuan,
Haibo; Liu, Dezi; Zhou, Zhimin; Liu, Wei; Chen, Jiamin; He, Zizhao
Bibcode: 2022A&A...658A..51W
Altcode: 2021arXiv211107798W
Context. Identification of new star cluster candidates in M 31 is
fundamental for the study of the M 31 stellar cluster system. The
machine-learning method convolutional neural network (CNN) is
an efficient algorithm for searching for new M 31 star cluster
candidates from tens of millions of images from wide-field photometric
surveys.
Aims: We search for new M 31 cluster candidates from the
high-quality g- and i-band images of 21 245 632 sources obtained from
the Pan-Andromeda Archaeological Survey (PAndAS) through a CNN.
Methods: We collected confirmed M 31 clusters and noncluster objects
from the literature as our training sample. Accurate double-channel CNNs
were constructed and trained using the training samples. We applied
the CNN classification models to the PAndAS g- and i-band images of
over 21 million sources to search new M 31 cluster candidates. The CNN
predictions were finally checked by five experienced human inspectors
to obtain high-confidence M 31 star cluster candidates.
Results: After the inspection, we identified a catalogue of 117
new M 31 cluster candidates. Most of the new candidates are young
clusters that are located in the M 31 disk. Their morphology,
colours, and magnitudes are similar to those of the confirmed young
disk clusters. We also identified eight globular cluster candidates
that are located in the M 31 halo and exhibit features similar to
those of confirmed halo globular clusters. The projected distances
to the M 31 centre for three of them are larger than 100 kpc. Full Table 2 is only available at the CDS via anonymous ftp to cdsarc.u-strasbg.fr
(ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/cat/J/A+A/658/A51
Title: VizieR Online Data Catalog: NH3 isotope ratios of Galactic
disk sources (Chen+, 2021)
Authors: Chen, J. L.; Zhang, J. S.; Henkel, C.; Yan, Y. T.; Yu, H. Z.;
Qiu, J. J.; Tang, X. D.; Wang, J.; Liu, W.; Wang, Y. X.; Zheng, Y. H.;
Zhao, J. Y.; Zou, Y. P.
Bibcode: 2022yCat..22570039C
Altcode:
For our sample of 210 sources, we made observations of the
(J,K)=(1,1), (2,2), and (3,3) lines of 14NH3
and 15NH3 (23694.5MHz, 23722.6MHz, 23870.1MHz,
22624.9MHz, 22649.8MHz and 22789.4MHz, respectively), first with
the Shanghai Tianma 65m radio telescope (TMRT) in 2019 April, May,
November, and December, with a beam size of ~50". We also used the
Effelsberg 100m telescope to observe the (J,K)=(1,1), (2,2), and (3,3)
lines of 14NH3 and 15NH3
toward 36 selected sources with strong 14NH3
signals from previous TMRT observations in 2019 December and 2020
January. (4 data files).
Title: Winter mixing accelerates decomposition of sedimentary organic
carbon in seasonally hypoxic coastal seas
Authors: Wei, Lin; Cai, Pinghe; Shi, Xiangming; Cai, Wei-Jun; Liu,
Wei; Hong, Qingquan; Wu, Tong; Bai, Yan; Cheng, Peng; Sun, Zhenyu
Bibcode: 2022GeCoA.317..457W
Altcode:
Deltaic systems are characterized by the highest sedimentation
rates in the globe. Meanwhile, sedimentary organic matter therein
can be efficiently decomposed so that these depositional systems
may deviate substantially from the oft-quoted correlation between
net sediment accumulation and preservation of organic matter. The
exact mechanisms that cause such a deviation in any given case,
however, remain poorly understood. In this study, we utilize a novel
224Ra/228Th disequilibrium method to examine
sediment oxygen consumption and the release of diagenetic products of
organic matter along the major mud wedge system in the inner shelf
of the East China Sea. Our sampling campaign was carried out in two
contrasting seasons: the summer when seasonal hypoxia was at its peak
and physical conditions were relatively quiescent, and the winter
when the water column was well oxygenated by intense winter mixing and
underlying deposits were subjected to reworking. Unexpectedly, during
summer 2017 when the seafloor received the annual maximum supply of
organic matter, sediment oxygen consumption rates and benthic fluxes
of NH4+ were relatively low, ranging from 6 to
59 mmol O2 m-2 d-1 and from 1.6 to
13 mmol N m-2 d-1, respectively. In contrast,
during winter 2018 sediment oxygen consumption rates and benthic fluxes
of NH4+ surged to 44-690 mmol O2
m-2 d-1 and 22-58 mmol N m-2
d-1, respectively. We have also identified an exponential
relationship between amplification factor of sediment surface area
and oxygen concentration in the bottom water. This relationship
suggests that kinetic energy dissipation in the water column not only
controlled air-sea exchange and seawater mixing, but also intensified
sediment-water interaction. Importantly, sediment oxygen consumption
rates (FO2) in the mud wedge can be empirically
described using a modified form of Michaelis-Menten kinetics, suggesting
that FO2and the associated benthic consumption
and production of chemicals are controlled by both the transport and
reaction processes. We have further demonstrated that a large portion
of the organic matter deposited over the seafloor in summer is likely
decomposed in winter. Overall, this study highlights intense winter
mixing as an important mechanism that causes the highly efficient
decomposition of sedimentary organic matter in coastal seas.
Title: Development of 1.2-2.2 GHz Wideband Low Noise Amplifier
Authors: Liu, W. H.; Jiang, P.; Liu, H. F.; Lei, H. K.; Jiang, L.;
Hu, H.
Bibcode: 2022AcASn..63....3L
Altcode:
In order to detect the weak radio signal, the telescope receiver
requires good noise performance. As the key circuit of the receiver
front end, the noise coefficient and gain of the low noise amplifier
(LNA) determine the noise performance of the whole machine. A 1.2--2.2
GHz low noise amplifier is designed. The circuit adopts a two-stage
cascade structure. The second stage introduces negative feedback to
improve the gain flatness and broaden the bandwidth while reducing
the noise. After the post-stage input impedance optimization, only one
capacitor is needed between the stages. Lossy output matching network is
introduced to realize high gain, low noise, good return loss and flat
broadband LNA design. The test results show that the gain is 30--33
dB in the 1.2--2.2 GHz band, the average noise temperature is 47 K,
and the output 1 dB compression point is greater than 11.3 dBm. Test
results show that the device has good performance, which can be used
in the receiver system in this frequency band.
Title: The status and future of direct nuclear reaction measurements
for stellar burning
Authors: Aliotta, M.; Buompane, R.; Couder, M.; Couture, A.; deBoer,
R. J.; Formicola, A.; Gialanella, L.; Glorius, J.; Imbriani, G.;
Junker, M.; Langer, C.; Lennarz, A.; Litvinov, Yu A.; Liu, W. -P.;
Lugaro, M.; Matei, C.; Meisel, Z.; Piersanti, L.; Reifarth, R.;
Robertson, D.; Simon, A.; Straniero, O.; Tumino, A.; Wiescher, M.;
Xu, Y.
Bibcode: 2022JPhG...49a0501A
Altcode: 2021arXiv210914418A
The study of stellar burning began just over 100 years ago. Nonetheless,
we do not yet have a detailed picture of the nucleosynthesis within
stars and how nucleosynthesis impacts stellar structure and the remnants
of stellar evolution. Achieving this understanding will require precise
direct measurements of the nuclear reactions involved. This report
summarizes the status of direct measurements for stellar burning,
focusing on developments of the last couple of decades, and offering
a prospectus of near-future developments.
Title: A Real-time, Pipelined Incoherent Dedispersion Method and
Implementation in FPGA
Authors: Liu, Wei; Meng, Qiao; Wang, Chen; Zhou, Chenye; Yao, Shunyu;
Tariq, Irfan
Bibcode: 2022PASP..134a5008L
Altcode:
In pulsar observation, dispersion occurs due to the interstellar
medium. The dispersion significantly affects the detection of pulsar
signals. To overcome the dispersion effect, incoherent dedispersion
methods are often applied. The tranditional inchoherent dedispersion
methods are computationally expensive and troublesome. To deal with this
problem, in this paper, we developed a Real-Time, Pipelined Incoherent
Dedispersion Method (RT-PIDM). RT-PIMD only caches the summed-up time
series, instead of all the frequency spectra, so the memory consumption
is determined by the number of DM trails, whereas the traditional
method's memory consumption is determined by the number of frequency
channels. In most of the situations, the number of frequency channels
is several times more than that of DM trails, which means the memory
consumption of traditional methods is more than that of RT-PIDM. With
RT-PIDM, we designed a 1.2 GHz bandwidth prototype digital backend,
and we finished pulsar observation with the 40 m radio telescope at
Yunnan Observatory. The results demonstrate that the RT-PIDM can be
implemented inside a single FPGA chip with less Block RAM, and the
proposed RT-PIDM dedisperses the pulsar signal in real time and achieves
the same result as compared to traditional incoherent dedispersion.
Title: Compact Scintillator Array Detector (ComSAD) for Sounding
Rocket and CubeSat Missions
Authors: Wang, Pu Kai; Chen, Chih-Yun; Hsu, Hsiang-Chieh; Chang,
Mu-Hsin; Liu, Wei Tai; Fang, Hui-Kuan; Wu, Ting-Chou; Chen, Wen-Hao;
Tsai, Chin Cheng; Chen, Alfred Bing-Chih; Yang, Yi
Bibcode: 2022JAI....1150007W
Altcode: 2021arXiv211012500W
The development of CubeSats and more frequent launch chances of
sounding rockets are a total game changer to the space program,
and it allows us to build space instruments that are technologically
feasible and affordable. Therefore, it gives us a good opportunity to
build a small cosmic-ray detector which has capabilities to measure
the flux, direction, and even energy of cosmic rays at an altitude
above the limitation of balloon experiments, and it may open a new
door for building a constellation of detectors to study cosmic-ray
physics. Compact Scintillator Array Detector (ComSAD) is a funded
sounding rocket mission of Taiwan’s National Space Organization. In
this paper, we present the concept, design, and performance of ComSAD
which is also suitable for future CubeSat missions.
Title: Reconciling ultra-high-energy diffuse $\gamma$-rays and the
knee of cosmic ray light nuclei
Authors: Zhang, Pei-pei; Guo, Yi-qing; Qiao, Bing-qiang; Liu, Wei
Bibcode: 2021arXiv211204651Z
Altcode:
The diffuse $\gamma$-ray was measured up to 957 TeV by the
Tibet-AS$\gamma$ experiment. Presuming it is produced by the hadronic
interaction between cosmic ray nuclei and the interstellar medium,
it requires that the cosmic ray nuclei should be accelerated well
beyond PeV energies. However, measurements of the spectrum of proton
and Helium by a few experiments show break below PeV. To solve this
apparent discrepancy, we propose in this work that a new structure of
cosmic rays may exist beyond PeV, which can contribute to the highest
energy diffuse $\gamma$ rays. This additional component may serve
as another population of Galactic cosmic ray accelerators, and can
contribute to the cosmic ray fluxes beyond the second knee. Future
measurements of the energy spectra of different nuclei species may
test the existence of this new component.
Title: The Role of a Weakened Atlantic Meridional Overturning
Circulation in Modulating Marine Heatwaves in a Warming Climate
Authors: Ren, Xianglin; Liu, Wei
Bibcode: 2021GeoRL..4895941R
Altcode:
We explore the effect of Atlantic meridional overturning circulation
(AMOC) slowdown on global marine heatwaves (MHWs) under anthropogenic
warming by maintaining AMOC strength in climate model simulations
throughout the 21st century. The AMOC slowdown has an insignificant
effect on global MHWs during the past four decades, except those
over the North Atlantic warming hole (NAWH) where the weakened AMOC
reduces the occurrence and duration of MHWs by about half by creating
a cooler mean-state sea surface temperature. As the AMOC continues
weakening in current century, its effect becomes significant on MHWs
in the North Atlantic and Pacific Oceans. The weakened AMOC induces
a bipolar-seesaw-like change in MHW frequencies, with more frequent
MHWs in the Southern Hemisphere but less frequent MHWs in the North
Hemisphere except over the NAWH. The reason for the exception is that
the NAWH region would enter a near-permanent MHW state without an
AMOC slowdown.
Title: Prospects for the Detection of the Prompt Very-high-energy
Emission from γ-ray Bursts with the High Altitude Detection of
Astronomical Radiation Experiment
Authors: Xin, Guang-Guang; Yao, Yu-Hua; Qian, Xiang-Li; Liu, Cheng;
Gao, Qi; Luo-Bu, Dan-Zeng; Feng, You-Liang; Gou, Quan-Bu; Hu, Hong-Bo;
Li, Hai-Jin; Liu, Mao-Yuan; Liu, Wei; Qiao, Bing-Qiang; Wang, Zhen;
Zhang, Yi; Cai, Hao; Chen, Tian-Lu; Guo, Yi-Qing
Bibcode: 2021ApJ...923..112X
Altcode: 2021arXiv210304381X
The observation of very-high-energy (VHE; > 10 GeV) γ-ray emission
from γ-ray bursts (GRBs), especially in the prompt phase, will provide
critical information for understanding many aspects of their nature
including the physical environment, the relativistic bulk motion, the
mechanisms of particle acceleration of GRBs, and for studying Lorentz
invariance violation, etc. For the afterglow phase, the highest-energy
photons detected to date by the imaging atmospheric Cherenkov telescopes
extend to the TeV regime. However, for the prompt phase, years of
efforts in searching for the VHE emission has yielded no statistically
significant detections. A wide field of view and large effective area
above tens of GeV are essential for detecting the VHE emissions from
GRBs in the prompt phase. The High Altitude Detection of Astronomical
Radiation (HADAR) experiment has such merits. In this paper, we report
the estimates of its expected annual GRB detection rate, which are
obtained by combining the performance of the HADAR instrument with the
theoretical calculations based on a phenomenological model to generate
the pseudo-GRB population. The expected detectable gamma-ray signal
from GRBs above the background is then obtained to give the detection
rate. In the spectral model, an extra component is assigned to every GRB
event in addition to the Band function. The results indicate that if the
energy of the cutoff due to internal absorption is higher than 50 GeV,
the detection rate for GRBs for the HADAR experiment is approximately
two or three GRBs per year, which varies slightly depending upon the
characteristics of the extra component.
Title: Interstellar Nitrogen Isotope Ratios: New NH3
Data from the Galactic Center out to the Perseus Arm
Authors: Chen, J. L.; Zhang, J. S.; Henkel, C.; Yan, Y. T.; Yu, H. Z.;
Qiu, J. J.; Tang, X. D.; Wang, J.; Liu, W.; Wang, Y. X.; Zheng, Y. H.;
Zhao, J. Y.; Zou, Y. P.
Bibcode: 2021ApJS..257...39C
Altcode: 2022arXiv220803977C
Our aim is to measure the interstellar 14N/15N
ratio across the Galaxy, to establish a standard data set on
interstellar ammonia isotope ratios, and to provide new constraints on
the Galactic chemical evolution. The (J, K) = (1, 1), (2, 2), and (3,
3) lines of 14NH3 and 15NH3
were observed with the Shanghai Tianma 65 m radio telescope (TMRT)
and the Effelsberg 100 m telescope toward a large sample of 210
sources. One hundred fourty-one of these sources were detected by the
TMRT in 14NH3. Eight of them were also detected
in 15NH3. For 10 of the 36 sources with strong
NH3 emission, the Effelsberg 100 m telescope successfully
detected their 15NH3(1, 1) lines, including
3 sources (G081.7522, W51D, and Orion-KL) with detections by the
TMRT telescope. Thus, a total of 15 sources are detected in both the
14NH3 and 15NH3 lines. Line
and physical parameters for these 15 sources are derived, including
optical depths, rotation and kinetic temperatures, and total column
densities. 14N/15N isotope ratios were determined
from the 14NH3/15NH3
abundance ratios. The isotope ratios obtained from both telescopes
agree for a given source within the uncertainties, and no
dependence on heliocentric distance and kinetic temperature
is seen. 14N/15N ratios tend to increase
with galactocentric distance, confirming a radial nitrogen isotope
gradient. This is consistent with results from recent Galactic chemical
model calculations, including the impact of superasymptotic giant
branch stars and novae.
Title: Study on the Pointing Error Model of Terahertz Telescopes
with Optically Assisted Pointing Measurements
Authors: Ying, X. K.; Luo, Z.; Liu, W.; Zuo, Y. X.
Bibcode: 2021AcASn..62...69Y
Altcode:
In view of the scarcity of terahertz astronomical point source targets,
this paper studies the method of using a small optical telescope coaxial
with terahertz antenna to assist the pointing measurement of terahertz
telescope and establish the pointing error correction model. Based on
the 1.2 m oblique axis terahertz antenna of Purple Mountain Observatory,
the experiment of optical aided pointing measurement is carried out. A
100 mm aperture refractive optical telescope mounted on the antenna
back frame is used to obtain the pointing measurement accuracy better
than 2''. In addition, by analyzing the structure of the slant axis
antenna and the error sources of atmospheric refraction and local
star time deviation, a slant axis optical pointing correction model
with 23 error terms is established, and the fitting accuracy of about
3'' is achieved. Finally, with the help of high-precision digital
photogrammetry, the photoelectric axis consistency is calibrated,
and its influence on the pointing model accuracy is discussed. The
research results of this paper will provide technical reference for the
5 m Dome A Terahertz Explorer (DATE5) and other terahertz telescopes
in pointing measurement and correction.
Title: Panoramic SETI: overall mechanical system design
Authors: Brown, Aaron M.; Aronson, Michael L; Wright, Shelley A.;
Maire, Jérôme; Cosens, Maren; Wiley, James H.; Antonio, Franklin;
Horowitz, Paul; Raffanti, Rick; Werthimer, Dan; Liu, Wei
Bibcode: 2021arXiv211112771B
Altcode:
PANOSETI (Pulsed All-Sky Near-infrared Optical Search for
Extra Terrestrial Intelligence) is a dedicated SETI (Search for
Extraterrestrial Intelligence) observatory that is being designed to
observe 4,441 sq. deg. to search for nano- to milli-second transient
events. The experiment will have a dual observatory system that has
a total of 90 identical optical 0.48 m telescopes that each have a 99
square degree field of view. The two observatory sites will be separated
by 1 km distance to help eliminate false positives and register a
definitive signal. We discuss the overall mechanical design of the
telescope modules which includes a Fresnel lens housing, a shutter,
three baffles, an 32x32 array of Hamamatsu Multi-Photon Pixel Counting
(MPPC) detectors that reside on a linear stage for focusing. Each
telescope module will be housed in a triangle of a 3rd tessellation
frequency geodesic dome that has the ability to have directional
adjustment to correct for manufacturing tolerances and astrometric
alignment to the second observatory site. Each observatory will have
an enclosure to protect the experiment, and an observatory room for
operations and electronics. We will review the overall design of the
geodesic domes and mechanical telescope attachments, as well as the
overall cabling and observatory infrastructure layout.
Title: New experimental measurement of natEr(n ,γ )
cross sections between 1 and 100 eV
Authors: Li, X. X.; Liu, L. X.; Jiang, W.; Ren, J.; Wang, H. W.; Fan,
G. T.; Cao, X. G.; Zhang, Y.; Hu, X. R.; Hao, Z. R.; Kuang, P.; Jiang,
B.; Wang, X. H.; Hu, J. F.; Wang, J. C.; Wang, D. X.; Zhang, S. Y.;
Liu, Y. D.; Ma, X.; Ma, C. W.; Wang, Y. T.; An, Z. D.; He, J. J.;
Su, J.; Zhang, L. Y.; Yang, Y. X.; Liu, W. B.; Su, W. Q.
Bibcode: 2021PhRvC.104e4302L
Altcode:
162Er and 164Er are two of the 35 p nuclei,
and their (n ,γ ) cross sections are important input parameters in
nuclear astrophysics network calculations. The neutron capture cross
section in the resonance region of isotopes and even the natural erbium
(natEr) sample has not been measured experimentally according
to the EXFOR database. The (n ,γ ) cross section of natEr,
using C6D6 liquid scintillator and pulse height
weighting techniques to measure prompt γ rays, has been measured in the
energy range of 1-100 eV using a back streaming white neutron facility
at China Spallation Neutron Source. The deduced neutron capture cross
sections matches the evaluation databases ENDF/B-VIII.0, ENDF/B-VII.1,
JENDL-4.0, and ROSFOND-2010, and resonance parameters extracted from
the R -matrix code in the 1-100 eV region.
Title: White-light Continuum Observation of the Off-limb Loops of
the SOL2017-09-10 X8.2 Flare: Temporal and Spatial Variations
Authors: Zhao, Junwei; Liu, Wei; Vial, Jean-Claude
Bibcode: 2021ApJ...921L..26Z
Altcode: 2021arXiv211014130Z
Observations of the Sun's off-limb white-light (WL) flares offer rare
opportunities to study the energy release and transport mechanisms
in flare loops. One of the best such events was SOL2017-09-10, an
X8.2 flare that occurred near the Sun's west limb on 2017 September
10 and produced a WL loop system lasting more than 60 minutes and
reaching an altitude higher than 30 Mm. The event was well observed
by a suite of ground- and space-based instruments, including the
Solar Dynamics Observatory/Helioseismic and Magnetic Imager (SDO/HMI)
that captured its off-limb loops in WL continuum near Fe I 6173 Å,
and the Atmospheric Imager Assembly (SDO/AIA) that observed its
ultraviolet (UV) and extreme-ultraviolet (EUV) counterparts. We
found quasi-periodic pulsations in the WL and UV emissions at the
flare loop-top with a period around 8.0 minutes. Each pulsation
appears to have an EUV counterpart that occurs earlier in time and
higher in altitude. Despite many similarities in the WL and UV images
and light curves, the WL flux at the loop-top continues to grow for
about 16 minutes while the UV fluxes gradually decay. We discuss the
implication of these unprecedented observations on the understanding
of the enigmatic off-limb WL flare emission mechanisms.
Title: A strange star scenario for the formation of eccentric
millisecond pulsar PSR J1946+3417
Authors: Jiang, Long; Wang, Na; Chen, Wen-Cong; Liu, Wei-Min; Leng,
Chun-Wei; Yuan, Jian-Ping; Qian, Xiang-Li
Bibcode: 2021RAA....21..231J
Altcode: 2021arXiv210605717J
PSR J1946+3417 is a millisecond pulsar (MSP) with a spin period P ≃
3.17 ms. Harbored in a binary with an orbital period Pb ≃
27 days, the MSP is accompanied by a white dwarf (WD). The masses of
the MSP and the WD were determined to be 1.83 M⊙ and 0.266
M⊙, respectively. Specially, its orbital eccentricity is e
≃ 0.134, which is challenging the recycling model of MSPs. Assuming
that the neutron star in a binary may collapse to a strange star when
its mass reaches a critical limit, we propose a phase transition (PT)
scenario to account for the origin of the system. The sudden mass loss
and the kick induced by asymmetric collapse during the PT may result in
the orbital eccentricity. If the PT event takes place after the mass
transfer ceases, the eccentric orbit cannot be re-circularized in the
Hubble time. Aiming at the masses of both components, we simulate
the evolution of the progenitor of PSR J1946+3417 via MESA. The
simulations show that an NS / main sequence star binary with initial
masses of 1.4+1.6 M⊙ in an initial orbit of 2.59 days
will evolve into a binary consisting of a 2.0 M⊙ MSP and
a 0.27 M⊙ WD in an orbit of ~21.5 days. Assuming that
the gravitational mass loss fraction during PT is 10%, we simulate
the effect of PT via the kick program of BSE with a velocity of
σPT = 60 km s-1. The results show that the PT
scenario can reproduce the observed orbital period and eccentricity
with higher probability than other values.
Title: Measurements of the center-of-mass energies of {{\boldsymbol
e(+}{\boldsymbol) e(-}}) collisions at BESIII
Authors: Ablikim, M.; Achasov, M. N.; Adlarson, P.; Ahmed, S.;
Albrecht, M.; Aliberti, R.; Amoroso, A.; An, M. R.; An, Q.; Bai,
X. H.; Bai, Y.; Bakina, O.; Baldini Ferroli, R.; Balossino, I.; Ban,
Y.; Begzsuren, K.; Berger, N.; Bertani, M.; Bettoni, D.; Bianchi,
F.; Bloms, J.; Bortone, A.; Boyko, I.; Briere, R. A.; Cai, H.; Cai,
X.; Calcaterra, A.; Cao, G. F.; Cao, N.; Cetin, S. A.; Chang, J. F.;
Chang, W. L.; Chelkov, G.; Chen, D. Y.; Chen, G.; Chen, H. S.; Chen,
M. L.; Chen, S. J.; Chen, X. R.; Chen, Y. B.; J. Chen, Z.; Cheng,
W. S.; Cibinetto, G.; Cossio, F.; Cui, X. F.; Dai, H. L.; Dai, X. C.;
Dbeyssi, A.; de Boer, R. E.; Dedovich, D.; Deng, Z. Y.; Denig, A.;
Denysenko, I.; Destefanis, M.; de Mori, F.; Ding, Y.; Dong, C.; Dong,
J.; Dong, L. Y.; Dong, M. Y.; Dong, X.; Du, S. X.; Fan, Y. L.; Fang,
J.; Fang, S. S.; Fang, Y.; Farinelli, R.; Fava, L.; Feldbauer, F.;
Felici, G.; Feng, C. Q.; Feng, J. H.; Fritsch, M.; Fu, C. D.; Gao,
Y.; Gao, Y.; Gao, Y.; Gao, Y. G.; Garzia, I.; Ge, P. T.; Geng, C.;
Gersabeck, E. M.; Gilman, A.; Goetzen, K.; Gong, L.; Gong, W. X.;
Gradl, W.; Greco, M.; Gu, L. M.; Gu, M. H.; Gu, Y. T.; Y Guan, C.; Guo,
A. Q.; Guo, L. B.; Guo, R. P.; Guo, Y. P.; Guskov, A.; Han, T. T.; Han,
W. Y.; Hao, X. Q.; Harris, F. A.; He, K. L.; Heinsius, F. H.; Heinz,
C. H.; Held, T.; Heng, Y. K.; Herold, C.; Himmelreich, M.; Holtmann,
T.; Hou, G. Y.; Hou, Y. R.; Hou, Z. L.; Hu, H. M.; Hu, J. F.; Hu, T.;
Hu, Y.; Huang, G. S.; Huang, L. Q.; Huang, X. T.; Huang, Y. P.; Huang,
Z.; Hussain, T.; Husken, N.; Ikegami Andersson, W.; Imoehl, W.; Irshad,
M.; Jaeger, S.; Janchiv, S.; Ji, Q.; Ji, Q. P.; Ji, X. B.; Ji, X. L.;
Ji, Y. Y.; Jiang, H. B.; Jiang, X. S.; Jiao, J. B.; Jiao, Z.; Jin, S.;
Jin, Y.; Jing, M. Q.; Johansson, T.; Kalantar-Nayestanaki, N.; Kang,
X. S.; Kappert, R.; Kavatsyuk, M.; Ke, B. C.; Keshk, I. K.; Khoukaz,
A.; Kiese, P.; Kiuchi, R.; Kliemt, R.; Koch, L.; Kolcu, O. B.; Kopf,
B.; Kuemmel, M.; Kuessner, M.; Kupsc, A.; Kurth, M. G.; Kuhn, W.; Lane,
J. J.; Lange, J. S.; Larin, P.; Lavania, A.; Lavezzi, L.; Lei, Z. H.;
Leithoff, H.; Lellmann, M.; Lenz, T.; Li, C.; Li, C. H.; Li, Cheng;
Li, D. M.; Li, F.; Li, G.; Li, H.; Li, H.; Li, H. B.; Li, H. J.; Li,
J. L.; Li, J. Q.; Li, J. S.; Li, Ke; Li, L. K.; Li, Lei; Li, P. R.;
Li, S. Y.; Li, W. D.; Li, W. G.; Li, X. H.; Li, X. L.; Li, Xiaoyu;
Li, Z. Y.; Liang, H.; Liang, H.; Liang, H.; Liang, Y. F.; Liang,
Y. T.; Liao, G. R.; Liao, L. Z.; Libby, J.; Lin, C. X.; Liu, B. J.;
Liu, C. X.; Liu, D.; Liu, F. H.; Liu, Fang; Liu, Feng; Liu, H. B.;
Liu, H. M.; Liu, Huanhuan; Liu, Huihui; Liu, J. B.; Liu, J. L.; Liu,
J. Y.; Liu, K.; Liu, K. Y.; Liu, L.; Liu, M. H.; Liu, P. L.; Liu,
Q.; Liu, Q.; Liu, S. B.; Liu, Shuai; Liu, T.; Liu, W. M.; Liu, X.;
Liu, Y.; Liu, Y. B.; Liu, Z. A.; Liu, Z. Q.; Lou, X. C.; Lu, F. X.;
Lu, H. J.; Lu, J. D.; Lu, J. G.; Lu, X. L.; Lu, Y.; Lu, Y. P.; Luo,
C. L.; Luo, M. X.; Luo, P. W.; Luo, T.; Luo, X. L.; Lyu, X. R.; Ma,
F. C.; Ma, H. L.; Ma, L. L.; Ma, M. M.; Ma, Q. M.; Ma, R. Q.; Ma,
R. T.; Ma, X. X.; Ma, X. Y.; Maas, F. E.; Maggiora, M.; Maldaner,
S.; Malde, S.; Malik, Q. A.; Mangoni, A.; Mao, Y. J.; Mao, Z. P.;
Marcello, S.; Meng, Z. X.; Messchendorp, J. G.; Mezzadri, G.; Min,
T. J.; Mitchell, R. E.; Mo, X. H.; Yu. Muchnoi, N.; Muramatsu, H.;
Nakhoul, S.; Nefedov, Y.; Nerling, F.; Nikolaev, I. B.; Ning, Z.;
Nisar, S.; Olsen, S. L.; Ouyang, Q.; Pacetti, S.; Pan, X.; Pan, Y.;
Pathak, A.; Pathak, A.; Patteri, P.; Pelizaeus, M.; Peng, H. P.;
Peters, K.; Pettersson, J.; Ping, J. L.; Ping, R. G.; Pogodin, S.;
Poling, R.; Prasad, V.; Qi, H.; Qi, H. R.; Qi, K. H.; Qi, M.; Qi,
T. Y.; Qian, S.; Qian, W. B.; Qian, Z.; Qiao, C. F.; Qin, L. Q.; Qin,
X. P.; Qin, X. S.; Qin, Z. H.; Qiu, J. F.; Qu, S. Q.; Rashid, K. H.;
Ravindran, K.; Redmer, C. F.; Rivetti, A.; Rodin, V.; Rolo, M.; Rong,
G.; Rosner, Ch.; Rump, M.; Sang, H. S.; Sarantsev, A.; Schelhaas, Y.;
Schnier, C.; Schoenning, K.; Scodeggio, M.; Shan, D. C.; Shan, W.;
Shan, X. Y.; Shangguan, J. F.; Shao, M.; Shen, C. P.; Shen, H. F.;
Shen, P. X.; Shen, X. Y.; Shi, H. C.; Shi, R. S.; Shi, X.; D Shi,
X.; Song, J. J.; Song, W. M.; Song, Y. X.; Sosio, S.; Spataro, S.;
Su, K. X.; Su, P. P.; Sui, F. F.; Sun, G. X.; Sun, H. K.; Sun, J. F.;
Sun, L.; Sun, S. S.; Sun, T.; Sun, W. Y.; Sun, W. Y.; Sun, X.; Sun,
Y. J.; Sun, Y. K.; Sun, Y. Z.; Sun, Z. T.; Tan, Y. H.; Tan, Y. X.;
Tang, C. J.; Tang, G. Y.; Tang, J.; Teng, J. X.; Thoren, V.; Tian,
W. H.; Tian, Y. T.; Uman, I.; Wang, B.; Wang, C. W.; Wang, D. Y.;
Wang, H. J.; Wang, H. P.; Wang, K.; Wang, L. L.; Wang, M.; Wang,
M. Z.; Wang, Meng; Wang, W.; Wang, W. H.; Wang, W. P.; Wang, X.; Wang,
X. F.; Wang, X. L.; Wang, Y.; Wang, Y.; Wang, Y. D.; Wang, Y. F.;
Wang, Y. Q.; Wang, Y. Y.; Wang, Z.; Wang, Z. Y.; Wang, Ziyi; Wang,
Zongyuan; Wei, D. H.; Weidner, F.; Wen, S. P.; White, D. J.; Wiedner,
U.; Wilkinson, G.; Wolke, M.; Wollenberg, L.; Wu, J. F.; Wu, L. H.;
Wu, L. J.; Wu, X.; Wu, Z.; Xia, L.; Xiao, H.; Xiao, S. Y.; Xiao, Z. J.;
Xie, X. H.; Xie, Y. G.; Xie, Y. H.; Xing, T. Y.; Xu, G. F.; Xu, Q. J.;
Xu, W.; Xu, X. P.; Xu, Y. C.; Yan, F.; Yan, L.; Yan, W. B.; Yan, W. C.;
Yan, Xu; Yang, H. J.; Yang, H. X.; Yang, L.; Yang, S. L.; Yang, Y. X.;
Yang, Yifan; Yang, Zhi; Ye, M.; Ye, M. H.; Yin, J. H.; You, Z. Y.;
Yu, B. X.; Yu, C. X.; Yu, G.; Yu, J. S.; Yu, T.; Yuan, C. Z.; Yuan,
L.; Yuan, X. Q.; Yuan, Y.; Yuan, Z. Y.; Yue, C. X.; Zafar, A. A.;
Zeng Zeng, X.; Zeng, Y.; Zhang, A. Q.; Zhang, B. X.; Zhang, Guangyi;
Zhang, H.; Zhang, H. H.; Zhang, H. H.; Zhang, H. Y.; Zhang, J. J.;
Zhang, J. L.; Zhang, J. Q.; Zhang, J. W.; Zhang, J. Y.; Zhang, J. Z.;
Zhang, Jianyu; Zhang, Jiawei; Zhang, L. M.; Zhang, L. Q.; Zhang, Lei;
Zhang, S.; Zhang, S. F.; Zhang, Shulei; Zhang, X. D.; Zhang, X. Y.;
Zhang, Y.; Zhang, Y. T.; Zhang, Y. H.; Zhang, Yan; Zhang, Yao; Zhang,
Z. Y.; Zhao, G.; Zhao, J.; Zhao, J. Y.; Zhao, J. Z.; Zhao, Lei; Zhao,
Ling; Zhao, M. G.; Zhao, Q.; Zhao, S. J.; Zhao, Y. B.; Zhao, Y. X.;
Zhao, Z. G.; Zhemchugov, A.; Zheng, B.; Zheng, J. P.; Zheng, Y. H.;
Zhong, B.; Zhong, C.; Zhou, L. P.; Zhou, Q.; Zhou, X.; Zhou, X. K.;
Zhou, X. R.; Zhou, X. Y.; Zhu, A. N.; Zhu, J.; Zhu, K.; Zhu, K. J.;
Zhu, S. H.; Zhu, T. J.; Zhu, W. J.; Zhu, W. J.; Zhu, Y. C.; Zhu,
Z. A.; Zou, B. S.; Zou, J. H.; Collaboration), (Besiii
Bibcode: 2021ChPhC..45j3001A
Altcode:
During the 2016-17 and 2018-19 running periods, the BESIII
experiment collected 7.5 fb $ ^{-1} $ of $ e^+e^- $ collision data
at center-of-mass energies ranging from 4.13 to 4.44 GeV. These data
samples are primarily used for the study of excited charmonium and
charmoniumlike states. By analyzing the di-muon process $e^+e^- \to $
$ (\gamma_{\rm ISR/FSR}) \mu^+\mu^-$ , we measure the center-of-mass
energies of the data samples with a precision of 0.6 MeV. Through a
run-by-run study, we find that the center-of-mass energies were stable
throughout most of the data-collection period. * Supported in part by
National Key Research and Development Program of China (2020YFA0406300,
2020YFA0406400); National Natural Science Foundation of China
(NSFC) (11625523, 11635010, 11735014, 11822506, 11835012, 11935015,
11935016, 11935018, 11961141012); the Chinese Academy of Sciences
(CAS) Large-Scale Scientific Facility Program; Joint Large-Scale
Scientific Facility Funds of the NSFC and CAS (U1732263, U1832207);
CAS Key Research Program of Frontier Sciences (QYZDJ-SSW-SLH003,
QYZDJ-SSW-SLH040); 100 Talents Program of CAS; INPAC and Shanghai
Key Laboratory for Particle Physics and Cosmology; ERC (758462);
European Union Horizon 2020 research and innovation programme
(Marie Sklodowska-Curie grant agreement No 894790); German Research
Foundation DFG (443159800), Collaborative Research Center CRC 1044,
FOR 2359, FOR 2359, GRK 214; Istituto Nazionale di Fisica Nucleare,
Italy; Ministry of Development of Turkey (DPT2006K-120470); National
Science and Technology fund; Olle Engkvist Foundation (200-0605); STFC
(United Kingdom); The Knut and Alice Wallenberg Foundation (Sweden)
(2016.0157); The Royal Society, UK (DH140054, DH160214); The Swedish
Research Council; U. S. Department of Energy (DE-FG02-05ER41374,
DE-SC-0012069)
Title: Constraining the cosmic ray propagation halo thickness using
Fermi-LAT observations of high-latitude clouds
Authors: Yao, Yuhua; Qiao, Bing-Qiang; Liu, Wei; Yuan, Qiang; Hu,
Hong-Bo; Bi, Xiao-Jun; Yang, Chao-Wen; Guo, Yi-Qing
Bibcode: 2021ChPhC..45j5104Y
Altcode: 2021arXiv210300727Y
The diffusive halo is a basic characteristic of cosmic ray (CR)
propagation and can advance our understanding of many CR-related
phenomena and indirect dark matter. The method used to derive the
halo size often has degeneracy problems and is thus affected by large
uncertainties. The diffuse $\rm\gamma$ rays from high-latitude clouds
might shed light on the halo size independently. Because predictions
using the spatially dependent propagation (SDP) model have better
agreement with the observed CRs than those of the conventional
propagation model, in this work, we investigated halo thickness based
on the SDP model using Fermi-LAT $\rm\gamma$ -ray observations of high-
and intermediate-velocity clouds. We found that to avoid exceeding the
relative $\gamma$ -ray emissivity in high-latitude clouds, the halo
thickness should be in the range of 3.3-9 kpc. Moreover, the spatial
morphology of $\rm\gamma$ -rays estimated based on the SDP model for
different values of the halo thickness are distinctive, which provides
us with a tool to determine the halo size. This newly developed model
can be tested and tuned using multi-wavelength observations in future
studies. * Supported by the National Key R&D Program of China
(2018YFA0404202) and the National Natural Science Foundation of China
(11635011, 11875264, 11722328, 11851305, U1738205, U2031110)
Title: Laboratory Observation of C and O Emission Lines of the White
Dwarf H1504+65-like Atmosphere Model
Authors: Ma, Bu-Bo; Ren, Jie-Ru; Wang, Shao-Yi; Hoffmann, Dieter H. H.;
Deng, Zhi-Gang; Qi, Wei; Wang, Xing; Yin, Shuai; Feng, Jian-Hua; Fan,
Quan-Ping; Liu, Wei; Xu, Zhong-Feng; Chen, Yong; Cui, Bo; He, Shu-Kai;
Cao, Zhu-Rong; Zhao, Zong-Qing; Gu, Yu-Qiu; Zhu, Shao-Ping; Cheng,
Rui; Zhou, Xian-Ming; Xiao, Guo-Qing; Zhao, Hong-Wei; Zhang, Yi-Hang;
Zhang, Zhe; Li, Yu-Tong; Xu, Xing; Wei, Wen-Qing; Chen, Ben-Zheng;
Zhang, Shi-Zheng; Hu, Zhong-Min; Liu, Li-Rong; Li, Fang-Fang; Xu,
Hao; Zhou, Wei-Min; Cao, Lei-Feng; Zhao, Yong-Tao
Bibcode: 2021ApJ...920..106M
Altcode:
White dwarfs play important roles in stellar evolution and help us
gauge the age of our galaxy. The white dwarf H1504+65, the hottest
known post-asymptotic giant branch star, is peculiar due to its C- and
O-rich but He- and H- deficient atmosphere whose composition cannot
be well predicted by current stellar evolution models. The analysis
of the elemental abundance and the benchmark of stellar atmospheric
models depends heavily on spectral data under cosmic conditions, which
are currently extremely scarce. We created a well-defined, uniform,
relatively large-scale ~millimeter plasma sample in the laboratory
with a temperature and a C/O ratio similar to those of H1504+65's
atmosphere. The emission spectra with high precision in the range of
10-80 nm were obtained and identified according to databases such as
NIST and Kelly. A detailed comparison between our emission lines and the
Chandra-observed white dwarf H1504+65 atmosphere's absorption lines was
performed. The stongly isolated O VI lines in the range of 10-13 nm are
observed in both cases. We observed a wealth of O V lines in the range
of 13-14 nm that cannot be well identified or predicted by models due
to the weak flux and also probably due to the blending effect of Fe
group elements in the Chandra spectrum. Long-wavelength lines ranging
from 14 to 80 nm, which are not observed in the Chandra spectrum
because of the high interstellar neutral hydrogen column density,
show abundant O IV-V, C IV lines, and strong O VI lines. Moreover,
the intensities of the lines at 62.973 and 17.216 nm are analyzed to
characterize the plasma temperature.
Title: Property investigation of the wedge-shaped CsI(Tl) crystals
for a charged-particle telescope
Authors: Li, G.; Lou, J. L.; Ye, Y. L.; Hua, H.; Wang, H.; Han, J. X.;
Liu, W.; Bai, S. W.; Tan, Z. W.; Ma, K.; Chen, J. H.; Yang, L. S.;
Wang, S. J.; Hu, Z. Y.; Yu, H. Z.; Zhu, H. Y.; Xia, B. L.; Jiang, Y.;
Liu, Y.; Yang, X. F.; Li, Q. T.; Xu, J. Y.; Wang, J. S.; Yang, Y. Y.;
Ma, J. B.; Chen, R. F.; Ma, P.; Bai, Z.; Duan, F. F.; Hu, L. Y.; Li,
J. W.; Li, Y.,; Song, Y. S.; Zhang, Suyalatu; Huang, M. R.
Bibcode: 2021NIMPA101365637L
Altcode:
Two types of wedge-shaped CsI(Tl) crystals were designed to be placed
behind an annular double-sided silicon detector to identify light
charged-particles with the ΔE - E method. The properties of the CsI(Tl)
detectors with different shapes and sizes were investigated using an α
source and a radioactive beam of 15C. The larger crystal
was found to have better energy resolution, smaller light output
non-uniformity, as well as better particle identification capability,
and was finally adopted to form the ΔE - E telescope. The performance
of the two types of CsI(Tl) crystals are interpreted based on Geant4
simulation results.
Title: Discovery of the Ultrahigh-energy Gamma-Ray Source LHAASO
J2108+5157
Authors: Cao, Zhen; Aharonian, F.; An, Q.; Axikegu; Bai, L. X.; Bai,
Y. X.; Bao, Y. W.; Bastieri, D.; Bi, X. J.; Bi, Y. J.; Cai, H.; Cai,
J. T.; Cao, Zhe; Chang, J.; Chang, J. F.; Chen, B. M.; Chen, E. S.;
Chen, J.; Chen, Liang; Chen, Long; Chen, M. J.; Chen, M. L.; Chen,
Q. H.; Chen, S. H.; Chen, S. Z.; Chen, T. L.; Chen, X. L.; Chen, Y.;
Cheng, N.; Cheng, Y. D.; Cui, S. W.; Cui, X. H.; Cui, Y. D.; Piazzoli,
B. D'Ettorre; Dai, B. Z.; Dai, H. L.; Dai, Z. G.; Dan-Zeng-Luo-Bu,
Dan-Zeng; Volpe, D. della; Dong, X. J.; Duan, K. K.; Fan, J. H.; Fan,
Y. Z.; Fan, Z. X.; Fang, J.; Fang, K.; Feng, C. F.; Feng, L.; Feng,
S. H.; Feng, Y. L.; Gao, B.; Gao, C. D.; Gao, L. Q.; Gao, Q.; Gao,
W.; Ge, M. M.; Geng, L. S.; Gong, G. H.; Gou, Q. B.; Gu, M. H.; Guo,
F. L.; Guo, J. G.; Guo, X. L.; Guo, Y. Q.; Guo, Y. Y.; Han, Y. A.; He,
H. H.; He, H. N.; He, J. C.; He, S. L.; He, X. B.; He, Y.; Heller, M.;
Hor, Y. K.; Hou, C.; Hu, H. B.; Hu, S.; Hu, S. C.; Hu, X. J.; Huang,
D. H.; Huang, Q. L.; Huang, W. H.; Huang, X. T.; Huang, X. Y.; Huang,
Z. C.; Ji, F.; Ji, X. L.; Jia, H. Y.; Jiang, K.; Jiang, Z. J.; Jin,
C.; Ke, T.; Kuleshov, D.; Levochkin, K.; Li, B. B.; Li, Cheng; Li,
Cong; Li, F.; Li, H. B.; Li, H. C.; Li, H. Y.; Li, J.; Li, K.; Li,
W. L.; Li, X. R.; Li, Xin; Li, Xin; Li, Y.; Li, Y. Z.; Li, Zhe; Li,
Zhuo; Liang, E. W.; Liang, Y. F.; Lin, S. J.; Liu, B.; Liu, C.; Liu,
D.; Liu, H.; Liu, H. D.; Liu, J.; Liu, J. L.; Liu, J. S.; Liu, J. Y.;
Liu, M. Y.; Liu, R. Y.; Liu, S. M.; Liu, W.; Liu, Y.; Liu, Y. N.;
Liu, Z. X.; Long, W. J.; Lu, R.; Lv, H. K.; Ma, B. Q.; Ma, L. L.; Ma,
X. H.; Mao, J. R.; Masood, A.; Min, Z.; Mitthumsiri, W.; Montaruli,
T.; Nan, Y. C.; Pang, B. Y.; Pattarakijwanich, P.; Pei, Z. Y.; Qi,
M. Y.; Qi, Y. Q.; Qiao, B. Q.; Qin, J. J.; Ruffolo, D.; Rulev, V.;
Sáiz, A.; Shao, L.; Shchegolev, O.; Sheng, X. D.; Shi, J. Y.; Song,
H. C.; Stenkin, Yu. V.; Stepanov, V.; Su, Y.; Sun, Q. N.; Sun, X. N.;
Sun, Z. B.; Tam, P. H. T.; Tang, Z. B.; Tian, W. W.; Wang, B. D.;
Wang, C.; Wang, H.; Wang, H. G.; Wang, J. C.; Wang, J. S.; Wang,
L. P.; Wang, L. Y.; Wang, R. N.; Wang, W.; Wang, W.; Wang, X. G.;
Wang, X. J.; Wang, X. Y.; Wang, Y.; Wang, Y. D.; Wang, Y. J.; Wang,
Y. P.; Wang, Z. H.; Wang, Z. X.; Wang, Zhen; Wang, Zheng; Wei, D. M.;
Wei, J. J.; Wei, Y. J.; Wen, T.; Wu, C. Y.; Wu, H. R.; Wu, S.; Wu,
W. X.; Wu, X. F.; Xi, S. Q.; Xia, J.; Xia, J. J.; Xiang, G. M.; Xiao,
D. X.; Xiao, G.; Xiao, H. B.; Xin, G. G.; Xin, Y. L.; Xing, Y.; Xu,
D. L.; Xu, R. X.; Xue, L.; Yan, D. H.; Yan, J. Z.; Yang, C. W.; Yang,
F. F.; Yang, J. Y.; Yang, L. L.; Yang, M. J.; Yang, R. Z.; Yang, S. B.;
Yao, Y. H.; Yao, Z. G.; Ye, Y. M.; Yin, L. Q.; Yin, N.; You, X. H.;
You, Z. Y.; Yu, Y. H.; Yuan, Q.; Zeng, H. D.; Zeng, T. X.; Zeng, W.;
Zeng, Z. K.; Zha, M.; Zhai, X. X.; Zhang, B. B.; Zhang, H. M.; Zhang,
H. Y.; Zhang, J. L.; Zhang, J. W.; Zhang, L. X.; Zhang, Li; Zhang,
Lu; Zhang, P. F.; Zhang, P. P.; Zhang, R.; Zhang, S. R.; Zhang, S. S.;
Zhang, X.; Zhang, X. P.; Zhang, Y. F.; Zhang, Y. L.; Zhang, Yi; Zhang,
Yong; Zhao, B.; Zhao, J.; Zhao, L.; Zhao, L. Z.; Zhao, S. P.; Zheng,
F.; Zheng, Y.; Zhou, B.; Zhou, H.; Zhou, J. N.; Zhou, P.; Zhou, R.;
Zhou, X. X.; Zhu, C. G.; Zhu, F. R.; Zhu, H.; Zhu, K. J.; Zuo, X.
Bibcode: 2021ApJ...919L..22C
Altcode: 2021arXiv210609865T
We report the discovery of an ultrahigh-energy (UHE) gamma-ray source,
LHAASO J2108+5157, by analyzing the LHAASO-KM2A data of 308.33 live
days. A significant excess of gamma ray-induced showers is observed
in both energy bands of 25-100 and >100 TeV with 9.5σ and 8.5σ,
respectively. This source is not significantly favored as an extended
source with an angular extension smaller than the point-spread function
of KM2A. The measured energy spectrum from 20 to 200 TeV can be
approximately described by a power-law function with an index of -2.83
± 0.18stat. A harder spectrum is demanded at lower energies
considering the flux upper limit set by Fermi-LAT observations. The
position of the gamma-ray emission is correlated with a giant molecular
cloud, which favors a hadronic origin. No obvious counterparts have
been found, and deeper multiwavelength observations will help to cast
new light on this intriguing UHE source.
Title: VizieR Online Data Catalog: Sulfur isotopes in SFR with 12m
ARO and 30m IRAM (Yu+, 2020)
Authors: Yu, H. Z.; Zhang, J. S.; Henkel, C.; Yan, Y. T.; Liu, W.;
Tang, X. D.; Langer, N.; Luan, T. C.; Chen, J. L.; Wang, Y. X.; Deng,
G. G.; Zou, Y. P.
Bibcode: 2021yCat..18990145Y
Altcode:
The observations were performed in 2018 November and December using
the Arizona Radio Observatory (ARO) 12m telescope toward 95 massive
star-forming regions. A 3mm sideband separating (SBS) receiver was
employed covering Atacama Large Millimeter/submillimeter Array (ALMA)
band 3 (84-116GHz). The center frequencies were set at 97.980986,
96.412982, 92.494299, and 97.172086GHz for the CS, C34S, 13CS, and
C33S lines, respectively; the beam size was ~63". Six sources
among our sample were also observed by the Institut de radioastronomie
millimetrique (IRAM) 30m with the Eight MIxer Receive (EMIR) heterodyne
receiver during June 2016. We applied the {lmabda}~3mm E090 band to
observe the J=2-1 lines of the CS, C34S, 13CS, and C33S isotopologs. A
fast Fourier transform spectrometer (FTS) backend in the wideband mode
was employed in our observations, with a spectral resolution of 400kHz
(~0.6km/s at 96GHz). (3 data files).
Title: Direct Measurement of the Astrophysical F 19 (p ,α γ )O 16
Reaction in the Deepest Operational Underground Laboratory
Authors: Zhang, L. Y.; Su, J.; He, J. J.; Wiescher, M.; deBoer, R. J.;
Kahl, D.; Chen, Y. J.; Li, X. Y.; Wang, J. G.; Zhang, L.; Cao, F. Q.;
Zhang, H.; Zhang, Z. C.; Jiao, T. Y.; Sheng, Y. D.; Wang, L. H.;
Song, L. Y.; Jiang, X. Z.; Li, Z. M.; Li, E. T.; Wang, S.; Lian, G.;
Li, Z. H.; Tang, X. D.; Zhao, H. W.; Sun, L. T.; Wu, Q.; Li, J. Q.;
Cui, B. Q.; Chen, L. H.; Ma, R. G.; Guo, B.; Xu, S. W.; Li, J. Y.;
Qi, N. C.; Sun, W. L.; Guo, X. Y.; Zhang, P.; Chen, Y. H.; Zhou, Y.;
Zhou, J. F.; He, J. R.; Shang, C. S.; Li, M. C.; Zhou, X. H.; Zhang,
Y. H.; Zhang, F. S.; Hu, Z. G.; Xu, H. S.; Chen, J. P.; Liu, W. P.
Bibcode: 2021PhRvL.127o2702Z
Altcode:
Fluorine is one of the most interesting elements in nuclear
astrophysics, where the F 19 (p ,α )O 16 reaction is of crucial
importance for Galactic F 19 abundances and CNO cycle loss in first
generation Population III stars. As a day-one campaign at the Jinping
Underground Nuclear Astrophysics experimental facility, we report
direct measurements of the essential F 19 (p ,α γ )O 16 reaction
channel. The γ -ray yields were measured over Ec .m .=72.4
- 344 keV , covering the Gamow window; our energy of 72.4 keV is
unprecedentedly low, reported here for the first time. The experiment
was performed under the extremely low cosmic-ray-induced background
environment of the China JinPing Underground Laboratory, one of the
deepest underground laboratories in the world. The present low-energy
S factors deviate significantly from previous theoretical predictions,
and the uncertainties are significantly reduced. The thermonuclear F
19 (p ,α γ )O 16 reaction rate has been determined directly at the
relevant astrophysical energies.
Title: The 59Fe (n,γ) 60Fe Cross Section from
the Surrogate Ratio Method and Its Effect on the 60Fe
Nucleosynthesis
Authors: Yan, S. Q.; Li, X. Y.; Nishio, K.; Lugaro, M.; Li, Z. H.;
Makii, H.; Pignatari, M.; Wang, Y. B.; Orlandi, R.; Hirose, K.;
Tsukada, K.; Mohr, P.; Li, G. S.; Wang, J. G.; Gao, B. S.; Han, Y. L.;
Guo, B.; Li, Y. J.; Shen, Y. P.; Sato, T. K.; Ito, Y.; Suzaki, F.; Su,
J.; Yang, Y. Y.; Wang, J. S.; Ma, J. B.; Ma, P.; Bai, Z.; Xu, S. W.;
Ren, J.; Fan, Q. W.; Zeng, S.; Han, Z. Y.; Nan, W.; Nan, W. K.; Chen,
C.; Lian, G.; Hu, Q.; Duan, F. F.; Jin, S. Y.; Tang, X. D.; Liu, W. P.
Bibcode: 2021ApJ...919...84Y
Altcode: 2021arXiv210912654Y
The long-lived 60Fe (with a half-life of 2.62 Myr) is a
crucial diagnostic of active nucleosynthesis in the Milky Way galaxy
and in supernovae near the solar system. The neutron-capture reaction
59Fe(n,γ)60Fe on 59Fe (half-life =
44.5 days) is the key reaction for the production of 60Fe
in massive stars. This reaction cross section has been previously
constrained by the Coulomb dissociation experiment, which offered
partial constraint on the E1 γ-ray strength function but a negligible
constraint on the M1 and E2 components. In this work, for the first
time, we use the surrogate ratio method to experimentally determine
the 59Fe(n,γ)60Fe cross sections in which all
the components are included. We derived a Maxwellian-averaged cross
section of 27.5 ± 3.5 mb at kT = 30 keV and 13.4 ± 1.7 mb at kT =
90 keV, roughly 10%-20% higher than previous estimates. We analyzed the
impact of our new reaction rates in nucleosynthesis models of massive
stars and found that uncertainties in the production of 60Fe
from the 59Fe(n,γ)60Fe rate are at most 25%. We
conclude that stellar physics uncertainties now play a major role in
the accurate evaluation of the stellar production of 60Fe.
Title: VizieR Online Data Catalog: Quiet-Sun MgII h & k line
profiles from IRIS (Gunar+, 2021)
Authors: Gunar, S.; Koza, J.; Schwartz, P.; Heinzel, P.; Liu, W.
Bibcode: 2021yCat..22550016G
Altcode:
Since its launch, the Interface Region Imaging Spectrograph (IRIS)
commenced a quasi-regular acquisition of maps of the entire solar
disk in both NUV and FUV spectral ranges. At the time of writing,
the archive of the IRIS full-Sun mosaics contained 91 observations
spanning the period from 2013 September 30 to 2020 October 19 which
cover two spectral windows of +/-1.75Å centered at 2803.53Å (MgII h)
and 2796.35Å (MgII k). (4 data files).
Title: Calibration of the air shower energy scale of the water and
air Cherenkov techniques in the LHAASO experiment
Authors: Aharonian, F.; An, Q.; Axikegu, Bai, L. X.; Bai, Y. X.; Bao,
Y. W.; Bastieri, D.; Bi, X. J.; Bi, Y. J.; Cai, H.; Cai, J. T.; Cao,
Zhen; Cao, Zhe; Chang, J.; Chang, J. F.; Chen, B. M.; Chen, E. S.;
Chen, J.; Chen, Liang; Chen, Liang; Chen, Long; Chen, M. J.; Chen,
M. L.; Chen, Q. H.; Chen, S. H.; Chen, S. Z.; Chen, T. L.; Chen, X. L.;
Chen, Y.; Cheng, N.; Cheng, Y. D.; Cui, S. W.; Cui, X. H.; Cui, Y. D.;
Dai, B. Z.; Dai, H. L.; Dai, Z. G.; Danzengluobu, Della Volpe, D.;
Piazzoli, B. D'ettorre; Dong, X. J.; Duan, K. K.; Fan, J. H.; Fan,
Y. Z.; Fan, Z. X.; Fang, J.; Fang, K.; Feng, C. F.; Feng, L.; Feng,
S. H.; Feng, Y. L.; Gao, B.; Gao, C. D.; Gao, L. Q.; Gao, Q.; Gao,
W.; Ge, M. M.; Geng, L. S.; Gong, G. H.; Gou, Q. B.; Gu, M. H.; Guo,
F. L.; Guo, J. G.; Guo, X. L.; Guo, Y. Q.; Guo, Y. Y.; Han, Y. A.; He,
H. H.; He, H. N.; He, J. C.; He, S. L.; He, X. B.; He, Y.; Heller, M.;
Hor, Y. K.; Hou, C.; Hu, H. B.; Hu, S.; Hu, S. C.; Hu, X. J.; Huang,
D. H.; Huang, Q. L.; Huang, W. H.; Huang, X. T.; Huang, X. Y.; Huang,
Z. C.; Ji, F.; Ji, X. L.; Jia, H. Y.; Jiang, K.; Jiang, Z. J.; Jin,
C.; Ke, T.; Kuleshov, D.; Levochkin, K.; Li, B. B.; Li, Cong; Li,
Cheng; Li, F.; Li, H. B.; Li, H. C.; Li, H. Y.; Li, J.; Li, K.; Li,
W. L.; Li, Xin; Li, Xin; Li, X. R.; Li, Y.; Li, Y. Z.; Li, Zhe; Li,
Zhuo; Liang, E. W.; Liang, Y. F.; Lin, S. J.; Liu, B.; Liu, C.; Liu,
D.; Liu, H.; Liu, H. D.; Liu, J.; Liu, J. L.; Liu, J. S.; Liu, J. Y.;
Liu, M. Y.; Liu, R. Y.; Liu, S. M.; Liu, W.; Liu, Y.; Liu, Y. N.;
Liu, Z. X.; Long, W. J.; Lu, R.; Lv, H. K.; Ma, B. Q.; Ma, L. L.; Ma,
X. H.; Mao, J. R.; Masood, A.; Min, Z.; Mitthumsiri, W.; Montaruli, T.;
Nan, Y. C.; Pang, B. Y.; Pattarakijwanich, P.; Pei, Z. Y.; Qi, M. Y.;
Qi, Y. Q.; Qiao, B. Q.; Qin, J. J.; Ruffolo, D.; Rulev, V.; Sáiz,
A.; Shao, L.; Shchegolev, O.; Sheng, X. D.; Shi, J. Y.; Song, H. C.;
Stenkin, Yu. V.; Stepanov, V.; Su, Y.; Sun, Q. N.; Sun, X. N.; Sun,
Z. B.; Tam, P. H. T.; Tang, Z. B.; Tian, W. W.; Wang, B. D.; Wang,
C.; Wang, H.; Wang, H. G.; Wang, J. C.; Wang, J. S.; Wang, L. P.;
Wang, L. Y.; Wang, R. N.; Wang, W.; Wang, W.; Wang, X. G.; Wang,
X. J.; Wang, X. Y.; Wang, Y.; Wang, Y. D.; Wang, Y. J.; Wang, Y. P.;
Wang, Z. H.; Wang, Z. X.; Wang, Zhen; Wang, Zheng; Wei, D. M.; Wei,
J. J.; Wei, Y. J.; Wen, T.; Wu, C. Y.; Wu, H. R.; Wu, S.; Wu, W. X.;
Wu, X. F.; Xi, S. Q.; Xia, J.; Xia, J. J.; Xiang, G. M.; Xiao, D. X.;
Xiao, G.; Xiao, H. B.; Xin, G. G.; Xin, Y. L.; Xing, Y.; Xu, D. L.;
Xu, R. X.; Xue, L.; Yan, D. H.; Yan, J. Z.; Yang, C. W.; Yang, F. F.;
Yang, J. Y.; Yang, L. L.; Yang, M. J.; Yang, R. Z.; Yang, S. B.; Yao,
Y. H.; Yao, Z. G.; Ye, Y. M.; Yin, L. Q.; Yin, N.; You, X. H.; You,
Z. Y.; Yu, Y. H.; Yuan, Q.; Zeng, H. D.; Zeng, T. X.; Zeng, W.; Zeng,
Z. K.; Zha, M.; Zhai, X. X.; Zhang, B. B.; Zhang, H. M.; Zhang, H. Y.;
Zhang, J. L.; Zhang, J. W.; Zhang, Lu; Zhang, Li; Zhang, L. X.; Zhang,
P. F.; Zhang, P. P.; Zhang, R.; Zhang, S. R.; Zhang, S. S.; Zhang,
X.; Zhang, X. P.; Zhang, Y. F.; Zhang, Y. L.; Zhang, Yong; Zhang,
Yi; Zhao, B.; Zhao, J.; Zhao, L.; Zhao, L. Z.; Zhao, S. P.; Zheng,
F.; Zheng, Y.; Zhou, B.; Zhou, H.; Zhou, J. N.; Zhou, P.; Zhou, R.;
Zhou, X. X.; Zhu, C. G.; Zhu, F. R.; Zhu, H.; Zhu, K. J.; Zuo, X.;
Lhaaso Collaboration
Bibcode: 2021PhRvD.104f2007A
Altcode: 2021arXiv210404965A
The Wide Field-of-View Cherenkov Telescope Array (WFCTA) and the Water
Cherenkov Detector Array (WCDA) of LHAASO are designed to work in
combination for measuring the energy spectra of the cosmic ray species
over a very wide energy range from a few TeV to 10 PeV. The energy
calibration can be achieved with a proven technique of measuring
the westward shift of the Moon shadow cast by galactic cosmic rays
due to the geomagnetic field. This deflection angle Δ is inversely
proportional to the cosmic ray rigidity. The precise measurement of the
shifts by WCDA allows us to calibrate its energy scale for energies as
high as 35 TeV. Through a set of commonly triggered events, the energy
scales can be propagated to WFCTA. The energies of the events can be
derived both by WCDA-1 and WFCTA with the median energies 23.4 ±0.1
±1.3 TeV and (21.9 ±0.1 TeV ), respectively, which are consistent
within uncertainties. In addition, the propagation of the energy scale
is also validated by the Moon shadow based on the same data selection
criteria of the commonly triggered events. This paper reports, for
the first time, an observational measurement of the absolute energy
scale of the primary cosmic rays generating showers observed by air
Cherenkov telescopes.
Title: Energy Flux Densities at Dipolarization Fronts
Authors: Liu, C. M.; Fu, H. S.; Yu, Y. Q.; Lu, H. Y.; Liu, W. L.;
Xu, Y.; Giles, B. L.; Burch, J. L.
Bibcode: 2021GeoRL..4894932L
Altcode:
Dipolarization fronts (DFs) have been suggested as crucial energy
conversion sites contributing significantly to global energy transfer
in the magnetosphere. However, energy partitioning of DF-driven energy
transfer remains hitherto elusive. Using high-cadence data from
MMS spacecraft, we present a detailed investigation of energy flux
densities at two DFs with/without surface ripples. We find that during
both DF intervals, electron enthalpy flux increases dramatically,
carries the greatest energy, and well correlates with local energy
conversion. Poynting flux also increases but contributes to a relatively
smaller portion. Ion enthalpy flux which in magnitude is slightly
smaller than electron enthalpy flux barely changes. Particle kinetic
energy and heat fluxes are negligible. Strong difference in energy
fluxes observed by different spacecraft is found at the rippled DF,
indicating three-dimensional energy transport. These results indicate
that energy budgets at the DFs are dominated by electron physics,
rather than ion dynamics suggested by previous studies.
Title: An efficient channelization architecture and its implementation
for radio astronomy
Authors: Liu, W.; Meng, Q.; Wang, C.; Zhou, C.; Yao, S.; Tariq, I.
Bibcode: 2021JInst..16P8047L
Altcode:
Channelization is one of the most important parts in a Digital
Back-End(DBE) for radio astronomy. A DBE with wider bandwidth and
higher resolution consumes larger amount of computing and memory
resources, which results in much higher hardware cost. This paper
presents an efficient channelization architecture, which consists
of Bit-Inverted, Parallel Complex Fast Fourier Transform(BIPC-FFT)
and In-place Forward-Backward Decomposition(IPFBD). The efficient
architecture can assist with saving a lot of resources, so a wide-band
and high-resolution DBE can be implemented on an resource restricted
platform. Based on the efficient channelization architecture,
we designed a Dual-Input, 64K-Channelized prototype DBE with 1.2
GHz bandwidth on a Xilinx Virtex-6 LX240T Field Programmable Gate
Array(FPGA) chip. The test results in the lab and observation results at
Yunnan Observatory demonstrate the DBE can be used for radio astronomy.
Title: Direct measurement of the resonance strengths and branching
ratios of low-energy (p, γ) reactions on Mg isotopes
Authors: Zhang, Hao; Li, Zhi-Hong; Su, Jun; Li, Yun-Ju; Chen, Chen;
Zhang, Long; Cao, Fu-Qiang; Shen, Yang-Ping; Nan, Wei; Nan, Wei-Ke;
Li, Xin-Yue; Chen, Li-Hua; Lian, Gang; Cui, Bao-Qun; Guo, Bing;
Liu, Wei-Ping
Bibcode: 2021ChPhC..45h4108Z
Altcode:
Proton capture reactions on Mg isotopes are significant in the Mg-Al
cycle in stellar H-burning. In particular, the resonance strengths
and branching ratios of low-energy resonances in 25Mg(
$ p,\gamma$ )26Al reactions determine the production
of 26Al, which is one of the most important long-lived
radioactive nuclei in nuclear astrophysics. In this article, we report
our first experiment using the intense proton beam of approximately 2 mA
provided by the JUNA accelerator ground laboratory and a new technique
that can minimize the composition change of targets under intense beam
irradiation. The resonance strengths and branching ratios of E = 214,
304, and 326 keV resonances in the reactions of 24Mg(
$ p,\gamma$ )25Al, 25Mg( $ p,\gamma$
)26Al, and 26Mg( $ p,\gamma$ )27Al,
respectively, were measured with high accuracy. The success of this
experiment provides a good calibration for the nuclear astrophysical
experiment at the Jinping underground laboratory. * Supported by the
National Natural Science Foundation of China (11490563, 11961141003)
and the Continuous Basic Scientific Research Project (WDJC-2019-13)
Title: Discovery of a New Gamma-Ray Source, LHAASO J0341+5258,
with Emission up to 200 TeV
Authors: Cao, Zhen; Aharonian, F.; An, Q.; Axikegu; Bai, L. X.; Bai,
Y. X.; Bao, Y. W.; Bastieri, D.; Bi, X. J.; Bi, Y. J.; Cai, H.; Cai,
J. T.; Cao, Zhe; Chang, J.; Chang, J. F.; Chen, B. M.; Chen, E. S.;
Chen, J.; Chen, Liang; Chen, Liang; Chen, Long; Chen, M. J.; Chen,
M. L.; Chen, Q. H.; Chen, S. H.; Chen, S. Z.; Chen, T. L.; Chen,
X. L.; Chen, Y.; Cheng, N.; Cheng, Y. D.; Cui, S. W.; Cui, X. H.; Cui,
Y. D.; D'Ettorre Piazzoli, B.; Dai, B. Z.; Dai, H. L.; Dai, Z. G.;
Danzengluobu; Volpe, D. della; Dong, X. J.; Duan, K. K.; Fan, J. H.;
Fan, Y. Z.; Fan, Z. X.; Fang, J.; Fang, K.; Feng, C. F.; Feng, L.;
Feng, S. H.; Feng, Y. L.; Gao, B.; Gao, C. D.; Gao, L. Q.; Gao, Q.;
Gao, W.; Ge, M. M.; Geng, L. S.; Gong, G. H.; Gou, Q. B.; Gu, M. H.;
Guo, F. L.; Guo, J. G.; Guo, X. L.; Guo, Y. Q.; Guo, Y. Y.; Han, Y. A.;
He, H. H.; He, H. N.; He, J. C.; He, S. L.; He, X. B.; He, Y.; Heller,
M.; Hor, Y. K.; Hou, C.; Hu, H. B.; Hu, S.; Hu, S. C.; Hu, X. J.;
Huang, D. H.; Huang, Q. L.; Huang, W. H.; Huang, X. T.; Huang, X. Y.;
Huang, Z. C.; Ji, F.; Ji, X. L.; Jia, H. Y.; Jiang, K.; Jiang, Z. J.;
Jin, C.; Ke, T.; Kuleshov, D.; Levochkin, K.; Li, B. B.; Li, Cheng;
Li, Cong; Li, F.; Li, H. B.; Li, H. C.; Li, H. Y.; Li, J.; Li, K.;
Li, W. L.; Li, X. R.; Li, Xin; Li, Xin; Li, Y.; Li, Y. Z.; Li, Zhe;
Li, Zhuo; Liang, E. W.; Liang, Y. F.; Lin, S. J.; Liu, B.; Liu, C.;
Liu, D.; Liu, H.; Liu, H. D.; Liu, J.; Liu, J. L.; Liu, J. S.; Liu,
J. Y.; Liu, M. Y.; Liu, R. Y.; Liu, S. M.; Liu, W.; Liu, Y.; Liu,
Y. N.; Liu, Z. X.; Long, W. J.; Lu, R.; Lv, H. K.; Ma, B. Q.; Ma,
L. L.; Ma, X. H.; Mao, J. R.; Masood, A.; Min, Z.; Mitthumsiri, W.;
Montaruli, T.; Nan, Y. C.; Pang, B. Y.; Pattarakijwanich, P.; Pei,
Z. Y.; Qi, M. Y.; Qi, Y. Q.; Qiao, B. Q.; Qin, J. J.; Ruffolo, D.;
Rulev, V.; Sáiz, A.; Shao, L.; Shchegolev, O.; Sheng, X. D.; Shi,
J. Y.; Song, H. C.; Stenkin, Yu. V.; Stepanov, V.; Su, Y.; Sun, Q. N.;
Sun, X. N.; Sun, Z. B.; Tam, P. H. T.; Tang, Z. B.; Tian, W. W.; Wang,
B. D.; Wang, C.; Wang, H.; Wang, H. G.; Wang, J. C.; Wang, J. S.;
Wang, L. P.; Wang, L. Y.; Wang, R. N.; Wang, W.; Wang, W.; Wang,
X. G.; Wang, X. J.; Wang, X. Y.; Wang, Y.; Wang, Y. D.; Wang, Y. J.;
Wang, Y. P.; Wang, Z. H.; Wang, Z. X.; Wang, Zhen; Wang, Zheng; Wei,
D. M.; Wei, J. J.; Wei, Y. J.; Wen, T.; Wu, C. Y.; Wu, H. R.; Wu, S.;
Wu, W. X.; Wu, X. F.; Xi, S. Q.; Xia, J.; Xia, J. J.; Xiang, G. M.;
Xiao, D. X.; Xiao, G.; Xiao, H. B.; Xin, G. G.; Xin, Y. L.; Xing, Y.;
Xu, D. L.; Xu, R. X.; Xue, L.; Yan, D. H.; Yan, J. Z.; Yang, C. W.;
Yang, F. F.; Yang, J. Y.; Yang, L. L.; Yang, M. J.; Yang, R. Z.; Yang,
S. B.; Yao, Y. H.; Yao, Z. G.; Ye, Y. M.; Yin, L. Q.; Yin, N.; You,
X. H.; You, Z. Y.; Yu, Y. H.; Yuan, Q.; Zeng, H. D.; Zeng, T. X.;
Zeng, W.; Zeng, Z. K.; Zha, M.; Zhai, X. X.; Zhang, B. B.; Zhang,
H. M.; Zhang, H. Y.; Zhang, J. L.; Zhang, J. W.; Zhang, L. X.; Zhang,
Li; Zhang, Lu; Zhang, P. F.; Zhang, P. P.; Zhang, R.; Zhang, S. R.;
Zhang, S. S.; Zhang, X.; Zhang, X. P.; Zhang, Y. F.; Zhang, Y. L.;
Zhang, Yi; Zhang, Yong; Zhao, B.; Zhao, J.; Zhao, L.; Zhao, L. Z.;
Zhao, S. P.; Zheng, F.; Zheng, Y.; Zhou, B.; Zhou, H.; Zhou, J. N.;
Zhou, P.; Zhou, R.; Zhou, X. X.; Zhu, C. G.; Zhu, F. R.; Zhu, H.;
Zhu, K. J.; Zuo, X.
Bibcode: 2021ApJ...917L...4C
Altcode: 2021arXiv210702020L
We report the discovery of a new unidentified extended γ-ray source in
the Galactic plane named LHAASO J0341+5258 with a pretrial significance
of 8.2 standard deviations above 25 TeV. The best-fit position is R.A. =
55°34 ± 0°11 and decl. = 52°97 ± 0°07. The angular size of LHAASO
J0341+5258 is 0°29 ± 0°06stat ± 0°02sys. The
flux above 25 TeV is about 20% of the flux of the Crab Nebula. Although
a power-law fit of the spectrum from 10 to 200 TeV with the photon
index α = 2.98 ± 0.19stat ± 0.02sys is not
excluded, the LHAASO data together with the flux upper limit at 10 GeV
set by the Fermi-LAT observation, indicate a noticeable steepening of
an initially hard power-law spectrum with a cutoff at ≍50 TeV. We
briefly discuss the origin of ultra-high-energy gamma rays. The lack
of an energetic pulsar and a young supernova remnant inside or in the
vicinity of LHAASO J0341+5258 challenge, but do not exclude, both the
leptonic and hadronic scenarios of gamma-ray production.
Title: Performance of LHAASO-WCDA and observation of the Crab Nebula
as a standard candle
Authors: Aharonian, F.; An, Q.; Axikegu; Bai, L. X.; Bai, Y. X.; Bao,
Y. W.; Bastieri, D.; Bi, X. J.; Bi, Y. J.; Cai, H.; Cai, J. T.; Cao,
Z.; Cao, Z.; Chang, J.; Chang, J. F.; Chang, X. C.; Chen, B. M.; Chen,
J.; Chen, L.; Chen, L.; Chen, L.; Chen, M. J.; Chen, M. L.; Chen,
Q. H.; Chen, S. H.; Chen, S. Z.; Chen, T. L.; Chen, X. L.; Chen,
Y.; Cheng, N.; Cheng, Y. D.; Cui, S. W.; Cui, X. H.; Cui, Y. D.;
Dai, B. Z.; Dai, H. L.; Dai, Z. G.; Danzengluobu; Della Volpe, D.;
Piazzoli, B. D'ettorre; Dong, X. J.; Fan, J. H.; Fan, Y. Z.; Fan,
Z. X.; Fang, J.; Fang, K.; Feng, C. F.; Feng, L.; Feng, S. H.; Feng,
Y. L.; Gao, B.; Gao, C. D.; Gao, Q.; Gao, W.; Ge, M. M.; Geng, L. S.;
Gong, G. H.; Gou, Q. B.; Gu, M. H.; Guo, J. G.; Guo, X. L.; Guo,
Y. Q.; Guo, Y. Y.; Han, Y. A.; He, H. H.; He, H. N.; He, J. C.; He,
S. L.; He, X. B.; He, Y.; Heller, M.; Hor, Y. K.; Hou, C.; Hou, X.;
Hu, H. B.; Hu, S.; Hu, S. C.; Hu, X. J.; Huang, D. H.; Huang, Q. L.;
Huang, W. H.; Huang, X. T.; Huang, Z. C.; Ji, F.; Ji, X. L.; Jia,
H. Y.; Jiang, K.; Jiang, Z. J.; Jin, C.; Kuleshov, D.; Levochkin, K.;
Li, B. B.; Li, C.; Li, C.; Li, F.; Li, H. B.; Li, H. C.; Li, H. Y.; Li,
J.; Li, K.; Li, W. L.; Li, X.; Li, X.; Li, X. R.; Li, Y.; Li, Y. Z.;
Li, Z.; Li, Z.; Liang, E. W.; Liang, Y. F.; Lin, S. J.; Liu, B.; Liu,
C.; Liu, D.; Liu, H.; Liu, H. D.; Liu, J.; Liu, J. L.; Liu, J. S.;
Liu, J. Y.; Liu, M. Y.; Liu, R. Y.; Liu, S. M.; Liu, W.; Liu, Y. N.;
Liu, Z. X.; Long, W. J.; Lu, R.; Lv, H. K.; Ma, B. Q.; Ma, L. L.;
Ma, X. H.; Mao, J. R.; Masood, A.; Mitthumsiri, W.; Montaruli, T.;
Nan, Y. C.; Pang, B. Y.; Pattarakijwanich, P.; Pei, Z. Y.; Qi, M. Y.;
Qiao, B. Q.; Ruffolo, D.; Rulev, V.; Sáiz, A.; Shao, L.; Shchegolev,
O.; Sheng, X. D.; Shi, J. R.; Song, H. C.; Stenkin, Yu. V.; Stepanov,
V.; Sun, Q. N.; Sun, X. N.; Sun, Z. B.; Tam, P. H. T.; Tang, Z. B.;
Tian, W. W.; Wang, B. D.; Wang, C.; Wang, H.; Wang, H. G.; Wang, J. C.;
Wang, J. S.; Wang, L. P.; Wang, L. Y.; Wang, R. N.; Wang, W.; Wang, W.;
Wang, X. G.; Wang, X. J.; Wang, X. Y.; Wang, Y. D.; Wang, Y. J.; Wang,
Y. P.; Wang, Z.; Wang, Z.; Wang, Z. H.; Wang, Z. X.; Wei, D. M.; Wei,
J. J.; Wei, Y. J.; Wen, T.; Wu, C. Y.; Wu, H. R.; Wu, S.; Wu, W. X.;
Wu, X. F.; Xi, S. Q.; Xia, J.; Xia, J. J.; Xiang, G. M.; Xiao, G.;
Xiao, H. B.; Xin, G. G.; Xin, Y. L.; Xing, Y.; Xu, D. L.; Xu, R. X.;
Xue, L.; Yan, D. H.; Yang, C. W.; Yang, F. F.; Yang, J. Y.; Yang,
L. L.; Yang, M. J.; Yang, R. Z.; Yang, S. B.; Yao, Y. H.; Yao, Z. G.;
Ye, Y. M.; Yin, L. Q.; Yin, N.; You, X. H.; You, Z. Y.; Yu, Y. H.;
Yuan, Q.; Zeng, H. D.; Zeng, T. X.; Zeng, W.; Zeng, Z. K.; Zha, M.;
Zhai, X. X.; Zhang, B. B.; Zhang, H. M.; Zhang, H. Y.; Zhang, J. L.;
Zhang, J. W.; Zhang, L.; Zhang, L.; Zhang, L. X.; Zhang, P. F.; Zhang,
P. P.; Zhang, R.; Zhang, S. R.; Zhang, S. S.; Zhang, X.; Zhang, X. P.;
Zhang, Y.; Zhang, Y.; Zhang, Y. F.; Zhang, Y. L.; Zhao, B.; Zhao, J.;
Zhao, L.; Zhao, L. Z.; Zhao, S. P.; Zheng, F.; Zheng, Y.; Zhou, B.;
Zhou, H.; Zhou, J. N.; Zhou, P.; Zhou, R.; Zhou, X. X.; Zhu, C. G.;
Zhu, F. R.; Zhu, H.; Zhu, K. J.; Zuo, X.; Collaboration), (The Lhaaso
Bibcode: 2021ChPhC..45h5002A
Altcode:
The first Water Cherenkov detector of the LHAASO experiment (WCDA-1)
has been operating since April 2019. The data for the first year have
been analyzed to test its performance by observing the Crab Nebula
as a standard candle. The WCDA-1 achieves a sensitivity of 65 mCU per
year, with a statistical threshold of 5 $\sigma$ . To accomplish this,
a 97.7% cosmic-ray background rejection rate around 1 TeV and 99.8%
around 6 TeV with an approximate photon acceptance of 50% is achieved
after applying an algorithm to separate gamma-induced showers. The
angular resolution is measured using the Crab Nebula as a point source
to be approximately 0.45° at 1 TeV and better than 0.2° above 6 TeV,
with a pointing accuracy better than 0.05°. These values all match
the design specifications. The energy resolution is found to be 33% for
gamma rays around 6 TeV. The spectral energy distribution of the Crab
Nebula in the range from 500 GeV to 15.8 TeV is measured and found to be
in agreement with the results from other TeV gamma ray observatories. *
Supported by the following grants: the National Key R&D program of
China (2018YFA0404201, 2018YFA0404202, 2018YFA0404203), the National
Natural Science Foundation of China (12022502, 11905227, U1931112,
11635011, 11761141001, Y811A35, 11675187, U1831208, U1931111) and in
Thailand by RTA6280002 from Thailand Science Research and Innovation
Title: Progress in Nuclear Astrophysics of East and Southeast Asia
Authors: Aziz, Azni Abdul; Sofiah Ahmad, Nor; Ahn, S.; Aoki, Wako;
Bhuyan, Muruthujaya; Chen, Ke-Jung; Guo, Gang; Hahn, K. I.; Kajino,
Toshitaka; Abu Kassim, Hasan; Kim, D.; Kubono, Shigeru; Kusakabe,
Motohiko; Li, A.; Li, Haining; Li, Z. H.; Liu, W. P.; Liu, Z. W.;
Motobayashi, Tohru; Pan, Kuo-Chuan; Park, T. -S.; Shi, Jian-Rong;
Tang, Xiaodong; Wang, W.; Wen, Liangjian; Wu, Meng-Ru; Yan, Hong-Liang;
Yusof, Norhasliza
Bibcode: 2021AAPPS..31...18A
Altcode: 2021arXiv210803814A
Nuclear astrophysics is an interdisciplinary research field of
nuclear physics and astrophysics, seeking for the answer to a
question, how to understand the evolution of the Universe with
the nuclear processes which we learn. We review the research
activities of nuclear astrophysics in east and southeast Asia which
includes astronomy, experimental and theoretical nuclear physics and
astrophysics. Several hot topics such as the Li problems, critical
nuclear reactions and properties in stars, properties of dense matter,
r-process nucleosynthesis and ν-process nucleosynthesis are chosen and
discussed in further details. Some future Asian facilities, together
with physics perspectives, are introduced.
Title: Atmospheric Humic-Like Substances (HULIS) Act as Ice Active
Entities
Authors: Chen, J.; Wu, Z. J.; Zhao, X.; Wang, Y. J.; Chen, J. C.;
Qiu, Y. T.; Zong, T. M.; Chen, H. X.; Wang, B. B.; Lin, P.; Liu, W.;
Guo, S.; Yao, M. S.; Zeng, L. M.; Wex, H.; Liu, X.; Hu, M.; Li, S. M.
Bibcode: 2021GeoRL..4892443C
Altcode:
We investigated the ice nucleation activities of humic-like substances
(HULIS), an important component of organic aerosol (OA), derived
from atmospheric and biomass burning aerosols, and produced from
aqueous-phase chemical reactions. Respective HULIS can effectively
trigger heterogeneous IN under mixed-phase cloud conditions. HULIS
ice active entities (IAE) were aggregates in size between 0.02 and
0.10 μm. At −20°C, the IAE numbers per unit HULIS mass varied
from 213 to 8.7 × 104 mg−1. Such results
were different than those detected in aquatic humic substances (HS)
from previous studies, implying using HS as surrogates may not robustly
estimate the IAE concentrations in the real atmosphere. Combining the
abundance of atmospheric HULIS with the present results suggests that
HULIS could be an important IAE contributor in the atmosphere where
other ice nucleating particle species, such as dust and biological
particles, are either low in concentration or absent.
Title: High-efficient and high-accurate integrated division-of-time
polarimeter
Authors: Liu, Wei; Liao, Jiawen; Yu, Yu; Zhang, Xinliang
Bibcode: 2021APLP....6g1302L
Altcode:
The characterization of the state of polarization is of great importance
in broad applications, such as microscopy, communications, astronomy,
and remote sensing. In this Letter, we propose and demonstrate a novel
integrated division-of-time polarimeter (DOTP) based on a Mach-Zehnder
interferometer and two photodetectors (PDs). The proposed DOTP achieves
improved measuring efficiency and accuracy by measuring a pair of
orthogonal polarization states simultaneously. The analysis matrix,
which is used to recover the Stokes vector, is elaborately optimized to
reduce the influence of the PD noise. Compared to the conventionally
designed DOTP, the measuring efficiency is improved by 33% and the
equally weighted variance, a figure of merit used to characterize
the total variance of the Stokes vector, is also reduced by 33%. The
performance of the proposed device is experimentally characterized by
comparing with a commercial product. Furthermore, a method based on
the least-squares method and singular value decomposition is adopted
to quantize the deviation between the ideal optimal analysis matrix
and the practical one.
Title: Coeval Evolution of the Eastern Philippine Sea Plate and the
South China Sea in the Early Miocene: Paleomagnetic and Provenance
Constraints From ODP Site 1177
Authors: Liu, Wei; Gai, Congcong; Feng, Wanyi; Cao, Wei; Guo, Laiyin;
Zhong, Yi; Liu, Jiabo; Zhou, Yang; Chou, Yu-min; Lin, Jian; Liu,
Qingsong
Bibcode: 2021GeoRL..4893916L
Altcode:
The Philippine Sea Plate (PSP) and the South China Sea (SCS), located
at the intersection of the Eurasian, Pacific, and Indo-Australian
plates, are key areas for global plate reconstruction. However, the
relationships between the PSP and the SCS are still elusive. Here we
report a new paleolatitude determination (16.0° ± 4.5°N at ∼20 Ma)
from the Ocean Drilling Program Site 1177 in the Shikoku Basin (SB)
within the eastern PSP. The new results indicate that the SB had a
geographical affinity with the SCS in the early Miocene. Furthermore,
the similarity in the U-Pb zircon age spectra of early Miocene
turbidites from SB Site 1177 and SCS Site X28 implies that the two
sites might receive similar materials in the early Miocene. Based
on the new paleolatitude, provenance results, and other constraints,
we suggest that the eastern PSP might be coupled dynamically to the
SCS in the early Miocene.
Title: Gamma-Ray Observation of the Cygnus Region in the 100-TeV
Energy Region
Authors: Amenomori, M.; Bao, Y. W.; Bi, X. J.; Chen, D.; Chen, T. L.;
Chen, W. Y.; Chen, Xu; Chen, Y.; Cirennima, Cui, S. W.; Danzengluobu,
Ding, L. K.; Fang, J. H.; Fang, K.; Feng, C. F.; Feng, Zhaoyang;
Feng, Z. Y.; Gao, Qi; Gomi, A.; Gou, Q. B.; Guo, Y. Q.; Guo, Y. Y.;
He, H. H.; He, Z. T.; Hibino, K.; Hotta, N.; Hu, Haibing; Hu, H. B.;
Huang, J.; Jia, H. Y.; Jiang, L.; Jiang, P.; Jin, H. B.; Kasahara, K.;
Katayose, Y.; Kato, C.; Kato, S.; Kawata, K.; Kozai, M.; Kurashige,
D.; Labaciren, Le, G. M.; Li, A. F.; Li, H. J.; Li, W. J.; Li, Y.; Lin,
Y. H.; Liu, B.; Liu, C.; Liu, J. S.; Liu, L. Y.; Liu, M. Y.; Liu, W.;
Liu, X. L.; Lou, Y. -Q.; Lu, H.; Meng, X. R.; Munakata, K.; Nakada,
H.; Nakamura, Y.; Nakazawa, Y.; Nanjo, H.; Ning, C. C.; Nishizawa,
M.; Ohnishi, M.; Ohura, T.; Okukawa, S.; Ozawa, S.; Qian, L.; Qian,
X.; Qian, X. L.; Qu, X. B.; Saito, T.; Sakata, M.; Sako, T.; Sako,
T. K.; Shao, J.; Shibata, M.; Shiomi, A.; Sugimoto, H.; Takano, W.;
Takita, M.; Tan, Y. H.; Tateyama, N.; Torii, S.; Tsuchiya, H.; Udo,
S.; Wang, H.; Wang, Y. P.; Wangdui, Wu, H. R.; Wu, Q.; Xu, J. L.; Xue,
L.; Yamamoto, Y.; Yang, Z.; Yao, Y. Q.; Yin, J.; Yokoe, Y.; Yu, N. P.;
Yuan, A. F.; Zhai, L. M.; Zhang, C. P.; Zhang, H. M.; Zhang, J. L.;
Zhang, X.; Zhang, X. Y.; Zhang, Y.; Zhang, Yi; Zhang, Ying; Zhao,
S. P.; Zhaxisangzhu, Zhou, X. X.; Tibet ASγ Collaboration
Bibcode: 2021PhRvL.127c1102A
Altcode: 2021arXiv210701064A
We report observations of gamma-ray emissions with energies in the
100-TeV energy region from the Cygnus region in our Galaxy. Two
sources are significantly detected in the directions of the Cygnus
OB1 and OB2 associations. Based on their positional coincidences,
we associate one with a pulsar PSR J 2032 +4127 and the other mainly
with a pulsar wind nebula PWN G 75.2 +0.1 , with the pulsar moving
away from its original birthplace situated around the centroid of the
observed gamma-ray emission. This work would stimulate further studies
of particle acceleration mechanisms at these gamma-ray sources.
Title: Quasi-periodic oscillations and long-term orbital period
variation of the eclipsing dwarf nova EM Cyg
Authors: Liu, Wei; Qian, Sheng-Bang; Zhi, Qi-Jun; Han, Zhong-Tao;
Wang, Qi-Shan; Dong, Ai-Jun
Bibcode: 2021MNRAS.505..677L
Altcode: 2021MNRAS.tmp.1304L
EM Cyg is an eclipsing dwarf nova with an orbital period above the
period gap of cataclysmic variables. Based on the whole outburst of EM
Cyg observed by the Transiting Exoplanet Survey Satellite (TESS) from
2019 July 18-August 14, the evolution of quasi-periodic oscillations
(QPOs) in EM Cyg was investigated. A QPO with a period of about 1000
s was found during both outburst and quiescence. In addition, we found
another QPO with a period of about 500 s, which was present during the
outburst but disappeared as the outburst ended. QPOs should be caused
by the activity of the accretion disc. Using the data obtained during
the outburst, we analysed the characteristics of the light curves and
found that the eclipsing depth increased and the light-minimum moment
earlier during the outburst. In addition, with the new eclipse times
obtained by TESS and from our observations, an O - C diagram for this
system was produced. According to the O - C analysis, the orbital period
is increasing at a rate of $\dot{P} = 1.66(\pm 0.36) \times 10^{-8}\,
\mathrm{d\,yr^{-1}}$. There is a cyclic variation in the O - C curve
that might be caused by the light-traveltime effect. A third body may
exist in the EM Cyg system with the mass $m_3\sin {i{^{\prime }}} =
0.097(\pm 0.000\,35) \, \mathrm{M}_{\odot }$.
Title: Alpha-cluster transfer reactions: A tool for understanding
stellar helium burning
Authors: Shen, Y. P.; Guo, B.; Liu, W. P.
Bibcode: 2021PrPNP.11903857S
Altcode:
Nuclear processes not only generate the energy and drive the
evolution of stars, but also are responsible for the synthesis of
the elements in the Universe. Helium (4He, or α) is the
second most abundant element after hydrogen, thus α-particle induced
reactions such as (α , γ) , (α , n) and (α , p) play a crucial
role in nuclear astrophysics, especially for understanding stellar
helium burning. Direct measurement of the cross sections for these
α-capture reactions at stellar energies is greatly hindered because
of the strong Coulomb repulsion. Alpha-cluster transfer reaction is
a powerful tool for investigation of astrophysical (α , γ) , (α ,
n) and (α , p) reactions since it can preferentially populate the
natural-parity states with an α-cluster structure which dominantly
contribute to these astrophysical α-capture reactions during stellar
helium burning. In this review we summarize the theoretical scheme,
the experimental technique, astrophysical applications and the future
perspectives of such approach based on α-cluster transfer reactions.
Title: Construction and on-site performance of the LHAASO WFCTA camera
Authors: Aharonian, F.; An, Q.; Axikegu, Bai, L. X.; Bai, Y. X.; Bao,
Y. W.; Bastieri, D.; Bi, X. J.; Bi, Y. J.; Cai, H.; Cai, J. T.; Cao,
Z.; Cao, Z.; Chang, J.; Chang, J. F.; Chang, X. C.; Chen, B. M.;
Chen, J.; Chen, L.; Chen, L.; Chen, L.; Chen, M. J.; Chen, M. L.;
Chen, Q. H.; Chen, S. H.; Chen, S. Z.; Chen, T. L.; Chen, X. L.; Chen,
Y.; Cheng, N.; Cheng, Y. D.; Cui, S. W.; Cui, X. H.; Cui, Y. D.; Dai,
B. Z.; Dai, H. L.; Dai, Z. G.; Danzengluobu, Volpe, D. Della; Piazzoli,
B. D'ettorre; Dong, X. J.; Fan, J. H.; Fan, Y. Z.; Fan, Z. X.; Fang,
J.; Fang, K.; Feng, C. F.; Feng, L.; Feng, S. H.; Feng, Y. L.; Gao,
B.; Gao, C. D.; Gao, Q.; Gao, W.; Ge, M. M.; Geng, L. S.; Gong, G. H.;
Gou, Q. B.; Gu, M. H.; Guo, J. G.; Guo, X. L.; Guo, Y. Q.; Guo, Y. Y.;
Han, Y. A.; He, H. H.; He, H. N.; He, J. C.; He, S. L.; He, X. B.;
He, Y.; Heller, M.; Hor, Y. K.; Hou, C.; Hou, X.; Hu, H. B.; Hu,
S.; Hu, S. C.; Hu, X. J.; Huang, D. H.; Huang, Q. L.; Huang, W. H.;
Huang, X. T.; Huang, Z. C.; Ji, F.; Ji, X. L.; Jia, H. Y.; Jiang, K.;
Jiang, Z. J.; Jin, C.; Kuleshov, D.; Levochkin, K.; Li, B. B.; Li,
C.; Li, C.; Li, F.; Li, H. B.; Li, H. C.; Li, H. Y.; Li, J.; Li, K.;
Li, W. L.; Li, X.; Li, X.; Li, X. R.; Li, Y.; Li, Y. Z.; Li, Z.; Li,
Z.; Liang, E. W.; Liang, Y. F.; Lin, S. J.; Liu, B.; Liu, C.; Liu, D.;
Liu, H.; Liu, H. D.; Liu, J.; Liu, J. L.; Liu, J. S.; Liu, J. Y.; Liu,
M. Y.; Liu, R. Y.; Liu, S. M.; Liu, W.; Liu, Y. N.; Liu, Z. X.; Long,
W. J.; Lu, R.; Lv, H. K.; Ma, B. Q.; Ma, L. L.; Ma, X. H.; Mao, J. R.;
Masood, A.; Mitthumsiri, W.; Montaruli, T.; Nan, Y. C.; Pang, B. Y.;
Pattarakijwanich, P.; Pei, Z. Y.; Qi, M. Y.; Ruffolo, D.; Rulev, V.;
Sáiz, A.; Shao, L.; Shchegolev, O.; Sheng, X. D.; Shi, J. R.; Song,
H. C.; Stenkin, Yu. V.; Stepanov, V.; Sun, Q. N.; Sun, X. N.; Sun,
Z. B.; Tam, P. H. T.; Tang, Z. B.; Tian, W. W.; Wang, B. D.; Wang,
C.; Wang, H.; Wang, H. G.; Wang, J. C.; Wang, J. S.; Wang, L. P.;
Wang, L. Y.; Wang, R. N.; Wang, W.; Wang, W.; Wang, X. G.; Wang,
X. J.; Wang, X. Y.; Wang, Y. D.; Wang, Y. J.; Wang, Y. P.; Wang,
Z.; Wang, Z.; Wang, Z. H.; Wang, Z. X.; Wei, D. M.; Wei, J. J.;
Wei, Y. J.; Wen, T.; Wu, C. Y.; Wu, H. R.; Wu, S.; Wu, W. X.; Wu,
X. F.; Xi, S. Q.; Xia, J.; Xia, J. J.; Xiang, G. M.; Xiao, G.; Xiao,
H. B.; Xin, G. G.; Xin, Y. L.; Xing, Y.; Xu, D. L.; Xu, R. X.; Xue,
L.; Yan, D. H.; Yang, C. W.; Yang, F. F.; Yang, J. Y.; Yang, L. L.;
Yang, M. J.; Yang, R. Z.; Yang, S. B.; Yao, Y. H.; Yao, Z. G.; Ye,
Y. M.; Yin, L. Q.; Yin, N.; You, X. H.; You, Z. Y.; Yu, Y. H.; Yuan,
Q.; Zeng, H. D.; Zeng, T. X.; Zeng, W.; Zeng, Z. K.; Zha, M.; Zhai,
X. X.; Zhang, B. B.; Zhang, H. M.; Zhang, H. Y.; Zhang, J. L.; Zhang,
J. W.; Zhang, L.; Zhang, L.; Zhang, L. X.; Zhang, P. F.; Zhang, P. P.;
Zhang, R.; Zhang, S. R.; Zhang, S. S.; Zhang, X.; Zhang, X. P.; Zhang,
Y.; Zhang, Y.; Zhang, Y. F.; Zhang, Y. L.; Zhao, B.; Zhao, J.; Zhao,
L.; Zhao, L. Z.; Zhao, S. P.; Zheng, F.; Zheng, Y.; Zhou, B.; Zhou,
H.; Zhou, J. N.; Zhou, P.; Zhou, R.; Zhou, X. X.; Zhu, C. G.; Zhu,
F. R.; Zhu, H.; Zhu, K. J.; Zuo, X.; Lhaaso Collaboration
Bibcode: 2021EPJC...81..657A
Altcode: 2020arXiv201214622A
The focal plane camera is the core component of the Wide
Field-of-view Cherenkov/fluorescence Telescope Array (WFCTA) of
the Large High-Altitude Air Shower Observatory (LHAASO). Because
of the capability of working under moonlight without aging, silicon
photomultipliers (SiPM) have been proven to be not only an alternative
but also an improvement to conventional photomultiplier tubes (PMT) in
this application. Eighteen SiPM-based cameras with square light funnels
have been built for WFCTA. The telescopes have collected more than 100
million cosmic ray events and preliminary results indicate that these
cameras are capable of working under moonlight. The characteristics
of the light funnels and SiPMs pose challenges (e.g. dynamic range,
dark count rate, assembly techniques). In this paper, we present the
design features, manufacturing techniques and performances of these
cameras. Finally, the test facilities, the test methods and results
of SiPMs in the cameras are reported here.
Title: A scenario for the anisotropy of galactic cosmic rays related
to nearby source and local interstellar magnetic field
Authors: Li, Ai-feng; Yuan, Qiang; Liu, Wei; Guo, Yi-qing
Bibcode: 2021arXiv210700313L
Altcode:
In our recent work, we build a propagation scenario to simultaneously
explain the spectra and anisotropy of cosmic rays (CRs) by considering
spatially dependent propagation (SDP) model and nearby Geminga
supernova remnant (SNR) source. But the phase of anisotropy is still
inconsistent with the experimental data. Recent observations of CR
anisotropy show that the phase is consistent with local regular
magnetic field (LRMF) observed by Interstellar Boundary Explorer
(IBEX) below 100 TeV, which indicates that diffusion along LRMF is
important. In this work, we further introduce the LRMF and take into
account the effect of corresponding anisotropic diffusion to explain
the anisotropy of CRs. We find that when the diffusion coefficient
perpendicular to the LRMF is much smaller than the parallel one, the
phase of anisotropy points to $\sim R.A.= 3^h$, which accords with
experimental observation below 100 TeV. We also analyze the influence
of the ratio of perpendicular and parallel diffusion coefficient on
the anisotropy and the energy dependence of the ratio. The results
illustrate that with the decrease of perpendicular diffusion, the
anisotropic phase changes from the direction of nearby source to the
LRMF below 100 TeV, meanwhile it changes from the galactic center (GC)
to opposite direction of LRMF above 100 TeV. When the perpendicular
diffusion coefficient grows faster than the parallel one with energy,
the diffusion approaches to the isotropic at high energy, the phase
of anisotropy shifts from the LRMF to the GC above 100 TeV. This could
be helpful to ascertain the energy dependence of diffusion coefficients.
Title: Peta-electron volt gamma-ray emission from the Crab Nebula
Authors: Lhaaso Collaboration; Cao, Zhen; Aharonian, F.; An, Q.;
Axikegu; Bai, L. X.; Bai, Y. X.; Bao, Y. W.; Bastieri, D.; Bi, X. J.;
Bi, Y. J.; Cai, H.; Cai, J. T.; Cao, Zhe; Chang, J.; Chang, J. F.;
Chen, B. M.; Chen, E. S.; Chen, J.; Chen, Liang; Chen, Liang; Chen,
Long; Chen, M. J.; Chen, M. L.; Chen, Q. H.; Chen, S. H.; Chen, S. Z.;
Chen, T. L.; Chen, X. L.; Chen, Y.; Cheng, N.; Cheng, Y. D.; Cui,
S. W.; Cui, X. H.; Cui, Y. D.; D'Ettorre Piazzoli, B.; Dai, B. Z.;
Dai, H. L.; Dai, Z. G.; Danzengluobu; Della Volpe, D.; Dong, X. J.;
Duan, K. K.; Fan, J. H.; Fan, Y. Z.; Fan, Z. X.; Fang, J.; Fang,
K.; Feng, C. F.; Feng, L.; Feng, S. H.; Feng, Y. L.; Gao, B.; Gao,
C. D.; Gao, L. Q.; Gao, Q.; Gao, W.; Ge, M. M.; Geng, L. S.; Gong,
G. H.; Gou, Q. B.; Gu, M. H.; Guo, F. L.; Guo, J. G.; Guo, X. L.;
Guo, Y. Q.; Guo, Y. Y.; Han, Y. A.; He, H. H.; He, H. N.; He, J. C.;
He, S. L.; He, X. B.; He, Y.; Heller, M.; Hor, Y. K.; Hou, C.; Hou,
X.; Hu, H. B.; Hu, S.; Hu, S. C.; Hu, X. J.; Huang, D. H.; Huang,
Q. L.; Huang, W. H.; Huang, X. T.; Huang, X. Y.; Huang, Z. C.; Ji,
F.; Ji, X. L.; Jia, H. Y.; Jiang, K.; Jiang, Z. J.; Jin, C.; Ke, T.;
Kuleshov, D.; Levochkin, K.; Li, B. B.; Li, Cheng; Li, Cong; Li, F.;
Li, H. B.; Li, H. C.; Li, H. Y.; Li, Jian; Li, Jie; Li, K.; Li, W. L.;
Li, X. R.; Li, Xin; Li, Xin; Li, Y.; Li, Y. Z.; Li, Zhe; Li, Zhuo;
Liang, E. W.; Liang, Y. F.; Lin, S. J.; Liu, B.; Liu, C.; Liu, D.;
Liu, H.; Liu, H. D.; Liu, J.; Liu, J. L.; Liu, J. S.; Liu, J. Y.;
Liu, M. Y.; Liu, R. Y.; Liu, S. M.; Liu, W.; Liu, Y.; Liu, Y. N.;
Liu, Z. X.; Long, W. J.; Lu, R.; Lv, H. K.; Ma, B. Q.; Ma, L. L.; Ma,
X. H.; Mao, J. R.; Masood, A.; Min, Z.; Mitthumsiri, W.; Montaruli,
T.; Nan, Y. C.; Pang, B. Y.; Pattarakijwanich, P.; Pei, Z. Y.; Qi,
M. Y.; Qi, Y. Q.; Qiao, B. Q.; Qin, J. J.; Ruffolo, D.; Rulev, V.;
Saiz, A.; Shao, L.; Shchegolev, O.; Sheng, X. D.; Shi, J. Y.; Song,
H. C.; Stenkin, Yu. V.; Stepanov, V.; Su, Y.; Sun, Q. N.; Sun, X. N.;
Sun, Z. B.; Tam, P. H. T.; Tang, Z. B.; Tian, W. W.; Wang, B. D.;
Wang, C.; Wang, H.; Wang, H. G.; Wang, J. C.; Wang, J. S.; Wang,
L. P.; Wang, L. Y.; Wang, R. N.; Wang, Wei; Wang, Wei; Wang, X. G.;
Wang, X. J.; Wang, X. Y.; Wang, Y.; Wang, Y. D.; Wang, Y. J.; Wang,
Y. P.; Wang, Z. H.; Wang, Z. X.; Wang, Zhen; Wang, Zheng; Wei, D. M.;
Wei, J. J.; Wei, Y. J.; Wen, T.; Wu, C. Y.; Wu, H. R.; Wu, S.; Wu,
W. X.; Wu, X. F.; Xi, S. Q.; Xia, J.; Xia, J. J.; Xiang, G. M.; Xiao,
D. X.; Xiao, G.; Xiao, H. B.; Xin, G. G.; Xin, Y. L.; Xing, Y.; Xu,
D. L.; Xu, R. X.; Xue, L.; Yan, D. H.; Yan, J. Z.; Yang, C. W.; Yang,
F. F.; Yang, J. Y.; Yang, L. L.; Yang, M. J.; Yang, R. Z.; Yang, S. B.;
Yao, Y. H.; Yao, Z. G.; Ye, Y. M.; Yin, L. Q.; Yin, N.; You, X. H.;
You, Z. Y.; Yu, Y. H.; Yuan, Q.; Zeng, H. D.; Zeng, T. X.; Zeng, W.;
Zeng, Z. K.; Zha, M.; Zhai, X. X.; Zhang, B. B.; Zhang, H. M.; Zhang,
H. Y.; Zhang, J. L.; Zhang, J. W.; Zhang, L. X.; Zhang, Li; Zhang,
Lu; Zhang, P. F.; Zhang, P. P.; Zhang, R.; Zhang, S. R.; Zhang, S. S.;
Zhang, X.; Zhang, X. P.; Zhang, Y. F.; Zhang, Y. L.; Zhang, Yi; Zhang,
Yong; Zhao, B.; Zhao, J.; Zhao, L.; Zhao, L. Z.; Zhao, S. P.; Zheng,
F.; Zheng, Y.; Zhou, B.; Zhou, H.; Zhou, J. N.; Zhou, P.; Zhou, R.;
Zhou, X. X.; Zhu, C. G.; Zhu, F. R.; Zhu, H.; Zhu, K. J.; Zuo, X.
Bibcode: 2021Sci...373..425L
Altcode: 2021arXiv211106545T
The Crab Nebula is a bright source of gamma rays powered by the Crab
Pulsar's rotational energy through the formation and termination of
a relativistic electron-positron wind. We report the detection of
gamma rays from this source with energies from 5 × 10^{-4} to 1.1
peta-electron volts with a spectrum showing gradual steepening over
three energy decades. The ultrahigh-energy photons imply the presence
of a peta-electron volt electron accelerator (a pevatron) in the
nebula, with an acceleration rate exceeding 15% of the theoretical
limit. We constrain the pevatron' size between 0.025 and 0.1 parsecs
and the magnetic field to ≍110 microgauss. The production rate
of peta-electron volt electrons, 2.5 × 10^{36} ergs per second,
constitutes 0.5% of the pulsar spin-down luminosity, although we cannot
exclude a contribution of peta-electron volt protons to the production
of the highest-energy gamma rays.
Title: Extended Very-High-Energy Gamma-Ray Emission Surrounding PSR
J 0622 +3749 Observed by LHAASO-KM2A
Authors: Aharonian, F.; An, Q.; Axikegu, Bai, L. X.; Bai, Y. X.; Bao,
Y. W.; Bastieri, D.; Bi, X. J.; Bi, Y. J.; Cai, H.; Cai, J. T.; Cao,
Z.; Cao, Z.; Chang, J.; Chang, J. F.; Chang, X. C.; Chen, B. M.; Chen,
J.; Chen, L.; Chen, L.; Chen, L.; Chen, M. J.; Chen, M. L.; Chen,
Q. H.; Chen, S. H.; Chen, S. Z.; Chen, T. L.; Chen, X. L.; Chen,
Y.; Cheng, N.; Cheng, Y. D.; Cui, S. W.; Cui, X. H.; Cui, Y. D.;
Dai, B. Z.; Dai, H. L.; Dai, Z. G.; Danzengluobu; Della Volpe, D.;
D'Ettorre Piazzoli, B.; Dong, X. J.; Fan, J. H.; Fan, Y. Z.; Fan,
Z. X.; Fang, J.; Fang, K.; Feng, C. F.; Feng, L.; Feng, S. H.; Feng,
Y. L.; Gao, B.; Gao, C. D.; Gao, Q.; Gao, W.; Ge, M. M.; Geng, L. S.;
Gong, G. H.; Gou, Q. B.; Gu, M. H.; Guo, J. G.; Guo, X. L.; Guo,
Y. Q.; Guo, Y. Y.; Han, Y. A.; He, H. H.; He, H. N.; He, J. C.; He,
S. L.; He, X. B.; He, Y.; Heller, M.; Hor, Y. K.; Hou, C.; Hou, X.;
Hu, H. B.; Hu, S.; Hu, S. C.; Hu, X. J.; Huang, D. H.; Huang, Q. L.;
Huang, W. H.; Huang, X. T.; Huang, Z. C.; Ji, F.; Ji, X. L.; Jia,
H. Y.; Jiang, K.; Jiang, Z. J.; Jin, C.; Kuleshov, D.; Levochkin, K.;
Li, B. B.; Li, C.; Li, C.; Li, F.; Li, H. B.; Li, H. C.; Li, H. Y.;
Li, J.; Li, K.; Li, W. L.; Li, X.; Li, X.; Li, X. R.; Li, Y.; Li,
Y. Z.; Li, Z.; Li, Z.; Liang, E. W.; Liang, Y. F.; Lin, S. J.; Liu,
B.; Liu, C.; Liu, D.; Liu, H.; Liu, H. D.; Liu, J.; Liu, J. L.; Liu,
J. S.; Liu, J. Y.; Liu, M. Y.; Liu, R. Y.; Liu, S. M.; Liu, W.; Liu,
Y. N.; Liu, Z. X.; Long, W. J.; Lu, R.; Lv, H. K.; Ma, B. Q.; Ma,
L. L.; Ma, X. H.; Mao, J. R.; Masood, A.; Mitthumsiri, W.; Montaruli,
T.; Nan, Y. C.; Pang, B. Y.; Pattarakijwanich, P.; Pei, Z. Y.; Qi,
M. Y.; Ruffolo, D.; Rulev, V.; Sáiz, A.; Shao, L.; Shchegolev, O.;
Sheng, X. D.; Shi, J. R.; Song, H. C.; Stenkin, Yu. V.; Stepanov, V.;
Sun, Q. N.; Sun, X. N.; Sun, Z. B.; Tam, P. H. T.; Tang, Z. B.; Tian,
W. W.; Wang, B. D.; Wang, C.; Wang, H.; Wang, H. G.; Wang, J. C.; Wang,
J. S.; Wang, L. P.; Wang, L. Y.; Wang, R. N.; Wang, W.; Wang, W.; Wang,
X. G.; Wang, X. J.; Wang, X. Y.; Wang, Y. D.; Wang, Y. J.; Wang, Y. P.;
Wang, Z.; Wang, Z.; Wang, Z. H.; Wang, Z. X.; Wei, D. M.; Wei, J. J.;
Wei, Y. J.; Wen, T.; Wu, C. Y.; Wu, H. R.; Wu, S.; Wu, W. X.; Wu,
X. F.; Xi, S. Q.; Xia, J.; Xia, J. J.; Xiang, G. M.; Xiao, G.; Xiao,
H. B.; Xin, G. G.; Xin, Y. L.; Xing, Y.; Xu, D. L.; Xu, R. X.; Xue,
L.; Yan, D. H.; Yang, C. W.; Yang, F. F.; Yang, J. Y.; Yang, L. L.;
Yang, M. J.; Yang, R. Z.; Yang, S. B.; Yao, Y. H.; Yao, Z. G.; Ye,
Y. M.; Yin, L. Q.; Yin, N.; You, X. H.; You, Z. Y.; Yu, Y. H.; Yuan,
Q.; Zeng, H. D.; Zeng, T. X.; Zeng, W.; Zeng, Z. K.; Zha, M.; Zhai,
X. X.; Zhang, B. B.; Zhang, H. M.; Zhang, H. Y.; Zhang, J. L.; Zhang,
J. W.; Zhang, L.; Zhang, L.; Zhang, L. X.; Zhang, P. F.; Zhang, P. P.;
Zhang, R.; Zhang, S. R.; Zhang, S. S.; Zhang, X.; Zhang, X. P.; Zhang,
Y.; Zhang, Y.; Zhang, Y. F.; Zhang, Y. L.; Zhao, B.; Zhao, J.; Zhao,
L.; Zhao, L. Z.; Zhao, S. P.; Zheng, F.; Zheng, Y.; Zhou, B.; Zhou,
H.; Zhou, J. N.; Zhou, P.; Zhou, R.; Zhou, X. X.; Zhu, C. G.; Zhu,
F. R.; Zhu, H.; Zhu, K. J.; Zuo, X.; LHAASO Collaboration; Huang, X. Y.
Bibcode: 2021PhRvL.126x1103A
Altcode: 2021arXiv210609396L
We report the discovery of an extended very-high-energy (VHE) gamma-ray
source around the location of the middle-aged (207.8 kyr) pulsar
PSR J 0622 +3749 with the Large High-Altitude Air Shower Observatory
(LHAASO). The source is detected with a significance of 8.2 σ for
E >25 TeV assuming a Gaussian template. The best-fit location
is (right ascension, declination) =(95.47 ° ±0.11 ° ,37.92 °
±0.09 ° ) , and the extension is 0.40 ° ±0.07 ° . The energy
spectrum can be described by a power-law spectrum with an index of
-2.92 ±0.17stat±0.02sys . No clear extended
multiwavelength counterpart of the LHAASO source has been found from
the radio to sub-TeV bands. The LHAASO observations are consistent
with the scenario that VHE electrons escaped from the pulsar,
diffused in the interstellar medium, and scattered the interstellar
radiation field. If interpreted as the pulsar halo scenario, the
diffusion coefficient, inferred for electrons with median energies
of ∼160 TeV , is consistent with those obtained from the extended
halos around Geminga and Monogem and much smaller than that derived
from cosmic ray secondaries. The LHAASO discovery of this source thus
likely enriches the class of so-called pulsar halos and confirms that
high-energy particles generally diffuse very slowly in the disturbed
medium around pulsars.
Title: Large-scale EUV Waves and Their Implications for Global
Coronal Seismology
Authors: Liu, W.; Jin, M.; Wang, T.; Ofman, L.; Sun, X.
Bibcode: 2021AAS...23832817L
Altcode:
Large-scale extreme ultraviolet (EUV) waves associated with coronal mass
ejections (CMEs) and solar flares can provide novel diagnostics of the
solar corona on global scales, an area yet to be fully exploited. We
perform detailed analysis of various behaviors, such as reflection,
refraction, and diffraction of several well-observed EUV waves,
including those associated with the SOL2017-09-10 X8.2 flare and
the SOL2011-02-15 X2 flare. We also performed data-constrained MHD
simulations of these events using the University of Michigan Alfven Wave
Solar Model (AWSoM). By comparing the observations and simulations,
we benchmark diagnostics of the magnetic field strengths and thermal
properties of the solar corona. This opens the door to the full
applications to global coronal seismology using large-scale EUV waves.
Title: Solar Prominence Bubbles and Associated Plasma Instabilities:
IRIS and SDO/AIA Observations
Authors: Liu, W.; Berger, T.
Bibcode: 2021AAS...23811311L
Altcode:
Solar prominences are cool and dense plasma in the hot corona. The
so-called prominence bubbles are mysterious, dome-shaped, apparently
void structures residing in the lower portions of prominences. Such
bubbles are associated with various plasma instabilities, such as the
Rayleigh-Taylor (RT) and Kelvin-Helmholtz (KH) instabilities. The
former is manifested in plumes that are often produced at the top
boundary of a bubble and intrude upward into the dense prominence
material. The latter is found to be triggered by shear flows at
the bubble boundaries. We present recent observations of prominence
bubbles by IRIS and SDO/AIA, focusing on the diagnostic potential of
RT and KH instabilities on the physical conditions of the prominence
and its supporting magnetic field. We search for evidence of magnetic
flux emergence as the origin of prominence bubbles. We discuss their
role in mass ad magnetic flux transport in the solar atmosphere.
Title: Applications of AOTF Spectrometers in In Situ Lunar
Measurements
Authors: Li, Jinning; Gui, Yuhua; Xu, Rui; Zhang, Zehong; Liu, Wei;
Lv, Gang; Wang, Meizhu; Li, Chunlai; He, Zhiping
Bibcode: 2021Mate...14.3454L
Altcode:
No abstract at ADS
Title: Radio frequency interference detection based on the AC-UNet
model
Authors: Yan, Rui-Qing; Dai, Cong; Liu, Wei; Li, Ji-Xia; Chen, Si-Ying;
Yu, Xian-Chuan; Zuo, Shi-Fan; Chen, Xue-Lei
Bibcode: 2021RAA....21..119Y
Altcode:
Radio frequency interference (RFI) is a serious issue in radio
astronomy. This paper proposes a U-Net network model with atrous
convolution to detect RFI. Using the ability of convolutional
neural networks to extract image features of RFI, and learning RFI
distribution patterns, the detection model of the RFI is established. We
use observational data containing real RFIs obtained by the Tianlai
telescope to train the model so that the model can detect RFI. Calculate
the probability of a data point being RFI pixel by pixel, and set
a threshold. At the same time the dropout layer was added to avoid
overfitting problems. If the predicted probability of a data point
exceeds the threshold, it is considered that there is RFI, and if the
predicted probability of a data point does not exceed the threshold,
then it is considered that there is no RFI, so that the part of the
image with RFI is flagged. Experimental results show that this approach
can achieve satisfactory accuracy in the detection of radio observation
images with a small amount of RFI.
Title: Ultrahigh-energy photons up to 1.4 petaelectronvolts from 12
γ-ray Galactic sources
Authors: Cao, Zhen; Aharonian, F. A.; An, Q.; Axikegu, Bai, L. X.;
Bai, Y. X.; Bao, Y. W.; Bastieri, D.; Bi, X. J.; Bi, Y. J.; Cai, H.;
Cai, J. T.; Cao, Zhe; Chang, J.; Chang, J. F.; Chang, X. C.; Chen,
B. M.; Chen, J.; Chen, L.; Chen, Liang; Chen, Long; Chen, M. J.;
Chen, M. L.; Chen, Q. H.; Chen, S. H.; Chen, S. Z.; Chen, T. L.; Chen,
X. L.; Chen, Y.; Cheng, N.; Cheng, Y. D.; Cui, S. W.; Cui, X. H.; Cui,
Y. D.; Dai, B. Z.; Dai, H. L.; Dai, Z. G.; Danzengluobu; della Volpe,
D.; D'Ettorre Piazzoli, B.; Dong, X. J.; Fan, J. H.; Fan, Y. Z.;
Fan, Z. X.; Fang, J.; Fang, K.; Feng, C. F.; Feng, L.; Feng, S. H.;
Feng, Y. L.; Gao, B.; Gao, C. D.; Gao, Q.; Gao, W.; Ge, M. M.; Geng,
L. S.; Gong, G. H.; Gou, Q. B.; Gu, M. H.; Guo, J. G.; Guo, X. L.;
Guo, Y. Q.; Guo, Y. Y.; Han, Y. A.; He, H. H.; He, H. N.; He, J. C.;
He, S. L.; He, X. B.; He, Y.; Heller, M.; Hor, Y. K.; Hou, C.; Hou,
X.; Hu, H. B.; Hu, S.; Hu, S. C.; Hu, X. J.; Huang, D. H.; Huang,
Q. L.; Huang, W. H.; Huang, X. T.; Huang, Z. C.; Ji, F.; Ji, X. L.;
Jia, H. Y.; Jiang, K.; Jiang, Z. J.; Jin, C.; Kuleshov, D.; Levochkin,
K.; Li, B. B.; Li, Cong; Li, Cheng; Li, F.; Li, H. B.; Li, H. C.; Li,
H. Y.; Li, J.; Li, K.; Li, W. L.; Li, X.; Li, Xin; Li, X. R.; Li, Y.;
Li, Y. Z.; Li, Zhe; Li, Zhuo; Liang, E. W.; Liang, Y. F.; Lin, S. J.;
Liu, B.; Liu, C.; Liu, D.; Liu, H.; Liu, H. D.; Liu, J.; Liu, J. L.;
Liu, J. S.; Liu, J. Y.; Liu, M. Y.; Liu, R. Y.; Liu, S. M.; Liu, W.;
Liu, Y. N.; Liu, Z. X.; Long, W. J.; Lu, R.; Lv, H. K.; Ma, B. Q.; Ma,
L. L.; Ma, X. H.; Mao, J. R.; Masood, A.; Mitthumsiri, W.; Montaruli,
T.; Nan, Y. C.; Pang, B. Y.; Pattarakijwanich, P.; Pei, Z. Y.; Qi,
M. Y.; Ruffolo, D.; Rulev, V.; Sáiz, A.; Shao, L.; Shchegolev, O.;
Sheng, X. D.; Shi, J. R.; Song, H. C.; Stenkin, Yu. V.; Stepanov, V.;
Sun, Q. N.; Sun, X. N.; Sun, Z. B.; Tam, P. H. T.; Tang, Z. B.; Tian,
W. W.; Wang, B. D.; Wang, C.; Wang, H.; Wang, H. G.; Wang, J. C.;
Wang, J. S.; Wang, L. P.; Wang, L. Y.; Wang, R. N.; Wang, W.; Wang,
W.; Wang, X. G.; Wang, X. J.; Wang, X. Y.; Wang, Y. D.; Wang, Y. J.;
Wang, Y. P.; Wang, Zheng; Wang, Zhen; Wang, Z. H.; Wang, Z. X.; Wei,
D. M.; Wei, J. J.; Wei, Y. J.; Wen, T.; Wu, C. Y.; Wu, H. R.; Wu, S.;
Wu, W. X.; Wu, X. F.; Xi, S. Q.; Xia, J.; Xia, J. J.; Xiang, G. M.;
Xiao, G.; Xiao, H. B.; Xin, G. G.; Xin, Y. L.; Xing, Y.; Xu, D. L.;
Xu, R. X.; Xue, L.; Yan, D. H.; Yang, C. W.; Yang, F. F.; Yang, J. Y.;
Yang, L. L.; Yang, M. J.; Yang, R. Z.; Yang, S. B.; Yao, Y. H.; Yao,
Z. G.; Ye, Y. M.; Yin, L. Q.; Yin, N.; You, X. H.; You, Z. Y.; Yu,
Y. H.; Yuan, Q.; Zeng, H. D.; Zeng, T. X.; Zeng, W.; Zeng, Z. K.;
Zha, M.; Zhai, X. X.; Zhang, B. B.; Zhang, H. M.; Zhang, H. Y.; Zhang,
J. L.; Zhang, J. W.; Zhang, L.; Zhang, Li; Zhang, L. X.; Zhang, P. F.;
Zhang, P. P.; Zhang, R.; Zhang, S. R.; Zhang, S. S.; Zhang, X.; Zhang,
X. P.; Zhang, Yong; Zhang, Yi; Zhang, Y. F.; Zhang, Y. L.; Zhao, B.;
Zhao, J.; Zhao, L.; Zhao, L. Z.; Zhao, S. P.; Zheng, F.; Zheng, Y.;
Zhou, B.; Zhou, H.; Zhou, J. N.; Zhou, P.; Zhou, R.; Zhou, X. X.;
Zhu, C. G.; Zhu, F. R.; Zhu, H.; Zhu, K. J.; Zuo, X.
Bibcode: 2021Natur.594...33C
Altcode:
The extension of the cosmic-ray spectrum beyond 1 petaelectronvolt
(PeV; 1015 electronvolts) indicates the existence of the
so-called PeVatrons—cosmic-ray factories that accelerate particles
to PeV energies. We need to locate and identify such objects to
find the origin of Galactic cosmic rays1. The principal
signature of both electron and proton PeVatrons is ultrahigh-energy
(exceeding 100 TeV) γ radiation. Evidence of the presence of a
proton PeVatron has been found in the Galactic Centre, according
to the detection of a hard-spectrum radiation extending to 0.04 PeV
(ref. 2). Although γ-rays with energies slightly higher
than 0.1 PeV have been reported from a few objects in the Galactic
plane3-6, unbiased identification and in-depth exploration
of PeVatrons requires detection of γ-rays with energies well above 0.1
PeV. Here we report the detection of more than 530 photons at energies
above 100 teraelectronvolts and up to 1.4 PeV from 12 ultrahigh-energy
γ-ray sources with a statistical significance greater than seven
standard deviations. Despite having several potential counterparts in
their proximity, including pulsar wind nebulae, supernova remnants and
star-forming regions, the PeVatrons responsible for the ultrahigh-energy
γ-rays have not yet been firmly localized and identified (except for
the Crab Nebula), leaving open the origin of these extreme accelerators.
Title: Possible bump structure of cosmic ray electrons unveiled by
AMS-02 data and its common origin along with the nuclei and positron
Authors: Zhang, Pei-pei; Qiao, Bing-qiang; Liu, Wei; Cui, Shu-wang;
Yuan, Qiang; Guo, Yi-qing
Bibcode: 2021JCAP...05..012Z
Altcode: 2021arXiv210100189Z
The local pulsar and its progenitor, SNR, can together accelerate the
positron, electron and nuclei to very high energy. The famous excesses
of positron(nuclei) above 20(200) GeV possibly come from such kind of
local source. This hints that the primary electron should also hold
"excess" above 200 GeV, synchronously accelerated along with the
nuclei. The recent precise measurement of sharp dropoff at 284 GeV
of positron by AMS-02 experiment takes chance to study this expected
electron excess. In this work, the spatially-dependent propagation
with a local source is used to reproduce the spectrum of positron,
electron and proton. When considering the dropoff at 284 GeV of
positron, a sharp bump structure for primary electron above 284 GeV is
required to fit the total spectrum of positron and electron. Then we
systematically study the common origin of the excesses of positron,
electron and nuclei from Geminga pulsar and SNR. Those excesses can
be reproduced under this unified single-source model. Lastly, we hope
that the fine bump structure can be observed to support our model by
AMS-02 experiment in future.
Title: Oceanic Pathways of an Active Pacific Meridional Overturning
Circulation (PMOC)
Authors: Thomas, M. D.; Fedorov, A. V.; Burls, N. J.; Liu, W.
Bibcode: 2021GeoRL..4891935T
Altcode:
In contrast to the modern day climate, North Pacific deep water
formation and a Pacific meridional overturning circulation (PMOC)
may have been active during past climate conditions, in particular
during the Pliocene epoch (some 3-5 million years ago). Here, we use
a climate model simulation with a robust PMOC cell to investigate
the pathways of the North Pacific deep water from subduction to
upwelling, as revealed by Lagrangian particle trajectories. We find
that similar to the present day Atlantic Meridional Overturning
Circulation (AMOC), most subducted North Pacific deep water upwells
in the Southern Ocean. However, roughly 15% upwells in the tropical
Indo Pacific Oceans instead—a key feature distinguishing the PMOC
from the AMOC. The connection to the Indian Ocean is relatively fast,
at about 250 years. The connection to the tropical Pacific is slower
(∼800 years) as water first travels to the subtropical South Pacific
then gradually upwells through the thermocline.
Title: A New View of the Solar Interface Region from the Interface
Region Imaging Spectrograph (IRIS)
Authors: De Pontieu, Bart; Polito, Vanessa; Hansteen, Viggo; Testa,
Paola; Reeves, Katharine K.; Antolin, Patrick; Nóbrega-Siverio,
Daniel Elias; Kowalski, Adam F.; Martinez-Sykora, Juan; Carlsson,
Mats; McIntosh, Scott W.; Liu, Wei; Daw, Adrian; Kankelborg, Charles C.
Bibcode: 2021SoPh..296...84D
Altcode: 2021arXiv210316109D
The Interface Region Imaging Spectrograph (IRIS) has been obtaining
near- and far-ultraviolet images and spectra of the solar atmosphere
since July 2013. IRIS is the highest resolution observatory to provide
seamless coverage of spectra and images from the photosphere into the
low corona. The unique combination of near- and far-ultraviolet spectra
and images at sub-arcsecond resolution and high cadence allows the
tracing of mass and energy through the critical interface between the
surface and the corona or solar wind. IRIS has enabled research into the
fundamental physical processes thought to play a role in the low solar
atmosphere such as ion-neutral interactions, magnetic reconnection, the
generation, propagation, and dissipation of waves, the acceleration of
non-thermal particles, and various small-scale instabilities. IRIS has
provided insights into a wide range of phenomena including the discovery
of non-thermal particles in coronal nano-flares, the formation and
impact of spicules and other jets, resonant absorption and dissipation
of Alfvénic waves, energy release and jet-like dynamics associated
with braiding of magnetic-field lines, the role of turbulence and the
tearing-mode instability in reconnection, the contribution of waves,
turbulence, and non-thermal particles in the energy deposition during
flares and smaller-scale events such as UV bursts, and the role of flux
ropes and various other mechanisms in triggering and driving CMEs. IRIS
observations have also been used to elucidate the physical mechanisms
driving the solar irradiance that impacts Earth's upper atmosphere,
and the connections between solar and stellar physics. Advances in
numerical modeling, inversion codes, and machine-learning techniques
have played a key role. With the advent of exciting new instrumentation
both on the ground, e.g. the Daniel K. Inouye Solar Telescope (DKIST)
and the Atacama Large Millimeter/submillimeter Array (ALMA), and
space-based, e.g. the Parker Solar Probe and the Solar Orbiter, we aim
to review new insights based on IRIS observations or related modeling,
and highlight some of the outstanding challenges.
Title: Measurement of the Cosmic Ray Helium Energy Spectrum from 70
GeV to 80 TeV with the DAMPE Space Mission
Authors: Alemanno, F.; An, Q.; Azzarello, P.; Barbato, F. C. T.;
Bernardini, P.; Bi, X. J.; Cai, M. S.; Catanzani, E.; Chang, J.;
Chen, D. Y.; Chen, J. L.; Chen, Z. F.; Cui, M. Y.; Cui, T. S.; Cui,
Y. X.; Dai, H. T.; D'Amone, A.; de Benedittis, A.; de Mitri, I.;
de Palma, F.; Deliyergiyev, M.; di Santo, M.; Dong, T. K.; Dong,
Z. X.; Donvito, G.; Droz, D.; Duan, J. L.; Duan, K. K.; D'Urso, D.;
Fan, R. R.; Fan, Y. Z.; Fang, K.; Fang, F.; Feng, C. Q.; Feng, L.;
Fusco, P.; Gao, M.; Gargano, F.; Gong, K.; Gong, Y. Z.; Guo, D. Y.;
Guo, J. H.; Guo, X. L.; Han, S. X.; Hu, Y. M.; Huang, G. S.; Huang,
X. Y.; Huang, Y. Y.; Ionica, M.; Jiang, W.; Kong, J.; Kotenko, A.;
Kyratzis, D.; Lei, S. J.; Li, S.; Li, W. L.; Li, X.; Li, X. Q.;
Liang, Y. M.; Liu, C. M.; Liu, H.; Liu, J.; Liu, S. B.; Liu, W. Q.;
Liu, Y.; Loparco, F.; Luo, C. N.; Ma, M.; Ma, P. X.; Ma, T.; Ma,
X. Y.; Marsella, G.; Mazziotta, M. N.; Mo, D.; Niu, X. Y.; Pan, X.;
Parenti, A.; Peng, W. X.; Peng, X. Y.; Perrina, C.; Qiao, R.; Rao,
J. N.; Ruina, A.; Salinas, M. M.; Shang, G. Z.; Shen, W. H.; Shen,
Z. Q.; Shen, Z. T.; Silveri, L.; Song, J. X.; Stolpovskiy, M.; Su,
H.; Su, M.; Sun, Z. Y.; Surdo, A.; Teng, X. J.; Tykhonov, A.; Wang,
H.; Wang, J. Z.; Wang, L. G.; Wang, S.; Wang, X. L.; Wang, Y.; Wang,
Y. F.; Wang, Y. Z.; Wang, Z. M.; Wei, D. M.; Wei, J. J.; Wei, Y. F.;
Wen, S. C.; Wu, D.; Wu, J.; Wu, L. B.; Wu, S. S.; Wu, X.; Xia, Z. Q.;
Xu, H. T.; Xu, Z. H.; Xu, Z. L.; Xu, Z. Z.; Xue, G. F.; Yang, H. B.;
Yang, P.; Yang, Y. Q.; Yao, H. J.; Yu, Y. H.; Yuan, G. W.; Yuan, Q.;
Yue, C.; Zang, J. J.; Zhang, F.; Zhang, S. X.; Zhang, W. Z.; Zhang,
Y.; Zhang, Y. J.; Zhang, Y. L.; Zhang, Y. P.; Zhang, Y. Q.; Zhang,
Z.; Zhang, Z. Y.; Zhao, C.; Zhao, H. Y.; Zhao, X. F.; Zhou, C. Y.;
Zhu, Y.; Dampe Collaboration
Bibcode: 2021PhRvL.126t1102A
Altcode: 2021arXiv210509073A
The measurement of the energy spectrum of cosmic ray helium nuclei
from 70 GeV to 80 TeV using 4.5 years of data recorded by the Dark
Matter Particle Explorer (DAMPE) is reported in this work. A hardening
of the spectrum is observed at an energy of about 1.3 TeV, similar
to previous observations. In addition, a spectral softening at about
34 TeV is revealed for the first time with large statistics and well
controlled systematic uncertainties, with an overall significance of
4.3 σ . The DAMPE spectral measurements of both cosmic protons and
helium nuclei suggest a particle charge dependent softening energy,
although with current uncertainties a dependence on the number of
nucleons cannot be ruled out.
Title: Novel fluorescent probe based on dicoumarin for rapid on-site
detection of Hg2+ in loess
Authors: Jiang, Youhong; Li, Huiwen; Chen, Ruofei; Liu, Wei; Chen,
Chunyang; Li, Zhongguo; Liu, Weisheng
Bibcode: 2021AcSpA.25119438J
Altcode:
It is momentous to exploit rapid, specific and on-site detection
methods for mercury ion (Hg2+) in loess, as the severe
toxicity of Hg2+ and the fragile ecological environment
of Loess Plateau. In this paper, a novel fluorescent probe DC-Hg
(Dicoumarin-Hg) was synthesized by 3-hydroxybiscoumarin and phenyl
thiochloroformate at room temperature. DC-Hg could exclusively
combine with Hg2+ to 'turn-on' yellow fluorescence at
530 nm among various other metal ions. The relationship between the
remarkable increase in intensity and concentration of Hg2+
was associated with photoinduced electron transfer (PET), which was
founded by Job's plot and 1H NMR. The limit detection of
DC-Hg showed to 85.25 nM in aqueous medium, which could be applied to
varying situations. For the loess samples, they were only extracted by
hand-shake and filtration for quickly complete the treatment operation
on site, and the results proved that DC-Hg could satisfactorily detect
the Hg2+ in mercury pollution areas.
Title: Geometrical reconstruction of fluorescence events observed
by the LHAASO experiment
Authors: Aharonian, F.; An, Q.; Axikegu; Bai, L. X.; Bai, Y. X.; Bao,
Y. W.; Bastieri, D.; Bi, X. J.; Bi, Y. J.; Cai, H.; Cai, J. T.; Cao,
Z.; Cao, Z.; Chang, J.; Chang, J. F.; Chang, X. C.; Chen, B. M.; Chen,
J.; Chen, L.; Chen, L.; Chen, L.; Chen, M. J.; Chen, M. L.; Chen,
Q. H.; Chen, S. H.; Chen, S. Z.; Chen, T. L.; Chen, X. L.; Chen,
Y.; Cheng, N.; Cheng, Y. D.; Cui, S. W.; Cui, X. H.; Cui, Y. D.;
Dai, B. Z.; Dai, H. L.; Dai, Z. G.; Danzengluobu; Della Volpe, D.;
D'Ettorre Piazzoli, B.; Dong, X. J.; Fan, J. H.; Fan, Y. Z.; Fan,
Z. X.; Fang, J.; Fang, K.; Feng, C. F.; Feng, L.; Feng, S. H.; Feng,
Y. L.; Gao, B.; Gao, C. D.; Gao, Q.; Gao, W.; Ge, M. M.; Geng, L. S.;
Gong, G. H.; Gou, Q. B.; Gu, M. H.; Guo, J. G.; Guo, X. L.; Guo,
Y. Q.; Guo, Y. Y.; Han, Y. A.; He, H. H.; He, H. N.; He, J. C.; He,
S. L.; He, X. B.; He, Y.; Heller, M.; Hor, Y. K.; Hou, C.; Hou, X.;
Hu, H. B.; Hu, S.; Hu, S. C.; Hu, X. J.; Huang, D. H.; Huang, Q. L.;
Huang, W. H.; Huang, X. T.; Huang, Z. C.; Ji, F.; Ji, X. L.; Jia,
H. Y.; Jiang, K.; Jiang, Z. J.; Jin, C.; Kuleshov, D.; Levochkin, K.;
Li, B. B.; Li, C.; Li, C.; Li, F.; Li, H. B.; Li, H. C.; Li, H. Y.; Li,
J.; Li, K.; Li, W. L.; Li, X.; Li, X.; Li, X. R.; Li, Y.; Li, Y. Z.;
Li, Z.; Li, Z.; Liang, E. W.; Liang, Y. F.; Lin, S. J.; Liu, B.; Liu,
C.; Liu, D.; Liu, H.; Liu, H. D.; Liu, J.; Liu, J. L.; Liu, J. L.;
Liu, J. S.; Liu, J. Y.; Liu, M. Y.; Liu, R. Y.; Liu, S. M.; Liu, W.;
Liu, Y. N.; Liu, Z. X.; Long, W. J.; Lu, R.; Lv, H. K.; Ma, B. Q.; Ma,
L. L.; Ma, X. H.; Mao, J. R.; Masood, A.; Mitthumsiri, W.; Montaruli,
T.; Nan, Y. C.; Pang, B. Y.; Pattarakijwanich, P.; Pei, Z. Y.; Qi,
M. Y.; Ruffolo, D.; Rulev, V.; Sáiz, A.; Shao, L.; Shchegolev, O.;
Sheng, X. D.; Shi, J. R.; Song, H. C.; Stenkin, Yu. V.; Stepanov, V.;
Sun, Q. N.; Sun, X. N.; Sun, Z. B.; Tam, P. H. T.; Tang, Z. B.; Tian,
W. W.; Wang, B. D.; Wang, C.; Wang, H.; Wang, H. G.; Wang, J. C.; Wang,
J. S.; Wang, L. P.; Wang, L. Y.; Wang, R. N.; Wang, W.; Wang, W.; Wang,
X. G.; Wang, X. J.; Wang, X. Y.; Wang, Y. D.; Wang, Y. J.; Wang, Y. P.;
Wang, Z.; Wang, Z.; Wang, Z. H.; Wang, Z. X.; Wei, D. M.; Wei, J. J.;
Wei, Y. J.; Wen, T.; Wu, C. Y.; Wu, H. R.; Wu, S.; Wu, W. X.; Wu,
X. F.; Xi, S. Q.; Xia, J.; Xia, J. J.; Xiang, G. M.; Xiao, G.; Xiao,
H. B.; Xin, G. G.; Xin, Y. L.; Xing, Y.; Xu, D. L.; Xu, R. X.; Xue,
L.; Yan, D. H.; Yang, C. W.; Yang, F. F.; Yang, J. Y.; Yang, L. L.;
Yang, M. J.; Yang, R. Z.; Yang, S. B.; Yao, Y. H.; Yao, Z. G.; Ye,
Y. M.; Yin, L. Q.; Yin, N.; You, X. H.; You, Z. Y.; Yu, Y. H.; Yuan,
Q.; Zeng, H. D.; Zeng, T. X.; Zeng, W.; Zeng, Z. K.; Zha, M.; Zhai,
X. X.; Zhang, B. B.; Zhang, H. M.; Zhang, H. Y.; Zhang, J. L.; Zhang,
J. W.; Zhang, L.; Zhang, L.; Zhang, L. X.; Zhang, P. F.; Zhang, P. P.;
Zhang, R.; Zhang, S. R.; Zhang, S. S.; Zhang, X.; Zhang, X. P.; Zhang,
Y.; Zhang, Y.; Zhang, Y. F.; Zhang, Y. L.; Zhao, B.; Zhao, J.; Zhao,
L.; Zhao, L. Z.; Zhao, S. P.; Zheng, F.; Zheng, Y.; Zhou, B.; Zhou,
H.; Zhou, J. N.; Zhou, P.; Zhou, R.; Zhou, X. X.; Zhu, C. G.; Zhu,
F. R.; Zhu, H.; Zhu, K. J.; Zuo, X.; LHAASO Collaboration
Bibcode: 2021ChPhC..45d5101A
Altcode:
The LHAASO-WFCTA experiment, which aims to observe cosmic rays in the
sub-EeV range using the fluorescence technique, uses a new generation
of high-performance telescopes. To ensure that the experiment has
excellent detection capability associated with the measurement of
the energy spectrum, the primary composition of cosmic rays, and
so on, an accurate geometrical reconstruction of air-shower events
is fundamental. This paper describes the development and testing
of geometrical reconstruction for stereo viewed events using the
WFCTA (Wide Field of view Cherenkov/Fluorescence Telescope Array)
detectors. Two approaches, which take full advantage of the WFCTA
detectors, are investigated. One is the stereo-angular method,
which uses the pointing of triggered SiPMs in the shower trajectory,
and the other is the stereo-timing method, which uses the triggering
time of the fired SiPMs. The results show that both methods have good
geometrical resolution; the resolution of the stereo-timing method is
slightly better than the stereo-angular method because the resolution
of the latter is slightly limited by the shower track length. *
Supported by National Natural Science Foundation of China (11903005,
11563004, 11475190)
Title: IRIS observations of chromospheric heating by acoustic waves
in solar quiet and active regions
Authors: Abbasvand, V.; Sobotka, M.; Švanda, M.; Heinzel, P.; Liu,
W.; Mravcová, L.
Bibcode: 2021A&A...648A..28A
Altcode: 2021arXiv210208678A
Aims: To study the heating of solar chromospheric magnetic and
nonmagnetic regions by acoustic and magnetoacoustic waves, the deposited
acoustic-energy flux derived from observations of strong chromospheric
lines is compared with the total integrated radiative losses.
Methods: A set of 23 quiet-Sun and weak-plage regions were observed in
the Mg II k and h lines with the Interface Region Imaging Spectrograph
(IRIS). The deposited acoustic-energy flux was derived from Doppler
velocities observed at two different geometrical heights corresponding
to the middle and upper chromosphere. A set of scaled nonlocal
thermodynamic equilibrium 1D hydrostatic semi-empirical models -
obtained by fitting synthetic to observed line profiles - was applied
to compute the radiative losses. The characteristics of observed waves
were studied by means of a wavelet analysis.
Results: Observed
waves propagate upward at supersonic speed. In the quiet chromosphere,
the deposited acoustic flux is sufficient to balance the radiative
losses and maintain the semi-empirical temperatures in the layers under
study. In the active-region chromosphere, the comparison shows that
the contribution of acoustic-energy flux to the radiative losses is
only 10−30%.
Conclusions: Acoustic and magnetoacoustic waves
play an important role in the chromospheric heating, depositing a main
part of their energy in the chromosphere. Acoustic waves compensate
for a substantial fraction of the chromospheric radiative losses in
quiet regions. In active regions, their contribution is too small to
balance the radiative losses and the chromosphere has to be heated by
other mechanisms.
Title: Pedogenic processes in loess-paleosol sediments: Clues from
Li isotopes of leachate in Luochuan loess
Authors: He, Mao-Yong; Dong, Ji-Bao; Jin, Zhangdong; Liu, Chun-Yao;
Xiao, Jun; Zhang, Fei; Sun, He; Zhao, Zhi-Qi; Gou, Long-Fei; Liu,
Wei-Guo; Luo, Chong-Guang; Song, You-Gui; Ma, Long; Deng, Li
Bibcode: 2021GeCoA.299..151H
Altcode:
Tracing pedogenic processes is fundamental for reconstructing
climatic and environmental changes using loess deposits. Lithium
isotopes can serve as a sensitive tracer to unravel these processes,
owing to its active behaviors without effect by redox and biological
reactions. This study investigated the Li contents and δ7Li
values of leachate and residue ([Li]leachate,
[Li]residue, δ7Lileachate and
δ7Liresidue) of the upper 12.5 m Luochuan
loess-paleosol sediment (since the last interglacial) on the Chinese
Loess Plateau, in order to better understand pedogenic processes in
loess. The [Li]leachate, varying from 0.39 to 1.97 μg/g, is
mainly derived from the adsorption phase, with a significant variation
in δ7Lileachate, from -6.55‰ to +12.88‰. Both
[Li]leachate and δ7Lileachate
variations reflect weathering and adsorption processes during different
periods. The [Li]residue vary from 34.4 to 46.3 μg/g
(averaging 38.4 μg/g) and their δ7Liresidue
vary from -3.66‰ to +2.44‰ (averaging -0.22 ± 1.68‰), both
in agreement with the upper continental crust values. At initial
stage after loess deposited (stage I), high [Li]leachate
but low δ7Lileachate are results of
preferential adsorption of 6Li by clays and migration
of 7Li with soil solution during weathering and
eluviation processes. When overlying loess was deposited and
experienced pedogenesis as the stage I, 7Li migrated
downward and was adsorbed by clays (stage II), resulting in high
[Li]leachate and δ7Lileachate in
underlying loess. When loess has superimposed pedogenic and adsorption
processes as the stages I and II, loess became as paleosol with highest
δ7Lileachate in underlying carbonate accumulation
layer. A persistent increase in δ7Lileachate
indicates dominant control of post-depositional adsorptions on
Li fractionation along solution migrations during weathering
and eluviation of overlying deposits, and vice versa. These
results highlight that variations in [Li]leachate and
δ7Lileachate can be used to trace soil water
migration processes and the magnitude of pedogenic processes in
loess-paleosol sediment at different periods.
Title: Critical Science Plan for the Daniel K. Inouye Solar Telescope
(DKIST)
Authors: Rast, Mark P.; Bello González, Nazaret; Bellot Rubio,
Luis; Cao, Wenda; Cauzzi, Gianna; Deluca, Edward; de Pontieu, Bart;
Fletcher, Lyndsay; Gibson, Sarah E.; Judge, Philip G.; Katsukawa,
Yukio; Kazachenko, Maria D.; Khomenko, Elena; Landi, Enrico; Martínez
Pillet, Valentín; Petrie, Gordon J. D.; Qiu, Jiong; Rachmeler,
Laurel A.; Rempel, Matthias; Schmidt, Wolfgang; Scullion, Eamon; Sun,
Xudong; Welsch, Brian T.; Andretta, Vincenzo; Antolin, Patrick; Ayres,
Thomas R.; Balasubramaniam, K. S.; Ballai, Istvan; Berger, Thomas E.;
Bradshaw, Stephen J.; Campbell, Ryan J.; Carlsson, Mats; Casini,
Roberto; Centeno, Rebecca; Cranmer, Steven R.; Criscuoli, Serena;
Deforest, Craig; Deng, Yuanyong; Erdélyi, Robertus; Fedun, Viktor;
Fischer, Catherine E.; González Manrique, Sergio J.; Hahn, Michael;
Harra, Louise; Henriques, Vasco M. J.; Hurlburt, Neal E.; Jaeggli,
Sarah; Jafarzadeh, Shahin; Jain, Rekha; Jefferies, Stuart M.; Keys,
Peter H.; Kowalski, Adam F.; Kuckein, Christoph; Kuhn, Jeffrey R.;
Kuridze, David; Liu, Jiajia; Liu, Wei; Longcope, Dana; Mathioudakis,
Mihalis; McAteer, R. T. James; McIntosh, Scott W.; McKenzie, David
E.; Miralles, Mari Paz; Morton, Richard J.; Muglach, Karin; Nelson,
Chris J.; Panesar, Navdeep K.; Parenti, Susanna; Parnell, Clare E.;
Poduval, Bala; Reardon, Kevin P.; Reep, Jeffrey W.; Schad, Thomas A.;
Schmit, Donald; Sharma, Rahul; Socas-Navarro, Hector; Srivastava,
Abhishek K.; Sterling, Alphonse C.; Suematsu, Yoshinori; Tarr, Lucas
A.; Tiwari, Sanjiv; Tritschler, Alexandra; Verth, Gary; Vourlidas,
Angelos; Wang, Haimin; Wang, Yi-Ming; NSO and DKIST Project; DKIST
Instrument Scientists; DKIST Science Working Group; DKIST Critical
Science Plan Community
Bibcode: 2021SoPh..296...70R
Altcode: 2020arXiv200808203R
The National Science Foundation's Daniel K. Inouye Solar Telescope
(DKIST) will revolutionize our ability to measure, understand,
and model the basic physical processes that control the structure
and dynamics of the Sun and its atmosphere. The first-light DKIST
images, released publicly on 29 January 2020, only hint at the
extraordinary capabilities that will accompany full commissioning of
the five facility instruments. With this Critical Science Plan (CSP)
we attempt to anticipate some of what those capabilities will enable,
providing a snapshot of some of the scientific pursuits that the DKIST
hopes to engage as start-of-operations nears. The work builds on the
combined contributions of the DKIST Science Working Group (SWG) and
CSP Community members, who generously shared their experiences, plans,
knowledge, and dreams. Discussion is primarily focused on those issues
to which DKIST will uniquely contribute.
Title: First Detection of sub-PeV Diffuse Gamma Rays from the Galactic
Disk: Evidence for Ubiquitous Galactic Cosmic Rays beyond PeV Energies
Authors: Amenomori, M.; Bao, Y. W.; Bi, X. J.; Chen, D.; Chen,
T. L.; Chen, W. Y.; Chen, Xu; Chen, Y.; Cirennima, Cui, S. W.;
Danzengluobu, Ding, L. K.; Fang, J. H.; Fang, K.; Feng, C. F.;
Feng, Zhaoyang; Feng, Z. Y.; Gao, Qi; Gou, Q. B.; Guo, Y. Q.; Guo,
Y. Y.; He, H. H.; He, Z. T.; Hibino, K.; Hotta, N.; Hu, Haibing; Hu,
H. B.; Huang, J.; Jia, H. Y.; Jiang, L.; Jin, H. B.; Kasahara, K.;
Katayose, Y.; Kato, C.; Kato, S.; Kawata, K.; Kihara, W.; Ko, Y.;
Kozai, M.; Labaciren, Le, G. M.; Li, A. F.; Li, H. J.; Li, W. J.;
Lin, Y. H.; Liu, B.; Liu, C.; Liu, J. S.; Liu, M. Y.; Liu, W.; Lou,
Y. -Q.; Lu, H.; Meng, X. R.; Munakata, K.; Nakada, H.; Nakamura, Y.;
Nanjo, H.; Nishizawa, M.; Ohnishi, M.; Ohura, T.; Ozawa, S.; Qian,
X. L.; Qu, X. B.; Saito, T.; Sakata, M.; Sako, T. K.; Shao, J.;
Shibata, M.; Shiomi, A.; Sugimoto, H.; Takano, W.; Takita, M.; Tan,
Y. H.; Tateyama, N.; Torii, S.; Tsuchiya, H.; Udo, S.; Wang, H.; Wu,
H. R.; Xue, L.; Yamamoto, Y.; Yang, Z.; Yokoe, Y.; Yuan, A. F.; Zhai,
L. M.; Zhang, H. M.; Zhang, J. L.; Zhang, X.; Zhang, X. Y.; Zhang,
Y.; Zhang, Yi; Zhang, Ying; Zhao, S. P.; Zhaxisangzhu, Zhou, X. X.;
Tibet ASγ Collaboration
Bibcode: 2021PhRvL.126n1101A
Altcode: 2021arXiv210405181A
We report, for the first time, the long-awaited detection of diffuse
gamma rays with energies between 100 TeV and 1 PeV in the Galactic
disk. Particularly, all gamma rays above 398 TeV are observed apart
from known TeV gamma-ray sources and compatible with expectations from
the hadronic emission scenario in which gamma rays originate from the
decay of π0's produced through the interaction of protons
with the interstellar medium in the Galaxy. This is strong evidence
that cosmic rays are accelerated beyond PeV energies in our Galaxy
and spread over the Galactic disk.
Title: On the Progenitors of AM CVn Stars as LISA Sources: The
Evolved Donor Star Channel
Authors: Liu, Wei-Min; Jiang, Long; Chen, Wen-Cong
Bibcode: 2021ApJ...910...22L
Altcode: 2021arXiv210109850L
The space gravitational wave (GW) detector Laser Interferometer Space
Antenna (LISA) that is planned to be launched in the early 2030s will
detect the low-frequency GW signals in the Galaxy. AM CVn stars were
generally thought to be important low-frequency GW sources. Employing
the MESA code, in this work we calculate the evolution of a great number
of binary systems consisting of a white dwarf (WD) and a main sequence
(MS) star, and diagnose whether their descendant-AM CVn stars will be
visible with LISA. The simulated results show that the progenitors of
these LISA sources, within a distance of 1 kpc, are WD-MS binaries
with a donor star of 1.0-1.4 M⊙ (for initial WD mass
of 0.5 M⊙) or 1.0-2.0 M⊙ (for initial WD
mass of 0.7 M⊙), and an initial orbital period slightly
smaller than the bifurcation period. Our simulations also indicate
that 10 verification AM CVn sources can be reproduced by the standard
magnetic braking model, and are potential LISA sources. Based on the
birth rate of AM CVn stars simulated by the population synthesis, the
birth rate of AM CVn-LISA sources evolving from the evolved donor star
channel within a distance of 1 kpc can be estimated to be (0.6-1.4) ×
10-6 yr-1, and the predicted number of AM CVn-LISA
sources is about 340-810. Therefore, the evolved donor star channel
plays an important role in forming AM CVn-LISA sources in the Galaxy.
Title: The readout system design of 320x256 InGaAs astronomical camera
Authors: Liu, Wei; Men, Jinrui; Lou, Zheng
Bibcode: 2021SPIE11763E..0ML
Altcode:
InGaAs detector can be used as the image sensor in SWIR (Shortwave
Infrared) band as. Cameras with InGaAs detector have been widely used
in the astronomical observation field. Based on the optical band CCD
camera readout technologies that we have mastered, this paper introduced
one China domestic InGaAs detector, and proposed this camera readout
system with it, which includes the whole circuits structure, pixel
transferring timing and image acquisition method. We summarized these
technologies, presented the appropriate solutions and the simulation
results as well. These works provide technical support to develop
infrared scientific camera
Title: AA Tau polarimetric observation using Kanata HONIR instrument
Authors: Liu, Wei; Kawabata, Koji S.; Akitaya, Hiroshi
Bibcode: 2021SPIE11763E..0KL
Altcode:
Astronomical polarimetric observation is one of the important methods in
modern astrophysics research field. In the infrared bands, polarimetric
observation is one effective tool to study the evolution and formation
of star, and reveal multiband radiation characteristics of high-energy
celestial bodies and other aspects. This paper will introduce the system
composition, operating principle, calibration and data analysis method
of polarimetric observation using HONIR camera on Kanata telescope. We
also present part of the analysis results of AA Tau with polarimetric
observation, which is one young classical T Tauri star.
Title: Chemical Characterization of Surface Salts in Qaidam Basin:
Implications for Climates of Planet Earth and Mars
Authors: Kong, X.; Liu, W.; Li, J.; Santos, L.; Boman, J.; Zhang,
X.; Wang, S.
Bibcode: 2021LPI....52.1191K
Altcode:
The Qaidam Basin has been considered as a good terrestrial analogue
for Mars, so here we study the physical and chemical properties of salt
samples from the Qaidam Basin to shed light on the climate systems on
planet Earth and Mars.
Title: Evidence of a thick halo for the spatial-dependent propagation
model with Cosmic Ray anisotropy
Authors: Qiao, Bing-Qiang; Yao, Yu-Hua; Liu, Wei; Yuan, Qiang; Bi,
Xiao-Jun; Hu, Hong-Bo; Guo, Yi-Qing
Bibcode: 2021arXiv210213498Q
Altcode:
The spatial-dependent propagation (SDP) model with a nearby source
works well to reproduce the co-evolving features of both cosmic ray
(CR) nuclei spectra and anisotropy. However, it is well known that the
Sun is offset from the Galactic plane. This will lead to a dominating
anisotropy in perpendicular direction, which is discrepant with
observations. Thus it is necessary to reboot further investigation into
the effect of the solar offset. In this work, for the first time the
combined studies of the solar offset, nuclei spectra and anisotropy are
performed based on the SDP model. As a result, to reproduce CR spectra
and anisotropy, the thickness of the halo $\rm (\xi z_h)$ increases
linearly with the displacement of the Sun. When the offset is $\rm
\sim8~pc$ as estimated from the matter-borne methods, $\rm \xi z_h$
is about 0.9 kpc, which is a much thicker halo than usually. Moreover,
the PeV anisotropy could estimate the value of diffusion coefficient,
thus breaking the degeneracy of diffusion coefficient and halo
thickness. Therefore it is a good messenger to constrain the halo
thickness. On the other hand, the anisotropy in PeV energy region,
as a new probe, might also shed new light to constrain the solar
offset. We hope that the anisotropy at the energies of $\rm \sim TeV$
to $\rm PeV$ can be finely measured by LHAASO experiment, leading to
a better understanding about the thick halo.
Title: Earth Wind as a Possible Exogenous Source of Lunar Surface
Hydration
Authors: Wang, H. Z.; Zhang, J.; Shi, Q. Q.; Saito, Y.; Degeling,
A. W.; Rae, I. J.; Zong, Q. G.; Wei, Y.; Liu, J.; Guo, R. L.; Yao,
Z. H.; Tian, A. M.; Fu, X. H.; Liu, J. Z.; Ling, Z. C.; Fu, S. Y.;
Sun, W. J.; Bai, S. C.; Chen, J.; Yao, S. T.; Zhang, H.; Liu, W. L.;
Xia, L. D.; Feng, Y. Y.; Pu, Z. Y.
Bibcode: 2021ApJ...907L..32W
Altcode:
Understanding the sources of lunar water is crucial for studying
the history of lunar evolution, as well as the interaction of solar
wind with the Moon and other airless bodies. Recent orbital spectral
observations revealed that the solar wind is a significant exogenous
driver of lunar surficial hydration. However, the solar wind is shielded
over a period of 3-5 days per month as the Moon passes through the
Earth's magnetosphere, during which a significant loss of hydration
is expected. Here we report the temporal and spatial distribution
of polar surficial OH/H2O abundance, using Chandrayaan-1
Moon Mineralogy Mapper (M3) data, which covers the regions
inside/outside the Earth's magnetosphere. The data shows that polar
surficial OH/H2O abundance increases with latitude, and that
the probability of polar surficial OH/H2O abundance remains
at the same level when in the solar wind and in the magnetosphere
by controlling latitude, composition, and lunar local time. This
indicates that the OH/H2O abundance in the polar regions
may be saturated, or supplemented from other possible sources, such
as Earth wind (particles from the magnetosphere, distinct from the
solar wind), which may compensate for thermal diffusion losses while
the Moon lies within the Earth's magnetosphere. This work provides
some clues for studies of planet-moon systems, whereby the planetary
wind serves as a bridge connecting the planet with its moons.
Title: Study of BESIII trigger efficiencies with the 2018 J/ψ data
Authors: Ablikim, M.; Achasov, M. N.; Adlarson, P.; Ahmed, S.;
Albrecht, M.; Aliberti, R.; Amoroso, A.; An, M. R.; An, Q.; Bai,
X. H.; Bai, Y.; Bakina, O.; Ferroli, R. Baldini; Balossino, I.; Ban,
Y.; Begzsuren, K.; Berger, N.; Bertani, M.; Bettoni, D.; Bianchi,
F.; Bloms, J.; Bortone, A.; Boyko, I.; Briere, R. A.; Cai, H.; Cai,
X.; Calcaterra, A.; Cao, G. F.; Cao, N.; Cetin, S. A.; Chang, J. F.;
Chang, W. L.; Chelkov, G.; Chen, D. Y.; Chen, G.; Chen, H. S.; Chen,
M. L.; Chen, S. J.; Chen, X. R.; Chen, Y. B.; Chen, Z. J.; Cheng,
W. S.; Cibinetto, G.; Cossio, F.; Cui, X. F.; Dai, H. L.; Dai, X. C.;
Dbeyssi, A.; Boer, R. E. De; Dedovich, D.; Deng, Z. Y.; Denig, A.;
Denysenko, I.; Destefanis, M.; de Mori, F.; Ding, Y.; Dong, C.; Dong,
J.; Dong, L. Y.; Dong, M. Y.; Dong, X.; Du, S. X.; Fan, Y. L.; Fang,
J.; Fang, S. S.; Fang, Y.; Farinelli, R.; Fava, L.; Feldbauer, F.;
Felici, G.; Feng, C. Q.; Feng, J. H.; Fritsch, M.; Fu, C. D.; Gao,
Y.; Gao, Y.; Gao, Y.; Gao, Y. G.; Garzia, I.; Ge, P. T.; Geng, C.;
Gersabeck, E. M.; Gilman, A.; Goetzen, K.; Gong, L.; Gong, W. X.;
Gradl, W.; Greco, M.; Gu, L. M.; Gu, M. H.; Gu, S.; Gu, Y. T.; Guan,
C. Y.; Guo, A. Q.; Guo, L. B.; Guo, R. P.; Guo, Y. P.; Guskov, A.;
Han, T. T.; Han, W. Y.; Hao, X. Q.; Harris, F. A.; Hüsken, H.; He,
K. L.; Heinsius, F. H.; Heinz, C. H.; Held, T.; Heng, Y. K.; Herold,
C.; Himmelreich, M.; Holtmann, T.; Hou, Y. R.; Hou, Z. L.; Hu, H. M.;
Hu, J. F.; Hu, T.; Hu, Y.; Huang, G. S.; Huang, L. Q.; Huang, X. T.;
Huang, Y. P.; Huang, Z.; Hussain, T.; Ikegami Andersson, W.; Imoehl,
W.; Irshad, M.; Jaeger, S.; Janchiv, S.; Ji, Q.; Ji, Q. P.; Ji, X. B.;
Ji, X. L.; Jiang, H. B.; Jiang, X. S.; Jiao, J. B.; Jiao, Z.; Jin,
S.; Jin, Y.; Johansson, T.; Kalantar-Nayestanaki, N.; Kang, X. S.;
Kappert, R.; Kavatsyuk, M.; Ke, B. C.; Keshk, I. K.; Khoukaz, A.;
Kiese, P.; Kiuchi, R.; Kliemt, R.; Koch, L.; Kolcu, O. B.; Kopf, B.;
Kuemmel, M.; Kuessner, M.; Kupsc, A.; Kurth, M. G.; Kühn, W.; Lane,
J. J.; Lange, J. S.; Larin, P.; Lavania, A.; Lavezzi, L.; Lei, Z. H.;
Leithoff, H.; Lellmann, M.; Lenz, T.; Li, C.; Li, C. H.; Li, Cheng;
Li, D. M.; Li, F.; Li, G.; Li, H.; Li, H.; Li, H. B.; Li, H. J.; Li,
J. L.; Li, J. Q.; Li, J. S.; Li, Ke; Li, L. K.; Li, Lei; Li, P. R.;
Li, S. Y.; Li, W. D.; Li, W. G.; Li, X. H.; Li, X. L.; Li, Z. Y.;
Liang, H.; Liang, H.; Liang, H.; Liang, Y. F.; Liang, Y. T.; Liao,
L. Z.; Libby, J.; Lin, C. X.; Liu, B. J.; Liu, C. X.; Liu, D.; Liu,
F. H.; Liu, Fang; Liu, Feng; Liu, H. B.; Liu, H. M.; Liu, Huanhuan;
Liu, Huihui; Liu, J. B.; Liu, J. L.; Liu, J. Y.; Liu, K.; Liu, K. Y.;
Liu, Ke; Liu, L.; Liu, M. H.; Liu, P. L.; Liu, Q.; Liu, Q.; Liu, S. B.;
Liu, Shuai; Liu, T.; Liu, W. M.; Liu, X.; Liu, Y.; Liu, Y. B.; Liu,
Z. A.; Liu, Z. Q.; Lou, X. C.; Lu, F. X.; Lu, F. X.; Lu, H. J.; Lu,
J. D.; Lu, J. G.; Lu, X. L.; Lu, Y.; Lu, Y. P.; Luo, C. L.; Luo, M. X.;
Luo, P. W.; Luo, T.; Luo, X. L.; Lusso, S.; Lyu, X. R.; Ma, F. C.;
Ma, H. L.; Ma, L. L.; Ma, M. M.; Ma, Q. M.; Ma, R. Q.; Ma, R. T.;
Ma, X. X.; Ma, X. Y.; Maas, F. E.; Maggiora, M.; Maldaner, S.; Malde,
S.; Malik, Q. A.; Mangoni, A.; Mao, Y. J.; Mao, Z. P.; Marcello, S.;
Meng, Z. X.; Messchendorp, J. G.; Mezzadri, G.; Min, T. J.; Mitchell,
R. E.; Mo, X. H.; Mo, Y. J.; Muchnoi, N. Yu.; Muramatsu, H.; Nakhoul,
S.; Nefedov, Y.; Nerling, F.; Nikolaev, I. B.; Ning, Z.; Nisar, S.;
Olsen, S. L.; Ouyang, Q.; Pacetti, S.; Pan, X.; Pan, Y.; Pathak, A.;
Patteri, P.; Pelizaeus, M.; Peng, H. P.; Peters, K.; Pettersson, J.;
Ping, J. L.; Ping, R. G.; Poling, R.; Prasad, V.; Qi, H.; Qi, H. R.;
Qi, K. H.; Qi, M.; Qi, T. Y.; Qi, T. Y.; Qian, S.; Qian, W. -B.;
Qian, Z.; Qiao, C. F.; Qin, L. Q.; Qin, X. S.; Qin, Z. H.; Qiu, J. F.;
Qu, S. Q.; Rashid, K. H.; Ravindran, K.; Redmer, C. F.; Rivetti, A.;
Rodin, V.; Rolo, M.; Rong, G.; Rosner, Ch.; Rump, M.; Sang, H. S.;
Sarantsev, A.; Schelhaas, Y.; Schnier, C.; Schoenning, K.; Scodeggio,
M.; Shan, D. C.; Shan, W.; Shan, X. Y.; Shangguan, J. F.; Shao, M.;
Shen, C. P.; Shen, P. X.; Shen, X. Y.; Shi, H. C.; Shi, R. S.; Shi,
X.; Shi, X. D.; Song, W. M.; Song, Y. X.; Sosio, S.; Spataro, S.;
Su, K. X.; Su, P. P.; Sui, F. F.; Sun, G. X.; Sun, H. K.; Sun, J. F.;
Sun, L.; Sun, S. S.; Sun, T.; Sun, W. Y.; Sun, W. Y.; Sun, X.; Sun,
Y. J.; Sun, Y. K.; Sun, Y. Z.; Sun, Z. T.; Tan, Y. H.; Tan, Y. X.;
Tang, C. J.; Tang, G. Y.; Tang, J.; Teng, J. X.; Thoren, V.; Uman, I.;
Wang, B.; Wang, C. W.; Wang, D. Y.; Wang, H. J.; Wang, H. P.; Wang,
K.; Wang, L. L.; Wang, M.; Wang, M. Z.; Wang, Meng; Wang, W.; Wang,
W. H.; Wang, W. P.; Wang, X.; Wang, X. F.; Wang, X. L.; Wang, Y.;
Wang, Y.; Wang, Y. D.; Wang, Y. F.; Wang, Y. Q.; Wang, Y. Y.; Wang,
Z.; Wang, Z. Y.; Wang, Ziyi; Wang, Zongyuan; Wei, D. H.; Weidenkaff,
P.; Weidner, F.; Wen, S. P.; White, D. J.; Wiedner, U.; Wilkinson,
G.; Wolke, M.; Wollenberg, L.; Wu, J. F.; Wu, L. H.; Wu, L. J.; Wu,
X.; Wu, Z.; Xia, L.; Xiao, H.; Xiao, S. Y.; Xiao, Z. J.; Xie, X. H.;
Xie, Y. G.; Xie, Y. H.; Xing, T. Y.; Xu, G. F.; Xu, Q. J.; Xu, W.;
Xu, X. P.; Yan, F.; Yan, L.; Yan, W. B.; Yan, W. C.; Yan, Xu; Yang,
H. J.; Yang, H. X.; Yang, L.; Yang, S. L.; Yang, Y. X.; Yang, Yifan;
Yang, Zhi; Ye, M.; Ye, M. H.; Yin, J. H.; You, Z. Y.; Yu, B. X.; Yu,
C. X.; Yu, G.; Yu, J. S.; Yu, T.; Yuan, C. Z.; Yuan, L.; Yuan, X. Q.;
Yuan, Y.; Yuan, Z. Y.; Yue, C. X.; Yuncu, A.; Zafar, A. A.; Zeng,
Y.; Zhang, B. X.; Zhang, Guangyi; Zhang, H.; Zhang, H. H.; Zhang,
H. H.; Zhang, H. Y.; Zhang, J. J.; Zhang, J. L.; Zhang, J. Q.; Zhang,
J. W.; Zhang, J. Y.; Zhang, J. Z.; Zhang, Jianyu; Zhang, Jiawei;
Zhang, L. Q.; Zhang, Lei; Zhang, S.; Zhang, S. F.; Zhang, Shulei;
Zhang, X. D.; Zhang, X. Y.; Zhang, Y.; Zhang, Y. H.; Zhang, Y. T.;
Zhang, Yan; Zhang, Yao; Zhang, Yi; Zhang, Z. H.; Zhang, Z. Y.; Zhao,
G.; Zhao, J.; Zhao, J. Y.; Zhao, J. Z.; Zhao, Lei; Zhao, Ling; Zhao,
M. G.; Zhao, Q.; Zhao, S. J.; Zhao, Y. B.; Zhao, Y. X.; Zhao, Z. G.;
Zhemchugov, A.; Zheng, B.; Zheng, J. P.; Zheng, Y.; Zheng, Y. H.;
Zhong, B.; Zhong, C.; Zhou, L. P.; Zhou, Q.; Zhou, X.; Zhou, X. K.;
Zhou, X. R.; Zhu, A. N.; Zhu, J.; Zhu, K.; Zhu, K. J.; Zhu, S. H.;
Zhu, T. J.; Zhu, W. J.; Zhu, W. J.; Zhu, Y. C.; Zhu, Z. A.; Zou,
B. S.; Zou, J. H.; ( Besiii Collaboration )
Bibcode: 2021ChPhC..45b3002A
Altcode:
Using a dedicated data sample taken in 2018 on the J/ψ peak, we
perform a detailed study of the trigger efficiencies of the BESIII
detector. The efficiencies are determined from three representative
physics processes, namely Bhabha scattering, dimuon production
and generic hadronic events with charged particles. The combined
efficiency of all active triggers approaches 100% in most cases, with
uncertainties small enough not to affect most physics analyses. *
Supported in part by National Key Basic Research Program of China
(2015CB856700); National Natural Science Foundation of China (NSFC)
(11625523, 11635010, 11735014, 11822506, 11835012, 11935015,
11935016, 11935018, 11961141012); the Chinese Academy of Sciences
(CAS) Large-Scale Scientific Facility Program; Joint Large-Scale
Scientific Facility Funds of the NSFC and CAS (U1732263, U1832207);
CAS Key Research Program of Frontier Sciences (QYZDJ-SSW-SLH003,
QYZDJ-SSW-SLH040); 100 Talents Program of CAS; INPAC and Shanghai Key
Laboratory for Particle Physics and Cosmology; ERC (758462); German
Research Foundation DFG under Contracts Nos. Collaborative Research
Center CRC 1044, FOR 2359; Istituto Nazionale di Fisica Nucleare,
Italy; Ministry of Development of Turkey (DPT2006K-120470); National
Science and Technology fund; Olle Engkvist Foundation (200-0605); STFC
(United Kingdom); The Knut and Alice Wallenberg Foundation (Sweden)
(2016.0157); The Royal Society, UK (DH140054, DH160214); The Swedish
Research Council; U. S. Department of Energy (DE-FG02-05ER41374,
DE-SC-0012069)
Title: The noncommutative values of quantum observables
Authors: Kong, Otto C. W.; Liu, Wei-Yin
Bibcode: 2021ChJPh..69...70K
Altcode: 2019arXiv190309071K
We discuss the notion about physical quantities as having values
represented by real numbers, and its limiting to describe nature to be
understood in relation to our appreciation that the quantum theory is a
better theory of natural phenomena than its classical analog. Getting
from the algebra of physical observables to their values on a fixed
state is, at least for classical physics, really a homomorphic map from
the algebra into the real number algebra. The limitation of the latter
to represent the values of quantum observables with noncommutating
algebraic relation is obvious. We introduce and discuss the idea of
the noncommutative values of quantum observables and its feasibility,
arguing that at least in terms of the representation of such a value
as an infinite set of complex number, the idea makes reasonable sense
theoretically as well as practically.
Title: Multi-wavelength photometry during the 2018 superoutburst of
the WZ Sge-type dwarf nova EG Cancri
Authors: Kimura, Mariko; Isogai, Keisuke; Kato, Taichi; Kojiguchi,
Naoto; Wakamatsu, Yasuyuki; Ohnishi, Ryuhei; Sugiura, Yuki;
Matsumoto, Hanami; Sumiya, Sho; Ito, Daiki; Nikai, Kengo; Matsumoto,
Katsura; Shugarov, Sergey Yu; Katysheva, Natalia; Itoh, Hiroshi;
Dubovsky, Pavol A.; Kudzej, Igor; Akitaya, Hiroshi; Oide, Kohei;
Kanai, Takahiro; Ishioka, Chihiro; Uzawa, Yoshinori; Oasa, Yumiko;
Vanmunster, Tonny; Oksanen, Arto; Tordai, Tamás; Murata, Katsuhiro
L.; Shiraishi, Kazuki; Adachi, Ryo; Oeda, Motoki; Tachibana, Yutaro;
Kiyota, Seiichiro; Pavlenko, Elena P.; Antonyuk, Kirill; Antonyuk,
Oksana; Pit, Nikolai; Sosnovskij, Aleksei; Babina, Julia; Baklanov,
Alex; Kawabata, Koji S.; Kawabata, Miho; Nakaoka, Tatsuya; Yamanaka,
Masayuki; Kasai, Kiyoshi; Miller, Ian; Brincat, Stephen M.; Liu, Wei;
Sasada, Mahito; Nogami, Daisaku
Bibcode: 2021PASJ...73....1K
Altcode: 2020PASJ..tmp..247K; 2020arXiv200811871K
We report on the multi-wavelength photometry of the 2018 superoutburst
in EG Cnc. We have detected stage A superhumps and long-lasting
late-stage superhumps via the optical photometry and have constrained
the binary mass ratio and its possible range. The median value of
the mass ratio is 0.048 and the upper limit is 0.057, which still
implies that EG Cnc is one of the possible candidates for period
bouncers. This object also showed multiple rebrightenings in this
superoutburst which are the same as those in its previous superoutburst
in 1996-1997, despite the difference in the main superoutburst. This
would represent that the rebrightening type is inherent to each
object and is independent of the initial disk mass at the beginning
of superoutbursts. We also found that B - I and J - Ks
colors were unusually red just before the rebrightening phase and
became bluer during the quiescence between rebrightenings, which would
mean that the low-temperature mass reservoir at the outermost disk
accreted with time after the main superoutburst. Also, the ultraviolet
flux was sensitive to rebrightenings as well as the optical flux,
and the U - B color became redder during the rebrightening phase,
which would indicate that the inner disk became cooler when this object
repeated rebrightenings. Our results thus basically support the idea
that the cool mass reservoir in the outermost disk is responsible
for rebrightenings.
Title: Follow-up observations for IceCube-170922A: Detection of rapid
near-infrared variability and intensive monitoring of TXS 0506+056
Authors: Morokuma, Tomoki; Utsumi, Yousuke; Ohta, Kouji; Yamanaka,
Masayuki; Kawabata, Koji S.; Inoue, Yoshiyuki; Tanaka, Masaomi;
Yoshida, Michitoshi; Itoh, Ryosuke; Sasada, Mahito; Tominaga, Nozomu;
Mori, Hiroki; Kawabata, Miho; Nakaoka, Tatsuya; Chogi, Maiko; Abe,
Taisei; Huang, Ruochen; Kawahara, Naoki; Kimura, Hiroki; Nagashima,
Hiroki; Takagi, Kengo; Yamazaki, Yuina; Liu, Wei; Ohsawa, Ryou;
Sako, Shigeyuki; Murata, Katsuhiro L.; Morihana, Kumiko; Gilligan,
Christina K.; Isogai, Keisuke; Kimura, Mariko; Wakamatsu, Yasuyuki;
Ohnishi, Ryuhei; Takayama, Masaki; Honda, Satoshi; Matsuoka, Yoshiki;
Yamashita, Takuji; Nagataki, Shigehiro; Tanaka, Yasuyuki T.
Bibcode: 2021PASJ...73...25M
Altcode: 2021PASJ..tmp....5M; 2020arXiv201104957M
We present our follow-up observations to search for an
electromagnetic counterpart of the IceCube high-energy neutrino
IceCube-170922A. Monitoring observations of a likely counterpart,
TXS 0506+056, are also described. First, we quickly took optical and
near-infrared images of seven flat-spectrum radio sources within
the IceCube error region right after the neutrino detection and
found a rapid flux decline of TXS 0506+056 in Kanata/HONIR J-band
data. Motivated by this discovery, intensive follow-up observations
of TXS 0506+056 were continuously performed, including our monitoring
imaging observations, spectroscopic observations, and polarimetric
observations in optical and near-infrared wavelengths. TXS 0506+056
showed a large-amplitude (~1.0 mag) variability in a time scale of
several days or longer, although no significant variability was
detected in a time scale of a day or shorter. TXS 0506+056 also
showed a bluer-when-brighter trend in optical and near-infrared
wavelengths. Structure functions of the variabilities were examined
and indicate that TXS 0506+056 is not a special blazar in terms of
optical variability. Polarization measurement results of TXS 0506+056
are also discussed.
Title: Observation of the Crab Nebula with LHAASO-KM2A - a performance
study
Authors: Aharonian, F.; An, Q.; Axikegu; Bai, L. X.; Bai, Y. X.; Bao,
Y. W.; Bastieri, D.; Bi, X. J.; Bi, Y. J.; Cai, H.; Cai, J. T.; Cao,
Z.; Cao, Z.; Chang, J.; Chang, J. F.; Chang, X. C.; Chen, B. M.;
Chen, J.; Chen, L.; Chen, L.; Chen, L.; Chen, M. J.; Chen, M. L.;
Chen, Q. H.; Chen, S. H.; Chen, S. Z.; Chen, T. L.; Chen, X. L.; Chen,
Y.; Cheng, N.; Cheng, Y. D.; Cui, S. W.; Cui, X. H.; Cui, Y. D.; Dai,
B. Z.; Dai, H. L.; Dai, Z. G.; Danzengluobu; Della Volpe, D.; Piazzoli,
B. D'ettorre; Dong, X. J.; Fan, J. H.; Fan, Y. Z.; Fan, Z. X.; Fang,
J.; Fang, K.; Feng, C. F.; Feng, L.; Feng, S. H.; Feng, Y. L.; Gao,
B.; Gao, C. D.; Gao, Q.; Gao, W.; Ge, M. M.; Geng, L. S.; Gong, G. H.;
Gou, Q. B.; Gu, M. H.; Guo, J. G.; Guo, X. L.; Guo, Y. Q.; Guo, Y. Y.;
Han, Y. A.; He, H. H.; He, H. N.; He, J. C.; He, S. L.; He, X. B.;
He, Y.; Heller, M.; Hor, Y. K.; Hou, C.; Hou, X.; Hu, H. B.; Hu,
S.; Hu, S. C.; Hu, X. J.; Huang, D. H.; Huang, Q. L.; Huang, W. H.;
Huang, X. T.; Huang, Z. C.; Ji, F.; Ji, X. L.; Jia, H. Y.; Jiang, K.;
Jiang, Z. J.; Jin, C.; Kuleshov, D.; Levochkin, K.; Li, B. B.; Li,
C.; Li, C.; Li, F.; Li, H. B.; Li, H. C.; Li, H. Y.; Li, J.; Li, K.;
Li, W. L.; Li, X.; Li, X.; Li, X. R.; Li, Y.; Li, Y. Z.; Li, Z.; Li,
Z.; Liang, E. W.; Liang, Y. F.; Lin, S. J.; Liu, B.; Liu, C.; Liu, D.;
Liu, H.; Liu, H. D.; Liu, J.; Liu, J. L.; Liu, J. S.; Liu, J. Y.; Liu,
M. Y.; Liu, R. Y.; Liu, S. M.; Liu, W.; Liu, Y. N.; Liu, Z. X.; Long,
W. J.; Lu, R.; Lv, H. K.; Ma, B. Q.; Ma, L. L.; Ma, X. H.; Mao, J. R.;
Masood, A.; Mitthumsiri, W.; Montaruli, T.; Nan, Y. C.; Pang, B. Y.;
Pattarakijwanich, P.; Pei, Z. Y.; Qi, M. Y.; Ruffolo, D.; Rulev, V.;
Sáiz, A.; Shao, L.; Shchegolev, O.; Sheng, X. D.; Shi, J. R.; Song,
H. C.; Stenkin, Yu. V.; Stepanov, V.; Sun, Q. N.; Sun, X. N.; Sun,
Z. B.; Tam, P. H. T.; Tang, Z. B.; Tian, W. W.; Wang, B. D.; Wang,
C.; Wang, H.; Wang, H. G.; Wang, J. C.; Wang, J. S.; Wang, L. P.;
Wang, L. Y.; Wang, R. N.; Wang, W.; Wang, W.; Wang, X. G.; Wang,
X. J.; Wang, X. Y.; Wang, Y. D.; Wang, Y. J.; Wang, Y. P.; Wang,
Z.; Wang, Z.; Wang, Z. H.; Wang, Z. X.; Wei, D. M.; Wei, J. J.;
Wei, Y. J.; Wen, T.; Wu, C. Y.; Wu, H. R.; Wu, S.; Wu, W. X.; Wu,
X. F.; Xi, S. Q.; Xia, J.; Xia, J. J.; Xiang, G. M.; Xiao, G.; Xiao,
H. B.; Xin, G. G.; Xin, Y. L.; Xing, Y.; Xu, D. L.; Xu, R. X.; Xue,
L.; Yan, D. H.; Yang, C. W.; Yang, F. F.; Yang, J. Y.; Yang, L. L.;
Yang, M. J.; Yang, R. Z.; Yang, S. B.; Yao, Y. H.; Yao, Z. G.; Ye,
Y. M.; Yin, L. Q.; Yin, N.; You, X. H.; You, Z. Y.; Yu, Y. H.; Yuan,
Q.; Zeng, H. D.; Zeng, T. X.; Zeng, W.; Zeng, Z. K.; Zha, M.; Zhai,
X. X.; Zhang, B. B.; Zhang, H. M.; Zhang, H. Y.; Zhang, J. L.; Zhang,
J. W.; Zhang, L.; Zhang, L.; Zhang, L. X.; Zhang, P. F.; Zhang, P. P.;
Zhang, R.; Zhang, S. R.; Zhang, S. S.; Zhang, X.; Zhang, X. P.; Zhang,
Y.; Zhang, Y.; Zhang, Y. F.; Zhang, Y. L.; Zhao, B.; Zhao, J.; Zhao,
L.; Zhao, L. Z.; Zhao, S. P.; Zheng, F.; Zheng, Y.; Zhou, B.; Zhou,
H.; Zhou, J. N.; Zhou, P.; Zhou, R.; Zhou, X. X.; Zhu, C. G.; Zhu,
F. R.; Zhu, H.; Zhu, K. J.; Zuo, X.; (Lhaaso Collaboration)
Bibcode: 2021ChPhC..45b5002A
Altcode: 2020arXiv201006205A
A sub-array of the Large High Altitude Air Shower Observatory (LHAASO),
KM2A is mainly designed to observe a large fraction of the northern
sky to hunt for γ-ray sources at energies above 10 TeV. Even though
the detector construction is still underway, half of the KM2A array has
been operating stably since the end of 2019. In this paper, we present
the KM2A data analysis pipeline and the first observation of the Crab
Nebula, a standard candle in very high energy γ-ray astronomy. We
detect γ-ray signals from the Crab Nebula in both energy ranges of 10
$ - $ 100 TeV and $ \gt $ 100 TeV with high significance, by analyzing
the KM2A data of 136 live days between December 2019 and May 2020. With
the observations, we test the detector performance, including angular
resolution, pointing accuracy and cosmic-ray background rejection
power. The energy spectrum of the Crab Nebula in the energy range 10-250
TeV fits well with a single power-law function dN/dE = (1.13 $ \pm $
0.05 $ _{\rm stat} $ $ \pm $ 0.08 $ _{\rm sys} $ ) $ \times $ 10 $
^{-14} $ $ \cdot $ (E/20 TeV) $ ^{-3.09\pm0.06_{\rm stat}\pm0.02_{\rm
sys}} $ cm $ ^{-2} $ s $ ^{-1} $ TeV $ ^{-1} $ . It is consistent with
previous measurements by other experiments. This opens a new window of
γ-ray astronomy above 0.1 PeV through which new ultrahigh-energy γ-ray
phenomena, such as cosmic PeVatrons, might be discovered. * Supported
in China by National Key R&D program of China under the grants
(2018YFA0404201, 2018YFA0404202, 2018YFA0404203), by NSFC (12022502,
11905227, 11635011, 11761141001, U1931112, 11775131, U1931201, 11905043,
U1931108), by NSFSPC (ZR2019MA014), and in Thailand by RTA6280002 from
Thailand Science Research and Innovation
Title: Looking for the Detail and Context Devils: High-Resolution
Salient Object Detection
Authors: Zhang, Pingping; Liu, Wei; Zeng, Yi; Lei, Yinjie; Lu, Huchuan
Bibcode: 2021ITIP...30.3204Z
Altcode:
No abstract at ADS
Title: Exploration of Low-Energy Earth-Moon Transfer Orbit Based on
Crossing Orbit of Double Three-Body System
Authors: Zhang, Juan; Liu, Wei; Cao, Xiaofei
Bibcode: 2021JPhCS1739a2051Z
Altcode:
The design of low energy lunar transfer orbit and orbit optimization
method based on crossing orbit is studied in this paper. The four-body
problem of Sun-Earth-Moon-satellite is decoupled into two three-body
problems of Sun-Earth-satellite and Earth-Moon-satellite. Low-energy
lunar exploration orbit is designed by changing orbit at a certain
intersection field through manifold of two Halo orbit of three-body
system. A serial optimization design method for global initial value
search and local gradient optimization are designed. When a motion
state variable is partially modified, the differential correction
method combined with adaptive regression algorithm is adopted. For
the splicing points of manifolds of different systems, the velocity
vector is modified to make the spacecraft get into the target berthing
track, and to obtain the splicing points that can form crossing track
of the two three-body systems. An example of orbit design is given to
show that the Earth-Moon transfer orbit based on invariant manifold
splicing has the characteristics of energy saving and long-time
consumption, which can be used for the tasks with large loads and low
time requirements. This research provides a method for the design of
low energy lunar transfer orbit. It will benefit the energy consuming,
material design of spacecraft, and so on.
Title: On Cooling Condensation Near Magnetic Null Points and the
Formation of Solar Coronal Rain and Prominences
Authors: Liu, Wei; Titov, Viacheslav; Downs, Cooper; Antolin, Patrick;
Luna, Manuel; Sun, Xudong; Berger, Thomas; Yu, Sijie; Yoffe, Luke
Bibcode: 2021cosp...43E.975L
Altcode:
The Sun's outer atmosphere, the corona, is million-degrees hot and
tenuous. Such hot plasma, under certain conditions, can enigmatically
undergo a radiative cooling instability and condense into material of
100 times cooler in the form of coronal rain or prominences. Where,
when, and how such cooling condensation takes place remain poorly
understood. Answers to these questions are not only important in their
own right, but also bear implications for the fundamental question
of coronal heating and the chromosphere-corona mass cycle. Magnetic
fields in the magnetized corona undoubtedly play a crucial role (e.g.,
by trapping the plasma), but where and how? We report recent imaging
and spectroscopic observations from SDO/AIA/HMI and IRIS that can
shed light on this puzzle. Through a systematic survey, we found that
a large fraction of quiet-Sun condensations preferentially occur at
the dips of coronal loops or funnels. Such dips are located at/near
magnetic topological features, such as null points and quasi-separatrix
layers (QSLs), which are regions characterized by high values of the
squashing factor. We also identified evidence of magnetic reconnection
at such locations, which can produce favorable conditions, e.g., density
enhancement by compression and/or mass trapping in plasmoids, that can
trigger run-away radiative cooling. We present proof-of-concept MHD
simulations that demonstrate the role of reconnection in transporting
cooled mass from overlying, long loops to underlying, short loops where
it slides down as coronal rain. We will discuss the significance and
broader implications of these results beyond the Sun.
Title: Formation of α clusters in dilute neutron-rich matter
Authors: Tanaka, Junki; Yang, Zaihong; Typel, Stefan; Adachi, Satoshi;
Bai, Shiwei; van Beek, Patrik; Beaumel, Didier; Fujikawa, Yuki; Han,
Jiaxing; Heil, Sebastian; Huang, Siwei; Inoue, Azusa; Jiang, Ying;
Knösel, Marco; Kobayashi, Nobuyuki; Kubota, Yuki; Liu, Wei; Lou,
Jianling; Maeda, Yukie; Matsuda, Yohei; Miki, Kenjiro; Nakamura,
Shoken; Ogata, Kazuyuki; Panin, Valerii; Scheit, Heiko; Schindler,
Fabia; Schrock, Philipp; Symochko, Dmytro; Tamii, Atsushi; Uesaka,
Tomohiro; Wagner, Vadim; Yoshida, Kazuki; Zenihiro, Juzo; Aumann,
Thomas
Bibcode: 2021Sci...371..260T
Altcode:
The surface of neutron-rich heavy nuclei, with a neutron skin created by
excess neutrons, provides an important terrestrial model system to study
dilute neutron-rich matter. By using quasi-free α cluster-knockout
reactions, we obtained direct experimental evidence for the formation of
α clusters at the surface of neutron-rich tin isotopes. The observed
monotonous decrease of the reaction cross sections with increasing
mass number, in excellent agreement with the theoretical prediction,
implies a tight interplay between α-cluster formation and the neutron
skin. This result, in turn, calls for a revision of the correlation
between the neutron-skin thickness and the density dependence of
the symmetry energy, which is essential for understanding neutron
stars. Our result also provides a natural explanation for the origin
of α particles in α decay.
Title: Probing the Puzzle of Fermi Long-Duration Gamma-Ray Flares
by Data-driven Global MHD Simulations
Authors: Jin, Meng; Manchester, Ward, IV; Effenberger, Frederic;
Petrosian, Vahe; Nitta, Nariaki; Liu, Wei; Omodei, Nicola; Li, Gang;
Pesce-Rollins, Melissa; Allafort, Alice
Bibcode: 2021cosp...43E.906J
Altcode:
With the increasing number of long-duration gamma-ray solar flares
>100 MeV observed by Fermi/LAT, it poses a puzzle on the particle
acceleration and transport mechanisms. The recent detections of
behind-the-limb (BTL) solar flares (e.g., 2014 September 1 event),
in which the gamma-ray emission region is located away from the
BTL flare site by up to tens of degrees in heliographic longitude,
and on-disk flares with migration of gamma-ray emission centroid
hours past the impulsive phase (e.g., 2012 March 7 event), present
further new challenges on the theoretical models for interpreting the
observations. Since most of the long-duration events are associated
with fast CMEs, it is therefore intriguing to understand the role
of CMEs and CME-driven shocks in these events. To probe this puzzle,
we perform data-driven, global magnetohydrodynamics simulations of the
CMEs associated with the long-duration gamma-ray flares and investigate
the magnetic connectivity and evolution of the CME-driven shock, and
their relationship, in both space and time, with the observed gamma-ray
emission. Specifically, we derive and track the time-varying shock
parameters over the area that is magnetically connected to gamma-ray
emission region. Based on the modeling results, we discuss the causes
and implications of Fermi long-duration gamma-ray events, in the
framework of a potential shift of paradigm on particle acceleration
in solar flares and CMEs.
Title: Potential PeVatron supernova remnant G106.3+2.7 seen in the
highest-energy gamma rays
Authors: Tibet ASγ Collaboration; Amenomori, M.; Bao, Y. W.;
Bi, X. J.; Chen, D.; Chen, T. L.; Chen, W. Y.; Chen, Xu; Chen, Y.;
Cirennima, Cui, S. W.; Danzengluobu, Ding, L. K.; Fang, J. H.; Fang,
K.; Feng, C. F.; Feng, Zhaoyang; Feng, Z. Y.; Gao, Qi; Gou, Q. B.;
Guo, Y. Q.; Guo, Y. Y.; He, H. H.; He, Z. T.; Hibino, K.; Hotta, N.;
Hu, Haibing; Hu, H. B.; Huang, J.; Jia, H. Y.; Jiang, L.; Jin, H. B.;
Kasahara, K.; Katayose, Y.; Kato, C.; Kato, S.; Kawata, K.; Kihara,
W.; Ko, Y.; Kozai, M.; Labaciren, Le, G. M.; Li, A. F.; Li, H. J.; Li,
W. J.; Lin, Y. H.; Liu, B.; Liu, C.; Liu, J. S.; Liu, M. Y.; Liu, W.;
Lou, Y. -Q.; Lu, H.; Meng, X. R.; Munakata, K.; Nakada, H.; Nakamura,
Y.; Nanjo, H.; Nishizawa, M.; Ohnishi, M.; Ohura, T.; Ozawa, S.;
Qian, X. L.; Qu, X. B.; Saito, T.; Sakata, M.; Sako, T. K.; Shao, J.;
Shibata, M.; Shiomi, A.; Sugimoto, H.; Takano, W.; Takita, M.; Tan,
Y. H.; Tateyama, N.; Torii, S.; Tsuchiya, H.; Udo, S.; Wang, H.; Wu,
H. R.; Xue, L.; Yamamoto, Y.; Yang, Z.; Yokoe, Y.; Yuan, A. F.; Zhai,
L. M.; Zhang, H. M.; Zhang, J. L.; Zhang, X.; Zhang, X. Y.; Zhang,
Y.; Zhang, Yi; Zhang, Ying; Zhao, S. P.; Zhaxisangzhu, Zhou, X. X.
Bibcode: 2021NatAs...5..460T
Altcode: 2021NatAs.tmp...41T; 2021arXiv210902898A
Cosmic rays (protons and other atomic nuclei) are believed to gain
energies of petaelectronvolts (PeV) and beyond at astrophysical
particle accelerators called `PeVatrons' inside our Galaxy. Although
a characteristic feature of a PeVatron is expected to be a hard
gamma-ray energy spectrum that extends beyond 100 teraelectronvolts
(TeV) without a cut-off, none of the currently known sources exhibit
such a spectrum owing to the low maximum energy of accelerated cosmic
rays or owing to insufficient detector sensitivity around 100 TeV. Here,
we report the observation of gamma-ray emission from the supernova
remnant G106.3+2.7 (refs. 1,2) above 10 TeV. This work
provides flux data points up to and above 100 TeV and indicates that the
very-high-energy gamma-ray emission above 10 TeV is well correlated with
a molecular cloud3 rather than with the pulsar PSR J2229+6114
(refs. 4-8). Regarding the gamma-ray emission mechanism of
G106.3+2.7, this morphological feature appears to favour a hadronic
origin via the π0 decay caused by accelerated relativistic
protons9 over a leptonic origin via the inverse Compton
scattering by relativistic electrons10,11. Furthermore, we
point out that an X-ray flux upper limit on the synchrotron spectrum
would provide important information to firmly establish the hadronic
scenario as the mechanism of particle acceleration at the source.
Title: Probing the Puzzle of Fermi Long-Duration Gamma-Ray Flares
by Data-driven Global MHD Simulations
Authors: Jin, M.; Petrosian, V.; Liu, W.; Nitta, N.; Omodei, N.;
Effenberger, F.; Li, G.; Pesce-Rollins, M.; Allafort, A.; Manchester,
W.
Bibcode: 2020AGUFMSH008..03J
Altcode:
With the ever growing number of long-duration, >100 MeV gamma-ray
solar flares observed by Fermi/LAT, it poses a puzzle on the underlying
particle acceleration and transport mechanisms. Further challenges
come from (i) recent detection of gamma-rays in behind-the-limb (BTL)
flares (e.g., the 2014 September 1 event), in which the gamma-ray
emission region is located away from the BTL flare site by tens of
degrees in heliographic longitude, and (ii) migration of gamma-ray
emission centroids on the solar disk hours past the impulsive phase
(e.g., the 2012 March 7 event). Most of the long-duration events are
associated with fast CMEs, it is thus necessary to understand the role
of CMEs and CME-driven shocks in these events. To probe this puzzle,
we perform data-driven, global magnetohydrodynamics simulations of CMEs
associated with the long-duration gamma-ray flares. We investigate
the magnetic connectivity and evolution of the CME-driven shocks,
and their relationship, in both space and time, with the observed
gamma-ray emission. Specifically, we derive and track the time-varying
shock parameters over the area that is magnetically connected to the
gamma-ray emission region. Based on the modeling results, we discuss
the causes of Fermi long-duration gamma-ray events. In particular, we
address the possibility of CME shock-accelerated particles traveling
back to the Sun to produce gamma-rays, a scenario that bears potentially
paradigm-shifting implications on particle acceleration and transport
in solar eruptive events including flares and CMEs.
Title: Radial Diffusion of Energetic Protons in the Earth's Inner
Magnetosphere
Authors: Lyu, X.; Tu, W.; Liu, W.
Bibcode: 2020AGUFMSM0330011L
Altcode:
Radial diffusion is one of the main source mechanisms of ring current
ions and it could also contribute to the ring current loss by outward
radial diffusion to the magnetopause. However, the relative contribution
of radial diffusion to the dynamics of ring current ions has not been
well quantified. Our work uses a 1D radial diffusion with charge
exchange loss to simulate the long-term variations of ring current
protons observed by Van Allen Probes to quantitatively study how
much of the dynamics could be explained by radial diffusion. We first
convert the observed proton flux over the period of November 2012 to
September 2013 to phase space densities (PSD) as a function of adiabatic
invariants (μ, K, L*) using TS04 magnetic model. Then the
PSD variation at L*=5.5 is used as our outer boundary condition. Our
model uses empirical formulae of radial diffusion coefficient and
charge exchange lifetime as inputs but including a free parameter
in each formula to account for its uncertainties. The free parameter
values are determined by best fitting the model results to PSD data
at given μ and K values. The simulation results show that our model
generally captures the transport and acceleration of ring current
protons at μ=30,50,80 MeV/G and K=0.11G G1/2RE,
which demonstrates that radial diffusion is the dominant source of
>75 keV protons in the ring current. The observed fast decay of PSD
at lower μ and slow decay at higher μ is also well captured by the
charge exchange loss in the model. However, fast dropouts of PSD are
observed over a wide range of L*. The large-L* dropout at L*>4 is
reproduced by the model with outward radial diffusion to the reduced
outer boundary. But the smaller-L* loss (on the time scale of hours) is
too fast to be explained by charge exchange, which could potentially be
due to other loss mechanisms including EMIC wave scattering and field
line curvature scattering. These loss mechanisms will be included in
our model in the future.
Title: Solar Prominence Bubbles and Associated Plasma Instabilities:
IRIS Observations and MHD Modeling
Authors: Liu, W.; Berger, T. E.; Fan, Y.
Bibcode: 2020AGUFMSH0010014L
Altcode:
Solar prominences are cool and dense plasma in the hot corona. The
so-called prominence bubbles are mysterious, dome-shaped, apparently
void structures residing in the lower portions of prominences. Such
bubbles are associated with various plasma instabilities, such as the
Rayleigh-Taylor (RT) and Kelvin-Helmholtz (KH) instabilities. The
former is manifested in plumes that are often produced at the top
boundary of a bubble and intrude upward into the dense prominence
material. The latter is found to be triggered by shear flows at the
bubble boundaries. We present recent observations of prominence
bubbles by IRIS, focusing on the diagnostic potential of RT and
KH instabilities on the physical conditions of the prominence and
its supporting magnetic field. We search for evidence of magnetic
flux emergence as the origin of prominence bubbles. We also present
preliminary 3D MHD simulations of the interaction of a bipole, as a
hypothetical bubble, emerging into an overlying prominence-carrying
flux-rope system. The simulations can provide further clues to the
origin and nature of prominence bubbles. We discuss their roll in mass
ad magnetic flux transport in the solar atmosphere.
Title: The HinOTORI Telescope and its remote control system
Authors: Liu, Wei; Utsumi, Yousuke; Kawabata, Koji S.; Sasada, Mahito;
Yao, Yongqiang; Zuo, Yingxi; Lou, Zheng; Shi, Shengcai
Bibcode: 2020SPIE11451E..57L
Altcode:
HinOTORI is a China-Japan co-construction 50cm telescope with
three-color (u', RC, and IC) simultaneous imager. The main purpose
aims at identifying gravitational-wave electromagnetic counterpart and
performing follow-up observation from ultraviolet to near-infrared
band. The telescope locates at the Tibet plateau, China, with 5100
meters high altitude. The construction of the telescope has already
finished, and now it is going on commissioning. In this paper we focus
on the system and devices for remote control of multi-devices, including
telescope, mount, dome, three cameras, Power Distribution Units (PDUs),
sky monitor, and so on. We will also present system performance and
site condition based on observations collected during commissioning.
Title: Probing the magnetosphere via observations of electron flux
oscillations associated with broadband ULF waves
Authors: Sarris, T. E.; Li, X.; Temerin, M. A.; Zhao, H.; Khoo, L. Y.;
Turner, D. L.; Liu, W.; Claudepierre, S. G.
Bibcode: 2020AGUFMSM010..01S
Altcode:
Electron flux oscillations are produced in the magnetosphere in
association with broadband Ultra Low Frequency (ULF) waves. These
oscillations are observed in the form of drift-periodic flux
fluctuations, but are not associated with drift echoes following storm-
or substorm-related energetic particle injections. They are observed
in particular during quiet times, and could be used as indicators of
ongoing radial transport processes caused by ULF waves. The amplitudes
of such flux oscillations is dependent on a number of parameters,
such as the local phase space density gradient, the amplitude of ULF
waves and the width of electron energy channels. In particular, the
latter is a critical parameter affecting the observed amplitude of
flux oscillations, with narrower energy channel widths enabling the
observation of higher-amplitude flux oscillations; this potentially
explains why such features were not observed regularly before the
Van Allen Probes era, as previous spacecraft generally had lower
energy resolution. We present simulation and observation results
quantitatively associating the observed flux oscillations with the
electron detector width; we also present associations of the observed
flux oscillations with the local phase space density gradient and
the amplitude of electric and magnetic fluctuations in the ULF range,
both of which are expected to also affect radial transport rates.
Title: Anthropogenic aerosol forcing of the AMOC and the associated
mechanisms in CMIP6 models
Authors: Hassan, T.; Allen, R.; Liu, W.; Randles, C. A.
Bibcode: 2020AGUFMPP0350013H
Altcode:
By regulating the global transport of heat, freshwater and carbon,
the Atlantic Meridional Overturning Circulation (AMOC) serves as
an important component of the climate system. During the late 20th
and early 21st centuries, indirect observations and models suggest a
weakening of the AMOC. Direct AMOC observations also suggest a weakening
during the early 21st century, but with substantial interannual
variability. Long-term weakening of the AMOC has been associated with
increasing greenhouse gases (GHGs), but some modeling studies suggest
the build up of anthropogenic aerosols (AAs) may have offset part of the
GHG-induced weakening. Here, we quantify 1900-2020 AMOC variations and
assess the driving mechanisms in state-of-the-art climate models from
the Coupled Model Intercomparison Project phase 6 (CMIP6). The CMIP6 all
forcing (GHGs, anthropogenic and volcanic aerosols, solar variability,
and land use/land change) multi-model mean shows negligible AMOC
changes up to 1950, followed by robust AMOC strengthening during the
second half of the 20th century (1950-1990), and weakening afterwards
(1990-2020). These multi-decadal AMOC variations are related to changes
in North Atlantic atmospheric circulation, including an altered sea
level pressure gradient, storm track activity, surface winds and heat
fluxes, which drive changes in the subpolar North Atlantic surface
density flux. Similar to previous studies, CMIP6 GHG simulations yield
robust AMOC weakening, particularly during the second half of the 20th
century. Changes in natural forcings, including solar variability and
volcanic aerosols, yield negligible AMOC changes. In contrast, CMIP6 AA
simulations yield robust AMOC strengthening (weakening) in response to
increasing (decreasing) anthropogenic aerosols. Moreover, the CMIP6
all-forcing AMOC variations and atmospheric circulation responses
also occur in the CMIP6 AA simulations, which suggests these are
largely driven by changes in anthropogenic aerosol emissions. Although
aspects of the CMIP6 all-forcing multi-model mean response resembles
observations, notable differences exist. This includes CMIP6 AMOC
strengthening from 1950-1990, when the indirect estimates suggest AMOC
weakening. The CMIP6 multi-model mean also underestimates the observed
increase in North Atlantic Ocean heat content. And although the CMIP6
North Atlantic atmospheric circulation responses-particularly the
overall patterns-are similar to observations, the simulated responses
are weaker than those observed, implying they are only partially
externally forced. The possible causes of these differences include
internal climate variability, observational uncertainties and model
shortcomings-including excessive aerosol forcing. A handful of CMIP6
realizations yield AMOC evolution since 1900 similar to the indirect
observations, implying the inferred AMOC weakening from 1950-1990 (and
even from 1930-1990) may have a significant contribution from internal
(i.e.,~unforced) climate variability. Nonetheless, CMIP6 models yield
robust, externally forced AMOC changes, the bulk of which are due to
anthropogenic aerosols.
Title: Panoramic SETI: on-sky results from prototype telescopes and
instrumental design
Authors: Maire, Jérôme; Wright, Shelley A.; Werthimer, Dan; Antonio,
Franklin P.; Brown, Aaron; Horowitz, Paul; Lee, Ryan; Liu, Wei;
Raffanti, Rick; Wiley, James; Cosens, Maren; Heffner, Carolyn M.;
Howard, Andrew W.; Stone, Remington P. S.; Treffers, Richard R.
Bibcode: 2020SPIE11454E..3CM
Altcode: 2021arXiv211111080M
The Panoramic SETI (Search for Extraterrestrial Intelligence) experiment
(PANOSETI) aims to detect and quantify optical transients from
nanosecond to second precision over a large field-of-view (∼4,450
square-degrees). To meet these challenging timing and wide-field
requirements, the PANOSETI experiment will use two assemblies of ∼45
telescopes to reject spurious signals by coincidence detection, each
one comprising custom-made fast photon-counting hardware combined
with (f/1.32) focusing optics. Preliminary on-sky results from
pairs of PANOSETI prototype telescopes (100 sq.deg.) are presented
in terms of instrument performance and false alarm rates. We found
that a separation of >1 km between telescopes surveying the same
field-of-view significantly reduces the number of false positives due
to nearby sources (e.g., Cherenkov showers) in comparison to a side-
by-side configuration of telescopes. Design considerations on the
all-sky PANOSETI instrument and expected field-of-views are reported.
Title: Mapping diffuse emission in Lyman UV band
Authors: Ji, Li; Lou, Zheng; Zhang, Jinlong; Qiu, Keqiang; Li,
Shuangying; Sun, Wei; Yan, Shuping; Zhang, Shuinai; Qian, Yuan; Wang,
Sen; Werner, Klaus; Fang, Taotao; Wang, Tinggui; Barnstedt, Jürgen;
Buntrock, Sebastian; Cai, Mingsheng; Chen, Wen; Conti, Lauro; Deng,
Lei; Diebold, Sebastian; Fu, Shaojun; Guo, Jianhua; Hanke, Lars; Hong,
Yilin; Kalkuhl, Christoph; Kappelmann, Norbert; Kaufmann, Thomas; Lei,
Shijun; Li, Fu; Li, Xinfeng; Liu, Wei; Meyer, Kevin; Rauch, Thomas;
Ruan, Ping; Schaadt, Daniel M.; Schanz, Thomas; Song, Qian; Stelzer,
Beate; Wang, Zhanshan; Yang, Jianfeng; Zhang, Wei
Bibcode: 2020SPIE11444E..07J
Altcode: 2020arXiv201207384J
The CAFE (Census of warm-hot intergalactic medium, Accretion, and
Feedback Explorer) and LyRIC (Lyman UV Radiation from Interstellar
medium and Circum-galactic medium) have been proposed to the space
agencies in China respectively. CAFE was first proposed as a joint
scientific CAS-ESA small space mission in 2015. LyRIC was proposed as
the independent external payload operating on the Chinese Space Station
(CSS) in 2019. Both missions are dedicated to mapping the Lyman UV
emissions ( ionized oxygen (OVI) resonance lines at 103.2
and 103.8 nm, and Lyman series) for the diffuse sources either in
our Galaxy or the circum-galactic mediums of the nearby galaxies. We
present the primary science objectives, mission concepts, the enabling
technologies, as well as the current status.
Title: Hot Plasma Flows and Oscillations in the Loop-top Region
During the 2017 September 10 X8.2 Solar Flare
Authors: Reeves, Katharine K.; Polito, Vanessa; Chen, Bin; Galan,
Giselle; Yu, Sijie; Liu, Wei; Li, Gang
Bibcode: 2020ApJ...905..165R
Altcode: 2020arXiv201012049R
In this study, we investigate motions in the hot plasma above the
flare loops during the 2017 September 10 X8.2 flare event. We examine
the region to the south of the main flare arcade, where there is data
from the Interface Region Imaging Spectrograph (IRIS) and the Extreme
ultraviolet Imaging Spectrometer (EIS) on Hinode. We find that there are
initial blueshifts of 20-60 km s-1 observed in this region
in the Fe XXI line in IRIS and the Fe XXIV line in EIS, and that the
locations of these blueshifts move southward along the arcade over the
course of about 10 minutes. The cadence of IRIS allows us to follow
the evolution of these flows, and we find that at each location where
there is an initial blueshift in the Fe XXI line, there are damped
oscillations in the Doppler velocity with periods of ∼400 s. We
conclude that these periods are independent of loop length, ruling
out magnetoacoustic standing modes as a possible mechanism. Microwave
observations from the Expanded Owens Valley Solar Array (EOVSA)
indicate that there are nonthermal emissions in the region where the
Doppler shifts are observed, indicating that accelerated particles
are present. We suggest that the flows and oscillations are due to
motions of the magnetic field that are caused by reconnection outflows
disturbing the loop-top region.
Title: Two distinct electron populations in the 2001 April 25 event
Authors: Li, G.; Zhao, L.; Wang, L.; Liu, W.; Wu, X.
Bibcode: 2020AGUFMSH008..05L
Altcode:
We examine the release times of energetic electrons in the 2001 April
25 event. A M2.7 flare occurred in 2001 April 25, from AR09433,
located at N18W09. The flare was observed in X-rays by GOES and
the Yohkoh spacecraft. The Yohkoh observation also included hard
X-ray images for all four energy channels: L, M1, M2, and H. We use
Yohkoh observation times as a proxy for the release time of energetic
electrons that propagated downward, which are responsible for the hard
X-rays. In-situ > ∼ 25 keV electrons were observed by the Wind
spacecraft. For these electrons, we obtain the release time at the Sun
using the recently developed Fractional Velocity Dispersion Analysis
(FVDA) method. We find that the release times of outward propagating
energetic electrons are clearly delayed from those that propagated
downward. Furthermore, these delayed releases are energy dependent. The
implication of this delay on the underlying acceleration and trapping
process of the > ∼ 25 keV electrons at solar flares is discussed.
Title: Panoramic SETI: overall focal plane electronics and timing
and network protocols
Authors: Liu, Wei; Werthimer, Dan; Lee, Ryan; Antonio, Franklin;
Aronson, Michael; Brown, Aaron; Drake, Frank; Howard, Andrew;
Horowitz, Paul; Maire, Jerome; Raffanti, Rick; Stone, Remington;
Treffers, Richard; Wright, Shelley A.
Bibcode: 2020SPIE11447E..7GL
Altcode: 2021arXiv211111476L
The PANOSETI experiment is an all-sky, all-the-time visible search
for nanosecond to millisecond time-scale transients. The experiment
will deploy observatory domes at several sites, each dome containing
~45 telescopes and covering ~4,440 square degrees. Here we describe
the focal-plane electronics for the visible wavelength telescopes,
each of which contains a Mother Board and four Quadrant Boards. On each
quadrant board, 256 silicon photomultiplier (SiPM) photon detectors are
arranged to measure pulse heights to search for nanosecond time-scale
pulses. To simultaneously examine pulse widths over a large range of
time scales (nanoseconds to milliseconds), the instrument implements
both a Continuous Imaging Mode (CI-Mode) and a Pulse Height Mode
(PH-Mode). Precise timing is implemented in the gateware with the
White Rabbit protocol.
Title: Contribution of High-energy GRB Emissions to the Spectrum of
the Isotropic Diffuse γ-Ray Background
Authors: Yao, Yu-Hua; Chang, Xiao-Chuan; Hu, Hong-Bo; Pan, Yi-Bin;
Zhang, Hai-Ming; Li, Hua-Yang; Qiao, Bing-Qiang; Kang, Ming-Ming;
Yang, Chao-Wen; Liu, Wei; Guo, Yi-Qing
Bibcode: 2020ApJ...901..106Y
Altcode:
High-precision measurement of the isotropic diffuse γ-ray background
(IGRB) has been extrapolated to the TeV energy region using the
Fermi-LAT experiment. Various kinds of astrophysical sources are
candidates for its origin. However, a consensus on the dominant source
has been difficult to reach. Recent observations of the γ-ray emission
of γ-ray bursts (GRBs), denoted as the synchrotron self-Compton
(SSC) component in the afterglow phase, in the sub-TeV energy region
by MAGIC and HESS experiments shed new light on this topic. In this
work, we revisit the contribution from the SSC component of GRBs to
the IGRB. First, a sample set of GRB events is obtained and examined
using observations from Fermi-LAT. Second, the SSC component,
described by the energy ratio Rext and spectral index
βext, is assigned to every GRB event. We can obtain the
total spectrum contribution based on this GRB sample. We find that
when Rext and βext reach ∼20% and -1.6,
respectively, the contribution from GRB emission dominates in the
energy region of hundreds of GeV. We hope that the LHAASO and CTA
experiments under construction can observe a large number of GRBs to
fix those parameters in coming years. A surviving tail is expected,
which can serve to check our calculations based on future satellite
experiments such as HERD and GAMMA400.
Title: Identification of Two Distinct Electron Populations in an
Impulsive Solar Energetic Electron Event
Authors: Li, G.; Zhao, L.; Wang, L.; Liu, W.; Wu, X.
Bibcode: 2020ApJ...900L..16L
Altcode:
We examine the release times of energetic electrons in the 2001 April
25 event. An M2.7 flare occurred on 2001 April 25, from AR 09433,
located at N18W09. The flare was observed in X-rays by GOES and the
Yohkoh spacecraft. The Yohkoh observation also included hard X-ray (HXR)
images for all four energy channels: L, M1, M2, and H. We use Yohkoh
observation times as a proxy for the release time of energetic electrons
that propagated downward, which are responsible for the HXRs. In situ
>∼25 keV electrons were observed by the Wind spacecraft. For
these electrons, we obtain the release time at the Sun using the
recently developed Fractional Velocity Dispersion Analysis method. We
find that the release times of outward-propagating energetic electrons
are clearly delayed from those that propagated downward. Furthermore,
these delayed releases are energy dependent. The implication of this
delay on the underlying acceleration and trapping process of the
>∼25 keV electrons at solar flares is discussed.
Title: Major Scientific Challenges and Opportunities in Understanding
Magnetic Reconnection and Related Explosive Phenomena in Solar and
Heliospheric Plasmas
Authors: Ji, H.; Karpen, J.; Alt, A.; Antiochos, S.; Baalrud, S.;
Bale, S.; Bellan, P. M.; Begelman, M.; Beresnyak, A.; Bhattacharjee,
A.; Blackman, E. G.; Brennan, D.; Brown, M.; Buechner, J.; Burch, J.;
Cassak, P.; Chen, B.; Chen, L. -J.; Chen, Y.; Chien, A.; Comisso,
L.; Craig, D.; Dahlin, J.; Daughton, W.; DeLuca, E.; Dong, C. F.;
Dorfman, S.; Drake, J.; Ebrahimi, F.; Egedal, J.; Ergun, R.; Eyink,
G.; Fan, Y.; Fiksel, G.; Forest, C.; Fox, W.; Froula, D.; Fujimoto,
K.; Gao, L.; Genestreti, K.; Gibson, S.; Goldstein, M.; Guo, F.; Hare,
J.; Hesse, M.; Hoshino, M.; Hu, Q.; Huang, Y. -M.; Jara-Almonte, J.;
Karimabadi, H.; Klimchuk, J.; Kunz, M.; Kusano, K.; Lazarian, A.; Le,
A.; Lebedev, S.; Li, H.; Li, X.; Lin, Y.; Linton, M.; Liu, Y. -H.;
Liu, W.; Longcope, D.; Loureiro, N.; Lu, Q. -M.; Ma, Z-W.; Matthaeus,
W. H.; Meyerhofer, D.; Mozer, F.; Munsat, T.; Murphy, N. A.; Nilson,
P.; Ono, Y.; Opher, M.; Park, H.; Parker, S.; Petropoulou, M.; Phan,
T.; Prager, S.; Rempel, M.; Ren, C.; Ren, Y.; Rosner, R.; Roytershteyn,
V.; Sarff, J.; Savcheva, A.; Schaffner, D.; Schoeffier, K.; Scime, E.;
Shay, M.; Sironi, L.; Sitnov, M.; Stanier, A.; Swisdak, M.; TenBarge,
J.; Tharp, T.; Uzdensky, D.; Vaivads, A.; Velli, M.; Vishniac, E.;
Wang, H.; Werner, G.; Xiao, C.; Yamada, M.; Yokoyama, T.; Yoo, J.;
Zenitani, S.; Zweibel, E.
Bibcode: 2020arXiv200908779J
Altcode:
Magnetic reconnection underlies many explosive phenomena in the
heliosphere and in laboratory plasmas. The new research capabilities in
theory/simulations, observations, and laboratory experiments provide the
opportunity to solve the grand scientific challenges summarized in this
whitepaper. Success will require enhanced and sustained investments
from relevant funding agencies, increased interagency/international
partnerships, and close collaborations of the solar, heliospheric,
and laboratory plasma communities. These investments will deliver
transformative progress in understanding magnetic reconnection and
related explosive phenomena including space weather events.
Title: VizieR Online Data Catalog: Galactic interstellar ratio
18O/17O. I.
Authors: Zhang, J. S.; Liu, W.; Yan, Y. T.; Yu, H. Z.; Liu, J. T.;
Zheng, Y. H.; Romano, D.; Zhang, Z. -Y.; Wang, J. Z.; Chen, J. L.;
Wang, Y. X.; Zhang, W. J.; Lu, H. H.; Chen, L. S.; Zou, Y. P.; Yang,
H. Q.; Wen, T.; Lu, F. S.
Bibcode: 2020yCat..22490006Z
Altcode:
The C18O and C17O J=1-0 lines were observed
from July 1, with the Institut de Radio Astronomie Millimetrique
(IRAM) 30m single dish telescope, at the Pico Veleta Observatory
(Granada, Spain). The center frequencies were set at 109.782182 and
112.359277GHz for the C18O and C17O, respectively,
with a corresponding beam size of ~23". With the IRAM 30m we observed
50 sources of our sample. The parameters of their observations are
summarized in Table 1. Other observations of the J=1-0 lines of
C18O and C17O were also carried out using the
Arizona Radio Observatory (ARO) 12m telescope on Kitt Peak, Tuscon,
AZ, USA, with a corresponding beam size of ~64". Observations were
performed remotely from Guangzhou University, China, in 2016 November
and December, 2017 January, November, and December, and 2018 May and
December. Table 1 presents the parameters of the observational
results of ARO for the sample of 260 sources, including 24 sources
observed by both IRAM 30m and ARO 12m telescopes. (3 data files).
Title: Galactic Interstellar Sulfur Isotopes: A Radial
32S/34S Gradient?
Authors: Yu, H. Z.; Zhang, J. S.; Henkel, C.; Yan, Y. T.; Liu, W.;
Tang, X. D.; Langer, N.; Luan, T. C.; Chen, J. L.; Wang, Y. X.; Deng,
G. G.; Zou, Y. P.
Bibcode: 2020ApJ...899..145Y
Altcode: 2020arXiv200804916Y
We present observations of 12C32S,
12C34S, 13C32S,
and 12C33S J = 2-1 lines toward a large
sample of massive star-forming regions by using the Arizona
Radio Observatory 12 m telescope and the IRAM 30 m. Taking new
measurements of the carbon 12C/13C ratio, the
32S/34S isotope ratio was determined from the
integrated 13C32S/12C34S
line intensity ratios for our sample. Our analysis shows a
32S/34S gradient from the inner Galaxy out to
a galactocentric distance of 12 kpc. An unweighted least-squares
fit to our data yields 32S/34S = (1.56 ±
0.17)DGC + (6.75 ± 1.22) with a correlation coefficient
of 0.77. Errors represent 1σ standard deviations. Testing this
result by (a) excluding the Galactic center region, (b) excluding all
sources with C34S opacities >0.25, (c) combining our
data and old data from previous study, and (d) using different sets
of carbon isotope ratios leads to the conclusion that the observed
32S/34S gradient is not an artifact but persists
irrespective of the choice of sample and carbon isotope data. A gradient
with rising 32S/34S values as a function of
galactocentric radius implies that the solar system ratio should be
larger than that of the local interstellar medium. With the new carbon
isotope ratios, we indeed obtain a local 32S/34S
isotope ratio about 10% below the solar system one, as expected in the
case of decreasing 32S/34S ratios with time and
increased amounts of stellar processing. However, taking older carbon
isotope ratios based on a lesser amount of data, such a decrease is
not seen. No systematic variation of 34S/33S
ratios along galactocentric distance was found. The average value is
5.9 ± 1.5, the error denoting the standard deviation of an individual
measurement.
Title: Electron and positron spectra in three-dimensional
spatial-dependent propagation model
Authors: Tian, Zhen; Liu, Wei; Yang, Bo; Fu, Xue-Dong; Xu, Hai-Bo;
Yao, Yu-Hua; Guo, Yi-Qing
Bibcode: 2020ChPhC..44h5102T
Altcode: 2019arXiv190410663T
The spatial-dependent propagation (SDP) model has been demonstrated
to account for the spectral hardening of both primary and secondary
Cosmic Rays (CRs) nuclei above about 200 GV. In this work, we further
apply this model to the latest AMS-02 observations of electrons and
positrons. To investigate the effect of different propagation models,
both homogeneous diffusion and SDP are compared. In contrast to the
homogeneous diffusion, SDP brings about harder spectra of background
CRs and thus enhances background electron and positron fluxes
above tens of GeV. Thereby, the SDP model could better reproduce
both electron and positron energy spectra when introducing a local
pulsar. The influence of the background source distribution is also
investigated, where both axisymmetric and spiral distributions are
compared. We find that considering the spiral distribution leads to
a larger contribution of positrons for energies above multi-GeV than
the axisymmetric distribution. In the SDP model, when including a
spiral distribution of sources, the all-electron spectrum above TeV
energies is thus naturally described. In the meantime, the estimated
anisotropies in the all-electrons spectrum show that in contrary to the
homogeneous diffusion model, the anisotropy under SDP is well below
the observational limits set by the Fermi-LAT experiment, even when
considering a local source. * Supported by the National Key Research
and Development Program of China (2016YFA0400200), the National Natural
Science Foundation of China (11875264, 11635011, 11761141001, 11663006)
Title: Indirect measurement of the 57.7 keV resonance strength
for the astrophysical γ -ray source of the 25Mg(p ,γ
)26Al reaction
Authors: Li, Y. J.; Li, Z. H.; Li, E. T.; Li, X. Y.; Ma, T. L.; Shen,
Y. P.; Liu, J. C.; Gan, L.; Su, Y.; Qiao, L. H.; Han, Z. Y.; Zhou,
Y.; Su, J.; Yan, S. Q.; Zeng, S.; Wang, Y. B.; Guo, B.; Lian, G.;
Nan, D.; Bai, X. X.; Liu, W. P.
Bibcode: 2020PhRvC.102b5804L
Altcode:
25Mg(p ,γ )26Al is the most important reaction
in the Mg-Al cycle in the hydrogen burning regions of stars. Its
cross sections at stellar energies are essential to understand
the issues of radioactive 26Al in the galaxy and
meteorites. The 57.7 keV resonance dominate the 25Mg(p
,γ )26Al astrophysical reaction rates at relative
low temperature, but it is very difficult to measure its resonance
strength directly, and the indirect measurement results deviate by a
factor of about 2 by far. In this work, the angular distributions of
25Mg(7Li,6He)26Al leading
to 6.364 MeV and eleven low-lying states in 26Al have
been measured by the Q3D magnetic spectrometer of the HI-13 tandem
accelerator. The spectroscopic factors were derived and used to deduce
the proton width and 57.7 keV resonance strength. The astrophysical
25Mg(p ,γ )26Al reaction rates at stellar
energies have been updated by using the present result.
Title: Method for retrieval of atmospheric water vapor using OH
airglow for correction of astronomical observations
Authors: Xu, J. Y.; Liu, W. J.; Bian, J. C.; Liu, X.; Yuan, W.;
Wang, C.
Bibcode: 2020A&A...639A..29X
Altcode:
Context. Water vapor in the atmosphere undergoes quick spatial
and temporal variations. This has a serious impact on ground-based
astronomical observations from the visible band to the infrared band
resulting from water vapor attenuation and emission.
Aims: We
seek to show how the sky spectrum of an astronomical observation can be
used to determine the amount of precipitable water vapor (PWV) along the
line of sight toward the science target.
Methods: In this work,
we discuss a method to retrieve the PWV from the OH(8-3) band airglow
spectrum. We analyzed the influences of the pressure and temperature
of the atmosphere and the different water vapor vertical distributions
on the PWV retrieval method in detail. Meanwhile, the accuracy of
the method was analyzed via Monte Carlo simulations. To further
verify the method of PWV retrieval, we carried out cross comparisons
between the PWV retrieved from OH airglow and PWV from the standard
star spectra of UVES using equivalent widths of telluric absorption
lines observed from 2000 to 2016 at Cerro Paranal in Chile.
Results: The Monte Carlo tests and the comparison between the two
different methods prove the availability the PWV retrieval method
from OH airglow. These results show that using OH airglow spectra
in astronomical observations, PWVs along the same line of sight as
the astronomical observations can be retrieved in real time.
Conclusions: We provide a quick and economical method for retrieving the
water vapor along the same line of sight of astronomical observation
in the real time. This is especially helpful to correcting the effect
of water vapor on astronomical observations.
Title: Studies of drag-free control methods for
space-basedgravitational-wave detection
Authors: GAO, Yang; LIU, Wei
Bibcode: 2020SSPMA..50g9503G
Altcode:
No abstract at ADS
Title: Astrophysical 22Mg(p, γ)23Al
reaction rates from asymptotic normalization coefficient of
23Ne→22Ne+n
Authors: Li, Xin-Yue; Guo, Bing; Li, Zhi-Hong; Liu, Wei-Ping
Bibcode: 2020ChPhC..44g4001L
Altcode:
The radionuclide 22Na generates the emission of a
characteristic 1.275 MeV $\gamma$?--> -ray. This is a potential
astronomical observable, whose occurrence is suspected in classical
novae. The $^{22}{{\rm{Mg}}}(p,\,\gamma)^{23}{{\rm{Al}}}$?-->
reaction is relevant to the nucleosynthesis of 22Na in
Ne-rich novae. In this study, employing the adiabatic distorted wave
approximation and continuum discretized coupled channel methods,
the squared neutron asymptotic normalization coefficients
(ANCs) for the virtual decay of $^{23}{{\rm{Ne}}}$?-->
$\to$?--> $^{22}{{\rm{Ne}}}$?--> + n were extracted,
and determined as $(0.483\pm0.060)$?--> fm-1 and
$(9.7\pm2.3)$?--> fm-1 for the ground state and the
first excited state from the experimental angular distributions
of ${}^{22}{{\rm{Ne}}}(d,\,p){}^{23}{{\rm{Ne}}}$?-->
populating the ground state and the first excited state of
$^{23}{{\rm{Ne}}}$?--> , respectively. Then, the squared proton
ANC of ${}^{23}{{\rm{Al}}}_{\rm{g.s.}}$?--> was obtained as
$C_{d5/2}^{2}({}^{23}{{\rm{Al}}})=(2.65\pm0.33)\times10^{3}$?-->
fm-1 according to the charge symmetry of
the strong interaction. The astrophysical S-factors and
reaction rates for the direct capture contribution in
${}^{22}{{\rm{Mg}}}(p,\,\gamma){}^{23}{{\rm{Al}}}$?-->
were also presented. Furthermore, the proton width of the
first excited state of $^{23}{{\rm{Al}}}$?--> was derived
to be $(57\pm14)$?--> eV from the neutron ANC of its mirror
state in $^{23}{{\rm{Ne}}}$?--> and used to compute the
contribution from the first resonance of $^{23}{{\rm{Al}}}$?-->
. This result demonstrates that the direct capture dominates the
$^{22}{{\rm{Mg}}}(p,\,\gamma)^{23}{{\rm{Al}}}$?--> reaction at
most temperatures of astrophysical relevance for $0.33 \lt T_9
\lt 0.64$?--> . * Supported by the National Key Research and
Development Program of China (2016YFA0400502), the National Natural
Science Foundation of China (11975316, 11490561, 11535004, 11775013),
the Continuous Basic Scientific Research Project (WDJC-2019-13) and
the 973 Program (2013CB834406)
Title: A Systematic Observational Study on Galactic Interstellar Ratio
18O/17O. I. C18O and C17O
J = 1-0 Data Analysis
Authors: Zhang, J. S.; Liu, W.; Yan, Y. T.; Yu, H. Z.; Liu, J. T.;
Zheng, Y. H.; Romano, D.; Zhang, Z. -Y.; Wang, J. Z.; Chen, J. L.;
Wang, Y. X.; Zhang, W. J.; Lu, H. H.; Chen, L. S.; Zou, Y. P.; Yang,
H. Q.; Wen, T.; Lu, F. S.
Bibcode: 2020ApJS..249....6Z
Altcode: 2020arXiv200700361Z
The interstellar oxygen isotopic ratio of 18O/17O
can reflect the relative amount of the secular enrichment by ejecta
from high-mass versus intermediate-mass stars. Previous observations
found a Galactic gradient of 18O/17O,
i.e., low ratios in the Galactic center and large values in the
Galactic disk, which supports the inside-out formation scenario of
our Galaxy. However, there are not many observed objects and, in
particular, there are not many at large galactocentric distances. For
this reason, we started a systematic study on Galactic interstellar
18O/17O, through observations of C18O
and C17O multi-transition lines toward a large sample of
286 sources (at least one order of magnitude larger than previous
ones), from the Galactic center region to the far outer Galaxy (∼22
kpc). In this article, we present our observations of J = 1-0 lines
of C18O and C17O, with the 12 m antenna of
the Arizona Radio Observatory (ARO 12 m) and the Institut de Radio
Astronomie Millimétrique (IRAM) 30 m telescopes. Among our IRAM 30 m
sample of 50 targets, we detected successfully both C18O
and C17O 1-0 lines for 34 sources. Similarly, our sample
of 260 targets for ARO 12 m observations resulted in the detection of
both lines for 166 sources. The C18O optical depth effect
on our ratio results, evaluated by fitting results of C17O
spectra with hyperfine components (assuming ${\tau }_{C18O}=4{\tau
}_{C17O}$ ) and our radiative transfer and excitation model nonlocal
thermodynamic equilibrium (non-LTE) model calculation for the strongest
source, was found to be insignificant. Beam dilution does not seem to
be a problem either, which was supported by the fact that there is no
systematic variation between the isotopic ratio and the heliocentric
distance, and ratios are consistently measured from two telescopes
for most of those detected sources. With this study we obtained
18O/17O isotopic ratios for a large sample of
molecular clouds with different galactocentric distances. Our results,
though there are still very few detections made for sources in the outer
Galaxy, confirm the apparent 18O/17O gradient
of 18O/17O=(0.10 ± 0.03)RGC+(2.95 ±
0.30), with a Pearson's rank correlation coefficient of R = 0.69. This
is supported by the newest Galactic chemical evolution model including
the impact of massive stellar rotators and novae. Our future J =
2-1 and J = 3-2 observations of C18O and C17O
toward the same sample would be important to determine their physical
parameters (opacities, abundances, etc.) and further accurately
determine the Galactic radial gradient of the isotopic ratio
18O/17O.
Title: Space target extraction and detection for wide-field
surveillance
Authors: Liu, D.; Wang, X.; Xu, Z.; Li, Y.; Liu, W.
Bibcode: 2020A&C....3200408L
Altcode:
A wide-field surveillance system with a long exposure time has a
stronger capability of space target detection. However, it also produces
some complicated situations that make it difficult to detect space
targets; some stars appear as streak-like sources, countless object
points, and possible discontinuous or nonlinear target trajectories. We
present a space target detection method with high detection probability
and low computational cost to overcome these obstacles. Firstly, the
improved adaptive threshold method and the omnidirectional morphological
filtering method are implemented to remove stars and noise. Secondly,
the relative inter frame motion distance can be used as the basis for
predicting the valid state transition region in each image. Finally,
a state transition multistage hypothesis testing method is proposed
to detect targets with linear, nonlinear, continuous or discontinuous
trajectories. As demonstrated by the experimental results in simulated
image sequences and real image sequences, the proposed algorithm can
effectively detect space targets in wide-field surveillance with
long exposure time, and has a high detection probability and low
computational cost.
Title: An Empirical Power Density-Based Friction Law and Its
Implications for Coherent Landslide Mobility
Authors: Deng, Yu; Yan, Shuaixing; Scaringi, Gianvito; Liu, Wei;
He, Siming
Bibcode: 2020GeoRL..4787581D
Altcode:
The evolution of the shear resistance at the base of a
coherent landslide body can effectively control its dynamic
behavior. High-velocity rotary shear experiments have allowed
scientists to explore stress-strain conditions close to those found
in large landslides and faults. These experiments have led to two
alternative models being proposed, which describe the evolution
of the shear resistance through friction laws that depend either on
normal stress or on velocity. Here, we discuss an integrated approach,
first proposed to study seismic fault behavior, that reconciles these
two models under a single parameter—the power density—which we
utilize for the first time to investigate landslide dynamics. Using
thermodynamic and process-based considerations, different soil and
rock types can be related to different weakening mechanisms, which in
turn can determine different landslide behaviors.
Title: Entanglement-based secure quantum cryptography over 1,120
kilometres
Authors: Yin, Juan; Li, Yu-Huai; Liao, Sheng-Kai; Yang, Meng; Cao,
Yuan; Zhang, Liang; Ren, Ji-Gang; Cai, Wen-Qi; Liu, Wei-Yue; Li,
Shuang-Lin; Shu, Rong; Huang, Yong-Mei; Deng, Lei; Li, Li; Zhang,
Qiang; Liu, Nai-Le; Chen, Yu-Ao; Lu, Chao-Yang; Wang, Xiang-Bin; Xu,
Feihu; Wang, Jian-Yu; Peng, Cheng-Zhi; Ekert, Artur K.; Pan, Jian-Wei
Bibcode: 2020Natur.582..501Y
Altcode:
Quantum key distribution (QKD)1-3 is a theoretically
secure way of sharing secret keys between remote users. It has been
demonstrated in a laboratory over a coiled optical fibre up to 404
kilometres long4-7. In the field, point-to-point QKD has been
achieved from a satellite to a ground station up to 1,200 kilometres
away8-10. However, real-world QKD-based cryptography targets
physically separated users on the Earth, for which the maximum distance
has been about 100 kilometres11,12. The use of trusted
relays can extend these distances from across a typical metropolitan
area13-16 to intercity17 and even intercontinental
distances18. However, relays pose security risks, which
can be avoided by using entanglement-based QKD, which has inherent
source-independent security19,20. Long-distance entanglement
distribution can be realized using quantum repeaters21,
but the related technology is still immature for practical
implementations22. The obvious alternative for extending
the range of quantum communication without compromising its security
is satellite-based QKD, but so far satellite-based entanglement
distribution has not been efficient23 enough to support
QKD. Here we demonstrate entanglement-based QKD between two ground
stations separated by 1,120 kilometres at a finite secret-key rate of
0.12 bits per second, without the need for trusted relays. Entangled
photon pairs were distributed via two bidirectional downlinks from
the Micius satellite to two ground observatories in Delingha and
Nanshan in China. The development of a high-efficiency telescope and
follow-up optics crucially improved the link efficiency. The generated
keys are secure for realistic devices, because our ground receivers
were carefully designed to guarantee fair sampling and immunity to all
known side channels24,25. Our method not only increases the
secure distance on the ground tenfold but also increases the practical
security of QKD to an unprecedented level.
Title: Prospects for a multi-TeV gamma-ray sky survey with the LHAASO
water Cherenkov detector array
Authors: Aharonian, F.; Alekseenko, V.; An, Q.; Axikegu; Bai, L. X.;
Bao, Y. W.; Bastieri, D.; Bi, X. J.; Cai, H.; Cao, Zhe; Cao, Zhen;
Chang, J.; Chang, J. F.; Chang, X. C.; Chao, S. P.; Chen, B. M.;
Chen, J.; Chen, L.; Chen, L.; Chen, M. L.; Chen, M. J.; Chen, Q. H.;
Chen, S. H.; Chen, S. Z.; Chen, T. L.; Chen, X. L.; Chen, Y.; Cheng,
N.; Cheng, Y. D.; Cui, S. W.; Cui, X. H.; Cui, Y. D.; Dai, B. Z.;
Dai, H. L.; Dai, Z. G.; Danzengluobu; D'Ettorre Piazzoli, B.; Fang,
J.; Fan, J. H.; Fan, Y. Z.; Feng, C. F.; Feng, L.; Feng, S. H.; Feng,
Y. L.; Gao, B.; Gao, Q.; Gao, W.; Ge, M. M.; Geng, L. S.; Gong, G. H.;
Gou, Q. B.; Gu, M. H.; Guo, Y. Q.; Guo, Y. Y.; Han, Y. A.; He, H. H.;
He, J. C.; Heller, M.; He, S. L.; He, Y.; Hou, C.; Huang, D. H.;
Huang, Q. L.; Huang, W. H.; Huang, X. T.; Hu, H. B.; Hu, S.; Jia,
H. Y.; Jiang, K.; Ji, F.; Jin, C.; Ji, X. L.; Levochkin, K.; Liang,
E. W.; Liang, Y. F.; Li, Cheng; Li, Cong; Li, F.; Li, H.; Li, H. B.;
Li, H. C.; Li, H. M.; Li, J.; Li, K.; Li, W. L.; Li, X.; Li, X. R.;
Li, Y.; Li, Z.; Li, Z.; Liu, B.; Liu, C.; Liu, D.; Liu, H. D.; Liu,
H.; Liu, J.; Liu, J. Y.; Liu, M. Y.; Liu, R. Y.; Liu, S. M.; Liu, W.;
Liu, Y. N.; Liu, Z. X.; Long, W. J.; Lu, R.; Lv, H. K.; Ma, B. Q.; Ma,
L. L.; Mao, J. R.; Masood, A.; Ma, X. H.; Mitthumsiri, W.; Montaruli,
T.; Nan, Y. C.; Pattarakijwanich, P.; Pei, Z. Y.; Qiao, B. Q.; Qi,
M. Y.; Ruffolo, D.; Rulev, V.; Sáiz, A.; Shao, L.; Shchegolev, O.;
Sheng, X. D.; Shi, J. R.; Stenkin, Y.; Stepanov, V.; Sun, Z. B.; Tam,
P. H. T.; Tang, Z. B.; Tian, W. W.; Volpe, D. D.; Wang, C.; Wang, H.;
Wang, H. G.; Wang, J. C.; Wang, L. Y.; Wang, W.; Wang, W.; Wang, X. G.;
Wang, X. Y.; Wang, X. J.; Wang, Y. D.; Wang, Y. J.; Wang, Y. N.; Wang,
Y. P.; Wang, Z.; Wang, Z. H.; Wang, Z. X.; Wei, D. M.; Wei, J. J.;
Wen, T.; Wu, C. Y.; Wu, H. R.; Wu, S.; Wu, W. X.; Wu, X. F.; Xiang,
G. M.; Xiao, G.; Xin, G. G.; Xing, Y.; Xu, R. X.; Xue, L.; Yan, D. H.;
Yang, C. W.; Yang, F. F.; Yang, L. L.; Yang, M. J.; Yang, R. Z.; Yang,
S. B.; Yao, Y. H.; Yao, Z. G.; Ye, Y. M.; Yin, L. Q.; Yin, N.; You,
X. H.; You, Z. Y.; Yuan, Q.; Yu, Y. H.; Jiang, Z. J.; Zeng, H. D.;
Zeng, T. X.; Zeng, W.; Zeng, Z. K.; Zha, M.; Zhang, B. B.; Zhang,
H. M.; Zhang, H. Y.; Zhang, J. L.; Zhang, J. W.; Zhang, L.; Zhang,
P. F.; Zhang, P. P.; Zhang, S. R.; Zhang, S. S.; Zhang, X.; Zhang,
X. P.; Zhang, Yi; Zhang, Yong; Zhang, Y. F. G.; Zhao, B.; Zhao, J.;
Zhao, L.; Zhao, L. Z.; Zheng, F.; Zheng, Y.; Zhou, J. N.; Zhou, P.;
Zhou, R.; Zhou, X. X.; Zhu, C. G.; Zhu, F. R.; Zhu, H.; Zhu, K. J.;
Zuo, X.; LHAASO Collaboration
Bibcode: 2020ChPhC..44f5001A
Altcode: 2020arXiv200204819G
The Water Cherenkov Detector Array (WCDA) is a major component of
the Large High Altitude Air Shower Array Observatory (LHAASO), a new
generation cosmic-ray experiment with unprecedented sensitivity,
currently under construction. WCDA is aimed at the study of
TeV $\gamma$?--> -rays. In order to evaluate the prospects of
searching for TeV $\gamma$?--> -ray sources with WCDA, we present a
projection of the one-year sensitivity of WCDA to TeV $\gamma$?-->
-ray sources from TeVCat using an all-sky approach. Out of 128 TeVCat
sources observable by WCDA up to a zenith angle of $45^\circ$?--> ,
we estimate that 42 would be detectable in one year of observations at
a median energy of 1 TeV. Most of them are Galactic sources, and the
extragalactic sources are Active Galactic Nuclei (AGN). * Supported by
National Natural Science Foundation of China (11761141001, 11635011,
11873005). The LHAASO project is supported by the National Key R &
D Program of China (2018YFA0404200), the Chinese Academy of Sciences,
the Key Laboratory of Particle Astrophysics, IHEP, CAS
Title: Best focus approach of HinOTORI telescope
Authors: Liu, Wei; Nagashima, Hiroki; Kawabata, Koji; Sasada, Mahito;
Yao, Yongqiang; Shi, Shengcai
Bibcode: 2020SPIE11455E..1TL
Altcode:
HinOTORI is a 50cm telescope which is co-constructed and shared by
China and Japan. It can image in u', Rc and Ic bands simultaneously,
its main scientific observation targets are gravitational waves (GWs)
optical counterparts (OTs). The installation of the telescope has been
finished, and the engineering first light observation was carried out in
May 2018. This paper will give an overall introduction and parameters
of the telescope and then concentrate on a focusing method, which aims
at obtaining the best focus position from the fitting equation. The
reason of the best position shifting is also discussed.
Title: Constraining the External Capture to the 16O
Ground State and the E 2 S Factor of the 12C (α ,γ
)16O Reaction
Authors: Shen, Y. P.; Guo, B.; deBoer, R. J.; Li, Z. H.; Li, Y. J.;
Tang, X. D.; Pang, D. Y.; Adhikari, S.; Basu, C.; Su, J.; Yan, S. Q.;
Fan, Q. W.; Liu, J. C.; Chen, C.; Han, Z. Y.; Li, X. Y.; Lian, G.;
Ma, T. L.; Nan, W.; Nan, W. K.; Wang, Y. B.; Zeng, S.; Zhang, H.;
Liu, W. P.
Bibcode: 2020PhRvL.124p2701S
Altcode:
The 12C (α ,γ )16O reaction is one of the most
crucial reactions in nuclear astrophysics. The E 2 external capture to
the 16O ground state (GS) has not been emphasized in previous
analyses but may make a significant contribution to the 12C
(α ,γ )16O cross section depending on the value of the
GS asymptotic normalization coefficient (ANC). In the present work,
we determine this ANC to be 337 ±45 fm-1 /2 through the
12C (11B, 7Li) 16O reaction
using a high-precision magnetic spectrograph. This sheds light on
the existing large discrepancy of more than 2 orders of magnitude
between the previously reported ANC values. Based on the new ANC, we
experimentally constrain the GS external capture and show that through
interference with the high energy tail of the 2+ subthreshold
state, a substantial enhancement in the GS SE 2(300 ) factor
can be obtained (70 ±7 keV b ) compared to that of a recent review
(45 keV b), resulting in an increase of the total S factor from 140 to
162 keV b, which is now in good agreement with the value obtained by
reproducing supernova nucleosynthesis calculations with the solar-system
abundances. This work emphasizes that the external capture contribution
for the ground state transition cannot be neglected in future analyses
of the 12C(α ,γ )16O reaction.
Title: Deep Learning for Supernova Remnants Detection and Localization
Authors: Liu, W.; Yu, X. C.; Wang, B. Y.
Bibcode: 2020ASPC..522..451L
Altcode: 2020adass..27..451L
Detecting candidates of supernova remnants (SNRs) in the interstellar
medium is a challenging task because SNRs have weak radio signals
and irregular shapes. The use of a convolutional neural network is a
deep learning method that can help us extract various features from
images. To extract SNRs from astronomical images and estimate the
positions of SNR candidates, we design the SNR-Net model composed
of a training component and a detection component. In addition,
migration learning is used to initialize the network parameters, which
improves the speed and accuracy of network training.To accelerate the
scientific computing process, we take advantage of innovative hardware
architecture, such as deep learning optimized graphics processing units,
which increase the speed of computation by a factor of 5. A case study
suggests that SNR-Net may be applicable to detecting extended sources
in the images automatically.
Title: Carbon and nutrient export from intertidal sand systems
elucidated by 224Ra/228Th disequilibria
Authors: Cai, Pinghe; Wei, Lin; Geibert, Walter; Koehler, Dennis;
Ye, Ying; Liu, Wei; Shi, Xiangming
Bibcode: 2020GeCoA.274..302C
Altcode:
We propose an alternative scheme for the use of
224Ra/228Th disequilibria to investigate
carbon and nutrient export from a permeable sandy seabed. Sediment
profiles of dissolved 224Ra, total 224Ra
and 228Th were determined at two different intertidal
sand systems - an intertidal sandy beach near Weitou Bay in Fujian
(China), and a tidal sand flat in the Wadden Sea near Cuxhaven
(Germany). Dramatic deficit of total 224Ra relative to
228Th was identified in the upper 20 or 30 cm sand layer
over the sand systems. We construct a simple two-dimensional advective
cycling model to simulate interfacial fluid transport in a sand system
that is subject to periodic tidal inundation and swash actions. Based on
the 224Ra/228Th disequilibria in the sediment,
the model gives estimates of 20.3, 9.1, and 1.9 L m-2
h-1 for water exchange flux at the high tide, mid-tide, and
low tide position over the sandy beach at Weitou Bay, respectively. In
comparison, the model provides an estimate of 7.2 L m-2
h-1 for water exchange flux at the tidal sand flat in the
Wadden Sea. The production of dissolved inorganic carbon (DIC) in
porewater is the rate-limiting step for DIC export from the sandy beach
into the sea, and can be reasonably simulated as a first-order kinetic
reaction. The pattern of interfacial fluid transport over the beach
facilitates a horizontal zonation of redox condition in the sediment,
which evolves progressively from a fully oxic state at the high tide
position to a suboxic state at the low tide position. There is clear
evidence of nitrogen loss via denitrification in the suboxic status,
and we estimate a nitrogen removal rate of 3.3 mmolN m-2
d-1 at this site. For the two intertidal sand systems,
DIC export fluxes range from 20.1 to 89.4 mmolC m-2
d-1, comparable in magnitude to fluxes determined in organic
rich estuarine sediments. In the meantime, export fluxes of dissolved
inorganic nitrogen (DIN) change from 0.8 to 18.6 mmolN m-2
d-1. Overall, this study suggests that the role of sandy
sediments in the biogeochemical cycling of carbon and nutrients needs
to be revisited.
Title: Optical telescope with Cassegrain metasurfaces
Authors: Liu, Xuan; Deng, Junhong; Li, King Fai; Jin, Mingke; Tang,
Yutao; Zhang, Xuecai; Cheng, Xing; Wang, Hong; Liu, Wei; Li, Guixin
Bibcode: 2020Nanop...9...12L
Altcode:
The Cassegrain telescope, made of a concave primary mirror and a
convex secondary mirror, is widely utilized for modern astronomical
observation. However, the existence of curved mirrors inevitably
results in bulky configurations. Here, we propose a new design of the
miniaturized Cassegrain telescope by replacing the curved mirrors with
planar reflective metasurfaces. The focusing and imaging properties of
the Cassegrain metasurface telescopes are experimentally verified for
circularly polarized incident light at near infrared wavelengths. The
concept of the metasurface telescopes can be employed for applications
in telescopes working at infrared, Terahertz, and microwave and even
radio frequencies.
Title: Systematic observations on Galactic Interstellar isotope ratios
Authors: Zhang, J. S.; Yan, Y. T.; Liu, W.; Yu, H. Z.; Chen, J. L.;
Henkel, C.
Bibcode: 2020IAUGA..30..278Z
Altcode:
We are performing systematic observation studies on the Galactic
interstellar isotopic ratios, including 18O/17O,
12C/13C, 14N/15N and
32S/34S. Our strategy focuses on combination
of multi-transition observation data toward large samples with
different Galactocentric distances. Our preliminary results show
positive Galactic radial gradients of 18O/17O
and 12C/13C. In both cases, the ratio increases
with the Galactocentric distance, which agrees with the inside-out
scenario of our Galaxy. Observations of other isotopes such as
14N/15N and 32S/34S are
on-going.
Title: Major Scientific Challenges and Opportunities in Understanding
Magnetic Reconnection and Related Explosive Phenomena throughout
the Universe
Authors: Ji, H.; Alt, A.; Antiochos, S.; Baalrud, S.; Bale, S.;
Bellan, P. M.; Begelman, M.; Beresnyak, A.; Blackman, E. G.; Brennan,
D.; Brown, M.; Buechner, J.; Burch, J.; Cassak, P.; Chen, L. -J.;
Chen, Y.; Chien, A.; Craig, D.; Dahlin, J.; Daughton, W.; DeLuca, E.;
Dong, C. F.; Dorfman, S.; Drake, J.; Ebrahimi, F.; Egedal, J.; Ergun,
R.; Eyink, G.; Fan, Y.; Fiksel, G.; Forest, C.; Fox, W.; Froula, D.;
Fujimoto, K.; Gao, L.; Genestreti, K.; Gibson, S.; Goldstein, M.; Guo,
F.; Hesse, M.; Hoshino, M.; Hu, Q.; Huang, Y. -M.; Jara-Almonte, J.;
Karimabadi, H.; Klimchuk, J.; Kunz, M.; Kusano, K.; Lazarian, A.;
Le, A.; Li, H.; Li, X.; Lin, Y.; Linton, M.; Liu, Y. -H.; Liu, W.;
Longcope, D.; Loureiro, N.; Lu, Q. -M.; Ma, Z-W.; Matthaeus, W. H.;
Meyerhofer, D.; Mozer, F.; Munsat, T.; Murphy, N. A.; Nilson, P.;
Ono, Y.; Opher, M.; Park, H.; Parker, S.; Petropoulou, M.; Phan, T.;
Prager, S.; Rempel, M.; Ren, C.; Ren, Y.; Rosner, R.; Roytershteyn,
V.; Sarff, J.; Savcheva, A.; Schaffner, D.; Schoeffier, K.; Scime, E.;
Shay, M.; Sitnov, M.; Stanier, A.; TenBarge, J.; Tharp, T.; Uzdensky,
D.; Vaivads, A.; Velli, M.; Vishniac, E.; Wang, H.; Werner, G.; Xiao,
C.; Yamada, M.; Yokoyama, T.; Yoo, J.; Zenitani, S.; Zweibel, E.
Bibcode: 2020arXiv200400079J
Altcode:
This white paper summarizes major scientific challenges and
opportunities in understanding magnetic reconnection and related
explosive phenomena as a fundamental plasma process.
Title: Two Numerical Methods for the 3D Anisotropic Propagation of
Galactic Cosmic Rays
Authors: Liu, Wei; Lin, Su-jie; Hu, Hong-bo; Guo, Yi-qing; Li, Ai-feng
Bibcode: 2020ApJ...892....6L
Altcode: 2019arXiv190902908L
Conventional cosmic-ray propagation models usually assume an isotropic
diffusion coefficient to account for the random deflection of cosmic
rays by the turbulent interstellar magnetic field. Such models very
successfully explain many observational phenomena related to the
propagation of Galactic cosmic rays, such as broken power-law energy
spectra, secondary-to-primary ratios, etc. However, the isotropic
diffusion presupposition is facing severe challenges from recent
observations. In particular, such observations on the large-scale
anisotropy of TeV cosmic rays show that the dipole direction differs
from the prediction of the conventional model. One possible reason
is that the large-scale regular magnetic field, which leads to an
anisotropic diffusion of cosmic rays, has not been included in the model
provided by the public numerical packages. In this work, we propose
two numerical schemes to solve the three-dimensional anisotropic
transport equation: the pseudo-source method and Hundsdorfer-Verwer
scheme. Both methods are verified by reproducing the measured B/C and
proton spectrum and the radial variation of spectral index expected by
former 2D simulation. As a demonstration of the prediction capability,
dipole anisotropy is also calculated by a toy simulation with a rough
magnetic field.
Title: Spot Model for Identifications of Periods in Asynchronous
Polars
Authors: Wang, Qishan; Qian, Shengbang; Han, Zhongtao; Fang, Xiaohui;
Zang, Lei; Liu, Wei
Bibcode: 2020ApJ...892...38W
Altcode: 2020arXiv201113123W
We improved the discless accretion models in Wynn & King considering
the effects of the changing aspect due to the white dwarf (WD) spin
and the variable feeding intensity caused by the asynchronism, and set
up a more general spot model that is not sensitive to the different
forms of these effects and can be applied for the period analysis
of the optical and X-ray light curve. The spot model can produce the
power spectra compatible with the observations, and its simulations
limit the ratio Pspin/Porb < 2 between the
powers at the WD spin and the binary orbital frequencies, which is
a strong criterion for identification of periods. Then we recognize
the periods for CD Ind, BY Cam, and 1RXS J083842.1-282723. The spot
model reveals a complex accretion geometry in the asynchronous polars
(APs), which may indicate that the complex magnetic field causes their
asynchronism. We think 1RXS J083842.1-282723 is a prepolar because of
its highest asynchronism and stable light curve. Giving the unstable
accretion process in APs, the period analysis of the long-term light
curve will make the orbital signal prominent.
Title: Rupture Process of the 26 May 2019 Mw 8.0 Northern
Peru Intermediate-Depth Earthquake and Insights Into Its Mechanism
Authors: Liu, Wei; Yao, Huajian
Bibcode: 2020GeoRL..4787167L
Altcode:
In the Nazca-South American subduction zone, the subducted slab is
flattened beneath northern Andes, called the Peruvian flat slab. The
2019 Mw 8.0 northern Peru intermediate-depth normal-faulting
earthquake occurred at the leading edge of the Peruvian flat slab, where
the slab rebends and sinks into greater depths. Here we investigate
this earthquake by back projection analysis and finite fault inversion
using seismic waveforms at teleseismic distances. The rupture process
indicates that this earthquake ruptured mainly along strike (353°)
~150 km north-northwestward within ~55 s (average rupture velocity
~2.7 km/s), resulting in two major slip areas with three high slip rate
areas, which are consistent with three high-frequency energy radiation
subevents. Our study suggests that such a heterogeneous rupture may be
caused by slab bending forces and dehydration embrittlement associated
with morphology of the slab.
Title: Real-time abnormal light curve detection based on a Gated
Recurrent Unit network
Authors: Yan, Rui-Qing; Liu, Wei; Zhu, Meng; Wang, Yi-Jing; Dai, Cong;
Cao, Shuo; Wu, Kang; Liang, Yu-Chen; Yu, Xian-Chuan; Zhang, Meng-Fei
Bibcode: 2020RAA....20....7Y
Altcode:
Targeting the problem of high real-time requirements in astronomical
data processing, this paper proposes a real-time early warning model
for light curves based on a Gated Recurrent Unit (GRU) network. Using
the memory function of the GRU network, a prediction model of the light
curve is established, and the model is trained using the collected
light curve data, so that the model can predict a star magnitude value
for the next moment based on historical star magnitude data. In this
paper,we calculate the difference between the model prediction value
and the actual observation value and set a threshold. If the difference
exceeds the set threshold, the observation value at the next moment is
considered to be an abnormal value, and a warning is given. Astronomers
can carry out further certification based on the early warning and in
combinationwith other means of observation. Themethod proposed in this
paper can be applied to real-time observations in time domain astronomy.
Title: High-energy-density physics based on HIAF
Authors: Kang, Wei; Du, Yingchao; Cao, Shuchun; Zhao, Hongwei; Lei,
Yu; Wang, Yuyu; He, Bin; Sheng, Lina; Song, Yuanhong; Xiao, Guoqing;
Zhang, Yanning; Li, Fuli; Cheng, Rui; Wang, Younian; Zhang, Lin; Zhao,
Zongqing; Yang, Jiancheng; Zhao, Quantang; Qi, Wei; Chen, Yanhong;
Ma, Bubo; Wang, Xing; Hu, Zhanghu; Liu, Wei; Hoffmann, Dieter; Gao,
Fei; Su, Youwu; Xu, Zhongfeng; Zhan, Wenlong; Zhang, Ya; Wu, Dong;
Zhao, Xiaoying; Zhang, Xiaoan; Wan, Feng; Qi, Xin; Chen, Benzheng;
Zhang, Zimin; Cao, Leifeng; Deng, Zhigang; Ren, Jieru; Huang, Wenhui;
Yang, Jie; Zhou, Xianming; Zhou, Zheng; Li, Jinyu; Zhang, Shizheng;
Zhou, Weimin; Yang, Lei; Zhao, Yongtao; Tang, Chuanxiang; Li, Jianxing
Bibcode: 2020SSPMA..50k2004K
Altcode:
No abstract at ADS
Title: X-ray merger shock and radio relic in Abell 1367
Authors: Ge, C.; Sun, M.; Liu, R.; Rudnick, L.; Sarazin, C.; Forman,
W.; Jones, C.; Chen, H.; Liu, W.; Yagi, M.; Boselli, A.; Fossati,
M.; Gavazzi, G.
Bibcode: 2020AAS...23545904G
Altcode:
Abell 1367 is a dynamically young galaxy cluster with at least two
subclusters merging along the SE-NW direction. With the wide-field
XMM-Newton mosaic, we discover a previously unknown merger shock at
the NW edge of the cluster. This shock region also corresponds to a
radio relic, which could be produced by the shock re-acceleration of
pre-existing relativistic seed electrons. We suggest that some of the
relativistic seed electrons originate from late-type, star-forming
galaxies through stripping. We expect mergers in spiral-rich galaxy
groups or proto-clusters to also generate radio relics in these systems.
Title: Fluctuation and inertia
Authors: Shu, Liangsuo; Liu, Xiaokang; Cui, Kaifeng; Liu, Zhichun;
Liu, Wei
Bibcode: 2020NuPhB.95014873S
Altcode: 2018arXiv180110018S
How the principle of inertia survives quantum fluctuations is an
interesting question. Smolin has proposed a hypothesis that quantum
fluctuations are in fact real statistical fluctuations. In this work,
combining the works on Hawking-Unruh radiation and Jacobson's idea
in his thermodynamics derivation of Einstein equation, we confirmed
Smolin's guess: the quantum fluctuations leading to Hawking-Unruh
radiation, satisfying the fluctuation theorem, are statistical
fluctuations. Therefore, inertia is found to be a result of the
second law of thermodynamics: the principle of entropy increases
has the tendency to eliminate the effects of fluctuations and makes
accelerated observers express inertia force.
Title: A strange star scenario for the formation of isolated
millisecond pulsars
Authors: Jiang, Long; Wang, Na; Chen, Wen-Cong; Li, Xiang-Dong; Liu,
Wei-Min; Gao, Zhi-Fu
Bibcode: 2020A&A...633A..45J
Altcode: 2019arXiv191111275J
According to the recycling model, neutron stars in low-mass
X-ray binaries were spun up to millisecond pulsars (MSPs), which
indicates that all MSPs in the Galactic plane ought to be harbored
in binaries. However, about 20% Galactic field MSPs are found to be
solitary. To interpret this problem, we assume that the accreting
neutron star in binaries may collapse and become a strange star when
it reaches some critical mass limit. Mass loss and a weak kick induced
by asymmetric collapse during the phase transition (PT) from neutron
star to strange star can result in isolated MSPs. In this work, we use a
population-synthesis code to examine the PT model. The simulated results
show that a kick velocity of ∼60 km s-1 can produce ∼6 ×
103 isolated MSPs and birth rate of ∼6.6 × 10-7
yr-1 in the Galaxy, which is approximately in agreement
with predictions from observations. For the purpose of comparisons
with future observation, we also give the mass distributions of radio
and X-ray binary MSPs, along with the delay time distribution.
Title: Detection of GWAC Abnormal Light Transform Based on Sparse
Autoencoder
Authors: Zhu, M.; Liu, W.; Yu, X. C.; Duan, F. Q.; Zhang, Y. G.
Bibcode: 2020ASPC..527..563Z
Altcode: 2020adass..29..563Z
The Geographic Wide Angle Camera Array (GWAC) is an important
ground-based observation device for the Sino-French astronomical
satellite project. It can get millions of light curves in just 15
seconds every night. This gives GWAC the advantages of observation and
research in gravitational microlenses (important probe observations
of exoplanets), flare stars, unknown transient objects (Gravitational
Wave Bursts). These transient sources have anomalous characteristics
in light and appear infrequently. It is a challenging task to
detect the celestial bodies with abnormal light from the observed
light curve. In order to improve the unfavorable conditions of
artificial interpretation of a light curve, such as low efficiency
and unavoidable errors or omissions, this paper proposes a light
curve anomaly detection method based on Sparse AutoEncoder (SAE). To
prove the effectiveness of the proposed algorithm, we performed some
experiments on the algorithm and compared it with K-means in terms
of false positive rate and time consumption. We identified 3 types of
unknown mutations and some individual outliers, which will be tracked
for deeper analysis. Experimental results show that the method has
better performance in anomaly detection.
Title: Probing the solar corona with Sun-grazing comets: comparing
MHDsimulations with EUV observations
Authors: Jia, Y. D.; Pesnell, W. D.; Liu, W.; Downs, C.; Bryans, P.
Bibcode: 2019AGUFMSH13A..03J
Altcode:
Sun -grazing comets can dive within one solar radii of the Sun
's surface. The cometary materials expand along the comet's orbit,
and undergo various stages of fierce thermal-chemical reactions on
the scales of seconds to minutes. These reactions ionize cometary
ions through successive charge states , which is revealed by certain
emission lines in the AIA images. Such plasma reaction processes are
significantly affected by the transient structures in the corona, and
thus these structures are revealed by the structures and shapes of the
comet tail. We combine three numerical models: a global corona model,
particle transportation model, and cometary plasma interaction model
into one framework to simulate the interaction of Sun -grazing comets
in the low corona. In our framework, cometary ejecta are vaporized
and then ionized via multiple channels, and then confined by the
coronal magnetic field. Constrained by imaging observations of the
and cometary interaction images, we apply our framework to trace back
to the local condition of the ambient corona, and its spatiotemporal
variation. Previously, our model confirmed the importance of the
ambient magnetic field vector in shaping the tail. In this study,
we use the C/2011 W3 (Lovejoy) perihelion to determine the local
plasma and field conditions in the corona. Our framework is capable of
resolving structures from thousands of meters to tens of million meters,
so we can identify the fine spatial variations in plasma density and
magnetic field intensity, which may be visible in future/on-going
close-up coronal observations.
Title: Global Magnetohydrodynamics Simulation of EUV Waves and Shocks
from the X8.2 Eruptive Flare on 2017 September 10
Authors: Jin, M.; Liu, W.; Cheung, C. M. M.; Nitta, N.; DeRosa,
M. L.; Manchester, W.; Ofman, L.; Downs, C.; Petrosian, V.; Omodei,
N.; Moschou, S. P.; Sokolov, I.
Bibcode: 2019AGUFMSH32A..01J
Altcode:
As one of the largest flare-CME eruptions during solar cycle 24, the
2017 September 10 X8.2 flare event is associated with spectacular
global EUV waves that transverse almost the entire visible solar
disk, a CME with speed > 3000 km/s, which is one of the fastest
CMEs ever recorded, and >100 MeV Gamma-ray emission lasting for
more than 12 hours. All these unique observational features pose new
challenge on current numerical models to reproduce the multi-wavelength
observations. To take this challenge, we simulate the September 10
event using a global MHD model (AWSoM: Alfven Wave Solar Model) within
the Space Weather Modeling Framework and initiate CMEs by Gibson-Low
flux rope. We assess several important observed and physical inputs
(e.g., flux rope properties, polar magnetic field) in the model to
better reproduce the multi-wavelength observations. We find that the
simulated EUV wave morphology and kinematics are sensitive to the
orientation of the initial flux rope introduced to the source active
region. An orientation with the flux-rope axis in the north-south
direction produces the best match to the observations, which suggests
that EUV waves may potentially be used to constrain the flux-rope
geometry for such limb or behind-the-limb eruptions that lack good
magnetic field observations. By further combining with the white
light and radio observations, we demonstrate the flux rope-corona
interaction can greatly impact the early phase shock evolution (e.g.,
geometry and shock parameters) therefore plays a significant role
for particle acceleration near the Sun in this event. By propagating
the CMEs into the heliosphere and beyond the Earth and Mars orbits, we
compare the model results with the in-situ measurements and demonstrate
the importance of input polar magnetic field on the realistic CME
modeling therefore space weather forecasting.
Title: On the nature of the X-ray outbursts in Be/X-ray binaries
Authors: Yan, Jingzhi; Liu, Wei; Zhang, Peng; Liu, Qingzhong
Bibcode: 2019IAUS..346..146Y
Altcode:
Be/X-ray binaries are a major subclass of high mass X-ray binaries. Two
different X-ray outbursts are displayed in the X-ray light curves of
such systems. It is generally believed that the X-ray outbursts are
connected with the neutron star periastron passage of the circumstellar
disk around the Be star. The optical emission of the Be star should
be very important to understand the X-ray emission of the compact
object. We have monitored several Be/X-ray binaries photometrically
and spectroscopically in the optical band. The relationship between
the optical emission and X-ray activity is described, which is very
useful to explain the X-ray outbursts in Be/X-ray binaries.
Title: Observations and simulations of electron flux oscillations
in response to broadband ULF wave
Authors: Sarris, T. E.; Li, X.; Temerin, M. A.; Zhao, H.; Khoo, L. Y.;
Liu, W.
Bibcode: 2019AGUFMSM23F3272S
Altcode:
It has recently been demonstrated through simulations and observations
that electron flux oscillations are produced in the magnetosphere in
association with broadband Ultra Low Frequency (ULF) waves. These
oscillations are observed in the form of drift-periodic flux
fluctuations, but are not associated with drift echoes following
storm- or substorm-related energetic particle injections. They are
observed in particular during quiet times, and it has been shown
that they could indicate ongoing radial transport processes caused by
ULF waves. It has also been shown that the width of electron energy
channels is a critical parameter affecting the observed amplitude of
flux oscillations, with narrower energy channel widths enabling the
observation of higher-amplitude flux oscillations; this potentially
explains why such features were not observed regularly before the Van
Allen Probes era, as previous spacecraft generally had lower energy
resolution. The amplitude of electric and magnetic fluctuations in
the ULF range are directly related to the amplitude of the resulting
flux oscillations. We extend these initial results by investigating
analytic functions that can associate the observed flux oscillations
with electric and magnetic fluctuations and with Phase Space Density
gradients, both of which are expected to also affect radial transport
rates.
Title: Loop-top oscillations observed with IRIS spatially correlated
with nonthermal emission from EOVSA in the September 10 2017 X8 Flare
Authors: Reeves, K.; Polito, V.; Galan, G.; Yu, S.; Chen, B.; Liu,
W.; Li, G.
Bibcode: 2019AGUFMSH13D3416R
Altcode:
he September 10 2017 X8 flare was a spectacular limb event complete with
a fast coronal mass ejection, a fully global EUV wave, a bright flare
loop arcade, and strong emission ranging from microwave to white-light
continuum and gamma-rays. We examine the IRIS Fe XXI data from this
event. Fe XXI is a coronal line that is formed at about 10 MK. The IRIS
pointing was just south of the main cusp-shaped loop structure visible
in AIA, but it did capture most of the flare arcade on the limb. We find
that the majority of the emission in the loops is slightly red shifted,
with speeds of about 20 km/s, probably due to chromospheric evaporation
and an inclined viewing angle. During the period from 16:05 - 16:15
UT, we find that faint blue-shifted regions appear at the top of the
flare loops, indicating plasma flows of 20-60 km/s. After the initial
blue shift at each location, the Fe XXI Doppler velocities exhibit a
damped oscillation with a period of about 40 sec. Interestingly, in
the minutes before the blue-shifted loop-top emission was observed,
the Expanded Owens Valley Solar Array observed nonthermal microwave
emission at the same location above the loop-tops, possibly indicative
of particle acceleration there. We will discuss possible mechanisms
for these observations.
Title: A new statistical study on the properties of cusp
Authors: Xiao, C.; Liu, W.
Bibcode: 2019AGUFMSM51D3227X
Altcode:
A statistical study of the mid- and high-altitude (2~9RE)
cusp is conducted with nine years (2001~2009) of data from the
Cluster spacecraft. The location, size and properties of the cusp
region are studied statistically in this work. The survey shows that
(1) the relations between X and Z are nearly linear for the poleward,
the equatorward boundaries and the center of the cusp respectively,
(2) the relationship between the cusp distance width in X direction
and Z can be expressed by a quadratic function, (3) the cusp region
is almost dawn-dusk symmetry for the distance width in X direction and
dawn-dusk asymmetry for the latitudinal width (the difference between
the invariant latitude of the poleward and the equatorward boundaries),
and (4) by using a new orbit-sampling methodology to order the data
in space, the statistical distributions of the magnetic field and
plasma parameters (including ion density, temperature and speed) in
XZ plane. The new cusp statistical method proposed in this work will
provide reference for future cusp research.
Title: On the Excitation of ULF Waves after Interplanetary
Shock-induced Impulses
Authors: Zhang, D.; Liu, W.
Bibcode: 2019AGUFMSM51C3203Z
Altcode:
We study the generation of the ULF wave during shock-related
sudden impulse in the Earth magnetosphere using Van Allen Probes
measurement. Among the 63 shock-related sudden impulses, there
are 39 cases with ULF wave induced and we find that in strong wave
cases the impulse frequency appears correlated to the induced wave
frequency which, at the same time, appears correlated to the local
eigen frequency. Our results show that the shock-related ULF wave can
be excited in the magnetosphere on condition that the shock-induced
impulse frequency matches the local eigen frequency. We also find
that the frequency of the first period of shock-related impulse is
likely determined by the local fast-mode speed instead of local eigen
frequency, which shows that the characteristic of the first impulse
period is more likely related to a propagation mechanism rather than
field-line resonance. A more detailed study using MMS measurement on
how shock impulse propagates from solar wind into magnetosphere is
in process.
Title: Anisotropies of different mass compositions of cosmic rays
Authors: Qiao, Bing-Qiang; Liu, Wei; Guo, Yi-Qing; Yuan, Qiang
Bibcode: 2019JCAP...12..007Q
Altcode: 2019arXiv190512505Q
The spectral hardenings of cosmic ray nuclei above ~ 200 GV followed by
softenings around 10 TV, the knee of the all-particle spectrum around
PeV energies, as well as the pattern change of the amplitude and phase
of the large-scale anisotropies around 100 TeV indicate the complexities
of the origin and transportation of Galactic cosmic rays. It has been
shown that nearby source(s) are most likely to be the cause of such
spectral features of both the spectra and the anisotropies. In this
work, we study the anisotropy features of different mass composition
(or mass groups) of cosmic rays in this nearby source model. We show
that even if the spectral features from the nearby source component
is less distinctive compared with the background component from e.g.,
the population of distant sources, the anisotropy features are more
remarkable to be identified. Measurements of the anisotropies of each
mass composition (group) of cosmic rays by the space experiments such
as DAMPE and HERD and the ground-based experiments such as LHAASO in the
near future are expected to be able to critically test this scenario.
Title: Calculation of corotation electric field in the inner
magnetosphere based on Van Allen Probes measurements
Authors: Liu, W.; Zhao, Z.
Bibcode: 2019AGUFMSM51F3247L
Altcode:
Corotation electric field is important in the inner magnetosphere
topology, which was usually calculated by assuming 24h corotation
period. However, some studies found that plasmasphere corotation
lag exists which suggests the overestimation of corotation electric
field in previous calculations. In this study, we use electric
field measurements from Van Allen Probes mission from 2013 to 2017 to
statistically calculate the distribution of large-scale electric field
in the inner magnetosphere. A new method is subsequently developed to
separate corotation electric field from convection electric field. Our
research shows electric field is inversely proportional to the square
of L, and, with the assumption of dipole magnetic field, the rotation
period of plasmasphere is estimated as 27h, consistent with previous
studies with EUV imaging of the plasmasphere. Based on the research,
a new empirical model of innermagnetospheric corotation electric field
was estibalished, which is significant for a more accurate understanding
the large-scale electric field in the inner magnetosphere.
Title: High-energy Observations of Solar Flares During Solar Cycle
24th with the Fermi Large Area Telescope
Authors: Omodei, N.; Pesce-Rollins, M.; Longo, F.; Petrosian, V.;
Liu, W.; Jin, M.
Bibcode: 2019AGUFMSH12B..02O
Altcode:
The Fermi Large Area Telescope (LAT) observations of the active Sun
provide the largest sample of detected solar flares with emission
greater than 30 MeV to date. These include detections of impulsive
and hours-long sustained emission coincident with GOES X-ray flares as
well as very fast Coronal Mass Ejections (CME). Of particular interest
is the first detection of >100 MeV gamma-ray emission from three
solar flares whose positions behind the limb were confirmed by the
STEREO spacecrafts and the 2017 September 10 X8.2 flare associated with
Ground Level Enhancement 72. Fermi-LAT detections of solar flares at
high energy present a unique opportunity to explore the mechanisms of
high-energy emission and particle acceleration and transport in solar
flares. We will review the Fermi-LAT observations of solar flares during
Solar Cycle 24, including correlation studies with Solar Energetic
Particles (SEP) and CMEs, and highlight possible interpretations and
theoretical modeling.
Title: Cooling Condensation at Coronal Null Points and
Quasi-Separatrix Layers Involving Magnetic Reconnection
Authors: Liu, W.; Sun, X.; Yu, S.; Luna Bennasar, M.; Antolin, P.;
Titov, V. S.; Downs, C.; Berger, T. E.
Bibcode: 2019AGUFMSH11C3394L
Altcode:
The solar corona, Sun's outer atmosphere, is million-degrees hot and
tenuous. This hot plasma, under certain conditions, can enigmatically
undergo a radiative cooling instability and condense into material of
100 times cooler in the form of prominences or coronal rain. Where,
when, and how such cooling condensation takes place remain poorly
understood. Answers to these questions are not only of scientific
importance in their own right, but also bear implications for the
fundamental question of coronal heating and the chromosphere-corona
mass cycle. Magnetic fields in the magnetized corona undoubtedly play
a crucial role (e.g., by trapping the plasma), but where and how? We
report recent imaging and spectroscopic observations from SDO/AIA/HMI
and IRIS that can shed light on these puzzles. Through a systematic
survey, we found that a large fraction of quiet-Sun condensations
preferentially occur at the dips of coronal loops or funnels. Such dips
are located at/near magnetic topological features, such as null points
and quasi-separatrix layers (QSLs), which are regions characterized by
high values of the squashing factor. We also identified evidence of
magnetic reconnection at such locations, which can produce favorable
conditions, e.g., density enhancement by compression and/or mass
trapping in plasmoids, that can trigger run-away radiative cooling. We
present proof-of-concept MHD simulations that demonstrate the role of
reconnection in transporting cooled mass from overlying, long loops to
underlying, short loops where it slide down as coronal rain. We will
discuss the significance and broader implications of these results
beyond solar physics.
Title: Simulations and software development for the Hard X-ray Imager
onboard ASO-S
Authors: Su, Yang; Liu, Wei; Li, You-Ping; Zhang, Zhe; Hurford,
Gordon J.; Chen, Wei; Huang, Yu; Li, Zhen-Tong; Jiang, Xian-Kai;
Wang, Hao-Xiang; Xia, Fan-Xiao-Yu; Chen, Chang-Xue; Yu, Wen-Hui; Yu,
Fu; Wu, Jian; Gan, Wei-Qun
Bibcode: 2019RAA....19..163S
Altcode:
China’s first solar mission, the Advanced Space-based Solar
Observatory (ASO-S), is now changing from Phase B to Phase C. Its
main scientific objectives are summarized as ‘1M2B’, namely
magnetic field and two types of bursts (solar flares and coronal
mass ejections). Among the three scientific payloads, Hard X-ray
Imager (HXI) observes images and spectra of X-ray bursts in solar
flares. In this paper, we briefly report on the progresses made by
the HXI science team (data and software team) during the design phase
(till May 2019). These include simulations of HXI imaging, optimization
of HXI grids, development of imaging algorithms, estimation of orbital
background, as well as in-orbit calibration plan. These efforts provided
guidance for the engineering, improved HXI’s imaging capability and
reduced the cost of the instrument.
Title: VizieR Online Data Catalog: A complete sample of broad-line
AGN from SDSS-DR7 (Liu+, 2019)
Authors: Liu, H. -Y.; Liu, W. -J.; Dong, X. -B.; Zhou, H.; Wang, T.;
Lu, H.; Yuan, W.
Bibcode: 2019yCat..22430021L
Altcode:
The SDSS is a comprehensive imaging and spectroscopic survey using a
dedicated 2.5m telescope located at Apache Point Observatory to image
over 10000deg2 of sky and to perform follow-up spectroscopic
observations. The telescope uses a wide-field imager (filters ugriz)
and a 640-fiber-fed pair of multiobjects double spectrographs covering
the wavelength 3800-9200Å with a resolution varying from 1850 to
2200. We have compiled a sample of 14584 type 1 AGNs based
on detection of a broad Hα line from a total of about one million
SDSS DR7 spectroscopic objects. Part I of the catalog (see Table 1)
is composed of the basic information of these sources. Part II of the
catalog (see Table 2) includes the emission line measurements derived
from the spectral analysis in this work. Finally, in part III of
the catalog (Table 3), we supplement photometric measurements in the
optical, ultraviolet (UV), near-infrared (NIR), mid-infrared (MIR),
X-ray, and radio drawn from GALEX, 2MASS, WISE, ROSAT, and FIRST;
see Section 4.3.3 for further details. (3 data files).
Title: Correction of Off-axis Aberration of the China Near Earth
Object Survey Telescope with 10k CCD
Authors: Zhaori, G. T.; Zhao, H. B.; Liu, W.; Li, B.
Bibcode: 2019AcASn..60...52Z
Altcode:
The SI600S (4k×4k) CCD of CNEOST (China Near Earth Object Survey
Telescope) now has been upgraded to STA1600LN (10k×10k), with the
image region size that becomes larger, and the observation field of
view (FoV) of telescope that enlarges from 4 to 9 °2. And
correspondingly, the diameter of the original available FoV is expanded,
from 3.14° to 4.28°, which is improved by 36% compared with the
original design. Moreover, the thickness of the field lens increases
by 8.75 mm. These two factors lead to the result that the off-axis
aberration increases and image quality becomes worse. In order to
solve this problem, based on the original optical design parameter
of the telescope, we try to improve the image quality with the ZEMAX
optical design software. The method is to design an additional field
corrector to correct the off-axis aberration. The corrector is composed
of two lenses with all spherical surfaces, and placed in front of the
existing field lens. Furthermore, we put forward a new optical design
which expands the available FoV from 14.38 to 28.27 °2.
Title: Indication of nearby source signatures of cosmic rays from
energy spectra and anisotropies
Authors: Liu, Wei; Guo, Yi-Qing; Yuan, Qiang
Bibcode: 2019JCAP...10..010L
Altcode: 2018arXiv181209673L
The origin of Galactic cosmic rays (GCRs) remains a mystery after
more than one century of their discovery. The diffusive propagation
of charged particles in the turbulent Galactic magnetic field makes us
unable to trace back to their acceleration sites. Nevertheless, nearby
GCR source(s) may leave imprints on the locally measured energy spectra
and the anisotropies of the arrival direction. In this work we propose
a simple but natural description of the GCR production and propagation,
within a two-zone disk-halo diffusion scenario together with a nearby
source, to understand the up-to-date precise measurements of the energy
spectra and anisotropies of GCRs. We find that a common energy scale of
~100 TeV appears in both energy spectra of protons and helium nuclei
measured recently by CREAM and large-scale anisotropies detected by
various experiments. These results indicate that one or more local
sources are very likely important contributors to GCRs below 100 TeV
. This study provides a probe to identify source(s) of GCRs by means
of joint efforts of spectral and anisotropy measurements.
Title: Lijiang 2.4-meter Telescope and its instruments
Authors: Wang, Chuan-Jun; Bai, Jin-Ming; Fan, Yu-Feng; Mao, Ji-Rong;
Chang, Liang; Xin, Yu-Xin; Zhang, Ju-Jia; Lun, Bao-Li; Wang, Jian-Guo;
Zhang, Xi-Liang; Ying, Mei; Lu, Kai-Xing; Wang, Xiao-Li; Ji, Kai-Fan;
Xiong, Ding-Rong; Yu, Xiao-Guang; Ding, Xu; Ye, Kai; Xing, Li-Feng; Yi,
Wei-Min; Xu, Liang; Zheng, Xiang-Ming; Feng, Yuan-Jie; He, Shou-Sheng;
Wang, Xue-Li; Liu, Zhong; Chen, Dong; Xu, Jun; Qin, Song-Nian; Zhang,
Rui-Long; Tan, Hui-Song; Li, Zhi; Lou, Ke; Li, Jian; Liu, Wei-Wei
Bibcode: 2019RAA....19..149W
Altcode: 2019arXiv190505915W
The Lijiang 2.4-meter Telescope (LJT), the largest common-purpose
optical telescope in China, has been available to the worldwide
astronomical community since 2008. It is located at the Gaomeigu site,
Lijiang Observatory (LJO), in the southwest of China. The site has very
good observational conditions. During its 10-year operation, several
instruments have been equipped on the LJT. Astronomers can perform both
photometric and spectral observations. The main scientific goals of LJT
include recording photometric and spectral evolution of supernovae,
reverberation mapping of active galactic nuclei, investigating the
physical properties of binary stars and near-earth objects (comets
and asteroids), and identification of exoplanets and all kinds of
transients. Until now, the masses of 41 high accretion rate black
holes have been measured, and more than 168 supernovae have been
identified by the LJT. More than 190 papers related to the LJT have
been published. In this paper, the general observation conditions of
the Gaomeigu site is introduced at first. Then, the structure of the
LJT is described in detail, including the optical, mechanical, motion
and control system. The specification of all the instruments and some
detailed parameters of the YFOSC is also presented. Finally, some
important scientific results and future expectations are summarized.
Title: A Method to Detect Radio Frequency Interference Based on
Convolutional Neural Networks
Authors: DAI, C.; ZUO, S. F.; Liu, W.; Li, J. X.; Zhu, M.; Wu, F. Q.;
Yu, X. C.
Bibcode: 2019ASPC..523...71D
Altcode:
RFI is an important challenge for radio astronomy. In this paper, we
adopt a deep convolution neural network with a symmetrical structure,
the U-Net, to detect RFI. The U-Net can perform the classification
task of clean signal and RFI. It extracts the features of RFI for
learning RFI distribution pattern and then calculates the probability
value of RFI for each pixel. Then we set a threshold to get the results
flagged by RFI. Experiments on Tianlai data (A radio telescope-array,
the observing time is from 20:15:45 to 24:18:45 on 27th of September
2016, and the frequency is from 744MHz to 756MHz) show that, compared
with the traditional RFI flagging method, this approach can get almost
consistent results with satisfying accuracy and take into account
the relationship between different baselines, which contributes to
correctly and effectively flag RFI.
Title: Panoramic SETI: An all-sky fast time-domain observatory
Authors: Wright, Shelley; Antonio, Franklin P.; Aronson, Michael L.;
Chaim-Weismann, Samuel A.; Cosens, Maren; Drake, Frank D.; Horowitz,
Paul; Howard, Andrew W.; Liu, Wei; Maire, Jerome; Siemion, Andrew
P. V.; Raffanti, Rick; Shippee, Guillaume D.; Stone, Remington P. S.;
Treffers, Richard R.; Uttamchandani, Avinash; Werthimer, Dan; Wiley,
James
Bibcode: 2019BAAS...51g.264W
Altcode: 2019astro2020U.264W
We are designing an optical and near-infrared observatory designed
to greatly enlarge the current SETI phase space. The Pulsed All-sky
Near-infrared Optical SETI (PANOSETI) observatory will be a dedicated
SETI facility that aims to increase sky area searched, wavelengths
covered, number of stellar systems observed, and duration of time
monitored.
Title: Measurement of the cosmic ray proton spectrum from 40 GeV to
100 TeV with the DAMPE satellite
Authors: An, Q.; Asfandiyarov, R.; Azzarello, P.; Bernardini, P.;
Bi, X. J.; Cai, M. S.; Chang, J.; Chen, D. Y.; Chen, H. F.; Chen,
J. L.; Chen, W.; Cui, M. Y.; Cui, T. S.; Dai, H. T.; D'Amone, A.;
De Benedittis, A.; De Mitri, I.; Di Santo, M.; Ding, M.; Dong, T. K.;
Dong, Y. F.; Dong, Z. X.; Donvito, G.; Droz, D.; Duan, J. L.; Duan,
K. K.; D'Urso, D.; Fan, R. R.; Fan, Y. Z.; Fang, F.; Feng, C. Q.;
Feng, L.; Fusco, P.; Gallo, V.; Gan, F. J.; Gao, M.; Gargano, F.; Gong,
K.; Gong, Y. Z.; Guo, D. Y.; Guo, J. H.; Guo, X. L.; Han, S. X.; Hu,
Y. M.; Huang, G. S.; Huang, X. Y.; Huang, Y. Y.; Ionica, M.; Jiang,
W.; Jin, X.; Kong, J.; Lei, S. J.; Li, S.; Li, W. L.; Li, X.; Li,
X. Q.; Li, Y.; Liang, Y. F.; Liang, Y. M.; Liao, N. H.; Liu, C. M.;
Liu, H.; Liu, J.; Liu, S. B.; Liu, W. Q.; Liu, Y.; Loparco, F.; Luo,
C. N.; Ma, M.; Ma, P. X.; Ma, S. Y.; Ma, T.; Ma, X. Y.; Marsella,
G.; Mazziotta, M. N.; Mo, D.; Niu, X. Y.; Pan, X.; Peng, W. X.;
Peng, X. Y.; Qiao, R.; Rao, J. N.; Salinas, M. M.; Shang, G. Z.;
Shen, W. H.; Shen, Z. Q.; Shen, Z. T.; Song, J. X.; Su, H.; Su, M.;
Sun, Z. Y.; Surdo, A.; Teng, X. J.; Tykhonov, A.; Vitillo, S.; Wang,
C.; Wang, H.; Wang, H. Y.; Wang, J. Z.; Wang, L. G.; Wang, Q.; Wang,
S.; Wang, X. H.; Wang, X. L.; Wang, Y. F.; Wang, Y. P.; Wang, Y. Z.;
Wang, Z. M.; Wei, D. M.; Wei, J. J.; Wei, Y. F.; Wen, S. C.; Wu, D.;
Wu, J.; Wu, L. B.; Wu, S. S.; Wu, X.; Xi, K.; Xia, Z. Q.; Xu, H. T.;
Xu, Z. H.; Xu, Z. L.; Xu, Z. Z.; Xue, G. F.; Yang, H. B.; Yang, P.;
Yang, Y. Q.; Yang, Z. L.; Yao, H. J.; Yu, Y. H.; Yuan, Q.; Yue, C.;
Zang, J. J.; Zhang, F.; Zhang, J. Y.; Zhang, J. Z.; Zhang, P. F.;
Zhang, S. X.; Zhang, W. Z.; Zhang, Y.; Zhang, Y. J.; Zhang, Y. L.;
Zhang, Y. P.; Zhang, Y. Q.; Zhang, Z.; Zhang, Z. Y.; Zhao, H.; Zhao,
H. Y.; Zhao, X. F.; Zhou, C. Y.; Zhou, Y.; Zhu, X.; Zhu, Y.; Zimmer, S.
Bibcode: 2019SciA....5.3793A
Altcode: 2019arXiv190912860A
The precise measurement of the spectrum of protons, the most abundant
component of the cosmic radiation, is necessary to understand the
source and acceleration of cosmic rays in the Milky Way. This work
reports the measurement of the cosmic ray proton fluxes with kinetic
energies from 40 GeV to 100 TeV, with two and a half years of data
recorded by the DArk Matter Particle Explorer (DAMPE). This is the
first time an experiment directly measures the cosmic ray protons up
to ~100 TeV with a high statistics. The measured spectrum confirms
the spectral hardening found by previous experiments and reveals a
softening at ~13.6 TeV, with the spectral index changing from ~2.60 to
~2.85. Our result suggests the existence of a new spectral feature of
cosmic rays at energies lower than the so-called knee, and sheds new
light on the origin of Galactic cosmic rays.
Title: Analysis of the 1.3-1.7 yr Oscillation Relationship between
Solar and Geomagnetic Activities
Authors: Qian, Ya-wen; Feng, Song; Deng, Lin-hua; Liu, Wei-hang
Bibcode: 2019ChA&A..43..365Q
Altcode: 2019ChA&A..43..365Y
The study on the 1.3-1.7 yr period of the solar and geomagnetic
activities is very important for understanding the possible physical
processes in the solar-terrestrial coupling system. The sunspot is
the most prominent magnetic field structure in the solar photosphere,
and the Ap index is an important indicator for the global geomagnetic
activity level. The 1.3-1.7 yr period for the sunspot number and the
geomagnetic Ap index is obtained by the synchro-squeezing wavelet
transform, and the phase relationship between them is studied by
the cross-correlation analysis. The main results are as follows: (1)
The 1.3-1.7 yr period of the geomagnetic Ap index and sunspot number
exhibits an intermittent evolutionary characteristics, and changes
continuously with the time; (2) the geomagnetic Ap index has a higher
periodic component in the odd solar cycles than the neighboring even
solar cycles, which is characterized by fluctuations; (3) the phase
relationship between the geomagnetic Ap index and the sunspot number
is not always invariant, in most cases the geomagnetic Ap index lags
behind the sunspot number, except in the 18th and 22th solar cycles.
Title: Study on the 3D anisotropic propagation of Galactic cosmic rays
Authors: Hu, H.; Liu, W.; Lin, S. J.; Guo, Y. Q.
Bibcode: 2019ICRC...36...80H
Altcode: 2019PoS...358...80H
No abstract at ADS
Title: Using Real-Time Drilling Data to Characterize Water-Ice on
the Moon
Authors: Joshi, D. R.; Eustes, A. W.; Rostami, J.; Dreyer, C.; Zody,
Z.; Liu, W.
Bibcode: 2019LPICo2152.5127J
Altcode:
This paper offers the details of the design of the test drill unit
based on heritage drill systems used by NASA and others. The paper
discusses the acquisition and analysis of the drilling data to assess
the strength and water content in the PSRs.
Title: Quasi-Periodic Pulsations Observed in White Light at the Loop
Top of the SOL2017-09-10 X8.2 Flare
Authors: Zhao, Junwei; Liu, Wei
Bibcode: 2019AAS...23421002Z
Altcode:
An X8.2 flare occurred on September 10, 2017 near the Sun's west
limb. Simultaneously with the observations of the SDO/AIA's multiple
UV/EUV channels, the continuum intensity of the SDO/HMI also observed
the evolution of the post-flare loop above the solar limb. This gives
us a rare opportunity to analyze the post-flare loop in visible light,
UV, and EUV channels. Quasi-periodic pulsations, with a period close
to about 8 minutes, are found in all these channels during the rise
of the loop top. We study the spatial and temporal relations of
the pulsations observed in different wavelengths, and find that EUV
pulsations occurred about 2-3 minutes earlier, and 2-6 Mm higher in
altitude, than the pulsations observed in UV and white light. While
the UV observations show many similarities in the pulsations with
the white light observations, the UV intensity decayed with the
rise of the loop but the white light intensity grew for about 20 more
minutes. These observations help shed light on our understanding of the
magnetohydrodynamics of the flare's loop-top, as well as the emission
mechanism of the white light off the solar limb.
Title: On the Origin of Quasi-periodic Fast-mode Propagating Wave
Trains (QFPs): A Statistical Survey
Authors: Silver, Jay; Liu, Wei; Ofman, Leon
Bibcode: 2019AAS...23421001S
Altcode:
The magnetized solar corona hosts a variety of waves that are physically
important and can serve as useful diagnostic tools. One type of such
coronal waves are Quasi-periodic Fast-mode Propagating wave trains
(QFPs), which were first detected in extreme ultraviolet (EUV) by
the Atmospheric Imaging Assembly (AIA) onboard the Solar Dynamics
Observatory (SDO). QFPs are not uncommon and are generally associated
with some, but not all solar flares and/or coronal mass ejections
(CMEs). To search for physical conditions that can contribute to QFP
production, we carried out a systematic survey of QFPs from the full
SDO mission. We found that about 1/5 of global EUV waves were associated
with QFPs. We also conducted a comparative study of two active regions
(ARs) visible between October and November 2014, AR12192 and AR12205,
with very different levels of QFP activity. AR12205 produced less
flares but more QFPs, which were all associated with blow-out,
eruptive flares and global EUV waves. In contrast, AR12192 produced
more (mostly confined) flares, but with virtually no QFPs and less
CMEs. This suggests that blow-out eruptions could be a necessary,
but not sufficient condition for QFP production and/or detectability.
Title: Long-lasting Conjugate Coronal Dimmings Produced by a Filament
Eruption: Implications for Global Magnetic Connectivity
Authors: Kocher, Manan; Liu, Wei; Downs, Cooper
Bibcode: 2019AAS...23411104K
Altcode:
Coronal dimmings, typically observed at extreme ultraviolet (EUV)
wavelengths, are commonly associated with solar eruptions, such as
coronal mass ejections (CMEs) and eruptive filaments. They offer
critical clues to our understanding of the underlying mechanisms and
consequences of solar eruptions. We present a study of an intriguing
dimming event associated with a quiescent filament eruption on March 6,
2018 observed by SDO/AIA, STEREO/SECCHI, and IRIS. There were notably
sigmoid-shaped, conjugate dimmings that appeared concurrently in
multiple EUV channels, but evolved asymmetrically with time. One of
the double dimmings lasted more than two days, which clearly sets it
apart from the typical lifetime of several hours in previously reported
dimmings. We investigated the temperature and density evolution of the
dimming features, as well as the eruptive filament itself. We uncovered
large-scale magnetic field connectivity between the conjugate dimmings
and remote coronal holes where brightenings were observed around the
time of the eruption. These remote brightenings are possible precursors
of the eruption or manifestations of its associated global magnetic
reconfiguration process. These results are significant because they
allow us to use dimmings as tracers to probe the Sun's magnetic
connectivity and the mechanisms responsible for the initiation of
space-weather driving solar eruptions.
Title: Coronal Condensation at Preferential Topological Locations:
The Birth of Solar Prominences and Coronal Rain
Authors: Liu, Wei; Sun, Xudong; Yu, Sijie; Antolin, Patrick; Titov,
Viacheslav; Downs, Cooper; Berger, Thomas
Bibcode: 2019AAS...23412502L
Altcode:
The million-degree hot and tenuous solar coronal plasma, under
certain conditions, can enigmatically undergo a radiative cooling
instability and condense into material of 100 times cooler in the form
of prominences or coronal rain. Where, when, and how such cooling
condensation takes place remain poorly understood. Answers to these
questions are not only of scientific importance in their own right,
but also bear implications for the fundamental question of coronal
heating and the chromosphere-corona mass cycle. Magnetic fields in the
magnetized corona undoubtedly play a crucial role (e.g., by trapping the
plasma), but where and how? We report recent imaging and spectroscopic
observations from SDO/AIA/HMI and IRIS that can shed light on these
puzzles. Through a systematic survey, we found that a large fraction
of quiet-Sun condensations preferentially occur at the dips of coronal
loops or funnels. Such dips are located at/near magnetic topological
features, such as null points and quasi-separatrix layers (QSLs), which
are regions characterized by high values of the squashing factor. We
also identified evidence of magnetic reconnection at such locations,
which can produce favorable conditions, e.g., density enhancement
by compression and/or mass trapping in plasmoids, that can trigger
run-away radiative cooling. We will discuss the significance and
broader implications of these novel observations.
Title: The Global EUV Wave Associated with the SOL2017-09-10 X8.2
Flare: SDO/AIA Observations and Data-constrained MHD Simulations
Authors: Liu, Wei; Jin, Meng; Ofman, Leon; DeRosa, Marc L.
Bibcode: 2019AAS...23430701L
Altcode:
While large-scale extreme ultraviolet (EUV) waves associated with
coronal mass ejections (CMEs) and solar flares are common, the EUV
wave triggered by the X8 flare-CME eruption on 2017 September 10
was an extreme. This was, to the best of our knowledge, the first
detection of an EUV wave traversing the full-Sun corona over the entire
visible disk and off-limb circumference, manifesting a truly global
nature. In addition to commonly observed reflections, it had strong
transmissions in and out of both polar coronal holes, at elevated
wave speeds of >2000 km/s within them. With an exceptionally large
wave amplitude, it produced significant compressional heating to local
coronal plasma. We present detailed analysis of SDO/AIA observations,
global magnetic field extrapolations with the potential-field source
surface (PFSS) model, and data-constrained MHD simulations of this
event using the University of Michigan Alfven Wave Solar Model
(AWSoM). By comparing the observations and simulations, we benchmark
diagnostics of the magnetic field strengths and thermal properties of
the solar corona on global scales. We discuss the future prospects of
using such extreme EUV waves as probes for global coronal seismology,
an area yet to be fully exploited.
Title: Major Scientific Challenges and Opportunities in Understanding
Magnetic Reconnection and Related Explosive Phenomena throughout
the Universe
Authors: Ji, Hantao; Alt, A.; Antiochos, S.; Baalrud, S.; Bale, S.;
Bellan, P. M.; Begelman, M.; Beresnyak, A.; Blackman, E. G.; Brennan,
D.; Brown, M.; Buechner, J.; Burch, J.; Cassak, P.; Chen, L. -J.;
Chen, Y.; Chien, A.; Craig, D.; Dahlin, J.; Daughton, W.; DeLuca, E.;
Dong, C. F.; Dorfman, S.; Drake, J.; Ebrahimi, F.; Egedal, J.; Ergun,
R.; Eyink, G.; Fan, Y.; Fiksel, G.; Forest, C.; Fox, W.; Froula, D.;
Fujimoto, K.; Gao, L.; Genestreti, K.; Gibson, S.; Goldstein, M.;
Guo, F.; Hesse, M.; Hoshino, M.; Hu, Q.; Huang, Y. -M.; Jara-Almonte,
J.; Karimabadi, H.; Klimchuk, J.; Kunz, M.; Kusano, K.; Lazarian,
A.; Le, A.; Li, H.; Li, X.; Lin, Y.; Linton, M.; Liu, Y. -H.; Liu,
W.; Longcope, D.; Louriero, N.; Lu, Q. -M.; Ma, Z. -W.; Matthaeus,
W. H.; Meyerhofer, D.; Mozer, F.; Munsat, T.; Murphy, N. A.; Nilson,
P.; Ono, Y.; Opher, M.; Park, H.; Parker, S.; Petropoulou, M.; Phan,
T.; Prager, S.; Rempel, M.; Ren, C.; Ren, Y.; Rosner, R.; Roytershteyn,
V.; Sarff, J.; Savcheva, A.; Schaffner, D.; Schoeffier, K.; Scime, E.;
Shay, M.; Sitnov, M.; Stanier, A.; TenBarge, J.; Tharp, T.; Uzdensky,
D.; Vaivads, A.; Velli, M.; Vishniac, E.; Wang, H.; Werner, G.; Xiao,
C.; Yamada, M.; Yokoyama, T.; Yoo, J.; Zenitani, S.; Zweibel, E.
Bibcode: 2019BAAS...51c...5J
Altcode: 2019astro2020T...5J
This is a group white paper of 100 authors (each with explicit
permission via email) from 51 institutions on the topic of magnetic
reconnection which is relevant to 6 thematic areas. Grand challenges
and research opportunities are described in observations, numerical
modeling and laboratory experiments in the upcoming decade.
Title: Lake Water Depth Controlling Archaeal Tetraether Distributions
in Midlatitude Asia: Implications for Paleo Lake-Level Reconstruction
Authors: Wang, H.; He, Y.; Liu, W.; Zhou, A.; Kolpakova, M.;
Krivonogov, S.; Liu, Z.
Bibcode: 2019GeoRL..46.5274W
Altcode:
Lake-level reconstructions, related to terrestrial hydrological
changes, are important for our understanding of past and future
climates. Currently, however, reliable lake-level proxies are still
limited. Here we report distributions of archaeal tetraether lipids in
70 surface sediment samples collected from 55 lakes in midlatitude
Asia. We have found that among various lake physico-chemical
characteristics, the relative abundances of crenarchaeol and
Hydroxylated isoprenoid glycerol dialkyl glycerol tetraethers (%cren
and %OH-GDGTs) are best correlated with lake water depth, due to a
preference of Thaumarchaeota, the producer of these biomarkers, for a
niche in subsurface lake water. This supports the recent hypothesis
based on single-lake investigations that %cren and %OH-GDGTs are
potentially novel lake-level proxies. Our results also suggest that
%OH-GDGTs is less affected by soil input than %cren. Nevertheless, other
confounding factors should be well constrained and local/site-specific
calibrations are needed before the two molecular proxies are used
quantitatively in down-core applications.
Title: Earth wind as a possible source of lunar surface hydration
Authors: Wang, H. Z.; Zhang, J.; Shi, Q. Q.; Saito, Y.; Degeling,
A. W.; Rae, I. J.; Liu, J.; Guo, R. L.; Yao, Z. H.; Tian, A. M.; Fu,
X. H.; Zong, Q. G.; Liu, J. Z.; Ling, Z. C.; Sun, W. J.; Bai, S. C.;
Chen, J.; Yao, S. T.; Zhang, H.; Wei, Y.; Liu, W. L.; Xia, L. D.;
Chen, Y.; Feng, Y. Y.; Fu, S. Y.; Pu, Z. Y.
Bibcode: 2019arXiv190304095W
Altcode:
Understanding the sources of lunar water is crucial for studying the
history of lunar evolution, and also the solar wind interaction with
the Moon and other airless bodies. Recent observations revealed lunar
hydration is very likely a surficial dynamic process driven by solar
wind. Solar wind is shielded over a period of 3-5 days as the Moon
passes through the Earth's magnetosphere, during which a significant
loss of hydration is expected from previous works.Here we study lunar
hydration inside the magnetosphere using orbital spectral data, which
unexpectedly found that the polar surficial OH/H2O abundance remains
at the same level when in the solar wind and in the magnetosphere. We
suggest that particles from the magnetosphere (Earth wind, naturally
different from solar wind) contribute to lunar hydration. From lunar
orbital plasma observations, we find the existence of optimal energy
ranges, other than 1 keV as previously thought, for surface hydration
formation. These optimal energy ranges deduced from space observations
may provide strong implications for laboratory experiments simulating
lunar hydration processes.
Title: Surface Tension of the Black Hole Horizon
Authors: Shu, Liangsuo; Cui, Kaifeng; Liu, Xiaokang; Liu, Zhichun;
Liu, Wei
Bibcode: 2019ForPh..6700076S
Altcode: 2018arXiv180203577S
The idea of treating the horizon of a black hole as a stretched
membrane with surface tension has a long history. In this work, we
discuss the microscopic origin of the surface tension of the horizon
in quantum pictures of spaces, which are Bose-Einstein condensates
of gravitons. The horizon is a phase interface of gravitons, the
surface tension of which is found to be a result of the difference
in the strength of the interaction between the gravitons on its two
sides. The gravitational source, such as a Schwarzschild black hole,
creates a transitional zone by changing the energy and distribution
of its surrounding gravitons. Archimedes' principle for gravity can
be expressed as follows: "the gravity on an object is equal to the
weight of the gravitons that it displaces."
Title: The on-orbit calibration of DArk Matter Particle Explorer
Authors: Ambrosi, G.; An, Q.; Asfandiyarov, R.; Azzarello, P.;
Bernardini, P.; Cai, M. S.; Caragiulo, M.; Chang, J.; Chen, D. Y.;
Chen, H. F.; Chen, J. L.; Chen, W.; Cui, M. Y.; Cui, T. S.; Dai, H. T.;
D'Amone, A.; De Benedittis, A.; De Mitri, I.; Ding, M.; Di Santo, M.;
Dong, J. N.; Dong, T. K.; Dong, Y. F.; Dong, Z. X.; Droz, D.; Duan,
K. K.; Duan, J. L.; D'Urso, D.; Fan, R. R.; Fan, Y. Z.; Fang, F.;
Feng, C. Q.; Feng, L.; Fusco, P.; Gallo, V.; Gan, F. J.; Gao, M.;
Gao, S. S.; Gargano, F.; Garrappa, S.; Gong, K.; Gong, Y. Z.; Guo,
J. H.; Hu, Y. M.; Huang, G. S.; Huang, Y. Y.; Ionica, M.; Jiang, D.;
Jiang, W.; Jin, X.; Kong, J.; Lei, S. J.; Li, S.; Li, X.; Li, W. L.;
Li, Y.; Liang, Y. F.; Liang, Y. M.; Liao, N. H.; Liu, C. M.; Liu,
H.; Liu, J.; Liu, S. B.; Liu, W. Q.; Liu, Y.; Loparco, F.; Ma, M.;
Ma, P. X.; Ma, S. Y.; Ma, T.; Ma, X. Q.; Ma, X. Y.; Marsella, G.;
Mazziotta, M. N.; Mo, D.; Niu, X. Y.; Pan, X.; Peng, X. Y.; Peng,
W. X.; Qiao, R.; Rao, J. N.; Salinas, M. M.; Shang, G. Z.; Shen,
W. H.; Shen, Z. Q.; Shen, Z. T.; Song, J. X.; Su, H.; Su, M.; Sun,
Z. Y.; Surdo, A.; Teng, X. J.; Tian, X. B.; Tykhonov, A.; Vitillo,
S.; Wang, C.; Wang, H.; Wang, H. Y.; Wang, J. Z.; Wang, L. G.; Wang,
Q.; Wang, S.; Wang, X. H.; Wang, X. L.; Wang, Y. F.; Wang, Y. P.;
Wang, Y. Z.; Wang, Z. M.; Wen, S. C.; Wei, D. M.; Wei, J. J.; Wei,
Y. F.; Wu, D.; Wu, J.; Wu, L. B.; Wu, S. S.; Wu, X.; Xi, K.; Xia,
Z. Q.; Xin, Y. L.; Xu, H. T.; Xu, Z. H.; Xu, Z. L.; Xu, Z. Z.; Xue,
G. F.; Yang, H. B.; Yang, P.; Yang, Y. Q.; Yang, Z. L.; Yao, H. J.;
Yu, Y. H.; Yuan, Q.; Yue, C.; Zang, J. J.; Zhang, D. L.; Zhang, F.;
Zhang, J. B.; Zhang, J. Y.; Zhang, J. Z.; Zhang, L.; Zhang, P. F.;
Zhang, S. X.; Zhang, W. Z.; Zhang, Y.; Zhang, Y. J.; Zhang, Y. Q.;
Zhang, Y. L.; Zhang, Y. P.; Zhang, Z.; Zhang, Z. Y.; Zhao, H.; Zhao,
H. Y.; Zhao, X. F.; Zhou, C. Y.; Zhou, Y.; Zhu, X.; Zhu, Y.; Zimmer, S.
Bibcode: 2019APh...106...18A
Altcode: 2019arXiv190702173A
The DArk Matter Particle Explorer (DAMPE), a satellite-based cosmic
ray and gamma-ray detector, was launched on December 17, 2015, and
began its on-orbit operation on December 24, 2015. In this work we
document the on-orbit calibration procedures used by DAMPE and report
the calibration results of the Plastic Scintillator strip Detector
(PSD), the Silicon-Tungsten tracKer-converter (STK), the BGO imaging
calorimeter (BGO), and the Neutron Detector (NUD). The results are
obtained using Galactic cosmic rays, bright known GeV gamma-ray
sources, and charge injection into the front-end electronics of each
sub-detector. The determination of the boundary of the South Atlantic
Anomaly (SAA), the measurement of the live time, and the alignments of
the detectors are also introduced. The calibration results demonstrate
the stability of the detectors in almost two years of the on-orbit
operation.
Title: Classification of large-scale stellar spectra based on deep
convolutional neural network
Authors: Liu, W.; Zhu, M.; Dai, C.; He, D. Y.; Yao, Jiawen; Tian,
H. F.; Wang, B. Y.; Wu, K.; Zhan, Y.; Chen, B. -Q.; Luo, A. -Li;
Wang, R.; Cao, Y.; Yu, X. C.
Bibcode: 2019MNRAS.483.4774L
Altcode: 2018MNRAS.tmp.2885L
Classification of stellar spectra from voluminous spectra is a
very important and challenging task. In order to better classify
stellar spectra, inspired by the principle of deep convolutional
neural network (CNN), we propose a supervised algorithm for stellar
spectra classification based on 1-D stellar spectra convolutional
neural network (1-D SSCNN). In 1-D SSCNN, we modify the traditional
2-D convolutional neural network into 1-D network to adapt to the
spectral classification. On the basis of using convolution algorithm,
the spectral features are extracted and used for classification. We
firstly use the stellar spectra data to train a 1-D SSCNN to obtain
a well-trained model, and then we apply the well-trained model to
classify the unknown spectra. To evaluate the performance of the
proposed algorithms, we apply 1-D SSCNN to classify three spectral
types: F-type spectra, G-type spectra and K-type spectra and ten
subclasses of K-type spectra: A0-type, A5-type, F0-type, F5-type,
G0-type, G5-type, K0-type, K5-type, M0-type and M5-type spectra from
Sloan Digital Sky Survey (SDSS). Our 1-D SSCNN algorithm obtain higher
classification accuracy compared with Support Vector Machine (SVM),
Random Forest (RF) and Artificial neural network (ANN).
Title: A deep learning approach for detecting candidates of supernova
remnants
Authors: Liu, Wei; Zhu, Meng; Dai, Cong; Wang, Bing-Yi; Wu, Kang;
Yu, Xian-Chuan; Tian, Wen-Wu; Zhang, Meng-Fei; Wang, Hong-Feng
Bibcode: 2019RAA....19...42L
Altcode:
Detecting supernova remnant (SNR) candidates in the interstellar
medium is a challenging task because SNRs have weak radio signals
and irregular shapes. The use of a convolutional neural network is a
deep learning method that can help us extract various features from
images. To extract SNRs from astronomical images and estimate the
positions of SNR candidates, we design the SNR-Net model composed of
a training component and a detection component. In addition, transfer
learning is used to initialize the network parameters, which improves
the speed and accuracy of network training. We apply a T-T plot (of
the different brightness temperatures of map pixels at two different
frequencies) to calculate the spectral index of SNR candidates. To
accelerate the scientific computing process, we take advantage of
innovative hardware architecture, such as deep learning optimized
graphics processing units, which increases the speed of computation
by a factor of 5. A case study suggests that SNR-Net may be applicable
to detecting extended sources in the images automatically.
Title: Noncommutative Coordinate Picture of the Quantum Phase Space
Authors: Kong, Otto C. W.; Liu, Wei-Yin
Bibcode: 2019arXiv190311962K
Altcode:
We illustrate an isomorphic representation of the observable algebra
for quantum mechanics in terms of the functions on the projective
Hilbert space, and its Hilbert space analog, with a noncommutative
product in terms of explicit coordinates and discuss the physical
and dynamical picture. The isomorphism is then used as a base for the
translation of the differential symplectic geometry of the infinite
dimensional manifolds onto the observable algebra as a noncommutative
geometry. Hence, we obtain the latter from the physical theory
itself. We have essentially an extended formalism of the Schrodinger
versus Heisenberg picture which we describe mathematically as like
a coordinate map from the phase space, for which we have presented
argument to be seen as the quantum model of the physical space, to the
noncommutative geometry coordinated by the six position and momentum
operators. The observable algebra is taken essentially as an algebra
of formal functions on the latter operators. The work formulates the
intuitive idea that the noncommutative geometry can be seen as an
alternative, noncommutative coordinate, picture of familiar quantum
phase space, at least so long as the symplectic geometry is concerned.
Title: Enhanced monopole transition strength from the cluster decay
of 13C
Authors: Feng, Jun; Ye, YanLin; Yang, Biao; Lin, ChengJian; Jia,
HuiMin; Pang, DanYang; Li, ZhiHuan; Lou, JianLing; Li, QiTe; Yang,
XiaoFei; Li, Jing; Zang, HongLiang; Liu, Qiang; Jiang, Wei; Li,
ChenGuang; Liu, Yang; Chen, ZhiQiang; Wu, HongYi; Wang, ChunGuang;
Liu, Wei; Wang, Xiang; Li, JingJing; Luo, DiWen; Jiang, Ying; Bai,
ShiWei; Xu, JinYan; Ma, NanRu; Sun, LiJie; Wang, DongXi
Bibcode: 2019SCPMA..6212011F
Altcode:
The inelastic excitations and cluster decay of
13C have been measured using the reaction,
9Be(13C,13C* → 9Be +
α)9Be. We observe strong excitation to the 14.3-MeV
(1/2-) resonant state from the cluster-decay channel,
leading to an enhanced monopole matrix element of (6.3 ± 0.6)
fm2. This large cluster-related monopole strength is a clear
indication of the cluster-structure domination of this state and is
consistent with the recent prediction of the orthogonality condition
model (OCM). It would be interesting to further explore the three-center
molecular rotational band that is initiated from the observed band-head.
Title: Global Impacts of Arctic Sea Ice Loss Mediated by the Atlantic
Meridional Overturning Circulation
Authors: Liu, Wei; Fedorov, Alexey V.
Bibcode: 2019GeoRL..46..944L
Altcode:
We explore the global impacts of Arctic sea ice decline in climate
model perturbation experiments focusing on the temporal evolution
of induced changes. We find that climate response to a realistic
reduction in sea ice cover varies dramatically between shorter decadal
and longer multidecadal to centennial timescales. During the first two
decades, when atmospheric processes dominate, sea ice decline induces
a "bipolar seesaw" pattern in surface temperature with warming in the
Northern and cooling in the Southern Hemisphere, leading to a northward
displacement of the Intertropical Convergence Zone and an expansion of
Antarctic sea ice. In contrast, on multidecadal and longer timescales,
the weakening of the Atlantic meridional overturning circulation,
caused by upper-ocean buoyancy anomalies spreading from the Arctic,
mediates direct sea ice impacts and nearly reverses the original
response pattern outside the Arctic. The Southern Hemisphere warms,
a Warming Hole emerges in the North Atlantic, the Intertropical
Convergence Zone shifts southward, and Antarctic sea ice contracts.
Title: Can the Friction of the Nova Envelope Account for the Extra
Angular Momentum Loss in Cataclysmic Variables?
Authors: Liu, Wei-Min; Li, Xiang-Dong
Bibcode: 2019ApJ...870...22L
Altcode: 2018arXiv181108648L
It has been shown that the rate of angular momentum loss (AML) in
cataclysmic variables (CVs) below the period gap is about 2.47 times
that caused by gravitational radiation (GR), suggesting an extra
AML mechanism aside from GR. Several potential mechanisms have been
proposed but none of them has been verified. In this work, we examine
whether AML caused by friction between the expanding nova envelope
and the donor star can account for the required AML rate. By adopting
various expanding velocities of the envelope, we have calculated the
evolution of CVs with typical initial parameters. Our results show
that this friction interaction unlikely solves the extra AML problem
unless the expanding velocities are extremely low. Thus, there should
be a more efficient AML mechanism that plays a role in CV evolution.
Title: Analysis of the 1.3-1.7 yr Oscillation Relationship between
Solar and Geomagnetic Activities
Authors: Qian, Y. W.; Feng, S.; Deng, L. H.; Liu, W. H.
Bibcode: 2019AcASn..60....3Q
Altcode:
The 1.3-1.7 yr periodic study of solar and geomagnetic activities is
very important for understanding the possible physical processes in the
solar-terrestrial coupling system. The sunspot is the most prominent
magnetic field structure in the solar photosphere, and the Ap index is
an important indicator of global geomagnetic activity. The 1.3-1.7 yr
period of the sunspot number and the geomagnetic Ap index is obtained
by the synchro-squeezing wavelet transform, and the phase relationship
between them is studied by cross-correlation analysis. The main results
are as following: (1) The 1.3-1.7 yr periods of the geomagnetic Ap index
and sunspot number exhibit intermittent evolutionary characteristics,
and change with time; (2) the geomagnetic Ap index has a higher
periodic component in odd solar cycles than the neighboring even
solar cycles, which is characterized by fluctuations; (3) the phase
relationship between geomagnetic Ap index and sunspot number is not
always consistent, in most cases the geomagnetic Ap index lags behind
the sunspot number, except in the 18th and 22th solar cycles.
Title: Understanding the Uncertainty in the 21st Century Dynamic
Sea Level Projections: The Role of the AMOC
Authors: Chen, Changlin; Liu, Wei; Wang, Guihua
Bibcode: 2019GeoRL..46..210C
Altcode:
Climate models show that the largest uncertainties in the 21st century
dynamic sea level (DSL) projections are in the high latitudes of the
North Atlantic and Southern Oceans. We conduct an intermodel singular
value decomposition analysis and find that the DSL uncertainties in
these two oceans are both intrinsically connected to the uncertainty
in the change of the Atlantic meridional overturning circulation
(AMOC). We further conduct a freshwater hosing experiment to show
that the AMOC decline not only accounts for the dipole pattern in the
DSL change in the North Atlantic but also remotely induces a poleward
shift in the Southern Hemisphere westerlies that helps build a belted
pattern of DSL change in the Southern Ocean. Our results suggest that
reducing the intermodel spread in the change of the AMOC can greatly
improve the consistency of DSL projection among models not only in
individual basins but over the global ocean.
Title: Revisiting the Spatially Dependent Propagation Model with
the Latest Observations of Cosmic-Ray Nuclei
Authors: Liu, Wei; Yao, Yu-hua; Guo, Yi-Qing
Bibcode: 2018ApJ...869..176L
Altcode: 2018arXiv180203602L
Recently the AMS-02 collaboration published detections of light
cosmic-ray nuclei, including lithium, beryllium, boron, carbon,
and oxygen. Combined with the released energy spectra of proton and
helium, both primary and secondary spectra have a prominent hardening
above ∼200 GV. In particular, the spectral variation of secondary
cosmic rays is greater than the primary ones. One of the plausible
interpretations for the above anomalies is the spatial-dependent
diffusion model. It has successfully described various observational
phenomena, e.g., hardening of primary nuclei, diffuse gamma-ray
distribution and cosmic-ray anisotropy, etc. In this work, we apply
the spatial-dependent propagation model to the latest observations,
including both primary and secondary nuclei. Apart from the primary
components, the spectra of secondary nuclei can be properly reproduced
as well, especially the upturn above 200 GV. We also calculate the
ratios of both secondary-to-primary and secondary-to-secondary. We
find that except for the Be/B ratio, the computations of the
spatial-dependent propagation model are in good agreement with the
current data.
Title: Global Magnetohydrodynamics Simulation of EUV Waves and Shocks
from the X8.2 Eruptive Flare on 2017 September 10
Authors: Jin, Meng; Liu, Wei; Cheung, Mark; Nitta, Nariaki; Manchester,
Ward; Ofman, Leon; Downs, Cooper; Petrosian, Vahe; Omodei, Nicola
Bibcode: 2018csc..confE..66J
Altcode:
As one of the largest flare-CME eruptions during solar cycle 24, the
2017 September 10 X8.2 flare event is associated with spectacular
global EUV waves that transverse almost the entire visible solar
disk, a CME with speed > 3000 km/s, which is one of the fastest
CMEs ever recorded, and >100 MeV Gamma-ray emission lasting for
more than 12 hours. All these unique observational features pose new
challenge on current numerical models to reproduce the multi-wavelength
observations. To take this challenge, we simulate the September 10 event
using a global MHD model (AWSoM: Alfven Wave Solar Model) within the
Space Weather Modeling Framework and initiate CMEs by Gibson-Low flux
rope. We conduct detailed comparisons of the synthesized EUV images with
SDO/AIA observations of global EUV waves. We find that the simulated
EUV wave morphology and kinematics are sensitive to the orientation
of the initial flux rope introduced to the source active region. An
orientation with the flux-rope axis in the north-south direction
produces the best match to the observations, which suggests that EUV
waves may potentially be used to constrain the flux-rope geometry for
such limb or behind-the-limb eruptions that lack good magnetic field
observations. We also compare observed and simulated EUV intensities
in multiple AIA channels to perform thermal seismology of the global
corona. Furthermore, we track the 3D CME-driven shock surface in the
simulation and derive the time-varying shock parameters together with
the dynamic magnetic connectivity between the shock and the surface
of the Sun, with which we discuss the role of CME-driven shocks in
the long-duration Gamma-ray events.
Title: A Truly Global Extreme Ultraviolet Wave from the SOL2017-09-10
X8.2+ Solar Flare-Coronal Mass Ejection
Authors: Liu, Wei; Jin, Meng; Downs, Cooper; Ofman, Leon; Cheung,
Mark C. M.; Nitta, Nariaki V.
Bibcode: 2018csc..confE..40L
Altcode:
We report SDO/AIA observations of an extraordinary global extreme
ultraviolet (EUV) wave triggered by the X8.2+ flare-CME eruption on 2017
September 10. This was one of the best EUV waves ever observed with
modern instruments, yet it was likely the last one of such magnitudes
of Solar Cycle 24 as the Sun heads toward the minimum. Its remarkable
characteristics include the following. (1) The wave was observed,
for the first time, to traverse the full-Sun corona over the entire
visible solar disk and off-limb circumference, manifesting a truly
global nature, owing to its exceptionally large amplitude, e.g., with
EUV enhancements by up to 300% at 1.1 Rsun from the eruption. (2)
This leads to strong transmissions (in addition to commonly observed
reflections) in and out of both polar coronal holes, which are usually
devoid of EUV waves. It has elevated wave speeds >2000 km/s within
them, consistent with the expected higher fast-mode magnetosonic wave
speeds. The coronal holes essentially serve as new "radiation centers"
for the waves being refracted out of them, which then travel toward the
equator and collide head-on, causing additional EUV enhancements. (3)
The wave produces significant compressional heating to local plasma
upon its impact, indicated by long-lasting EUV intensity changes and
differential emission measure increases at higher temperatures (e.g.,
log T=6.2) accompanied by decreases at lower temperatures (e.g.,
log T=6.0). These characteristics signify the potential of such EUV
waves for novel magnetic and thermal diagnostics of the solar corona
on global scales.
Title: Instrument Calibration of the Interface Region Imaging
Spectrograph (IRIS) Mission
Authors: Wülser, J. -P.; Jaeggli, S.; De Pontieu, B.; Tarbell,
T.; Boerner, P.; Freeland, S.; Liu, W.; Timmons, R.; Brannon, S.;
Kankelborg, C.; Madsen, C.; McKillop, S.; Prchlik, J.; Saar, S.;
Schanche, N.; Testa, P.; Bryans, P.; Wiesmann, M.
Bibcode: 2018SoPh..293..149W
Altcode:
The Interface Region Imaging Spectrograph (IRIS) is a NASA small
explorer mission that provides high-resolution spectra and images of
the Sun in the 133 - 141 nm and 278 - 283 nm wavelength bands. The
IRIS data are archived in calibrated form and made available to the
public within seven days of observing. The calibrations applied to
the data include dark correction, scattered light and background
correction, flat fielding, geometric distortion correction, and
wavelength calibration. In addition, the IRIS team has calibrated the
IRIS absolute throughput as a function of wavelength and has been
tracking throughput changes over the course of the mission. As a
resource for the IRIS data user, this article describes the details
of these calibrations as they have evolved over the first few years
of the mission. References to online documentation provide access to
additional information and future updates.
Title: Probing the Puzzle of Behind-the-limb γ-Ray Flares:
Data-driven Simulations of Magnetic Connectivity and CME-driven
Shock Evolution
Authors: Jin, Meng; Petrosian, Vahe; Liu, Wei; Nitta, Nariaki V.;
Omodei, Nicola; Rubio da Costa, Fatima; Effenberger, Frederic; Li,
Gang; Pesce-Rollins, Melissa; Allafort, Alice; Manchester, Ward, IV
Bibcode: 2018ApJ...867..122J
Altcode: 2018arXiv180701427J
Recent detections of high-energy γ-rays from behind-the-limb (BTL)
solar flares by the Fermi Gamma-ray Space Telescope pose a puzzle and
challenge on the particle acceleration and transport mechanisms. In
such events, the γ-ray emission region is located away from the BTL
flare site by up to tens of degrees in heliographic longitude. It
is thus hypothesized that particles are accelerated at the shock
driven by the coronal mass ejection (CME) and then travel from the
shock downstream back to the front side of the Sun to produce the
observed γ-rays. To test this scenario, we performed data-driven,
global magnetohydrodynamics simulations of the CME associated with a
well-observed BTL flare on 2014 September 1. We found that part of the
CME-driven shock develops magnetic connectivity with the γ-ray emission
region, facilitating transport of particles back to the Sun. Moreover,
the observed increase in γ-ray flux is temporally correlated with (1)
the increase of the shock compression ratio and (2) the presence of a
quasi-perpendicular shock over the area that is magnetically connected
to the γ-ray emitting region, both conditions favoring the diffusive
shock acceleration (DSA) of particles. These results support the above
hypothesis and can help resolve another puzzle, i.e., long-duration
(up to 20 hr) γ-rays flares. We suggest that, in addition to DSA,
stochastic acceleration by plasma turbulence may also play a role,
especially in the shock downstream region and during the early stage
when the shock Alfvén Mach number is small.
Title: Analysis of total reaction cross sections for deuterons on
1 p-shell-nuclei
Authors: Chen, YiDi; Zhang, Yun; Lou, JianLing; Pang, DanYang; Ye,
YanLin; Liu, Wei; Jiang, Ying; Li, Gen
Bibcode: 2018SCPMA..61k2011C
Altcode:
This study aims to analyze the differential cross sections (DCSs)
of elastic scattering and total reaction cross sections (TRCSs) of the
loosely-bound deuteron projectile impinging on 1 p-shell nuclei, such as
9Be, 12C, and 16O, at incident energies
ranging between 10.6 and 171 MeV using the continuum discretized coupled
channel (CDCC) method. By fitting the experimental data for the DCSs
and TRCSs, energy-dependent renormalization factors for the real and
imaginary parts of the nucleon-nucleus optical-model potentials deduced
from the studies proposed by Koning and Delaroche (KD02) and by Watson,
Singh, and Segel (WSS), are obtained. It is found that with the WSS
potential, which was obtained specifically for 1 p-shell nuclei, the
CDCC calculations can simultaneously reproduce both the DCSs and the
TRCSs. The results show that it is important to choose appropriate
optical potentials to describe deuteron-induced reactions.
Title: Late Paleozoic to early Triassic multiple roll-back and
oroclinal bending of the Mongolia collage in Central Asia
Authors: Xiao, Wenjiao; Windley, Brian F.; Han, Chunming; Liu, Wei;
Wan, Bo; Zhang, Ji'en; Ao, Songjian; Zhang, Zhiyong; Song, Dongfang
Bibcode: 2018ESRv..186...94X
Altcode:
The architecture and mechanics of an orogen can be understood in terms
of a system of collages that are characterized by a complex assemblage
of multiple components, but the fundamental paleogeographic framework
and the tectonic relationships between the different components are
often insufficiently defined, because of unavailable data. The Central
Asian Orogenic Belt (CAOB) provides an ideal opportunity to address
the fundamental framework of paleogeography and tectonic relationships
between the diverse and many components in this huge collage. In this
paper we review several lines of available evidence, which enable us to
propose a new tectonic model of huge roll-back in the formation of the
accretionary tectonics of the Mongolian collage in Central Asia. In the
early Paleozoic the Mongolia collage comprised the southern Siberian and
the Tuva-Mongol Oroclines. The Siberia Craton and the Mongolia collage
jointly formed a giant "tadpole-shape" within the Paleo-Asian and
Panthanlassic oceans; its head (Siberia) was to the south, and the tail
(Tuva-Mongol) to the northwest. The structures and tectonic zonation of
the Mongolia collage are characteristic of multiple arcs, which have
been separately described in detail in different segments southwards
from the Southern Siberia-East Sayan, West Sayan-Gorny Altai-Chara,
via the Lake Zone-Junggar-Tianshan, Gobi Altai-Beishan-Alxa, to the
Manlay-Hegenshan-Baolidao-Solonker segments. Almost all segments
underwent Early Paleozoic to Permian, or even Triassic, frontal
subduction and accretion, while rifting in the Late Carboniferous
to Permian or Triassic occurred in the outward/oceanward (westward)
advancing Mongolian collage. Therefore, we suggest that a huge complex
roll-back, active from the Carboniferous to Permian or even to late
Triassic, facilitated the formation of the Mongolian collage. The
outward multiple roll-back process was compatible and almost coeval
with the start of the Tuva-Mongol Orocline and rotation of the Siberian
Craton, as confirmed by paleomagnetic and structural data. During the
roll-back processes an archipelago paleogeography was formed behind the
frontal subduction and accretion, in which independent arcs or terranes
were amalgamated or collided to form composite arcs or terranes either
simultaneously or at slightly different times. The roll-back process was
affected by the collision of the Kazakhstan collage along the Chara and
Karamay zones in the Early Permian, the collision of the Tarim Craton
along the South Tianshan zone in the Early Permian, the collision of the
Dunhuang Block along the Liuyuan zone in the Early Permian-Triassic, the
collision of the Alxa block along the Qugan Qulu zone in the Permian,
and the collision of the North China Craton along the Solonker zone
in the Middle-Late Triassic. The tectonic styles and architecture of
accretionary orogenic belts like the CAOB are characterized both by
the amalgamation of multiple terranes and by oroclinal bending. The
systematic anatomy of the multiple roll-back processes and their
interactions with the adjacent collages shed light on the evolving
orogenic architecture and the crustal accretionary history of orogens.
Title: Investigating Sub-Pixel 45-Second Periodic Wobble in SDO/AIA
Data from January to August 2012
Authors: Yuan, Ding; Liu, Wei; Walsh, Robert
Bibcode: 2018SoPh..293..147Y
Altcode:
Artifacts could mislead interpretations in astrophysical observations. A
thorough understanding of an instrument will help in distinguishing
physical processes from artifacts. In this article, we investigate an
artifact of the Atmospheric Imaging Assembly (AIA) onboard the Solar
Dynamics Observatory. Time-series data and wavelet spectra revealed
periodic intensity perturbations in small regions over the entire
image in certain AIA extreme ultraviolet (EUV) passbands at a period of
about 45 seconds. These artificial intensity variations are prominently
detected in regions with sharp intensity contrast, such as sunspot light
bridges. This artifact was caused by a periodic pointing wobble of the
two AIA telescopes ATA 2 (193 and 211 Å channels) and ATA 3 (171 Å
and UV channels), to a lesser extent, while the other two telescopes
were not found to be affected. The peak-to-peak amplitude of the wobble
was about 0.2 pixel in ATA 2 and 0.1 pixel in ATA 3. This artifact was
intermittent and affected the data of seven months from 18 January to 28
August 2012, as a result of a thermal adjustment to the telescopes. We
recommend that standard pointing-correction techniques, such as local
correlation tracking, should be applied before any detailed scientific
analysis that requires sub-pixel pointing accuracy. Specifically, this
artificial 45-second periodicity was falsely interpreted as abnormal
sub-minute oscillations in a light bridge of a sunspot (Yuan and Walsh
in Astron. Astrophys.594, A101, 2016).
Title: High-temperature inter-mineral Cr isotope fractionation: A
comparison of ionic model predictions and experimental investigations
of mantle xenoliths from the North China Craton
Authors: Shen, Ji; Qin, Liping; Fang, Ziyao; Zhang, Yingnan; Liu,
Jia; Liu, Wei; Wang, Fangyue; Xiao, Yan; Yu, Huimin; Wei, Shiqiang
Bibcode: 2018E&PSL.499..278S
Altcode:
Recent works have proposed that chromium (Cr) isotopes could
be fractionated during peridotite partial melting and basaltic
magma crystallization. However, until now, inter-mineral Cr
isotope fractionation behavior for major mantle minerals has been
poorly constrained. To investigate the mechanism and magnitude of
equilibrium inter-mineral Cr isotope fractionation and to explore its
implications for planetary mantle and crust lithology evolutions, we
performed a systematic study of equilibrium Cr isotope fractionation
between major mantle minerals by coupling theoretical ionic modeling
with laboratory isotope analyses of natural samples and Cr valence
determinations by X-ray absorption near edge spectroscopy (XANES). The
ionic model considers both charges and coordination environments of Cr
species in mantle minerals, which have proven to be critical factors
affecting inter-mineral isotope fractionation. The ionic modeling
results predict a general order of spinel (Spl) > pyroxene (Py)
≥ olivine (Ol) in 53Cr/52Cr. Systematic
Cr isotope analyses of coexisting mantle minerals of seventeen
peridotite xenoliths from Beiyan in the North China craton were
performed. Chromium isotope results for different mineral pairs of
lherzolites (e.g., Δ53CrSpl-Ol of 0.11‰ to
0.16‰, Δ53CrSpl-Py of 0.04‰ to 0.11‰
and Δ53CrPy-Ol of 0.05‰ to 0.10‰ at 870
°C to 970 °C), document measurable and systematic inter-mineral
Cr isotope fractionation, in excellent agreement with the modeling
results predicted with XANES-determined Cr2+/ΣCr
values of the mineral separates. This fractionation order could
essentially account for Cr isotope behaviors during partial melting
and magmatic crystallization observed in terrestrial peridotites
and lunar basalts. In contrast, we found that metasomatisms
could influence Cr isotope compositions of minerals from Beiyan
metasomatized clinopyroxene- (Cpx-) rich lherzolites and wehrlites by
means of mineral-melt interaction and/or kinetic diffusion, leading
to disequilibrium inter-mineral Cr isotope fractionation.
Title: Statistical Correlation Analysis of Field-Aligned Currents
Measured by Swarm
Authors: Yang, J. -Y.; Dunlop, M. W.; Lühr, H.; Xiong, C.; Yang,
Y. -Y.; Cao, J. -B.; Wild, J. A.; Li, L. -Y.; Ma, Y. -D.; Liu, W. -L.;
Fu, H. -S.; Lu, H. -Y.; Waters, C.; Ritter, P.
Bibcode: 2018JGRA..123.8170Y
Altcode:
We investigate the statistical, dual-spacecraft correlations of
field-aligned current (FAC) signatures between two Swarm spacecraft. For
the first time, we infer the orientations of the current sheets of FACs
by directly using the maximum correlations obtained from sliding data
segments. The current sheet orientations are shown to broadly follow
the mean shape of the auroral boundary for the lower latitudes and that
these are most well ordered on the dusk side. Orientations at higher
latitudes are less well ordered. In addition, the maximum correlation
coefficients are explored as a function of magnetic local time and in
terms of either the time shift (δt) or the shift in longitude (δlon)
between Swarms A and C for various filtering levels and choice of
auroral region. We find that the low-latitude FACs show the strongest
correlations for a broad range of magnetic local time centered on dawn
and dusk, with a higher correlation coefficient on the dusk side and
lower correlations near noon and midnight. The positions of maximum
correlation are sensitive to the level of low-pass filter applied to
the data, implying temporal influence in the data. This study clearly
reflects the two different domains of FACs: small-scale (some tens
of kilometers), which are time variable, and large-scale (>50
km), which are rather stationary. The methodology is deliberately
chosen to highlight the locations of small-scale influences that are
generally variable in both time and space. We may fortuitously find a
potential new way to recognize bursts of irregular pulsations (Pi1B)
using low-Earth orbit satellites.
Title: GeV-TeV γ -ray energy spectral break of BL Lac objects
Authors: Zhong, W.; Liu, W. G.; Zheng, Y. G.
Bibcode: 2018Ap&SS.363..179Z
Altcode: 2018arXiv180800599Z
In this paper, we compile the very-high-energy and high-energy spectral
indices of 43 BL Lac objects from the literature. Based on a simple
math model, Δ Γ_{obs}= α {{{z}}}+β , we present evidence for the
origin of an observed spectral break that is denoted by the difference
between the observed very-high-energy and high-energy spectral indices,
Δ Γ_{obs}. We find by linear regression analysis that α ≠ 0 and
β ≠ 0. These results suggest that the extragalactic background
light attenuation and the intrinsic curvature dominate on the GeV-TeV
γ -ray energy spectral break of BL Lac objects. We argue that the
extragalactic background light attenuation is an exclusive explanation
for the redshift evolution of the observed spectral break.
Title: A Truly Global Extreme Ultraviolet Wave from the SOL2017-09-10
X8.2+ Solar Flare-Coronal Mass Ejection
Authors: Liu, Wei; Jin, Meng; Downs, Cooper; Ofman, Leon; Cheung,
Mark C. M.; Nitta, Nariaki V.
Bibcode: 2018ApJ...864L..24L
Altcode: 2018arXiv180709847L
We report Solar Dynamics Observatory/Atmospheric Imaging Assembly
(SDO/AIA) observations of an extraordinary global extreme ultraviolet
(EUV) wave triggered by the X8.2+ flare-CME eruption on 2017 September
10. This was one of the best EUV waves ever observed with modern
instruments, yet it was likely the last one of such magnitudes of
Solar Cycle 24 as the Sun heads toward the minimum. Its remarkable
characteristics include the following. (1) The wave was observed,
for the first time, to traverse the full-Sun corona over the entire
visible solar disk and off-limb circumference, manifesting a truly
global nature, owing to its exceptionally large amplitude, e.g.,
with EUV enhancements by up to 300% at 1.1 {R}⊙ from
the eruption. (2) This leads to strong transmissions (in addition to
commonly observed reflections) in and out of both polar coronal holes
(CHs), which are usually devoid of EUV waves. It has elevated wave
speeds >2000 {km} {{{s}}}-1 within the CHs, consistent
with the expected higher fast-mode magnetosonic wave speeds. The CHs
essentially serve as new “radiation centers” for the waves being
refracted out of them, which then travel toward the equator and collide
head-on, causing additional EUV enhancements. (3) The wave produces
significant compressional heating to local plasma upon its impact,
indicated by long-lasting EUV intensity changes and differential
emission measure increases at higher temperatures (e.g., {log}T=6.2)
accompanied by decreases at lower temperatures (e.g., {log}T=6.0). These
characteristics signify the potential of such EUV waves for novel
magnetic and thermal diagnostics of the solar corona on global scales.
Title: VizieR Online Data Catalog: Low-mass black holes in Sy1
galaxies. II. SDSS-DR7 (Liu+, 2018)
Authors: Liu, H. -Y.; Yuan, W.; Dong, X. -B.; Zhou, H.; Liu, W. -J.
Bibcode: 2018yCat..22350040L
Altcode:
A new sample of 204 low-mass black holes (LMBHs) in active galactic
nuclei (AGNs) is presented with black hole masses in the range of
(1-20)x105Mȯ. The AGNs are selected through
a systematic search among galaxies in the Seventh Data Release
(DR7) of the Sloan Digital Sky Survey (SDSS), and careful analyses
of their optical spectra and precise measurement of spectral
parameters. Combining them with our previous sample selected from
SDSS DR4 makes it the largest LMBH sample so far, totaling over 500
objects. Some of the statistical properties of the combined LMBH AGN
sample are briefly discussed in the context of exploring the low-mass
end of the AGN population. Their X-ray luminosities follow the extension
of the previously known correlation with the [OIII] luminosity. The
effective optical-to-X-ray spectral indices αOX, albeit
with a large scatter, are broadly consistent with the extension of the
relation with the near-UV luminosity L2500Å. Interestingly,
a correlation of αOX with black hole mass is also found,
with αOX being statistically flatter (stronger X-ray relative to
optical) for lower black hole masses. Only 26 objects, mostly radio
loud, were detected in radio at 20cm in the FIRST survey, giving a
radio-loud fraction of 4%. The host galaxies of LMBHs have stellar
masses in the range of 108.8-1012.4Mȯ
and optical colors typical of Sbc spirals. They are dominated by
young stellar populations that seem to have undergone continuous star
formation history. (5 data files).
Title: The nature of the lithium enrichment in the most Li-rich
giant star
Authors: Yan, Hong-Liang; Shi, Jian-Rong; Zhou, Yu-Tao; Chen,
Yong-Shou; Li, Er-Tao; Zhang, Suyalatu; Bi, Shao-Lan; Wu, Ya-Qian;
Li, Zhi-Hong; Guo, Bing; Liu, Wei-Ping; Gao, Qi; Zhang, Jun-Bo; Zhou,
Ze-Ming; Li, Hai-Ning; Zhao, Gang
Bibcode: 2018NatAs...2..790Y
Altcode: 2018arXiv180900187Y; 2018NatAs.tmp..111Y
About 1% of giant stars1 have anomalously high Li
abundances (ALi) in their atmospheres, conflicting
directly with the prediction of standard stellar evolution
models2. This finding makes the production and evolution
of Li in the Universe intriguing, not only in the sense of Big Bang
nucleosynthesis3,4 or the interstellar medium5,
but also for the evolution of stars. Decades of effort have been put
into explaining why such extreme objects exist6-8, yet the
origins of Li-rich giants are still being debated. Here, we report the
discovery of the most Li-rich giant known to date, with a very high
ALi of 4.51. This rare phenomenon was observed coincidentally
with another short-term event: the star is experiencing its luminosity
bump on the red giant branch. Such a high ALi indicates that
the star might be at the very beginning of its Li-rich phase, which
provides a great opportunity to investigate the origin and evolution
of Li in the Galaxy. A detailed nuclear simulation is presented with
up-to-date reaction rates to recreate the Li enrichment process in
this star. Our results provide tight constraints on both observational
and theoretical points of view, suggesting that low-mass giants can
internally produce Li to a very high level through 7Be
transportation during the red giant phase.
Title: Black hole as fireplace: limited communications across
the horizon
Authors: Shu, Liangsuo; Cui, Kaifeng; Liu, Xiaokang; Liu, Zhichun;
Liu, Wei
Bibcode: 2018arXiv180802642S
Altcode:
An insightful viewpoint was proposed by Susskind about AMPS firewall:
the region behind the firewall does not exist and the firewall
is an extension of the singularity. In this work, we provided a
possible picture of this idea by combining Newman's complex metric and
Dvali-Gomez BEC black holes, which are Bose-Einstein condensates of N
gravitons. The inner space behind the horizon is a realized imaginary
space encrusted by the real space outside the horizon. In this way,
the singularity extents to the horizon to make a firewall for the
infalling observer. Some gravitons escape during the fluctuation of the
BEC black hole, resulting in a micro-transparent horizon which makes
the firewall exposes slightly to an observer outside the horizon. This
picture allows limited communications across the horizon.
Title: Three-dimensional Velocity Measurements in Solar Prominence
Bubbles and Combined Kelvin-Helmholtz/Rayleigh-Taylor Instability
Authors: Berger, Thomas; Hillier, Andrew; Liu, Wei
Bibcode: 2018cosp...42E.293B
Altcode:
We present measurements of flow velocities in solar prominences that
display so-called "prominence bubble" events. Prominence bubbles
are large-scale buoyant intrusions into prominences that rise from
below and penetrate into the overlying plasma. They are believed to
be due to magnetic flux emergence below prominences and can trigger
Rayleigh-Taylor and Kelvin-Helmholtz instability flows as they interact
with the overlying prominence. Prominence bubbles frequently result
in the formation of plumes that rise into, or entirely through, the
overlying prominence. This presents a mechanism for increasing magnetic
flux and helicity in the associated coronal magnetic flux tubes,
which are key for their eventual loss of equilibrium and eruptions
as coronal mass ejections (CMEs). In this presentation, Hinode/Solar
Optical Telescope (SOT) and Interface Region Imaging Spectrograph (IRIS)
observations are analyzed to infer three-dimensional flow vectors
in the "boundary layer" above several prominence bubble events. IRIS
Doppler velocity measurements indicate flow speeds of 50-100 km/sec
perpendicular to the sky plane, consistent with flow speeds inferred
from combined Kelvin-Helmholtz/Rayleigh-Taylor instability analysis
using typical quiescent prominence density and magnetic flux density
values. With these typical values, flow speeds and magnetic flux
densities within the bubbles can be inferred to be on the order of
100 km/sec and 10 Gauss, respectively. We discuss the implications of
these novel results, and in particular, the potential for strong shear
flows at the bubble boundary to trigger Kelvin-Helmholtz instability
waves that develop into large-scale Rayleigh-Taylor instability plumes.
Title: High resolution observations of prominence rotation by Hinode
and IRIS
Authors: Okamoto, Joten; Liu, Wei
Bibcode: 2018cosp...42E2498O
Altcode:
Fine structures of prominences, especially threads, and their dynamics
provide physical information about the magnetic configuration and
property in the corona. Here we report two events of prominence rotation
observed by the Hinode and IRIS satellites. In the first event, we found
transverse motions of brightening threads at speeds up to 55 km/s seen
in the plane of the sky. Such motions appeared as sinusoidal space-time
trajectories with a typical period of 390 s, which is consistent
with plane-of-sky projections of rotational motions. At least 15
episodes of such motions occurred in two days, none associated with
any eruption. For these episodes, the plane-of-sky speed is linearly
correlated with the vertical travel distance, suggestive of a constant
angular speed. In the second event, spectral data taken by IRIS showed
strong blueshifts in the top portion of the prominence with a speed
of 30-40 km/s, while redshifts of similar speeds were detected at the
bottom. Line width of the bright threads were significantly larger
than those of stationary threads. These behaviors indicate rotations of
helical prominence threads. We interpreted the activations as evidence
of unwinding motions caused by magnetic reconnection between twisted
prominence fields and ambient coronal fields.
Title: Global Magnetohydrodynamics Simulation of EUV Waves and Shocks
from the X8.2 Eruptive Flare on 2017 September 10
Authors: Jin, Meng; Liu, Wei; Cheung, Mark; Nitta, Nariaki; Manchester,
Ward; Ofman, Leon; Downs, Cooper; Petrosian, Vahe; Omodei, Nicola
Bibcode: 2018shin.confE.207J
Altcode:
As one of the largest flare-CME eruptions during solar cycle 24, the
2017 September 10 X8.2 flare event is associated with spectacular
global EUV waves that transverse almost the entire visible solar
disk, a CME with speed > 3000 km/s, which is one of the fastest
CMEs ever recorded, and >100 MeV Gamma-ray emission lasting for
more than 12 hours. All these unique observational features pose new
challenge on current numerical models to reproduce the multi-wavelength
observations. To take this challenge, we simulate the September 10 event
using a global MHD model (AWSoM: Alfven Wave Solar Model) within the
Space Weather Modeling Framework and initiate CMEs by Gibson-Low flux
rope. We conduct detailed comparisons of the synthesized EUV images with
SDO/AIA observations of global EUV waves. We find that the simulated
EUV wave morphology and kinematics are sensitive to the orientation
of the initial flux rope introduced to the source active region. An
orientation with the flux-rope axis in the north-south direction
produces the best match to the observations, which suggests that EUV
waves may potentially be used to constrain the flux-rope geometry for
such limb or behind-the-limb eruptions that lack good magnetic field
observations. We also compare observed and simulated EUV intensities
in multiple AIA channels to perform thermal seismology of the global
corona. Furthermore, we track the 3D CME-driven shock surface in the
simulation and derive the time-varying shock parameters together with
the dynamic magnetic connectivity between the shock and the surface
of the Sun, with which we discuss the role of CME-driven shocks in
the long-duration Gamma-ray events.
Title: Development of a compact readout system for optical CCD in
Higashi-Hiroshima Observatory
Authors: Liu, Wei; Sako, Shigeyuki; Kawabata, Koji; Shi, Sheng-Cai;
Yoshida, Michitoshi; Utsumi, Yousuke
Bibcode: 2018SPIE10709E..1XL
Altcode:
We developed a new CCD readout system for the Kanata 1.5m telescope in
Higashi-Hiroshima Astronomical Observatory, Hiroshima University, Japan,
based on the system originally developed by the Kiso Array Controller
(KAC) project. In this development we aim at reducing the size and
the cost of the system. The system consists of CCD drive circuit,
three-order low-pass filters, differential input A/D converter,
FPGA, LVDC board, and can be operated by Linux host. We report the
current design and performances of this system, and the future work
as well. This readout system will be easily applicable to many other
astronomical instruments.
Title: High-Energy Aspects of Solar Flares: Recent Advances in
Observations and Models
Authors: Liu, Wei; Effenberger, Frederic; Petrosian, Vahe; Nitta,
Nariaki; Omodei, Nicola; Rubio da Costa, Fatima; Pesce-Rollins,
Melissa; Jin, Meng; Allafort, Alice
Bibcode: 2018cosp...42E2050L
Altcode:
Solar flares are one of the most spectacular manifestations of
solar activity with significant space-weather impacts. They also
serve as a unique laboratory for probing the underlying physics of
wide-ranging processes, including magnetic reconnection, generation
of plasma turbulence and shocks, particle acceleration, and plasma
heating. Solar flares thus bear important implications for physically
similar phenomena elsewhere in the universe, such as laboratory plasmas,
planetary magnetospheres, and flares on other stars or near compact
objects. In this presentation, we review recent observational and
modeling advances in solar flare research, with a focus on high-energy
aspects. Special attention will be paid to imaging and spectroscopic
observations, e.g., of long-duration and behind-the-limb gamma-ray
flares detected by Fermi, of coronal reconnection sites seen by
RHESSI, SDO, Hinode, and IRIS, and of the flaring lower atmosphere
(chromosphere and transition region) seen by IRIS. We will discuss
broad physical connections of flares to other phenomena on the Sun
(to a much greater extent than conventionally thought), such as the
correlation between quasi-periodic flare pulsations (seen from radio to
hard X-rays) and various MHD waves (some are directly imaged). We will
also review relevant modeling efforts to explain these observations,
focusing on a hybrid model of stochastic (by turbulence) plus shock
acceleration of particles, as well as combined kinetic and radiative
hydrodynamic simulations.
Title: Interaction between cool material from Sun-grazing comets
and the low corona
Authors: Jia, Yingdong; Pesnell, William; Liu, Wei; Downs, Cooper;
Bryans, Paul
Bibcode: 2018cosp...42E1613J
Altcode:
Sun-grazing comets dive into altitudes lower than 1 solar radius from
the chromosphere. Cool materials of temperature lower than 10 ^{3}K
explode from the comet into the 10 ^{6} K corona. These materials
undergone various stages of rapid chemical reactions in scales of
seconds to minutes. Such reactions Structures in such images of
various wavelengths indicate strong variation in ambient conditions
of the corona. We combine three numerical models: low corona model,
particle transportation model, and cometary plasma interaction model
into one framework to model the interaction of Sun-grazing comets in the
low corona. In our framework, cometary vapor are ionized via multiple
channels, and then detained by the coronal magnetic field. In seconds,
these ions are further ionized into their highest charge state, which
is revealed by certain emission lines. Constrained by coronal graphs
and cometary interaction images, we apply our framework to trace back
to the local condition of the ambient corona, and its spatial/time
variation. Our frame work is able to resolve structures of sub-million
meters to tens of million meters. Once trained by multiple stages of
the comet's journey in the low corona, this framework can identify the
fine spatial variations in plasma density and magnetic field intensity,
which may be visible to future close-up observations.
Title: Are "Solar Tornadoes" Really Rotating?
Authors: Liu, Wei; Chye Low, Boon; Okamoto, Joten; Berger, Thomas
Bibcode: 2018cosp...42E2053L
Altcode:
Solar "tornadoes" have been proposed to explain certain vertical
structures in prominences that exhibit apparent rotations. Yet, it
remains highly controversial whether such motions are real rotations
or transverse oscillations. We present a statistical study of IRIS
observations that reveal no clear evidence of systematic or coherent
rotations, which would otherwise result in opposite Doppler shifts,
i.e., blueshifts on the one side of the vertical structure and redshifts
on the other, which were not found in our sample of "tornadoes". In
addition, we find in one particular case observed by SDO/AIA that the
"tornado" disappeared upon the impact of an eruption that pushed
its mass away along a primarily horizontal trajectory (presumably
along magnetic field lines). This "tornado" shortly reformed with
the replenishment of material from the return flow of some of the
displaced mass back to its original location, at the dips of local
magnetic field lines, followed by back and forth transverse oscillations
around the dips. Such observations from both IRIS and AIA suggest that,
at least for the cases being analyzed here, the apparent oscillatory
motions of "tornadoes" are a result of longitudinal oscillations
(like a pendulum) of dense and heavy prominence material about the
local minimum of gravitational potential at the magnetic dips, an
interpretation proposed and supported by a number of authors.
Title: Cool Material in the Hot Solar Corona and the
Chromosphere-Corona Mass Cycle
Authors: Liu, Wei; Vial, Jean-Claude; Antolin, Patrick; Sun, Xudong;
Berger, Thomas
Bibcode: 2018cosp...42E2052L
Altcode:
In the million-degree hot and tenuous solar corona, under favorable
conditions, some mass can undergo a radiative cooling instability and
condense into material of 100 times cooler in two distinct forms -
prominences and coronal rain. Being at similar temperatures, they
exhibit contrasting morphologies and behaviors: a quiescent prominence
usually consists of numerous long-lasting, filamentary downflow
threads, while coronal rain consists of transient mass blobs falling
at comparably higher speeds along well-defined, curved paths (e.g.,
guided by coronal loops). We report recent imaging and spectroscopic
observations from SDO/AIA and IRIS of a hybrid prominence-coronal
rain complex structure that suggest different magnetic environments
being responsible for such distinctions. We also present an ensemble
of observations of the so-called funnel prominences that reside near
the dips of magnetic funnels. Regardless of their morphological and
behavioral differences, a large fraction of prominence and coronal
rain material eventually falls back to the chromosphere and serves as
the return flow of the so-called chromosphere-corona mass cycle (the
other half of this cycle is the upward transport of heated mass from
the chromosphere to the corona). We estimate the downflow mass fluxes
in prominences and coronal rain, and compare them with the coronal
mass budget in this cycle and with the mass loss to the solar wind
and coronal mass ejections (CMEs). We will discuss the broad physical
implications of these observations for fundamental questions, such as
coronal heating and beyond.
Title: Direct retrieval of stress and evaporation from space
observations
Authors: Liu, W. Timothy; Xie, Xiaosu
Bibcode: 2018cosp...42E2049L
Altcode:
Momentum flux (stress) and latent heat flux (evaporation) at ocean
surface are transported by turbulence, which is small scale random
process generated/subdued by wind shear and buoyancy (vertical wind
and density gradients). Turbulence is difficult to measure and,
traditionally, transfer coefficients (bulk parameterization formula)
are used to related them the mean parameter measured on ships, such
as, wind and humidity in air, and temperature and current at ocean
surface. Satellite sensors measure radiance and backscatter at the
ocean surface and there is no critical reason to reproduce measurements
of meteorological and oceanic sensors on ships. We show that direct
retrieval of latent heat flux from the radiance measured by microwave
radiometers mitigate errors caused by the multiplication of retrieval
uncertainties of wind to those of temperature or humidity while facing
the uncertainty of the transfer coefficient. We will address the
uncertainty of retrieving strong wind caused by backscatter saturation
and the change behavior of the transfer coefficient under tropical
cyclone by direct stress retrieval. We will show that scatterometers
measurements represent the vector difference between wind and current,
the characteristic of stress rather than wind. As different from the
prevailing winds, stress spins down the mesoscale eddies and reduce
the kinetic energy into the ocean.
Title: A Long-Lived Coronal Condensation Site Lasting Eight Months
Authors: Sun, Xudong; Liu, Wei; Yu, Sijie
Bibcode: 2018cosp...42E3295S
Altcode:
Cool plasma material, such as prominences or coronal rain, can
form in-situ by condensation in the solar corona due to a runaway
radiative cooling instability (a.k.a. thermal non-equilibrium). Recent
observations and numerical simulations suggest that such condensations
are quite common. In quiet-Sun regions, they occur preferentially
in locations where magnetic field is weak (e.g., null points) or
discontinuous (e.g., current sheets). Such events usually have short
lifetimes of hours to days. Surprisingly, we observed a high-latitude
condensation site lasting over eight months in 2014 with recurrent and
episodic condensations fueling a funnel-shaped prominence. Uplifting
V-shaped features suggest sustaining reconnection inside the funnel. We
analyze the coronal magnetic topology to investigate the necessary
condition of such a long-lived condensation site. We find that the
site was directly above a poleward photospheric flux surge when
the polar field polarity was close to its solar cycle reversal. The
large-scale magnetic cancellation front may have sustained interchange
reconnection at this location, creating suitable conditions for coronal
plasma condensation.
Title: Modeling Flare-Generated Quasi-Periodic Propagating Fast
Magnetosonic Waves Observed by SDO/AIA
Authors: Ofman, Leon; Liu, Wei
Bibcode: 2018cosp...42E2492O
Altcode:
Fast-propagating (phase speeds of ∼1000 km/s) quasi-periodic,
fast-mode wave (QFPs) accompanying many solar flares have been
discovered by SDO/AIA (Liu et al. 2011). They typically propagate in
funnel-like structures associated with the expanding magnetic field
topology of the active regions (ARs), driven by flare-pulsations
duration of impulsive phase. The fast magnetosonic waves provide
information on the magnetic, density, and temperature structure
through coronal seismology. While all previously reported QFP waves
originate from a single localized flaring source, we report the first
AIA observation and 3D MHD modeling of counter-QFPs originating from
two 'sympathetic' flares. The waves are excited at the two sources
associated with flare locations and connected by magnetic loops,
by time-depended forcing, constrained by the spatial (localized) and
quasi-periodic temporal evolution of the flare pulsations. With the
aid of 3D MHD modeling we investigate the excitation, propagation,
nonlinearity, and interaction of the counter-propagating waves for
a range of key parameters, such as the properties of the flaring
sources and the background magnetic topology. In addition to QFPs,
we find evidence of associated waves, such as trapped fast (kink)
modes in coronal loops, and slow mode waves propagating along the
AR loops. Our model results are in qualitative agreement with the
AIA-observed counter propagating waves providing the first direct
evidence of counter-propagating fast magnetosonic waves that carry
significant energy flux in low-corona magnetic structures.
Title: The Best and Last of Solar Cycle 24 - The Global EUV Wave from
the X8 Flare-CME Eruption on 2017-Sept-10: SDO/AIA Observations and
Data-constrained Simulations
Authors: Liu, Wei; Ofman, Leon; Nitta, Nariaki; Cheung, Mark; Downs,
Cooper; Jin, Meng
Bibcode: 2018cosp...42E2051L
Altcode:
Global extreme ultraviolet (EUV) waves are commonly associated with
coronal mass ejections (CMEs) and flares. One particular EUV wave
that was triggered by the X8 flare-CME eruption on 2017 September
10 was extraordinary - one of the best EUV waves ever observed with
modern instruments (e.g., SDO/AIA and GOES/SUVI), yet likely the last
one of such magnitudes in Cycle 24 as the Sun heads toward the solar
minimum. We present here detailed analysis of SDO/AIA observations
of this event and comparison with high-fidelity, data-constrained MHD
simulations using the University of Michigan Alfven Wave Solar Model
(AWSoM). Observational highlights include: (1) The EUV wave traverses
almost the entire visible solar disk and circumference, manifesting its
truly global nature. This vast range is mainly due to the exceptionally
large wave amplitude, with EUV intensity changes by up to a factor of
3 (as opposed to, e.g., 30% for moderate events). (2) The large wave
amplitude also leads to the novel detection of strong transmission
components (in addition to commonly observed reflections) into and
through both polar coronal holes, at elevated apparent wave speeds up
to 2600 km/s. (3) The wave also produces significant heating, indicated
by long-lasting EUV intensity changes. As such, this EUV wave offers
unique magnetic and thermal diagnostics of the global, CME-spawning
corona. Our MHD simulations have largely reproduced the observed
features. We find that the simulated EUV wave morphology and kinematics
are sensitive to the orientation of the initial flux rope introduced to
the host active region. An orientation with the flux-rope axis in the
north-south direction produces the best match to the observations. This
suggests that EUV waves may potentially be used to constrain the
flux-rope geometry for such limb or behind-the-limb eruptions, whose
source-region magnetic fields cannot be directly observed, and thus
offer useful implications for space-weather predictions.
Title: On the Nature of Funnel Prominences
Authors: Liu, Wei; Chye Low, Boon; Berger, Thomas
Bibcode: 2018cosp...42E2054L
Altcode:
It has been proposed that prominences are manifestations of a
magneto-thermal convection process that involves ever-present dynamic
descents of cool material threads and upflows of hot bubbles and plumes
(Berger et al. 2011 Nature). On global scales, prominences may play
an important role as the return flows of the chromosphere-corona
mass cycle. A critical step in this cycle is the condensation of
million-degree coronal plasma into T<10,000 K prominence material by
radiative cooling instability. Direct observational evidence has been
lacking for decades, a situation that has recently changed, especially
with the advent of the SDO mission. We present here SDO/AIA observations
of runaway cooling in coronal loops leading to condensation at magnetic
dips and formation of funnel-shaped prominences (e.g., Liu et al. 2012,
2014; Berger et al. 2012 ApJL). We find that a macroscopically quiescent
prominence is microscopically dynamic, involving the passage (through
condensation and drainage) of a significant mass of typically 10^{15}
gram/day (comparable to the mass of a typical CME). This picture
is further supported by the theoretical development on spontaneous
formation of current sheets and condensations (Low et al. 2012a, b,
ApJ). Such funnel prominences, usually small in size, can constitute
a new type of prominences. We suggest that similar processes could
produce elementary building blocks of large-scale quiescent prominences
in filament channels.
Title: Quasi-periodic Counter-propagating Fast Magnetosonic Wave
Trains from Neighboring Flares: SDO/AIA Observations and 3D MHD
Modeling
Authors: Ofman, Leon; Liu, Wei
Bibcode: 2018ApJ...860...54O
Altcode: 2018arXiv180500365O
Since their discovery by the Solar Dynamics Observatory/Atmospheric
Imaging Assembly (AIA) in the extreme ultraviolet, rapid (phase
speeds of ∼1000 km s-1), quasi-periodic, fast-mode
propagating (QFP) wave trains have been observed accompanying many solar
flares. They typically propagate in funnel-like structures associated
with the expanding magnetic field topology of the active regions
(ARs). The waves provide information on the associated flare pulsations
and the magnetic structure through coronal seismology (CS). The reported
waves usually originate from a single localized source associated with
the flare. Here we report the first detection of counter-propagating
QFPs associated with two neighboring flares on 2013 May 22, apparently
connected by large-scale, trans-equatorial coronal loops. We present
the first results of a 3D MHD model of counter-propagating QFPs in
an idealized bipolar AR. We investigate the excitation, propagation,
nonlinearity, and interaction of the counter-propagating waves for a
range of key model parameters, such as the properties of the sources
and the background magnetic structure. In addition to QFPs, we also
find evidence of trapped fast- (kink) and slow-mode waves associated
with the event. We apply CS to determine the magnetic field strength
in an oscillating loop during the event. Our model results are in
qualitative agreement with the AIA-observed counter-propagating waves
and used to identify the various MHD wave modes associated with the
observed event, providing insights into their linear and nonlinear
interactions. Our observations provide the first direct evidence of
counter-propagating fast magnetosonic waves that can potentially lead
to turbulent cascade and carry significant energy flux for coronal
heating in low-corona magnetic structures.
Title: On the PeV knee of the cosmic ray spectrum and the TeV cutoff
of the electron spectrum
Authors: Jin, Chao; Liu, Wei; Hu, Hong-Bo; Guo, Yi-Qing
Bibcode: 2018PhRvD..97l3005J
Altcode: 2016arXiv161108384J
Spectra of cosmic rays (CRs), and particularly their features, contain
a lot of important information about the astroparticle physics and the
fundamental physics. Realizing that the 4 PeV knee of CR nuclei and
the 1 TeV spectral cutoff of the electron share almost the same Lorentz
factor, we propose that CRs experience a threshold interaction with a
new light particle X abundant in the Galaxy. The interaction CR +X →CR
+X' can take place when the effective energy is sufficient
to convert it into another heavier unknown particle X' (as a
representative to all possible threshold inelastic interactions). Under
this scenario, we can reproduce the spectral break for both the nuclei
and the electron and predict a zigzag spectrum for them. Given that
there are great uncertainties in experiments, our model accommodates
a wide mass range of the X from the ultralow value to around 1 eV.
Title: Loop-top flows and Footpoint Motions in the September 10 2017
X8 Flare
Authors: Reeves, Katharine; Galan, Giselle; Polito, Vanessa; Chen,
Bin; Liu, Wei; Li, Gang
Bibcode: 2018tess.conf30604R
Altcode:
The September 10 2017 X8 flare was a spectacular limb event complete
with a coronal mass ejection and a bright flare loop arcade. We examine
the IRIS Fe XXI data from this event. Fe XXI is a coronal line that
is formed at about 10 MK. The IRIS pointing was just south of the main
cusp-shaped loop structure visible in AIA, but it did capture most of
the flare arcade on the limb. We find that the majority of the emission
in the loops is slightly red shifted, with speeds of about 20 km/s,
probably due to chromospheric evaporation and an inclined viewing
angle. During the period from 16:05 - 16:15 UT, we find that faint
blue-shifted regions appear at the tops of the loops, indicating plasma
flows of 20-60 km/s. The location where these blue shifts are observed
moves south along the flare arcade at a speed of about 17 km/s. The AIA
data shows flare ribbons moving to the south at the same time, though at
much faster speeds of 70-90 km/s. We speculate that the loop-top blue
shifts are connected to the footpoint motions and could be signatures
of deflected flows from the reconnection outflow jet. Interestingly,
in the minutes before the blue-shifted loop-top emission was observed,
the Expanded Owens Valley Solar Array observed nonthermal microwave
emission at the loop-tops indicative of particle acceleration there.
Title: OH megamasers: dense gas & the infrared radiation field
Authors: Huang, Yong; Zhang, JiangShui; Liu, Wei; Xu, Jie
Bibcode: 2018JApA...39...34H
Altcode:
To investigate possible factors related to OH megamaser formation (OH
MM, LH2O>10 L⊙ ), we compiled
a large HCN sample from all well-sampled HCN measurements so far
in local galaxies and identified with the OH MM, OH kilomasers
(LH2O<10 L⊙ , OH kMs), OH
absorbers and OH non-detections (non-OH MM). Through comparative
analysis on their infrared emission, CO and HCN luminosities (good
tracers for the low-density gas and the dense gas, respectively),
we found that OH MM galaxies tend to have stronger HCN emission
and no obvious difference on CO luminosity exists between OH MM and
non-OH MM. This implies that OH MM formation should be related to the
dense molecular gas, instead of the low-density molecular gas. It
can be also supported by other facts: (1) OH MMs are confirmed to
have higher mean molecular gas density and higher dense gas fraction
(LHCN/LCO ) than non-OH MMs. (2) After taking
the distance effect into account, the apparent maser luminosity
is still correlated with the HCN luminosity, while no significant
correlation can be found at all between the maser luminosity and the CO
luminosity. (3) The OH kMs tend to have lower values than those of OH
MMs, including the dense gas luminosity and the dense gas fraction. (4)
From analysis of known data of another dense gas tracer HCO+,
similar results can also be obtained. However, from our analysis, the
infrared radiation field can not be ruled out for the OH MM trigger,
which was proposed by previous works on one small sample (Darling in
ApJ 669:L9, 2007). On the contrary, the infrared radiation field should
play one more important role. The dense gas (good tracers of the star
formation) and its surrounding dust are heated by the ultra-violet
(UV) radiation generated by the star formation and the heating of the
high-density gas raises the emission of the molecules. The infrared
radiation field produced by the re-radiation of the heated dust in
turn serves for the pumping of the OH MM.
Title: Global Magnetohydrodynamics Simulation of EUV Waves and Shocks
from the X8.2 Eruptive Flare on 2017 September 10
Authors: Jin, Meng; Liu, Wei; Cheung, Chun Ming Mark; Nitta, Nariaki;
Manchester, Ward; Ofman, Leon; Downs, Cooper; Petrosian, Vahe;
Omodei, Nicola
Bibcode: 2018tess.conf31905J
Altcode:
As one of the largest flare-CME eruptions during solar cycle 24, the
2017 September 10 X8.2 flare event is associated with spectacular
global EUV waves that transverse almost the entire visible solar
disk, a CME with speed > 3000 km/s, which is one of the fastest
CMEs ever recorded, and >100 MeV Gamma-ray emission lasting for
more than 12 hours. All these unique observational features pose new
challenge on current numerical models to reproduce the multi-wavelength
observations. To take this challenge, we simulate the September 10 event
using a global MHD model (AWSoM: Alfven Wave Solar Model) within the
Space Weather Modeling Framework and initiate CMEs by Gibson-Low flux
rope. We conduct detailed comparisons of the synthesized EUV images with
SDO/AIA observations of global EUV waves. We find that the simulated
EUV wave morphology and kinematics are sensitive to the orientation
of the initial flux rope introduced to the source active region. An
orientation with the flux-rope axis in the north-south direction
produces the best match to the observations, which suggests that EUV
waves may potentially be used to constrain the flux-rope geometry for
such limb or behind-the-limb eruptions that lack good magnetic field
observations. We also compare observed and simulated EUV intensities
in multiple AIA channels to perform thermal seismology of the global
corona. Furthermore, we track the 3D CME-driven shock surface in the
simulation and derive the time-varying shock parameters together with
the dynamic magnetic connectivity between the shock and the surface
of the Sun, with which we discuss the role of CME-driven shocks in
the long-duration Gamma-ray events.
Title: A Study of Detector Response and Filter Optimization for the
Wide Field Survey Telescope
Authors: Shi, D. D.; Zheng, X. Z.; Zhao, H. B.; Lou, Z.; Wang, H. R.;
Qian, Y.; Liu, W.; Yao, D. Z.
Bibcode: 2018AcASn..59...22S
Altcode:
The Wide Field Survey Telescope (WFST) is designed to be a powerful
survey machine with prime-focus optics, 2.5 m diameter primary mirror,
and 3 degree field of view. It is dedicated to a northern sky imaging
survey over 20000 square degrees area. The main science goals include:
(1) characterizing the compositions and structures of the Milky Way
and local universe; (2) mapping the solar system objects; and (3)
exploring variable universe. We combine the optical throughput, charge
coupled device (CCD) quantum response, and filter transmission with
atmospheric transmission of a 5130 m-altitude site and sky emission
from the site of Mauna Kea to analyze the sensitivities of the telescope
with different types of CCD response curves. Our results denote that a
typical blue-sensitive CCD provides a higher sensitivity in observing
blue-color objects like supernova and quasar than a typical broadband
CCD, but a lower sensitivity in the r, i, and z bands, leading to a
lower survey efficiency to the same u, g, r, i, and z depths. We show
that the wavelength range of the w filter (≃ g+r+i) can be optimized
in terms of the energy distribution of survey targets, and give the
optimal wavelength range of 367-795 nm for the w filter. Finally,
we present the u, g, r, i, z, and w sensitivities as a function of
integration time to demonstrate the capability of WFST.
Title: Cyclostratigraphic calibration of the Famennian stage (Late
Devonian, Illinois Basin, USA)
Authors: Pas, Damien; Hinnov, Linda; Day, James E. (Jed); Kodama,
Kenneth; Sinnesael, Matthias; Liu, Wei
Bibcode: 2018E&PSL.488..102P
Altcode:
The Late Devonian biosphere was affected by two of the most severe
biodiversity crises in Earth's history, the Kellwasser and Hangenberg
events near the Frasnian-Famennian (F-F) and the Devonian-Carboniferous
(D-C) boundaries, respectively. Current hypotheses for the causes
of the Late Devonian extinctions are focused on climate changes and
associated ocean anoxia. Testing these hypotheses has been impeded by
a lack of sufficient temporal resolution in paleobiological, tectonic
and climate proxy records. While there have been recent advances
in astronomical calibration that have improved the accuracy of the
Frasnian time scale and part of the Famennian, the time duration
of the entire Famennian Stage remains poorly constrained. During
the Late Devonian, a complete Late Frasnian-Early Carboniferous
succession of deep-shelf deposits accumulated in the epieric sea
in Illinois Basin of the central North-American mid-continent. A
record of this sequence is captured in three overlapping cores (H-30,
Sullivan and H-32). The H-30 core section spans the F-F boundary;
the Sullivan section spans almost all of the Famennian and the H-32
section sampled spans the interval of the Upper Famennian and the D-C
boundary. To have the best chance of capturing Milankovitch cycles,
2000 rock samples were collected at minimum 5-cm-interval across the
entire sequence. Magnetic susceptibility (MS) was measured on each
sample and the preservation of climatic information into the MS signal
was verified through geochemical analyses and low-temperature magnetic
susceptibility acquisition. To estimate the duration of the Famennian
Stage, we applied multiple spectral techniques and tuned the MS signal
using the highly stable 405 kyr cycle for Sullivan and the obliquity
cycle for the H-30 and H-32 cores. Based on the correlation between
the cores we constructed a Famennian floating astronomical time scale,
which indicates a duration of 13.5 ± 0.5 myr. An uncertainty of 0.5
myr was estimated for the uncertainties arising from the errors in the
stratigraphic position of the F-F and D-C boundaries, and the 405 kyr
cycle counting. Interpolated from the high-resolution U-Pb radiometric
ages available for the Devonian-Carboniferous boundary we recalibrated
the Frasnian-Famennian boundary numerical age to 372.4 ± 0.9 Ma.
Title: Identification and mitigation of narrow spectral artifacts
that degrade searches for persistent gravitational waves in the
first two observing runs of Advanced LIGO
Authors: Covas, P. B.; Effler, A.; Goetz, E.; Meyers, P. M.; Neunzert,
A.; Oliver, M.; Pearlstone, B. L.; Roma, V. J.; Schofield, R. M. S.;
Adya, V. B.; Astone, P.; Biscoveanu, S.; Callister, T. A.; Christensen,
N.; Colla, A.; Coughlin, E.; Coughlin, M. W.; Crowder, S. G.; Dwyer,
S. E.; Eggenstein, H. -B.; Hourihane, S.; Kandhasamy, S.; Liu, W.;
Lundgren, A. P.; Matas, A.; McCarthy, R.; McIver, J.; Mendell, G.;
Ormiston, R.; Palomba, C.; Papa, M. A.; Piccinni, O. J.; Rao, K.;
Riles, K.; Sammut, L.; Schlassa, S.; Sigg, D.; Strauss, N.; Tao,
D.; Thorne, K. A.; Thrane, E.; Trembath-Reichert, S.; Abbott, B. P.;
Abbott, R.; Abbott, T. D.; Adams, C.; Adhikari, R. X.; Ananyeva, A.;
Appert, S.; Arai, K.; Aston, S. M.; Austin, C.; Ballmer, S. W.; Barker,
D.; Barr, B.; Barsotti, L.; Bartlett, J.; Bartos, I.; Batch, J. C.;
Bejger, M.; Bell, A. S.; Betzwieser, J.; Billingsley, G.; Birch, J.;
Biscans, S.; Biwer, C.; Blair, C. D.; Blair, R. M.; Bork, R.; Brooks,
A. F.; Cao, H.; Ciani, G.; Clara, F.; Clearwater, P.; Cooper, S. J.;
Corban, P.; Countryman, S. T.; Cowart, M. J.; Coyne, D. C.; Cumming,
A.; Cunningham, L.; Danzmann, K.; Costa, C. F. Da Silva; Daw, E. J.;
DeBra, D.; DeRosa, R. T.; DeSalvo, R.; Dooley, K. L.; Doravari, S.;
Driggers, J. C.; Edo, T. B.; Etzel, T.; Evans, M.; Evans, T. M.;
Factourovich, M.; Fair, H.; Galiana, A. Fernández; Ferreira, E. C.;
Fisher, R. P.; Fong, H.; Frey, R.; Fritschel, P.; Frolov, V. V.; Fulda,
P.; Fyffe, M.; Gateley, B.; Giaime, J. A.; Giardina, K. D.; Goetz, R.;
Goncharov, B.; Gras, S.; Gray, C.; Grote, H.; Gushwa, K. E.; Gustafson,
E. K.; Gustafson, R.; Hall, E. D.; Hammond, G.; Hanks, J.; Hanson,
J.; Hardwick, T.; Harry, G. M.; Heintze, M. C.; Heptonstall, A. W.;
Hough, J.; Inta, R.; Izumi, K.; Jones, R.; Karki, S.; Kasprzack, M.;
Kaufer, S.; Kawabe, K.; Kennedy, R.; Kijbunchoo, N.; Kim, W.; King,
E. J.; King, P. J.; Kissel, J. S.; Korth, W. Z.; Kuehn, G.; Landry, M.;
Lantz, B.; Laxen, M.; Liu, J.; Lockerbie, N. A.; Lormand, M.; MacInnis,
M.; Macleod, D. M.; Márka, S.; Márka, Z.; Markosyan, A. S.; Maros,
E.; Marsh, P.; Martin, I. W.; Martynov, D. V.; Mason, K.; Massinger,
T. J.; Matichard, F.; Mavalvala, N.; McClelland, D. E.; McCormick,
S.; McCuller, L.; McIntyre, G.; McRae, T.; Merilh, E. L.; Miller, J.;
Mittleman, R.; Mo, G.; Mogushi, K.; Moraru, D.; Moreno, G.; Mueller,
G.; Mukund, N.; Mullavey, A.; Munch, J.; Nelson, T. J. N.; Nguyen,
P.; Nuttall, L. K.; Oberling, J.; Oktavia, O.; Oppermann, P.; Oram,
Richard J.; O'Reilly, B.; Ottaway, D. J.; Overmier, H.; Palamos, J. R.;
Parker, W.; Pele, A.; Penn, S.; Perez, C. J.; Phelps, M.; Pierro, V.;
Pinto, I.; Principe, M.; Prokhorov, L. G.; Puncken, O.; Quetschke, V.;
Quintero, E. A.; Radkins, H.; Raffai, P.; Ramirez, K. E.; Reid, S.;
Reitze, D. H.; Robertson, N. A.; Rollins, J. G.; Romel, C. L.; Romie,
J. H.; Ross, M. P.; Rowan, S.; Ryan, K.; Sadecki, T.; Sanchez, E. J.;
Sanchez, L. E.; Sandberg, V.; Savage, R. L.; Sellers, D.; Shaddock,
D. A.; Shaffer, T. J.; Shapiro, B.; Shoemaker, D. H.; Slagmolen,
B. J. J.; Smith, B.; Smith, J. R.; Sorazu, B.; Spencer, A. P.; Staley,
A.; Strain, K. A.; Sun, L.; Tanner, D. B.; Tasson, J. D.; Taylor,
R.; Thomas, M.; Thomas, P.; Toland, K.; Torrie, C. I.; Traylor, G.;
Tse, M.; Tuyenbayev, D.; Vajente, G.; Valdes, G.; van Veggel, A. A.;
Vecchio, A.; Veitch, P. J.; Venkateswara, K.; Vo, T.; Vorvick, C.;
Wade, M.; Walker, M.; Ward, R. L.; Warner, J.; Weaver, B.; Weiss,
R.; Weßels, P.; Willke, B.; Wipf, C. C.; Wofford, J.; Worden, J.;
Yamamoto, H.; Yancey, C. C.; Yu, Hang; Yu, Haocun; Zhang, L.; Zhu,
S.; Zucker, M. E.; Zweizig, J.; LSC Instrument Authors
Bibcode: 2018PhRvD..97h2002C
Altcode: 2018arXiv180107204C
Searches are under way in Advanced LIGO and Virgo data for persistent
gravitational waves from continuous sources, e.g. rapidly rotating
galactic neutron stars, and stochastic sources, e.g. relic gravitational
waves from the Big Bang or superposition of distant astrophysical
events such as mergers of black holes or neutron stars. These searches
can be degraded by the presence of narrow spectral artifacts (lines)
due to instrumental or environmental disturbances. We describe a
variety of methods used for finding, identifying and mitigating these
artifacts, illustrated with particular examples. Results are provided
in the form of lists of line artifacts that can safely be treated as
non-astrophysical. Such lists are used to improve the efficiencies and
sensitivities of continuous and stochastic gravitational wave searches
by allowing vetoes of false outliers and permitting data cleaning.
Title: XOSS Transient Discovery Report for 2018-03-09
Authors: Xu, J.; Zhang, M.; Zhang, X.; Zhao, J.; Liu, W.; Ruan, J.;
Gao, X.
Bibcode: 2018TNSTR.326....1X
Altcode:
No abstract at ADS
Title: Ultraviolet Photooxidation of Fe2+ — Smectites and
Implications for Mars
Authors: Rivera-Banuchi, V. B.; Liu, W.; Yee, N.; Glotch, T. D.;
Legett, C.; Chemtob, S. M.
Bibcode: 2018LPI....49.2550R
Altcode:
Partial oxidation by UV radiation is shown for ferrous smectites,
providing another alteration pathway for the production of ferric
smectites on Mars.
Title: Oxidation Pathways for Ferrous Iron Smectites on Mars and
the Redox Evolution of Gale Crater
Authors: Chemtob, S. M.; Rivera-Banuchi, V. B.; Catalano, J. G.;
Nickerson, R. D.; Morris, R. V.; Agresti, D. G.; Liu, W.; Yee, N.
Bibcode: 2018LPI....49.2821C
Altcode:
Oxidation of ferrous smectites produces nontronite and iron oxides. We
discuss implications for the hematite-phyllosilicate facies of the
Murray Formation.
Title: Spatial Variation of Lunar Surface Hydration and the
Implications for Its Sources: Solar/Earth Winds or Others
Authors: Wang, H. Z.; Zhang, J.; Shi, Q. Q.; Khurana, K. K.; Rae,
I. J.; Liu, J.; Guo, R. L.; Chen, J.; Tian, A. M.; Yao, S. T.; Bai,
S. C.; Zhang, H.; Ling, Z. C.; Fu, X. H.; Wei, Y.; Liu, W. L.; Fu,
S. Y.; Zong, Q. G.; Pu, Z. Y.
Bibcode: 2018LPI....49.2066W
Altcode:
We studied lunar surface hydration in the polar regions, and correlated
its variations with incident ion flux when the Moon is inside/outside
the magnetosphere.
Title: High Resolution Digital Terrain Models of the Martian Surface:
Compensation of the Atmosphere on CTX Imagery
Authors: Wohlfarth, K. S.; Liu, W. C.; Wu, B.; Grumpe, A.; Wöhler, C.
Bibcode: 2018LPI....49.2498W
Altcode:
We present a framework for the construction of high-resolution digital
terrain models of the martian surface in the presence of strong
atmospheric disturbances.
Title: A challenge to identify an optical counterpart of the
gravitational wave event GW151226 with Hyper Suprime-Cam
Authors: Utsumi, Yousuke; Tominaga, Nozomu; Tanaka, Masaomi; Morokuma,
Tomoki; Yoshida, Michitoshi; Asakura, Yuichiro; Finet, François;
Furusawa, Hisanori; Kawabata, Koji S.; Liu, Wei; Matsubayashi,
Kazuya; Moritani, Yuki; Motohara, Kentaro; Nakata, Fumiaki; Ohta,
Kouji; Terai, Tsuyoshi; Uemura, Makoto; Yasuda, Naoki
Bibcode: 2018PASJ...70....1U
Altcode: 2017arXiv171000127U; 2017PASJ..tmp...21U
We present the results of detailed analysis of an optical imaging
survey conducted using the Subaru/Hyper Suprime-Cam (HSC) that aimed
to identify an optical counterpart to the gravitational wave event
GW151226. In half a night, the i- and z-band imaging survey by HSC
covered 63.5 deg2 of the error region, which contains
about 7% of the LIGO localization probability, and the same field was
observed in three different epochs. The detectable magnitude of the
candidates in a differenced image is evaluated as i ∼ 23.2 mag for the
requirement of at least two 5 σ detections, and 1744 candidates are
discovered. Assuming a kilonova as an optical counterpart, we compare
the optical properties of the candidates with model predictions. A red
and rapidly declining light curve condition enables the discrimination
of a kilonova from other transients, and a small number of candidates
satisfy this condition. The presence of stellar-like counterparts in
the reference frame suggests that the surviving candidates are likely
to be flare stars. The fact that most of those candidates are in the
galactic plane, |b| < 5°, supports this interpretation. We also
check whether the candidates are associated with the nearby GLADE
galaxies, which reduces the number of contaminants even with a looser
color cut. When a better probability map (with localization accuracy
of ∼50 deg2) is available, kilonova searches of up to
approximately 200 Mpc will become feasible by conducting immediate
follow-up observations with an interval of 3-6 d.
Title: Thermonuclear 19F(p, {{\boldsymbol{\alpha
}}}_{0})16O reaction rate
Authors: He, Jian-Jun; Lombardo, Ivano; Dell'Aquila, Daniele; Xu,
Yi; Zhang, Li-Yong; Liu, Wei-Ping
Bibcode: 2018ChPhC..42a5001H
Altcode: 2017arXiv170904170H
The thermonuclear 19F(p, {{{α }}}0)16O
reaction rate in the temperature region 0.007-10 GK has been derived
by re-evaluating the available experimental data, together with the
low-energy theoretical R-matrix extrapolations. Our new rate deviates by
up to about 30% compared to the previous results, although all rates are
consistent within the uncertainties. At very low temperature (e.g. 0.01
GK) our reaction rate is about 20% lower than the most recently
published rate, because of a difference in the low energy extrapolated
S-factor and a more accurate estimate of the reduced mass used in the
calculation of the reaction rate. At temperatures above ∼1 GK, our
rate is lower, for instance, by about 20% around 1.75 GK, because we
have re-evaluated the previous data (Isoya et al., Nucl. Phys. 7, 116
(1958)) in a meticulous way. The present interpretation is supported by
the direct experimental data. The uncertainties of the present evaluated
rate are estimated to be about 20% in the temperature region below
0.2 GK, and are mainly caused by the lack of low-energy experimental
data and the large uncertainties in the existing data. Asymptotic
giant branch (AGB) stars evolve at temperatures below 0.2 GK, where
the 19F(p, {{α }})16O reaction may play a very
important role. However, the current accuracy of the reaction rate
is insufficient to help to describe, in a careful way, the fluorine
over-abundances observed in AGB stars. Precise cross section (or
S factor) data in the low energy region are therefore needed for
astrophysical nucleosynthesis studies. Supported by National
Natural Science Foundation of China (11490562, 11490560, 11675229) and
National Key Research and Development Program of China (2016YFA0400503)
Title: The temporal evolution of explosive events and its implication
on reconnection dynamics
Authors: Guo, L.; Liu, W.; De Pontieu, B.; Huang, Y. M.; Peter, H.;
Bhattacharjee, A.
Bibcode: 2017AGUFMSH43A2803G
Altcode:
Transition-region explosive events and other bursts seen in extreme UV
light are characterized by broad spectral line profiles, and the more
violent ones show a strong enhancement of emission. They are thought
to be driven by magnetic reconnection, because of their characteristic
spectral profiles often indicating strong Alfvénic flows, and because
of the fact that they typically occur where magnetic flux concentrations
of opposite polarity intersect. In this presentation, we will focus
on the temporal evolution of transition-region explosive events. In
particular, we will investigate fast onsets of these events and the
rapid oscillations of intensity during these event. The fast onset
refers to the beginning of an explosive event, where the intensities
and the widths of its line profiles increase dramatically (often within
less than 10 seconds) and the rapid oscillations of intensity refer
to blinks of emission that usually last less than 10 seconds during
the event. In order to interpret and understand underlying mechanisms
of these observations, we conduct numerical simulation of an explosive
event and calculate its spectra. We observe a similar temporal evolution
in the synthetic Si IV spectra when the explosive event is driven by
time-dependent reconnection—plasmoid instability. The qualitative
agreement between observations and simulations suggests that the
temporal evolution of Si IV spectra of explosive events are closely
related to reconnection dynamics.
Title: Data-driven Simulations of Magnetic Connectivity in
Behind-the-Limb Gamma-ray Flares and Associated Coronal Mass Ejections
Authors: Jin, M.; Petrosian, V.; Liu, W.; Nitta, N.; Omodei, N.;
Rubio da Costa, F.; Effenberger, F.; Li, G.; Pesce-Rollins, M.
Bibcode: 2017AGUFMSH44B..03J
Altcode:
Recent Fermi detection of high-energy gamma-ray emission from the
behind-the-limb (BTL) solar flares pose a puzzle on the particle
acceleration and transport mechanisms in such events. Due to
the large separation between the flare site and the location of
gamma-ray emission, it is believed that the associated coronal
mass ejections (CMEs) play an important role in accelerating and
subsequently transporting particles back to the Sun to produce obseved
gamma-rays. We explore this scenario by simulating the CME associated
with a well-observed flare on 2014 September 1 about 40 degrees behind
the east solar limb and by comparing the simulation and observational
results. We utilize a data-driven global magnetohydrodynamics model
(AWSoM: Alfven-wave Solar Model) to track the dynamical evolution
of the global magnetic field during the event and investigate the
magnetic connectivity between the CME/CME-driven shock and the Fermi
emission region. Moreover, we derive the time-varying shock parameters
(e.g., compression ratio, Alfven Mach number, and ThetaBN) over the
area that is magnetically connected to the visible solar disk where
Fermi gamma-ray emission originates. Our simulation shows that the
visible solar disk develops connections both to the flare site and to
the CME-driven shock during the eruption, which indicate that the CME's
interaction with the global solar corona is critical for understanding
such Fermi BTL events and gamma-ray flares in general. We discuss
the causes and implications of Fermi BTL events, in the framework
of a potential shift of paradigm on particle acceleration in solar
flares/CMEs.
Title: Magnetic Topology of a Long-Lived Coronal Condensation Site
Lasting Eight Months
Authors: Sun, X.; Yu, S.; Liu, W.
Bibcode: 2017AGUFMSH13A2457S
Altcode:
It is well known that cool material, such as prominences or
coronal rain, can form in-situ by condensation of hot coronal
plasma due to a runaway radiative cooling instability (a.k.a. thermal
non-equilibrium). Recent observations and numerical simulations suggest
that such condensations are quite common, but in quiet-Sun regions,
they occur preferentially in locations where magnetic field is weak
(e.g., null points) or discontinuous (e.g., current sheets). Such
events usually have short lifetimes of hours to days. Surprisingly,
we observed a high-latitude condensation site lasting over eight
months in 2014 with recurrent and episodic condensations fueling a
funnel-shaped prominence. We analyze the coronal magnetic topology to
investigate the necessary condition of such a long-lived condensation
site. We find that the site was directly above a poleward photospheric
flux surge when the polar field polarity was close to its solar cycle
reversal. The large-scale magnetic cancellation front may have sustained
interchange reconnection at this location, creating suitable conditions
for coronal plasma condensation.
Title: J-GEM observations of an electromagnetic counterpart to the
neutron star merger GW170817
Authors: Utsumi, Yousuke; Tanaka, Masaomi; Tominaga, Nozomu; Yoshida,
Michitoshi; Barway, Sudhanshu; Nagayama, Takahiro; Zenko, Tetsuya;
Aoki, Kentaro; Fujiyoshi, Takuya; Furusawa, Hisanori; Kawabata, Koji
S.; Koshida, Shintaro; Lee, Chien-Hsiu; Morokuma, Tomoki; Motohara,
Kentaro; Nakata, Fumiaki; Ohsawa, Ryou; Ohta, Kouji; Okita, Hirofumi;
Tajitsu, Akito; Tanaka, Ichi; Terai, Tsuyoshi; Yasuda, Naoki; Abe,
Fumio; Asakura, Yuichiro; Bond, Ian A.; Miyazaki, Shota; Sumi,
Takahiro; Tristram, Paul J.; Honda, Satoshi; Itoh, Ryosuke; Itoh,
Yoichi; Kawabata, Miho; Morihana, Kumiko; Nagashima, Hiroki; Nakaoka,
Tatsuya; Ohshima, Tomohito; Takahashi, Jun; Takayama, Masaki; Aoki,
Wako; Baar, Stefan; Doi, Mamoru; Finet, Francois; Kanda, Nobuyuki;
Kawai, Nobuyuki; Kim, Ji Hoon; Kuroda, Daisuke; Liu, Wei; Matsubayashi,
Kazuya; Murata, Katsuhiro L.; Nagai, Hiroshi; Saito, Tomoki; Saito,
Yoshihiko; Sako, Shigeyuki; Sekiguchi, Yuichiro; Tamura, Yoichi;
Tanaka, Masayuki; Uemura, Makoto; Yamaguchi, Masaki S.
Bibcode: 2017PASJ...69..101U
Altcode: 2017arXiv171005848U
GW170817 is the first detected gravitational wave source from a
neutron star merger. We present the Japanese collaboration for
gravitational-wave electro-magnetic (J-GEM) follow-up observations
of SSS17a, an electromagnetic counterpart of GW170817. SSS17a shows
a 2.5 mag decline in the z band during the period between 1.7 and
7.7 d after the merger. Such a rapid decline is not comparable with
supernovae light curves at any epoch. The color of SSS17a also evolves
rapidly and becomes redder during later epochs: the z - H color has
changed by approximately 2.5 mag during the period between 0.7 and 7.7
d. The rapid evolutions of both the color and the optical brightness are
consistent with the expected properties of a kilonova that is powered by
the radioactive decay of newly synthesized r-process nuclei. Kilonova
models with Lanthanide elements can reproduce the aforementioned
observed properties well, which suggests that r-process nucleosynthesis
beyond the second peak takes place in SSS17a. However, the absolute
magnitude of SSS17a is brighter than the expected brightness of the
kilonova models with an ejecta mass of 0.01 M⊙, which
suggests a more intense mass ejection (∼0.03 M⊙) or
possibly an additional energy source.
Title: Evolution of Post-accretion-induced Collapse Binaries: The
Effect of Evaporation
Authors: Liu, Wei-Min; Li, Xiang-Dong
Bibcode: 2017ApJ...851...58L
Altcode: 2017arXiv171102011L
Accretion-induced collapse (AIC) is widely accepted to be one of
the formation channels for millisecond pulsars (MSPs). Since the
MSPs have high spin-down luminosities, they can immediately start to
evaporate their companion stars after birth. In this paper, we present
a detailed investigation on the evolution of the post-AIC binaries,
taking into account the effect of evaporation both before and during
the Roche-lobe overflow process. We discuss the possible influence
of the input parameters including the evaporation efficiency, the
initial spin period, and the initial surface magnetic field of the
newborn neutron star. We compare the calculated results with the
traditional low-mass X-ray binary evolution and suggest that they may
reproduce at least part of the observed redbacks and black widows in
the companion mass-orbital period plane depending on the mechanisms
of angular momentum loss associated with evaporation.
Title: Comparison of rotational temperature derived from ground-based
OH airglow observations with TIMED/SABER to evaluate the Einstein
Coefficients
Authors: Liu, W.; Xu, J.; Smith, A. K.; Yuan, W.
Bibcode: 2017AGUFMSA13B..09L
Altcode:
Ground-based observations of the OH(9-4, 8-3, 6-2, 5-1, 3-0) band
airglows over Xinglong, China (40°24'N, 117°35'E) from December 2011
to 2014 are used to calculate rotational temperatures. The temperatures
are calculated using five commonly used Einstein coefficient
datasets. The kinetic temperature from TIMED/SABER is completely
independent of the OH rotational temperature. SABER temperatures are
weighted vertically by weighting functions calculated for each emitting
vibrational state from two SABER OH volume emission rate profiles. By
comparing the ground-based OH rotational temperature with SABER's,
five Einstein coefficient datasets are evaluated. The results show that
temporal variations of the rotational temperatures are well correlated
with SABER's; the linear correlation coefficients are higher than 0.72,
but the slopes of the fit between the SABER and rotational temperatures
are not equal to 1. The rotational temperatures calculated using each
set of Einstein coefficients produce a different bias with respect
to SABER; these are evaluated over each of vibrational levels to
assess the best match. It is concluded that rotational temperatures
determined using any of the available Einstein coefficient datasets
have systematic errors. However, of the five sets of coefficients,
the rotational temperature derived with the Langhoff et al.'s (1986)
set is most consistent with SABER. In order to get a set of optimal
Einstein coefficients for rotational temperature derivation, we derive
the relative values from ground-based OH spectra and SABER temperatures
statistically using three year data. The use of a standard set of
Einstein coefficients will be beneficial for comparing rotational
temperatures observed at different sites.
Title: Digging into the corona: A modeling framework trained with
Sun-grazing comet observations
Authors: Jia, Y. D.; Pesnell, W. D.; Bryans, P.; Downs, C.; Liu, W.;
Schwartz, S. J.
Bibcode: 2017AGUFMSH11B2437J
Altcode:
Images of comets diving into the low corona have been captured a few
times in the past decade. Structures visible at various wavelengths
during these encounters indicate a strong variation of the ambient
conditions of the corona. We combine three numerical models: a global
coronal model, a particle transportation model, and a cometary plasma
interaction model into one framework to model the interaction of such
Sun-grazing comets with plasma in the low corona. In our framework,
cometary vapors are ionized via multiple channels and then captured
by the coronal magnetic field. In seconds, these ions are further
ionized into their highest charge state, which is revealed by certain
coronal emission lines. Constrained by observations, we apply our
framework to trace back to the local conditions of the ambient corona,
and their spatial/time variation over a broad range of scales. Once
trained by multiple stages of the comet's journey in the low corona,
we illustrate how this framework can leverage these unique observations
to probe the structure of the solar corona and solar wind.
Title: Broadband high-frequency waves and intermittent energy
conversion at dipolarization fronts
Authors: Yang, J.; Cao, J.; Fu, H.; Wang, T.; Liu, W.; Yao, Z., Sr.
Bibcode: 2017AGUFMSM13B2374Y
Altcode:
Dipolarization front (DF) is a sharp boundary most probably separating
the reconnection jet from the background plasma sheet. So far at this
boundary, the observed waves are mainly in low-frequency range (e.g.,
magnetosonic waves and lower hybrid waves). Few high-frequency waves
are observed in this region. In this paper, we report the broadband
high-frequency wave emissions at the DF. These waves, having frequencies
extending from the electron cyclotron frequency fce, up to the electron
plasma frequency fpe, could contribute 10% to the in situ measurement
of intermittent energy conversion at the DF layer. Their generation may
be attributed to electron beams, which are simultaneously observed at
the DF as well. Furthermore, we find intermittent energy conversion is
primarily to the broadband fluctuations in the lower hybrid frequency
range although the net energy conversion is small.
Title: A comparison of quiet time thermospheric winds between FPIs
and models
Authors: Jiang, G.; Xu, J.; Wang, W.; Yuan, W.; Zhang, S.; Yu, T.;
Zhang, X.; Huang, C.; Liu, W.; Li, Q.
Bibcode: 2017AGUFMSA41A2612J
Altcode:
Abstract:The Fabry-Perot Interferometer (FPI) instruments installed
at Xinglong, (geog.: 40.2oN, 117.4oE; geom.: 35oN), Kelan (geog.:
38.7oN, 111.6oE; geom.: 34oN) and Millstone Hill (geog.: 42.6oN,
71.5oW; geom.: 52oN) started to measure the thermosphere neutral
winds near 250 km since April 2010, March 2010 and November 2011,
respectively. In this work, the joined comparison of FPI observed
winds and two models during geomagnetic quiet time are processed for
the study of mid-latitudinal thermosphere. The years of FPI wind data
we use are from 2010 to 2014. The two models we use are NCAR TIE-GCM
(Thermosphere-Ionosphere-Electrodynamics General Circulation Model of
National Center for Atmospheric Research) and HWM07 (Horizontal Wind
Model, version 2007). The real solar and geomagnetic conditions were
applied to the models.
Title: Variation of plasmapause location during magnetic storms:
observations and modeling
Authors: Liu, W.
Bibcode: 2017AGUFMSM43C2731L
Altcode:
This paper investigates the dynamic evolutions of the plasmapause during
magnetic storms based on in situ observations and empirical modeling
results. Superposed epoch analysis is performed on the plasmapause
location identified from THEMIS in situ measurements during the 61
magnetic storms from 2009 to 2013. The evolution of the plasmapause
is generally consistent with the theory of erosion/refilling of the
plasmapause. From multi-spacecraft in situ measurements, we are able
to directly calculate the plasmapause radial velocity, Vpp. It is found
that the radial velocity is on average earthward during main phase and
turns outward during recovery phase. The empirical plasmapause model
by Liu et al. [2015] is further utilized to reproduce the plasmapause
location during these 61 storms to reveal the details of the evolution,
such as the local time dependence. It is shown that the expansion of
the plasmapause starts firstly on the midnight sector at t0+1hr, and
subsequently on the dawnside at t0+4hr, dayside at t0+8hr and duskside
at t0+11hr, where t0 corresponds to the time of Dst minimum. The
averaged Vpp is quantified based on modeling results as up to 0.17
RE/hr earthward in the main phase and 0.08 RE/hr outward in the recovery
phase. The knowledge of the dynamic evolution of plasmapause provided
in this paper is valuable to understand the dynamics of the inner
magnetosphere during magnetic storms.
Title: Multiple pathways in pressure-induced phase transition
of coesite
Authors: Liu, Wei; Wu, Xuebang; Liang, Yunfeng; Liu, Changsong;
Miranda, Caetano R.; Scandolo, Sandro
Bibcode: 2017PNAS..11412894L
Altcode:
High-pressure single-crystal X-ray diffraction method with precise
control of hydrostatic conditions, typically with helium or neon as
the pressure-transmitting medium, has significantly changed our view
on what happens with low-density silica phases under pressure. Coesite
is a prototype material for pressure-induced amorphization. However,
it was found to transform into a high-pressure octahedral (HPO) phase,
or coesite-II and coesite-III. Given that the pressure is believed to
be hydrostatic in two recent experiments, the different transformation
pathways are striking. Based on molecular dynamic simulations with
an ab initio parameterized potential, we reproduced all of the above
experiments in three transformation pathways, including the one leading
to an HPO phase. This octahedral phase has an oxygen hcp sublattice
featuring 2 × 2 zigzag octahedral edge-sharing chains, however with
some broken points (i.e., point defects). It transforms into α-PbO2
phase when it is relaxed under further compression. We show that
the HPO phase forms through a continuous rearrangement of the oxygen
sublattice toward hcp arrangement. The high-pressure amorphous phases
can be described by an fcc and hcp sublattice mixture.
Title: Direct detection of a break in the teraelectronvolt cosmic-ray
spectrum of electrons and positrons
Authors: DAMPE Collaboration; Ambrosi, G.; An, Q.; Asfandiyarov, R.;
Azzarello, P.; Bernardini, P.; Bertucci, B.; Cai, M. S.; Chang, J.;
Chen, D. Y.; Chen, H. F.; Chen, J. L.; Chen, W.; Cui, M. Y.; Cui,
T. S.; D'Amone, A.; de Benedittis, A.; De Mitri, I.; di Santo, M.;
Dong, J. N.; Dong, T. K.; Dong, Y. F.; Dong, Z. X.; Donvito, G.; Droz,
D.; Duan, K. K.; Duan, J. L.; Duranti, M.; D'Urso, D.; Fan, R. R.;
Fan, Y. Z.; Fang, F.; Feng, C. Q.; Feng, L.; Fusco, P.; Gallo, V.;
Gan, F. J.; Gao, M.; Gao, S. S.; Gargano, F.; Garrappa, S.; Gong, K.;
Gong, Y. Z.; Guo, D. Y.; Guo, J. H.; Hu, Y. M.; Huang, G. S.; Huang,
Y. Y.; Ionica, M.; Jiang, D.; Jiang, W.; Jin, X.; Kong, J.; Lei, S. J.;
Li, S.; Li, X.; Li, W. L.; Li, Y.; Liang, Y. F.; Liang, Y. M.; Liao,
N. H.; Liu, H.; Liu, J.; Liu, S. B.; Liu, W. Q.; Liu, Y.; Loparco, F.;
Ma, M.; Ma, P. X.; Ma, S. Y.; Ma, T.; Ma, X. Q.; Ma, X. Y.; Marsella,
G.; Mazziotta, M. N.; Mo, D.; Niu, X. Y.; Peng, X. Y.; Peng, W. X.;
Qiao, R.; Rao, J. N.; Salinas, M. M.; Shang, G. Z.; H. Shen, W.; Shen,
Z. Q.; Shen, Z. T.; Song, J. X.; Su, H.; Su, M.; Sun, Z. Y.; Surdo,
A.; Teng, X. J.; Tian, X. B.; Tykhonov, A.; Vagelli, V.; Vitillo, S.;
Wang, C.; Wang, H.; Wang, H. Y.; Wang, J. Z.; Wang, L. G.; Wang, Q.;
Wang, S.; Wang, X. H.; Wang, X. L.; Wang, Y. F.; Wang, Y. P.; Wang,
Y. Z.; Wen, S. C.; Wang, Z. M.; Wei, D. M.; Wei, J. J.; Wei, Y. F.;
Wu, D.; Wu, J.; Wu, L. B.; Wu, S. S.; Wu, X.; Xi, K.; Xia, Z. Q.; Xin,
Y. L.; Xu, H. T.; Xu, Z. L.; Xu, Z. Z.; Xue, G. F.; Yang, H. B.; Yang,
P.; Yang, Y. Q.; Yang, Z. L.; Yao, H. J.; Yu, Y. H.; Yuan, Q.; Yue,
C.; Zang, J. J.; Zhang, C.; Zhang, D. L.; Zhang, F.; Zhang, J. B.;
Zhang, J. Y.; Zhang, J. Z.; Zhang, L.; Zhang, P. F.; Zhang, S. X.;
Zhang, W. Z.; Zhang, Y.; Zhang, Y. J.; Zhang, Y. Q.; Zhang, Y. L.;
Zhang, Y. P.; Zhang, Z.; Zhang, Z. Y.; Zhao, H.; Zhao, H. Y.; Zhao,
X. F.; Zhou, C. Y.; Zhou, Y.; Zhu, X.; Zhu, Y.; Zimmer, S.
Bibcode: 2017Natur.552...63D
Altcode: 2017arXiv171110981A
High-energy cosmic-ray electrons and positrons (CREs), which lose
energy quickly during their propagation, provide a probe of Galactic
high-energy processes and may enable the observation of phenomena such
as dark-matter particle annihilation or decay. The CRE spectrum has been
measured directly up to approximately 2 teraelectronvolts in previous
balloon- or space-borne experiments, and indirectly up to approximately
5 teraelectronvolts using ground-based Cherenkov γ-ray telescope
arrays. Evidence for a spectral break in the teraelectronvolt energy
range has been provided by indirect measurements, although the results
were qualified by sizeable systematic uncertainties. Here we report
a direct measurement of CREs in the energy range 25 gigaelectronvolts
to 4.6 teraelectronvolts by the Dark Matter Particle Explorer (DAMPE)
with unprecedentedly high energy resolution and low background. The
largest part of the spectrum can be well fitted by a ‘smoothly broken
power-law’ model rather than a single power-law model. The direct
detection of a spectral break at about 0.9 teraelectronvolts confirms
the evidence found by previous indirect measurements, clarifies the
behaviour of the CRE spectrum at energies above 1 teraelectronvolt
and sheds light on the physical origin of the sub-teraelectronvolt CREs.
Title: Quiescent Prominence Dynamics Observed with the Hinode
Solar Optical Telescope. II. Prominence Bubble Boundary Layer
Characteristics and the Onset of a Coupled Kelvin-Helmholtz
Rayleigh-Taylor Instability
Authors: Berger, Thomas; Hillier, Andrew; Liu, Wei
Bibcode: 2017ApJ...850...60B
Altcode: 2017arXiv170705265B
We analyze solar quiescent prominence bubble characteristics and
instability dynamics using Hinode/Solar Optical Telescope data. We
measure the bubble expansion rate, prominence downflows, and the
profile of the boundary layer brightness and thickness as a function
of time. The largest bubble analyzed rises into the prominence with a
speed of about 1.3 {km} {{{s}}}-1 until it is destabilized by
a localized shear flow on the boundary. Boundary layer thickness grows
gradually as prominence downflows deposit plasma onto the bubble with
characteristic speeds of 20{--}35 {km} {{{s}}}-1. Lateral
downflows initiate from the thickened boundary layer with characteristic
speeds of 25{--}50 {km} {{{s}}}-1, “draining” the
layer of plasma. Strong shear flow across one bubble boundary leads
to an apparent coupled Kelvin-Helmholtz Rayleigh-Taylor (KH-RT)
instability. We measure shear flow speeds above the bubble of 10 {km}
{{{s}}}-1 and infer interior bubble flow speeds on the order
of 100 {km} {{{s}}}-1. Comparing the measured growth rate
of the instability to analytic expressions, we infer a magnetic flux
density across the bubble boundary of ∼10-3 T (10 Gauss)
at an angle of ∼ 70^\circ to the prominence plane. The results are
consistent with the hypothesis that prominence bubbles are caused by
magnetic flux that emerges below a prominence, setting up the conditions
for RT, or combined KH-RT, instability flows that transport flux,
helicity, and hot plasma upward into the overlying coronal magnetic
flux rope.
Title: The 95Zr(n, γ)96Zr Cross Section from
the Surrogate Ratio Method and Its Effect on s-process Nucleosynthesis
Authors: Yan, S. Q.; Li, Z. H.; Wang, Y. B.; Nishio, K.; Lugaro, M.;
Karakas, A. I.; Makii, H.; Mohr, P.; Su, J.; Li, Y. J.; Nishinaka,
I.; Hirose, K.; Han, Y. L.; Orlandi, R.; Shen, Y. P.; Guo, B.; Zeng,
S.; Lian, G.; Chen, Y. S.; Liu, W. P.
Bibcode: 2017ApJ...848...98Y
Altcode: 2017arXiv170904635Y
The 95Zr(n, γ)96Zr reaction cross section
is crucial in the modeling of s-process nucleosynthesis in
asymptotic giant branch stars because it controls the operation
of the branching point at the unstable 95Zr and the
subsequent production of 96Zr. We have carried out the
measurement of the 94Zr(18O, 16O)
and 90Zr(18O, 16O) reactions and
obtained the γ-decay probability ratio of 96Zr* and
92Zr* to determine the 95Zr(n, γ)96Zr
reaction cross sections with the surrogate ratio method. Our deduced
Maxwellian-averaged cross section of 66 ± 16 mb at 30 keV is close to
the value recommended by Bao et al., but 30% and more than a factor
of two larger than the values proposed by Toukan & Käppeler and
Lugaro et al., respectively, and routinely used in s-process models. We
tested the new rate in stellar models with masses between 2 and 6
M ⊙ and metallicities of 0.014 and 0.03. The largest
changes—up to 80% variations in 96Zr—are seen in models
of mass 3-4 M ⊙, where the 22Ne neutron source
is mildly activated. The new rate can still provide a match to data
from meteoritic stardust silicon carbide grains, provided that the
maximum mass of the parent stars is below 4 M ⊙, for a
metallicity of 0.03.
Title: The DArk Matter Particle Explorer mission
Authors: Chang, J.; Ambrosi, G.; An, Q.; Asfandiyarov, R.; Azzarello,
P.; Bernardini, P.; Bertucci, B.; Cai, M. S.; Caragiulo, M.; Chen,
D. Y.; Chen, H. F.; Chen, J. L.; Chen, W.; Cui, M. Y.; Cui, T. S.;
D'Amone, A.; De Benedittis, A.; De Mitri, I.; Di Santo, M.; Dong,
J. N.; Dong, T. K.; Dong, Y. F.; Dong, Z. X.; Donvito, G.; Droz, D.;
Duan, K. K.; Duan, J. L.; Duranti, M.; D'Urso, D.; Fan, R. R.; Fan,
Y. Z.; Fang, F.; Feng, C. Q.; Feng, L.; Fusco, P.; Gallo, V.; Gan,
F. J.; Gan, W. Q.; Gao, M.; Gao, S. S.; Gargano, F.; Gong, K.; Gong,
Y. Z.; Guo, J. H.; Hu, Y. M.; Huang, G. S.; Huang, Y. Y.; Ionica,
M.; Jiang, D.; Jiang, W.; Jin, X.; Kong, J.; Lei, S. J.; Li, S.; Li,
X.; Li, W. L.; Li, Y.; Liang, Y. F.; Liang, Y. M.; Liao, N. H.; Liu,
Q. Z.; Liu, H.; Liu, J.; Liu, S. B.; Liu, Q. Z.; Liu, W. Q.; Liu,
Y.; Loparco, F.; Lü, J.; Ma, M.; Ma, P. X.; Ma, S. Y.; Ma, T.; Ma,
X. Q.; Ma, X. Y.; Marsella, G.; Mazziotta, M. N.; Mo, D.; Miao, T. T.;
Niu, X. Y.; Pohl, M.; Peng, X. Y.; Peng, W. X.; Qiao, R.; Rao, J. N.;
Salinas, M. M.; Shang, G. Z.; Shen, W. H.; Shen, Z. Q.; Shen, Z. T.;
Song, J. X.; Su, H.; Su, M.; Sun, Z. Y.; Surdo, A.; Teng, X. J.; Tian,
X. B.; Tykhonov, A.; Vagelli, V.; Vitillo, S.; Wang, C.; Wang, Chi;
Wang, H.; Wang, H. Y.; Wang, J. Z.; Wang, L. G.; Wang, Q.; Wang, S.;
Wang, X. H.; Wang, X. L.; Wang, Y. F.; Wang, Y. P.; Wang, Y. Z.; Wen,
S. C.; Wang, Z. M.; Wei, D. M.; Wei, J. J.; Wei, Y. F.; Wu, D.; Wu,
J.; Wu, S. S.; Wu, X.; Xi, K.; Xia, Z. Q.; Xin, Y. L.; Xu, H. T.;
Xu, Z. L.; Xu, Z. Z.; Xue, G. F.; Yang, H. B.; Yang, J.; Yang, P.;
Yang, Y. Q.; Yang, Z. L.; Yao, H. J.; Yu, Y. H.; Yuan, Q.; Yue, C.;
Zang, J. J.; Zhang, C.; Zhang, D. L.; Zhang, F.; Zhang, J. B.; Zhang,
J. Y.; Zhang, J. Z.; Zhang, L.; Zhang, P. F.; Zhang, S. X.; Zhang,
W. Z.; Zhang, Y.; Zhang, Y. J.; Zhang, Y. Q.; Zhang, Y. L.; Zhang,
Y. P.; Zhang, Z.; Zhang, Z. Y.; Zhao, H.; Zhao, H. Y.; Zhao, X. F.;
Zhou, C. Y.; Zhou, Y.; Zhu, X.; Zhu, Y.; Zimmer, S.
Bibcode: 2017APh....95....6C
Altcode: 2017arXiv170608453T; 2017arXiv170608453C
The DArk Matter Particle Explorer (DAMPE), one of the four scientific
space science missions within the framework of the Strategic Pioneer
Program on Space Science of the Chinese Academy of Sciences, is
a general purpose high energy cosmic-ray and gamma-ray observatory,
which was successfully launched on December 17th, 2015 from the Jiuquan
Satellite Launch Center. The DAMPE scientific objectives include
the study of galactic cosmic rays up to ∼ 10 TeV and hundreds of
TeV for electrons/gammas and nuclei respectively, and the search for
dark matter signatures in their spectra. In this paper we illustrate
the layout of the DAMPE instrument, and discuss the results of beam
tests and calibrations performed on ground. Finally we present the
expected performance in space and give an overview of the mission key
scientific goals.
Title: Fermi Large Area Telescope observations of the Sun: The first
ten years
Authors: Pesce-Rollins, M.; Omodei, N.; Allafort, A.; Petrosian, V.;
Raino, S.; Liu, W.
Bibcode: 2017ifs..confE.173P
Altcode: 2017PoS...312E.173P
No abstract at ADS
Title: Multi-messenger Observations of a Binary Neutron Star Merger
Authors: Abbott, B. P.; Abbott, R.; Abbott, T. D.; Acernese, F.;
Ackley, K.; Adams, C.; Adams, T.; Addesso, P.; Adhikari, R. X.; Adya,
V. B.; Affeldt, C.; Afrough, M.; Agarwal, B.; Agathos, M.; Agatsuma,
K.; Aggarwal, N.; Aguiar, O. D.; Aiello, L.; Ain, A.; Ajith, P.;
Allen, B.; Allen, G.; Allocca, A.; Altin, P. A.; Amato, A.; Ananyeva,
A.; Anderson, S. B.; Anderson, W. G.; Angelova, S. V.; Antier, S.;
Appert, S.; Arai, K.; Araya, M. C.; Areeda, J. S.; Arnaud, N.; Arun,
K. G.; Ascenzi, S.; Ashton, G.; Ast, M.; Aston, S. M.; Astone, P.;
Atallah, D. V.; Aufmuth, P.; Aulbert, C.; AultONeal, K.; Austin,
C.; Avila-Alvarez, A.; Babak, S.; Bacon, P.; Bader, M. K. M.; Bae,
S.; Baker, P. T.; Baldaccini, F.; Ballardin, G.; Ballmer, S. W.;
Banagiri, S.; Barayoga, J. C.; Barclay, S. E.; Barish, B. C.; Barker,
D.; Barkett, K.; Barone, F.; Barr, B.; Barsotti, L.; Barsuglia,
M.; Barta, D.; Barthelmy, S. D.; Bartlett, J.; Bartos, I.; Bassiri,
R.; Basti, A.; Batch, J. C.; Bawaj, M.; Bayley, J. C.; Bazzan, M.;
Bécsy, B.; Beer, C.; Bejger, M.; Belahcene, I.; Bell, A. S.; Berger,
B. K.; Bergmann, G.; Bero, J. J.; Berry, C. P. L.; Bersanetti, D.;
Bertolini, A.; Betzwieser, J.; Bhagwat, S.; Bhandare, R.; Bilenko,
I. A.; Billingsley, G.; Billman, C. R.; Birch, J.; Birney, R.;
Birnholtz, O.; Biscans, S.; Biscoveanu, S.; Bisht, A.; Bitossi, M.;
Biwer, C.; Bizouard, M. A.; Blackburn, J. K.; Blackman, J.; Blair,
C. D.; Blair, D. G.; Blair, R. M.; Bloemen, S.; Bock, O.; Bode, N.;
Boer, M.; Bogaert, G.; Bohe, A.; Bondu, F.; Bonilla, E.; Bonnand, R.;
Boom, B. A.; Bork, R.; Boschi, V.; Bose, S.; Bossie, K.; Bouffanais,
Y.; Bozzi, A.; Bradaschia, C.; Brady, P. R.; Branchesi, M.; Brau,
J. E.; Briant, T.; Brillet, A.; Brinkmann, M.; Brisson, V.; Brockill,
P.; Broida, J. E.; Brooks, A. F.; Brown, D. A.; Brown, D. D.; Brunett,
S.; Buchanan, C. C.; Buikema, A.; Bulik, T.; Bulten, H. J.; Buonanno,
A.; Buskulic, D.; Buy, C.; Byer, R. L.; Cabero, M.; Cadonati, L.;
Cagnoli, G.; Cahillane, C.; Calderón Bustillo, J.; Callister, T. A.;
Calloni, E.; Camp, J. B.; Canepa, M.; Canizares, P.; Cannon, K. C.;
Cao, H.; Cao, J.; Capano, C. D.; Capocasa, E.; Carbognani, F.; Caride,
S.; Carney, M. F.; Casanueva Diaz, J.; Casentini, C.; Caudill, S.;
Cavaglià, M.; Cavalier, F.; Cavalieri, R.; Cella, G.; Cepeda, C. B.;
Cerdá-Durán, P.; Cerretani, G.; Cesarini, E.; Chamberlin, S. J.;
Chan, M.; Chao, S.; Charlton, P.; Chase, E.; Chassande-Mottin, E.;
Chatterjee, D.; Chatziioannou, K.; Cheeseboro, B. D.; Chen, H. Y.;
Chen, X.; Chen, Y.; Cheng, H. -P.; Chia, H.; Chincarini, A.; Chiummo,
A.; Chmiel, T.; Cho, H. S.; Cho, M.; Chow, J. H.; Christensen, N.;
Chu, Q.; Chua, A. J. K.; Chua, S.; Chung, A. K. W.; Chung, S.; Ciani,
G.; Ciolfi, R.; Cirelli, C. E.; Cirone, A.; Clara, F.; Clark, J. A.;
Clearwater, P.; Cleva, F.; Cocchieri, C.; Coccia, E.; Cohadon,
P. -F.; Cohen, D.; Colla, A.; Collette, C. G.; Cominsky, L. R.;
Constancio, M., Jr.; Conti, L.; Cooper, S. J.; Corban, P.; Corbitt,
T. R.; Cordero-Carrión, I.; Corley, K. R.; Cornish, N.; Corsi, A.;
Cortese, S.; Costa, C. A.; Coughlin, M. W.; Coughlin, S. B.; Coulon,
J. -P.; Countryman, S. T.; Couvares, P.; Covas, P. B.; Cowan, E. E.;
Coward, D. M.; Cowart, M. J.; Coyne, D. C.; Coyne, R.; Creighton,
J. D. E.; Creighton, T. D.; Cripe, J.; Crowder, S. G.; Cullen, T. J.;
Cumming, A.; Cunningham, L.; Cuoco, E.; Dal Canton, T.; Dálya,
G.; Danilishin, S. L.; D'Antonio, S.; Danzmann, K.; Dasgupta, A.;
Da Silva Costa, C. F.; Dattilo, V.; Dave, I.; Davier, M.; Davis, D.;
Daw, E. J.; Day, B.; De, S.; DeBra, D.; Degallaix, J.; De Laurentis,
M.; Deléglise, S.; Del Pozzo, W.; Demos, N.; Denker, T.; Dent, T.;
De Pietri, R.; Dergachev, V.; De Rosa, R.; DeRosa, R. T.; De Rossi,
C.; DeSalvo, R.; de Varona, O.; Devenson, J.; Dhurandhar, S.; Díaz,
M. C.; Di Fiore, L.; Di Giovanni, M.; Di Girolamo, T.; Di Lieto, A.;
Di Pace, S.; Di Palma, I.; Di Renzo, F.; Doctor, Z.; Dolique, V.;
Donovan, F.; Dooley, K. L.; Doravari, S.; Dorrington, I.; Douglas,
R.; Dovale Álvarez, M.; Downes, T. P.; Drago, M.; Dreissigacker,
C.; Driggers, J. C.; Du, Z.; Ducrot, M.; Dupej, P.; Dwyer, S. E.;
Edo, T. B.; Edwards, M. C.; Effler, A.; Ehrens, P.; Eichholz, J.;
Eikenberry, S. S.; Eisenstein, R. A.; Essick, R. C.; Estevez, D.;
Etienne, Z. B.; Etzel, T.; Evans, M.; Evans, T. M.; Factourovich,
M.; Fafone, V.; Fair, H.; Fairhurst, S.; Fan, X.; Farinon, S.; Farr,
B.; Farr, W. M.; Fauchon-Jones, E. J.; Favata, M.; Fays, M.; Fee,
C.; Fehrmann, H.; Feicht, J.; Fejer, M. M.; Fernandez-Galiana, A.;
Ferrante, I.; Ferreira, E. C.; Ferrini, F.; Fidecaro, F.; Finstad, D.;
Fiori, I.; Fiorucci, D.; Fishbach, M.; Fisher, R. P.; Fitz-Axen, M.;
Flaminio, R.; Fletcher, M.; Fong, H.; Font, J. A.; Forsyth, P. W. F.;
Forsyth, S. S.; Fournier, J. -D.; Frasca, S.; Frasconi, F.; Frei, Z.;
Freise, A.; Frey, R.; Frey, V.; Fries, E. M.; Fritschel, P.; Frolov,
V. V.; Fulda, P.; Fyffe, M.; Gabbard, H.; Gadre, B. U.; Gaebel,
S. M.; Gair, J. R.; Gammaitoni, L.; Ganija, M. R.; Gaonkar, S. G.;
Garcia-Quiros, C.; Garufi, F.; Gateley, B.; Gaudio, S.; Gaur, G.;
Gayathri, V.; Gehrels, N.; Gemme, G.; Genin, E.; Gennai, A.; George,
D.; George, J.; Gergely, L.; Germain, V.; Ghonge, S.; Ghosh, Abhirup;
Ghosh, Archisman; Ghosh, S.; Giaime, J. A.; Giardina, K. D.; Giazotto,
A.; Gill, K.; Glover, L.; Goetz, E.; Goetz, R.; Gomes, S.; Goncharov,
B.; González, G.; Gonzalez Castro, J. M.; Gopakumar, A.; Gorodetsky,
M. L.; Gossan, S. E.; Gosselin, M.; Gouaty, R.; Grado, A.; Graef, C.;
Granata, M.; Grant, A.; Gras, S.; Gray, C.; Greco, G.; Green, A. C.;
Gretarsson, E. M.; Griswold, B.; Groot, P.; Grote, H.; Grunewald, S.;
Gruning, P.; Guidi, G. M.; Guo, X.; Gupta, A.; Gupta, M. K.; Gushwa,
K. E.; Gustafson, E. K.; Gustafson, R.; Halim, O.; Hall, B. R.; Hall,
E. D.; Hamilton, E. Z.; Hammond, G.; Haney, M.; Hanke, M. M.; Hanks,
J.; Hanna, C.; Hannam, M. D.; Hannuksela, O. A.; Hanson, J.; Hardwick,
T.; Harms, J.; Harry, G. M.; Harry, I. W.; Hart, M. J.; Haster, C. -J.;
Haughian, K.; Healy, J.; Heidmann, A.; Heintze, M. C.; Heitmann,
H.; Hello, P.; Hemming, G.; Hendry, M.; Heng, I. S.; Hennig, J.;
Heptonstall, A. W.; Heurs, M.; Hild, S.; Hinderer, T.; Hoak, D.;
Hofman, D.; Holt, K.; Holz, D. E.; Hopkins, P.; Horst, C.; Hough,
J.; Houston, E. A.; Howell, E. J.; Hreibi, A.; Hu, Y. M.; Huerta,
E. A.; Huet, D.; Hughey, B.; Husa, S.; Huttner, S. H.; Huynh-Dinh,
T.; Indik, N.; Inta, R.; Intini, G.; Isa, H. N.; Isac, J. -M.; Isi,
M.; Iyer, B. R.; Izumi, K.; Jacqmin, T.; Jani, K.; Jaranowski,
P.; Jawahar, S.; Jiménez-Forteza, F.; Johnson, W. W.; Jones,
D. I.; Jones, R.; Jonker, R. J. G.; Ju, L.; Junker, J.; Kalaghatgi,
C. V.; Kalogera, V.; Kamai, B.; Kandhasamy, S.; Kang, G.; Kanner,
J. B.; Kapadia, S. J.; Karki, S.; Karvinen, K. S.; Kasprzack, M.;
Katolik, M.; Katsavounidis, E.; Katzman, W.; Kaufer, S.; Kawabe, K.;
Kéfélian, F.; Keitel, D.; Kemball, A. J.; Kennedy, R.; Kent, C.;
Key, J. S.; Khalili, F. Y.; Khan, I.; Khan, S.; Khan, Z.; Khazanov,
E. A.; Kijbunchoo, N.; Kim, Chunglee; Kim, J. C.; Kim, K.; Kim, W.;
Kim, W. S.; Kim, Y. -M.; Kimbrell, S. J.; King, E. J.; King, P. J.;
Kinley-Hanlon, M.; Kirchhoff, R.; Kissel, J. S.; Kleybolte, L.;
Klimenko, S.; Knowles, T. D.; Koch, P.; Koehlenbeck, S. M.; Koley,
S.; Kondrashov, V.; Kontos, A.; Korobko, M.; Korth, W. Z.; Kowalska,
I.; Kozak, D. B.; Krämer, C.; Kringel, V.; Krishnan, B.; Królak,
A.; Kuehn, G.; Kumar, P.; Kumar, R.; Kumar, S.; Kuo, L.; Kutynia,
A.; Kwang, S.; Lackey, B. D.; Lai, K. H.; Landry, M.; Lang, R. N.;
Lange, J.; Lantz, B.; Lanza, R. K.; Larson, S. L.; Lartaux-Vollard,
A.; Lasky, P. D.; Laxen, M.; Lazzarini, A.; Lazzaro, C.; Leaci, P.;
Leavey, S.; Lee, C. H.; Lee, H. K.; Lee, H. M.; Lee, H. W.; Lee, K.;
Lehmann, J.; Lenon, A.; Leonardi, M.; Leroy, N.; Letendre, N.; Levin,
Y.; Li, T. G. F.; Linker, S. D.; Littenberg, T. B.; Liu, J.; Lo,
R. K. L.; Lockerbie, N. A.; London, L. T.; Lord, J. E.; Lorenzini,
M.; Loriette, V.; Lormand, M.; Losurdo, G.; Lough, J. D.; Lousto,
C. O.; Lovelace, G.; Lück, H.; Lumaca, D.; Lundgren, A. P.; Lynch,
R.; Ma, Y.; Macas, R.; Macfoy, S.; Machenschalk, B.; MacInnis, M.;
Macleod, D. M.; Magaña Hernandez, I.; Magaña-Sandoval, F.; Magaña
Zertuche, L.; Magee, R. M.; Majorana, E.; Maksimovic, I.; Man, N.;
Mandic, V.; Mangano, V.; Mansell, G. L.; Manske, M.; Mantovani, M.;
Marchesoni, F.; Marion, F.; Márka, S.; Márka, Z.; Markakis, C.;
Markosyan, A. S.; Markowitz, A.; Maros, E.; Marquina, A.; Marsh,
P.; Martelli, F.; Martellini, L.; Martin, I. W.; Martin, R. M.;
Martynov, D. V.; Mason, K.; Massera, E.; Masserot, A.; Massinger,
T. J.; Masso-Reid, M.; Mastrogiovanni, S.; Matas, A.; Matichard, F.;
Matone, L.; Mavalvala, N.; Mazumder, N.; McCarthy, R.; McClelland,
D. E.; McCormick, S.; McCuller, L.; McGuire, S. C.; McIntyre, G.;
McIver, J.; McManus, D. J.; McNeill, L.; McRae, T.; McWilliams, S. T.;
Meacher, D.; Meadors, G. D.; Mehmet, M.; Meidam, J.; Mejuto-Villa, E.;
Melatos, A.; Mendell, G.; Mercer, R. A.; Merilh, E. L.; Merzougui, M.;
Meshkov, S.; Messenger, C.; Messick, C.; Metzdorff, R.; Meyers, P. M.;
Miao, H.; Michel, C.; Middleton, H.; Mikhailov, E. E.; Milano, L.;
Miller, A. L.; Miller, B. B.; Miller, J.; Millhouse, M.; Milovich-Goff,
M. C.; Minazzoli, O.; Minenkov, Y.; Ming, J.; Mishra, C.; Mitra, S.;
Mitrofanov, V. P.; Mitselmakher, G.; Mittleman, R.; Moffa, D.; Moggi,
A.; Mogushi, K.; Mohan, M.; Mohapatra, S. R. P.; Montani, M.; Moore,
C. J.; Moraru, D.; Moreno, G.; Morriss, S. R.; Mours, B.; Mow-Lowry,
C. M.; Mueller, G.; Muir, A. W.; Mukherjee, Arunava; Mukherjee, D.;
Mukherjee, S.; Mukund, N.; Mullavey, A.; Munch, J.; Muñiz, E. A.;
Muratore, M.; Murray, P. G.; Napier, K.; Nardecchia, I.; Naticchioni,
L.; Nayak, R. K.; Neilson, J.; Nelemans, G.; Nelson, T. J. N.; Nery,
M.; Neunzert, A.; Nevin, L.; Newport, J. M.; Newton, G.; Ng, K. K. Y.;
Nguyen, P.; Nguyen, T. T.; Nichols, D.; Nielsen, A. B.; Nissanke,
S.; Nitz, A.; Noack, A.; Nocera, F.; Nolting, D.; North, C.; Nuttall,
L. K.; Oberling, J.; O'Dea, G. D.; Ogin, G. H.; Oh, J. J.; Oh, S. H.;
Ohme, F.; Okada, M. A.; Oliver, M.; Oppermann, P.; Oram, Richard J.;
O'Reilly, B.; Ormiston, R.; Ortega, L. F.; O'Shaughnessy, R.; Ossokine,
S.; Ottaway, D. J.; Overmier, H.; Owen, B. J.; Pace, A. E.; Page,
J.; Page, M. A.; Pai, A.; Pai, S. A.; Palamos, J. R.; Palashov, O.;
Palomba, C.; Pal-Singh, A.; Pan, Howard; Pan, Huang-Wei; Pang, B.;
Pang, P. T. H.; Pankow, C.; Pannarale, F.; Pant, B. C.; Paoletti,
F.; Paoli, A.; Papa, M. A.; Parida, A.; Parker, W.; Pascucci, D.;
Pasqualetti, A.; Passaquieti, R.; Passuello, D.; Patil, M.; Patricelli,
B.; Pearlstone, B. L.; Pedraza, M.; Pedurand, R.; Pekowsky, L.; Pele,
A.; Penn, S.; Perez, C. J.; Perreca, A.; Perri, L. M.; Pfeiffer, H. P.;
Phelps, M.; Piccinni, O. J.; Pichot, M.; Piergiovanni, F.; Pierro,
V.; Pillant, G.; Pinard, L.; Pinto, I. M.; Pirello, M.; Pitkin, M.;
Poe, M.; Poggiani, R.; Popolizio, P.; Porter, E. K.; Post, A.; Powell,
J.; Prasad, J.; Pratt, J. W. W.; Pratten, G.; Predoi, V.; Prestegard,
T.; Price, L. R.; Prijatelj, M.; Principe, M.; Privitera, S.; Prodi,
G. A.; Prokhorov, L. G.; Puncken, O.; Punturo, M.; Puppo, P.; Pürrer,
M.; Qi, H.; Quetschke, V.; Quintero, E. A.; Quitzow-James, R.; Raab,
F. J.; Rabeling, D. S.; Radkins, H.; Raffai, P.; Raja, S.; Rajan,
C.; Rajbhandari, B.; Rakhmanov, M.; Ramirez, K. E.; Ramos-Buades,
A.; Rapagnani, P.; Raymond, V.; Razzano, M.; Read, J.; Regimbau, T.;
Rei, L.; Reid, S.; Reitze, D. H.; Ren, W.; Reyes, S. D.; Ricci, F.;
Ricker, P. M.; Rieger, S.; Riles, K.; Rizzo, M.; Robertson, N. A.;
Robie, R.; Robinet, F.; Rocchi, A.; Rolland, L.; Rollins, J. G.;
Roma, V. J.; Romano, R.; Romel, C. L.; Romie, J. H.; Rosińska,
D.; Ross, M. P.; Rowan, S.; Rüdiger, A.; Ruggi, P.; Rutins, G.;
Ryan, K.; Sachdev, S.; Sadecki, T.; Sadeghian, L.; Sakellariadou,
M.; Salconi, L.; Saleem, M.; Salemi, F.; Samajdar, A.; Sammut, L.;
Sampson, L. M.; Sanchez, E. J.; Sanchez, L. E.; Sanchis-Gual, N.;
Sandberg, V.; Sanders, J. R.; Sassolas, B.; Sathyaprakash, B. S.;
Saulson, P. R.; Sauter, O.; Savage, R. L.; Sawadsky, A.; Schale,
P.; Scheel, M.; Scheuer, J.; Schmidt, J.; Schmidt, P.; Schnabel,
R.; Schofield, R. M. S.; Schönbeck, A.; Schreiber, E.; Schuette,
D.; Schulte, B. W.; Schutz, B. F.; Schwalbe, S. G.; Scott, J.;
Scott, S. M.; Seidel, E.; Sellers, D.; Sengupta, A. S.; Sentenac,
D.; Sequino, V.; Sergeev, A.; Shaddock, D. A.; Shaffer, T. J.; Shah,
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Smith, J. R.; Smith, R. J. E.; Somala, S.; Son, E. J.; Sonnenberg,
J. A.; Sorazu, B.; Sorrentino, F.; Souradeep, T.; Spencer, A. P.;
Srivastava, A. K.; Staats, K.; Staley, A.; Steinke, M.; Steinlechner,
J.; Steinlechner, S.; Steinmeyer, D.; Stevenson, S. P.; Stone, R.;
Stops, D. J.; Strain, K. A.; Stratta, G.; Strigin, S. E.; Strunk, A.;
Sturani, R.; Stuver, A. L.; Summerscales, T. Z.; Sun, L.; Sunil, S.;
Suresh, J.; Sutton, P. J.; Swinkels, B. L.; Szczepańczyk, M. J.;
Tacca, M.; Tait, S. C.; Talbot, C.; Talukder, D.; Tanner, D. B.;
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R.; Tewari, S. V.; Theeg, T.; Thies, F.; Thomas, E. G.; Thomas, M.;
Thomas, P.; Thorne, K. A.; Thorne, K. S.; Thrane, E.; Tiwari, S.;
Tiwari, V.; Tokmakov, K. V.; Toland, K.; Tonelli, M.; Tornasi, Z.;
Torres-Forné, A.; Torrie, C. I.; Töyrä, D.; Travasso, F.; Traylor,
G.; Trinastic, J.; Tringali, M. C.; Trozzo, L.; Tsang, K. W.; Tse, M.;
Tso, R.; Tsukada, L.; Tsuna, D.; Tuyenbayev, D.; Ueno, K.; Ugolini,
D.; Unnikrishnan, C. S.; Urban, A. L.; Usman, S. A.; Vahlbruch, H.;
Vajente, G.; Valdes, G.; van Bakel, N.; van Beuzekom, M.; van den
Brand, J. F. J.; Van Den Broeck, C.; Vander-Hyde, D. C.; van der
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Varma, V.; Vass, S.; Vasúth, M.; Vecchio, A.; Vedovato, G.; Veitch,
J.; Veitch, P. J.; Venkateswara, K.; Venugopalan, G.; Verkindt, D.;
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Wang, Y. F.; Ward, R. L.; Warner, J.; Was, M.; Watchi, J.; Weaver,
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Wessel, E. K.; Wessels, P.; Westerweck, J.; Westphal, T.; Wette, K.;
Whelan, J. T.; Whitcomb, S. E.; Whiting, B. F.; Whittle, C.; Wilken,
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Labare, M.; Lanfranchi, J. L.; Larson, M. J.; Lauber, F.; Lesiak-Bzdak,
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Madsen, J.; Maggi, G.; Mahn, K. B. M.; Mancina, S.; Maruyama, R.;
Mase, K.; Maunu, R.; McNally, F.; Meagher, K.; Medici, M.; Meier,
M.; Menne, T.; Merino, G.; Meures, T.; Miarecki, S.; Micallef, J.;
Momenté, G.; Montaruli, T.; Moore, R. W.; Moulai, M.; Nahnhauer,
R.; Nakarmi, P.; Naumann, U.; Neer, G.; Niederhausen, H.; Nowicki,
S. C.; Nygren, D. R.; Obertacke Pollmann, A.; Olivas, A.; O'Murchadha,
A.; Palczewski, T.; Pandya, H.; Pankova, D. V.; Peiffer, P.; Pepper,
J. A.; Pérez de los Heros, C.; Pieloth, D.; Pinat, E.; Price, P. B.;
Przybylski, G. T.; Raab, C.; Rädel, L.; Rameez, M.; Rawlins, K.; Rea,
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Richman, M.; Robertson, S.; Rongen, M.; Rott, C.; Ruhe, T.; Ryckbosch,
D.; Rysewyk, D.; Sälzer, T.; Sanchez Herrera, S. E.; Sandrock, A.;
Sandroos, J.; Santander, M.; Sarkar, S.; Sarkar, S.; Satalecka, K.;
Schlunder, P.; Schmidt, T.; Schneider, A.; Schoenen, S.; Schöneberg,
S.; Schumacher, L.; Seckel, D.; Seunarine, S.; Soedingrekso, J.;
Soldin, D.; Song, M.; Spiczak, G. M.; Spiering, C.; Stachurska, J.;
Stamatikos, M.; Stanev, T.; Stasik, A.; Stettner, J.; Steuer, A.;
Stezelberger, T.; Stokstad, R. G.; Stössl, A.; Strotjohann, N. L.;
Stuttard, T.; Sullivan, G. W.; Sutherland, M.; Taboada, I.; Tatar,
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M.; Tung, C. F.; Turcati, A.; Turley, C. F.; Ty, B.; Unger, E.;
Usner, M.; Vandenbroucke, J.; Van Driessche, W.; van Eijndhoven, N.;
Vanheule, S.; van Santen, J.; Vehring, M.; Vogel, E.; Vraeghe, M.;
Walck, C.; Wallace, A.; Wallraff, M.; Wandler, F. D.; Wandkowsky,
N.; Waza, A.; Weaver, C.; Weiss, M. J.; Wendt, C.; Werthebach, J.;
Whelan, B. J.; Wiebe, K.; Wiebusch, C. H.; Wille, L.; Williams,
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K.; Xu, D. L.; Xu, X. W.; Xu, Y.; Yanez, J. P.; Yodh, G.; Yoshida,
S.; Yuan, T.; Zoll, M.; IceCube Collaboration; Balasubramanian, A.;
Mate, S.; Bhalerao, V.; Bhattacharya, D.; Vibhute, A.; Dewangan,
G. C.; Rao, A. R.; Vadawale, S. V.; AstroSat Cadmium Zinc Telluride
Imager Team; Svinkin, D. S.; Hurley, K.; Aptekar, R. L.; Frederiks,
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Ph. P.; Tsvetkova, A. E.; Ulanov, M. V.; Cline, T.; IPN Collaboration;
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X. L.; Chang, Z.; Chen, G.; Chen, L.; Chen, T. X.; Chen, Y.; Chen,
Y. B.; Chen, Y. P.; Cui, W.; Cui, W. W.; Deng, J. K.; Dong, Y. W.; Du,
Y. Y.; Fu, M. X.; Gao, G. H.; Gao, H.; Gao, M.; Ge, M. Y.; Gu, Y. D.;
Guan, J.; Guo, C. C.; Han, D. W.; Hu, W.; Huang, Y.; Huo, J.; Jia,
S. M.; Jiang, L. H.; Jiang, W. C.; Jin, J.; Jin, Y. J.; Li, B.; Li,
C. K.; Li, G.; Li, M. S.; Li, W.; Li, X.; Li, X. B.; Li, X. F.; Li,
Y. G.; Li, Z. J.; Li, Z. W.; Liang, X. H.; Liao, J. Y.; Liu, C. Z.;
Liu, G. Q.; Liu, H. W.; Liu, S. Z.; Liu, X. J.; Liu, Y.; Liu, Y. N.;
Lu, B.; Lu, X. F.; Luo, T.; Ma, X.; Meng, B.; Nang, Y.; Nie, J. Y.;
Ou, G.; Qu, J. L.; Sai, N.; Sun, L.; Tan, Y.; Tao, L.; Tao, W. H.;
Tuo, Y. L.; Wang, G. F.; Wang, H. Y.; Wang, J.; Wang, W. S.; Wang,
Y. S.; Wen, X. Y.; Wu, B. B.; Wu, M.; Xiao, G. C.; Xu, H.; Xu, Y. P.;
Yan, L. L.; Yang, J. W.; Yang, S.; Yang, Y. J.; Zhang, A. M.; Zhang,
C. L.; Zhang, C. M.; Zhang, F.; Zhang, H. M.; Zhang, J.; Zhang, Q.;
Zhang, S.; Zhang, T.; Zhang, W.; Zhang, W. C.; Zhang, W. Z.; Zhang,
Y.; Zhang, Y.; Zhang, Y. F.; Zhang, Y. J.; Zhang, Z.; Zhang, Z. L.;
Zhao, H. S.; Zhao, J. L.; Zhao, X. F.; Zheng, S. J.; Zhu, Y.; Zhu,
Y. X.; Zou, C. L.; Insight-HXMT Collaboration; Albert, A.; André,
M.; Anghinolfi, M.; Ardid, M.; Aubert, J. -J.; Aublin, J.; Avgitas,
T.; Baret, B.; Barrios-Martí, J.; Basa, S.; Belhorma, B.; Bertin, V.;
Biagi, S.; Bormuth, R.; Bourret, S.; Bouwhuis, M. C.; Brânzaş, H.;
Bruijn, R.; Brunner, J.; Busto, J.; Capone, A.; Caramete, L.; Carr,
J.; Celli, S.; Cherkaoui El Moursli, R.; Chiarusi, T.; Circella,
M.; Coelho, J. A. B.; Coleiro, A.; Coniglione, R.; Costantini, H.;
Coyle, P.; Creusot, A.; Díaz, A. F.; Deschamps, A.; De Bonis,
G.; Distefano, C.; Di Palma, I.; Domi, A.; Donzaud, C.; Dornic,
D.; Drouhin, D.; Eberl, T.; El Bojaddaini, I.; El Khayati, N.;
Elsässer, D.; Enzenhöfer, A.; Ettahiri, A.; Fassi, F.; Felis, I.;
Fusco, L. A.; Gay, P.; Giordano, V.; Glotin, H.; Grégoire, T.; Ruiz,
R. Gracia; Graf, K.; Hallmann, S.; van Haren, H.; Heijboer, A. J.;
Hello, Y.; Hernández-Rey, J. J.; Hössl, J.; Hofestädt, J.; Hugon,
C.; Illuminati, G.; James, C. W.; de Jong, M.; Jongen, M.; Kadler,
M.; Kalekin, O.; Katz, U.; Kiessling, D.; Kouchner, A.; Kreter, M.;
Kreykenbohm, I.; Kulikovskiy, V.; Lachaud, C.; Lahmann, R.; Lefèvre,
D.; Leonora, E.; Lotze, M.; Loucatos, S.; Marcelin, M.; Margiotta, A.;
Marinelli, A.; Martínez-Mora, J. A.; Mele, R.; Melis, K.; Michael,
T.; Migliozzi, P.; Moussa, A.; Navas, S.; Nezri, E.; Organokov, M.;
Păvălaş, G. E.; Pellegrino, C.; Perrina, C.; Piattelli, P.; Popa,
V.; Pradier, T.; Quinn, L.; Racca, C.; Riccobene, G.; Sánchez-Losa,
A.; Saldaña, M.; Salvadori, I.; Samtleben, D. F. E.; Sanguineti,
M.; Sapienza, P.; Sieger, C.; Spurio, M.; Stolarczyk, Th.; Taiuti,
M.; Tayalati, Y.; Trovato, A.; Turpin, D.; Tönnis, C.; Vallage, B.;
Van Elewyck, V.; Versari, F.; Vivolo, D.; Vizzoca, A.; Wilms, J.;
Zornoza, J. D.; Zúñiga, J.; ANTARES Collaboration; Beardmore, A. P.;
Breeveld, A. A.; Burrows, D. N.; Cenko, S. B.; Cusumano, G.; D'Aì, A.;
de Pasquale, M.; Emery, S. W. K.; Evans, P. A.; Giommi, P.; Gronwall,
C.; Kennea, J. A.; Krimm, H. A.; Kuin, N. P. M.; Lien, A.; Marshall,
F. E.; Melandri, A.; Nousek, J. A.; Oates, S. R.; Osborne, J. P.;
Pagani, C.; Page, K. L.; Palmer, D. M.; Perri, M.; Siegel, M. H.;
Sbarufatti, B.; Tagliaferri, G.; Tohuvavohu, A.; Swift Collaboration;
Tavani, M.; Verrecchia, F.; Bulgarelli, A.; Evangelista, Y.; Pacciani,
L.; Feroci, M.; Pittori, C.; Giuliani, A.; Del Monte, E.; Donnarumma,
I.; Argan, A.; Trois, A.; Ursi, A.; Cardillo, M.; Piano, G.; Longo,
F.; Lucarelli, F.; Munar-Adrover, P.; Fuschino, F.; Labanti, C.;
Marisaldi, M.; Minervini, G.; Fioretti, V.; Parmiggiani, N.; Gianotti,
F.; Trifoglio, M.; Di Persio, G.; Antonelli, L. A.; Barbiellini, G.;
Caraveo, P.; Cattaneo, P. W.; Costa, E.; Colafrancesco, S.; D'Amico,
F.; Ferrari, A.; Morselli, A.; Paoletti, F.; Picozza, P.; Pilia,
M.; Rappoldi, A.; Soffitta, P.; Vercellone, S.; AGILE Team; Foley,
R. J.; Coulter, D. A.; Kilpatrick, C. D.; Drout, M. R.; Piro, A. L.;
Shappee, B. J.; Siebert, M. R.; Simon, J. D.; Ulloa, N.; Kasen, D.;
Madore, B. F.; Murguia-Berthier, A.; Pan, Y. -C.; Prochaska, J. X.;
Ramirez-Ruiz, E.; Rest, A.; Rojas-Bravo, C.; 1M2H Team; Berger, E.;
Soares-Santos, M.; Annis, J.; Alexander, K. D.; Allam, S.; Balbinot,
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M. R.; Durret, F.; Eftekhari, T.; Finley, D. A.; Fong, W.; Frieman,
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W.; Herner, K.; Kessler, R.; Lin, H.; Lopes, P. A. A.; Lourenço,
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Metzger, B. D.; Muñoz, R. R.; Muir, J.; Nicholl, M.; Nugent, P.;
Palmese, A.; Paz-Chinchón, F.; Quataert, E.; Sako, M.; Sauseda, M.;
Schlegel, D. J.; Scolnic, D.; Secco, L. F.; Smith, N.; Sobreira, F.;
Villar, V. A.; Vivas, A. K.; Wester, W.; Williams, P. K. G.; Yanny,
B.; Zenteno, A.; Zhang, Y.; Abbott, T. M. C.; Banerji, M.; Bechtol,
K.; Benoit-Lévy, A.; Bertin, E.; Brooks, D.; Buckley-Geer, E.; Burke,
D. L.; Capozzi, D.; Carnero Rosell, A.; Carrasco Kind, M.; Castander,
F. J.; Crocce, M.; Cunha, C. E.; D'Andrea, C. B.; da Costa, L. N.;
Davis, C.; DePoy, D. L.; Desai, S.; Dietrich, J. P.; Eifler, T. F.;
Fernandez, E.; Flaugher, B.; Fosalba, P.; Gaztanaga, E.; Gerdes,
D. W.; Giannantonio, T.; Goldstein, D. A.; Gruen, D.; Gschwend, J.;
Gutierrez, G.; Honscheid, K.; James, D. J.; Jeltema, T.; Johnson,
M. W. G.; Johnson, M. D.; Kent, S.; Krause, E.; Kron, R.; Kuehn, K.;
Lahav, O.; Lima, M.; Maia, M. A. G.; March, M.; Martini, P.; McMahon,
R. G.; Menanteau, F.; Miller, C. J.; Miquel, R.; Mohr, J. J.; Nichol,
R. C.; Ogando, R. L. C.; Plazas, A. A.; Romer, A. K.; Roodman, A.;
Rykoff, E. S.; Sanchez, E.; Scarpine, V.; Schindler, R.; Schubnell,
M.; Sevilla-Noarbe, I.; Sheldon, E.; Smith, M.; Smith, R. C.; Stebbins,
A.; Suchyta, E.; Swanson, M. E. C.; Tarle, G.; Thomas, R. C.; Troxel,
M. A.; Tucker, D. L.; Vikram, V.; Walker, A. R.; Wechsler, R. H.;
Weller, J.; Carlin, J. L.; Gill, M. S. S.; Li, T. S.; Marriner, J.;
Neilsen, E.; Dark Energy Camera GW-EM Collaboration; DES Collaboration;
Haislip, J. B.; Kouprianov, V. V.; Reichart, D. E.; Sand, D. J.;
Tartaglia, L.; Valenti, S.; Yang, S.; DLT40 Collaboration; Benetti,
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P.; D'Elia, V.; Getman, F.; Ghirlanda, G.; Ghisellini, G.; Limatola,
L.; Nicastro, L.; Palazzi, E.; Pian, E.; Piranomonte, S.; Possenti,
A.; Rossi, A.; Salafia, O. S.; Tomasella, L.; Amati, L.; Antonelli,
L. A.; Bernardini, M. G.; Bufano, F.; Capaccioli, M.; Casella, P.;
Dadina, M.; De Cesare, G.; Di Paola, A.; Giuffrida, G.; Giunta,
A.; Israel, G. L.; Lisi, M.; Maiorano, E.; Mapelli, M.; Masetti,
N.; Pescalli, A.; Pulone, L.; Salvaterra, R.; Schipani, P.; Spera,
M.; Stamerra, A.; Stella, L.; Testa, V.; Turatto, M.; Vergani, D.;
Aresu, G.; Bachetti, M.; Buffa, F.; Burgay, M.; Buttu, M.; Caria,
T.; Carretti, E.; Casasola, V.; Castangia, P.; Carboni, G.; Casu,
S.; Concu, R.; Corongiu, A.; Deiana, G. L.; Egron, E.; Fara, A.;
Gaudiomonte, F.; Gusai, V.; Ladu, A.; Loru, S.; Leurini, S.; Marongiu,
L.; Melis, A.; Melis, G.; Migoni, Carlo; Milia, Sabrina; Navarrini,
Alessandro; Orlati, A.; Ortu, P.; Palmas, S.; Pellizzoni, A.; Perrodin,
D.; Pisanu, T.; Poppi, S.; Righini, S.; Saba, A.; Serra, G.; Serrau,
M.; Stagni, M.; Surcis, G.; Vacca, V.; Vargiu, G. P.; Hunt, L. K.;
Jin, Z. P.; Klose, S.; Kouveliotou, C.; Mazzali, P. A.; Møller, P.;
Nava, L.; Piran, T.; Selsing, J.; Vergani, S. D.; Wiersema, K.; Toma,
K.; Higgins, A. B.; Mundell, C. G.; di Serego Alighieri, S.; Gótz,
D.; Gao, W.; Gomboc, A.; Kaper, L.; Kobayashi, S.; Kopac, D.; Mao,
J.; Starling, R. L. C.; Steele, I.; van der Horst, A. J.; GRAWITA:
GRAvitational Wave Inaf TeAm; Acero, F.; Atwood, W. B.; Baldini,
L.; Barbiellini, G.; Bastieri, D.; Berenji, B.; Bellazzini, R.;
Bissaldi, E.; Blandford, R. D.; Bloom, E. D.; Bonino, R.; Bottacini,
E.; Bregeon, J.; Buehler, R.; Buson, S.; Cameron, R. A.; Caputo, R.;
Caraveo, P. A.; Cavazzuti, E.; Chekhtman, A.; Cheung, C. C.; Chiang,
J.; Ciprini, S.; Cohen-Tanugi, J.; Cominsky, L. R.; Costantin, D.;
Cuoco, A.; D'Ammando, F.; de Palma, F.; Digel, S. W.; Di Lalla,
N.; Di Mauro, M.; Di Venere, L.; Dubois, R.; Fegan, S. J.; Focke,
W. B.; Franckowiak, A.; Fukazawa, Y.; Funk, S.; Fusco, P.; Gargano,
F.; Gasparrini, D.; Giglietto, N.; Giordano, F.; Giroletti, M.;
Glanzman, T.; Green, D.; Grondin, M. -H.; Guillemot, L.; Guiriec,
S.; Harding, A. K.; Horan, D.; Jóhannesson, G.; Kamae, T.; Kensei,
S.; Kuss, M.; La Mura, G.; Latronico, L.; Lemoine-Goumard, M.;
Longo, F.; Loparco, F.; Lovellette, M. N.; Lubrano, P.; Magill,
J. D.; Maldera, S.; Manfreda, A.; Mazziotta, M. N.; McEnery, J. E.;
Meyer, M.; Michelson, P. F.; Mirabal, N.; Monzani, M. E.; Moretti,
E.; Morselli, A.; Moskalenko, I. V.; Negro, M.; Nuss, E.; Ojha, R.;
Omodei, N.; Orienti, M.; Orlando, E.; Palatiello, M.; Paliya, V. S.;
Paneque, D.; Pesce-Rollins, M.; Piron, F.; Porter, T. A.; Principe, G.;
Rainò, S.; Rando, R.; Razzano, M.; Razzaque, S.; Reimer, A.; Reimer,
O.; Reposeur, T.; Rochester, L. S.; Saz Parkinson, P. M.; Sgrò, C.;
Siskind, E. J.; Spada, F.; Spandre, G.; Suson, D. J.; Takahashi, M.;
Tanaka, Y.; Thayer, J. G.; Thayer, J. B.; Thompson, D. J.; Tibaldo,
L.; Torres, D. F.; Torresi, E.; Troja, E.; Venters, T. M.; Vianello,
G.; Zaharijas, G.; Fermi Large Area Telescope Collaboration; Allison,
J. R.; Bannister, K. W.; Dobie, D.; Kaplan, D. L.; Lenc, E.; Lynch,
C.; Murphy, T.; Sadler, E. M.; Australia Telescope Compact Array,
ATCA:; Hotan, A.; James, C. W.; Oslowski, S.; Raja, W.; Shannon,
R. M.; Whiting, M.; Australian SKA Pathfinder, ASKAP:; Arcavi,
I.; Howell, D. A.; McCully, C.; Hosseinzadeh, G.; Hiramatsu, D.;
Poznanski, D.; Barnes, J.; Zaltzman, M.; Vasylyev, S.; Maoz, D.; Las
Cumbres Observatory Group; Cooke, J.; Bailes, M.; Wolf, C.; Deller,
A. T.; Lidman, C.; Wang, L.; Gendre, B.; Andreoni, I.; Ackley, K.;
Pritchard, T. A.; Bessell, M. S.; Chang, S. -W.; Möller, A.; Onken,
C. A.; Scalzo, R. A.; Ridden-Harper, R.; Sharp, R. G.; Tucker, B. E.;
Farrell, T. J.; Elmer, E.; Johnston, S.; Venkatraman Krishnan, V.;
Keane, E. F.; Green, J. A.; Jameson, A.; Hu, L.; Ma, B.; Sun, T.;
Wu, X.; Wang, X.; Shang, Z.; Hu, Y.; Ashley, M. C. B.; Yuan, X.; Li,
X.; Tao, C.; Zhu, Z.; Zhang, H.; Suntzeff, N. B.; Zhou, J.; Yang, J.;
Orange, B.; Morris, D.; Cucchiara, A.; Giblin, T.; Klotz, A.; Staff,
J.; Thierry, P.; Schmidt, B. P.; OzGrav; (Deeper, DWF; Wider; program,
Faster; AST3; CAASTRO Collaborations; Tanvir, N. R.; Levan, A. J.;
Cano, Z.; de Ugarte-Postigo, A.; González-Fernández, C.; Greiner,
J.; Hjorth, J.; Irwin, M.; Krühler, T.; Mandel, I.; Milvang-Jensen,
B.; O'Brien, P.; Rol, E.; Rosetti, S.; Rosswog, S.; Rowlinson, A.;
Steeghs, D. T. H.; Thöne, C. C.; Ulaczyk, K.; Watson, D.; Bruun,
S. H.; Cutter, R.; Figuera Jaimes, R.; Fujii, Y. I.; Fruchter, A. S.;
Gompertz, B.; Jakobsson, P.; Hodosan, G.; Jèrgensen, U. G.; Kangas,
T.; Kann, D. A.; Rabus, M.; Schrøder, S. L.; Stanway, E. R.; Wijers,
R. A. M. J.; VINROUGE Collaboration; Lipunov, V. M.; Gorbovskoy, E. S.;
Kornilov, V. G.; Tyurina, N. V.; Balanutsa, P. V.; Kuznetsov, A. S.;
Vlasenko, D. M.; Podesta, R. C.; Lopez, C.; Podesta, F.; Levato,
H. O.; Saffe, C.; Mallamaci, C. C.; Budnev, N. M.; Gress, O. A.;
Kuvshinov, D. A.; Gorbunov, I. A.; Vladimirov, V. V.; Zimnukhov,
D. S.; Gabovich, A. V.; Yurkov, V. V.; Sergienko, Yu. P.; Rebolo,
R.; Serra-Ricart, M.; Tlatov, A. G.; Ishmuhametova, Yu. V.; MASTER
Collaboration; Abe, F.; Aoki, K.; Aoki, W.; Asakura, Y.; Baar, S.;
Barway, S.; Bond, I. A.; Doi, M.; Finet, F.; Fujiyoshi, T.; Furusawa,
H.; Honda, S.; Itoh, R.; Kanda, N.; Kawabata, K. S.; Kawabata, M.; Kim,
J. H.; Koshida, S.; Kuroda, D.; Lee, C. -H.; Liu, W.; Matsubayashi,
K.; Miyazaki, S.; Morihana, K.; Morokuma, T.; Motohara, K.; Murata,
K. L.; Nagai, H.; Nagashima, H.; Nagayama, T.; Nakaoka, T.; Nakata,
F.; Ohsawa, R.; Ohshima, T.; Ohta, K.; Okita, H.; Saito, T.; Saito,
Y.; Sako, S.; Sekiguchi, Y.; Sumi, T.; Tajitsu, A.; Takahashi,
J.; Takayama, M.; Tamura, Y.; Tanaka, I.; Tanaka, M.; Terai, T.;
Tominaga, N.; Tristram, P. J.; Uemura, M.; Utsumi, Y.; Yamaguchi,
M. S.; Yasuda, N.; Yoshida, M.; Zenko, T.; J-GEM; Adams, S. M.;
Anupama, G. C.; Bally, J.; Barway, S.; Bellm, E.; Blagorodnova, N.;
Cannella, C.; Chandra, P.; Chatterjee, D.; Clarke, T. E.; Cobb, B. E.;
Cook, D. O.; Copperwheat, C.; De, K.; Emery, S. W. K.; Feindt, U.;
Foster, K.; Fox, O. D.; Frail, D. A.; Fremling, C.; Frohmaier, C.;
Garcia, J. A.; Ghosh, S.; Giacintucci, S.; Goobar, A.; Gottlieb, O.;
Grefenstette, B. W.; Hallinan, G.; Harrison, F.; Heida, M.; Helou,
G.; Ho, A. Y. Q.; Horesh, A.; Hotokezaka, K.; Ip, W. -H.; Itoh, R.;
Jacobs, Bob; Jencson, J. E.; Kasen, D.; Kasliwal, M. M.; Kassim,
N. E.; Kim, H.; Kiran, B. S.; Kuin, N. P. M.; Kulkarni, S. R.;
Kupfer, T.; Lau, R. M.; Madsen, K.; Mazzali, P. A.; Miller, A. A.;
Miyasaka, H.; Mooley, K.; Myers, S. T.; Nakar, E.; Ngeow, C. -C.;
Nugent, P.; Ofek, E. O.; Palliyaguru, N.; Pavana, M.; Perley, D. A.;
Peters, W. M.; Pike, S.; Piran, T.; Qi, H.; Quimby, R. M.; Rana, J.;
Rosswog, S.; Rusu, F.; Sadler, E. M.; Van Sistine, A.; Sollerman, J.;
Xu, Y.; Yan, L.; Yatsu, Y.; Yu, P. -C.; Zhang, C.; Zhao, W.; GROWTH;
JAGWAR; Caltech-NRAO; TTU-NRAO; NuSTAR Collaborations; Chambers,
K. C.; Huber, M. E.; Schultz, A. S. B.; Bulger, J.; Flewelling, H.;
Magnier, E. A.; Lowe, T. B.; Wainscoat, R. J.; Waters, C.; Willman,
M.; Pan-STARRS; Ebisawa, K.; Hanyu, C.; Harita, S.; Hashimoto, T.;
Hidaka, K.; Hori, T.; Ishikawa, M.; Isobe, N.; Iwakiri, W.; Kawai,
H.; Kawai, N.; Kawamuro, T.; Kawase, T.; Kitaoka, Y.; Makishima,
K.; Matsuoka, M.; Mihara, T.; Morita, T.; Morita, K.; Nakahira, S.;
Nakajima, M.; Nakamura, Y.; Negoro, H.; Oda, S.; Sakamaki, A.; Sasaki,
R.; Serino, M.; Shidatsu, M.; Shimomukai, R.; Sugawara, Y.; Sugita,
S.; Sugizaki, M.; Tachibana, Y.; Takao, Y.; Tanimoto, A.; Tomida, H.;
Tsuboi, Y.; Tsunemi, H.; Ueda, Y.; Ueno, S.; Yamada, S.; Yamaoka,
K.; Yamauchi, M.; Yatabe, F.; Yoneyama, T.; Yoshii, T.; MAXI Team;
Coward, D. M.; Crisp, H.; Macpherson, D.; Andreoni, I.; Laugier,
R.; Noysena, K.; Klotz, A.; Gendre, B.; Thierry, P.; Turpin, D.;
Consortium, TZAC; Im, M.; Choi, C.; Kim, J.; Yoon, Y.; Lim, G.; Lee,
S. -K.; Lee, C. -U.; Kim, S. -L.; Ko, S. -W.; Joe, J.; Kwon, M. -K.;
Kim, P. -J.; Lim, S. -K.; Choi, J. -S.; KU Collaboration; Fynbo,
J. P. U.; Malesani, D.; Xu, D.; Optical Telescope, Nordic; Smartt,
S. J.; Jerkstrand, A.; Kankare, E.; Sim, S. A.; Fraser, M.; Inserra,
C.; Maguire, K.; Leloudas, G.; Magee, M.; Shingles, L. J.; Smith,
K. W.; Young, D. R.; Kotak, R.; Gal-Yam, A.; Lyman, J. D.; Homan,
D. S.; Agliozzo, C.; Anderson, J. P.; Angus, C. R.; Ashall, C.;
Barbarino, C.; Bauer, F. E.; Berton, M.; Botticella, M. T.; Bulla,
M.; Cannizzaro, G.; Cartier, R.; Cikota, A.; Clark, P.; De Cia,
A.; Della Valle, M.; Dennefeld, M.; Dessart, L.; Dimitriadis, G.;
Elias-Rosa, N.; Firth, R. E.; Flörs, A.; Frohmaier, C.; Galbany, L.;
González-Gaitán, S.; Gromadzki, M.; Gutiérrez, C. P.; Hamanowicz,
A.; Harmanen, J.; Heintz, K. E.; Hernandez, M. -S.; Hodgkin, S. T.;
Hook, I. M.; Izzo, L.; James, P. A.; Jonker, P. G.; Kerzendorf, W. E.;
Kostrzewa-Rutkowska, Z.; Kromer, M.; Kuncarayakti, H.; Lawrence,
A.; Manulis, I.; Mattila, S.; McBrien, O.; Müller, A.; Nordin, J.;
O'Neill, D.; Onori, F.; Palmerio, J. T.; Pastorello, A.; Patat, F.;
Pignata, G.; Podsiadlowski, P.; Razza, A.; Reynolds, T.; Roy, R.;
Ruiter, A. J.; Rybicki, K. A.; Salmon, L.; Pumo, M. L.; Prentice,
S. J.; Seitenzahl, I. R.; Smith, M.; Sollerman, J.; Sullivan, M.;
Szegedi, H.; Taddia, F.; Taubenberger, S.; Terreran, G.; Van Soelen,
B.; Vos, J.; Walton, N. A.; Wright, D. E.; Wyrzykowski, Ł.; Yaron,
O.; pre="(">ePESSTO, 2
at a luminosity distance of {40}-8+8 Mpc and
with component masses consistent with neutron stars. The component
masses were later measured to be in the range 0.86 to 2.26 {M}⊙
. An extensive observing campaign was launched across the
electromagnetic spectrum leading to the discovery of a bright optical
transient (SSS17a, now with the IAU identification of AT 2017gfo) in
NGC 4993 (at ∼ 40 {{Mpc}}) less than 11 hours after the merger by the
One-Meter, Two Hemisphere (1M2H) team using the 1 m Swope Telescope. The
optical transient was independently detected by multiple teams
within an hour. Subsequent observations targeted the object and its
environment. Early ultraviolet observations revealed a blue transient
that faded within 48 hours. Optical and infrared observations showed
a redward evolution over ∼10 days. Following early non-detections,
X-ray and radio emission were discovered at the transient's position ∼
9 and ∼ 16 days, respectively, after the merger. Both the X-ray and
radio emission likely arise from a physical process that is distinct
from the one that generates the UV/optical/near-infrared emission. No
ultra-high-energy gamma-rays and no neutrino candidates consistent with
the source were found in follow-up searches. These observations support
the hypothesis that GW170817 was produced by the merger of two neutron
stars in NGC 4993 followed by a short gamma-ray burst (GRB 170817A)
and a kilonova/macronova powered by the radioactive decay of r-process
nuclei synthesized in the ejecta. Any correspondence should be
addressed to .
Title: All-sky search for periodic gravitational waves in the O1
LIGO data
Authors: Abbott, B. P.; Abbott, R.; Abbott, T. D.; Acernese, F.;
Ackley, K.; Adams, C.; Adams, T.; Addesso, P.; Adhikari, R. X.; Adya,
V. B.; Affeldt, C.; Afrough, M.; Agarwal, B.; Agatsuma, K.; Aggarwal,
N.; Aguiar, O. D.; Aiello, L.; Ain, A.; Ajith, P.; Allen, B.; Allen,
G.; Allocca, A.; Altin, P. A.; Amato, A.; Ananyeva, A.; Anderson,
S. B.; Anderson, W. G.; Antier, S.; Appert, S.; Arai, K.; Araya,
M. C.; Areeda, J. S.; Arnaud, N.; Ascenzi, S.; Ashton, G.; Ast, M.;
Aston, S. M.; Astone, P.; Aufmuth, P.; Aulbert, C.; AultONeal, K.;
Avila-Alvarez, A.; Babak, S.; Bacon, P.; Bader, M. K. M.; Bae, S.;
Baker, P. T.; Baldaccini, F.; Ballardin, G.; Ballmer, S. W.; Banagiri,
S.; Barayoga, J. C.; Barclay, S. E.; Barish, B. C.; Barker, D.; Barone,
F.; Barr, B.; Barsotti, L.; Barsuglia, M.; Barta, D.; Bartlett, J.;
Bartos, I.; Bassiri, R.; Basti, A.; Batch, J. C.; Baune, C.; Bawaj,
M.; Bazzan, M.; Bécsy, B.; Beer, C.; Bejger, M.; Belahcene, I.; Bell,
A. S.; Berger, B. K.; Bergmann, G.; Berry, C. P. L.; Bersanetti, D.;
Bertolini, A.; Betzwieser, J.; Bhagwat, S.; Bhandare, R.; Bilenko,
I. A.; Billingsley, G.; Billman, C. R.; Birch, J.; Birney, R.;
Birnholtz, O.; Biscans, S.; Bisht, A.; Bitossi, M.; Biwer, C.;
Bizouard, M. A.; Blackburn, J. K.; Blackman, J.; Blair, C. D.;
Blair, D. G.; Blair, R. M.; Bloemen, S.; Bock, O.; Bode, N.; Boer,
M.; Bogaert, G.; Bohe, A.; Bondu, F.; Bonnand, R.; Boom, B. A.; Bork,
R.; Boschi, V.; Bose, S.; Bouffanais, Y.; Bozzi, A.; Bradaschia, C.;
Brady, P. R.; Braginsky, V. B.; Branchesi, M.; Brau, J. E.; Briant, T.;
Brillet, A.; Brinkmann, M.; Brisson, V.; Brockill, P.; Broida, J. E.;
Brooks, A. F.; Brown, D. A.; Brown, D. D.; Brown, N. M.; Brunett, S.;
Buchanan, C. C.; Buikema, A.; Bulik, T.; Bulten, H. J.; Buonanno,
A.; Buskulic, D.; Buy, C.; Byer, R. L.; Cabero, M.; Cadonati, L.;
Cagnoli, G.; Cahillane, C.; Calderón Bustillo, J.; Callister, T. A.;
Calloni, E.; Camp, J. B.; Canizares, P.; Cannon, K. C.; Cao, H.; Cao,
J.; Capano, C. D.; Capocasa, E.; Carbognani, F.; Caride, S.; Carney,
M. F.; Casanueva Diaz, J.; Casentini, C.; Caudill, S.; Cavaglià, M.;
Cavalier, F.; Cavalieri, R.; Cella, G.; Cepeda, C. B.; Cerboni Baiardi,
L.; Cerretani, G.; Cesarini, E.; Chamberlin, S. J.; Chan, M.; Chao,
S.; Charlton, P.; Chassande-Mottin, E.; Chatterjee, D.; Cheeseboro,
B. D.; Chen, H. Y.; Chen, Y.; Cheng, H. -P.; Chincarini, A.; Chiummo,
A.; Chmiel, T.; Cho, H. S.; Cho, M.; Chow, J. H.; Christensen, N.;
Chu, Q.; Chua, A. J. K.; Chua, S.; Chung, A. K. W.; Chung, S.; Ciani,
G.; Ciecielag, P.; Ciolfi, R.; Cirelli, C. E.; Cirone, A.; Clara, F.;
Clark, J. A.; Cleva, F.; Cocchieri, C.; Coccia, E.; Cohadon, P. -F.;
Colla, A.; Collette, C. G.; Cominsky, L. R.; Constancio, M.; Conti,
L.; Cooper, S. J.; Corban, P.; Corbitt, T. R.; Corley, K. R.; Cornish,
N.; Corsi, A.; Cortese, S.; Costa, C. A.; Coughlin, E.; Coughlin,
M. W.; Coughlin, S. B.; Coulon, J. -P.; Countryman, S. T.; Couvares,
P.; Covas, P. B.; Cowan, E. E.; Coward, D. M.; Cowart, M. J.; Coyne,
D. C.; Coyne, R.; Creighton, J. D. E.; Creighton, T. D.; Cripe, J.;
Crowder, S. G.; Cullen, T. J.; Cumming, A.; Cunningham, L.; Cuoco,
E.; Dal Canton, T.; Danilishin, S. L.; D'Antonio, S.; Danzmann, K.;
Dasgupta, A.; Da Silva Costa, C. F.; Dattilo, V.; Dave, I.; Davier,
M.; Davis, D.; Daw, E. J.; Day, B.; De, S.; DeBra, D.; Deelman, E.;
Degallaix, J.; De Laurentis, M.; Deléglise, S.; Del Pozzo, W.; Denker,
T.; Dent, T.; Dergachev, V.; De Rosa, R.; DeRosa, R. T.; DeSalvo, R.;
Devenson, J.; Devine, R. C.; Dhurandhar, S.; Díaz, M. C.; Di Fiore,
L.; Di Giovanni, M.; Di Girolamo, T.; Di Lieto, A.; Di Pace, S.;
Di Palma, I.; Di Renzo, F.; Doctor, Z.; Dolique, V.; Donovan, F.;
Dooley, K. L.; Doravari, S.; Dorosh, O.; Dorrington, I.; Douglas,
R.; Dovale Álvarez, M.; Downes, T. P.; Drago, M.; Drever, R. W. P.;
Driggers, J. C.; Du, Z.; Ducrot, M.; Duncan, J.; Dwyer, S. E.; Edo,
T. B.; Edwards, M. C.; Effler, A.; Eggenstein, H. -B.; Ehrens, P.;
Eichholz, J.; Eikenberry, S. S.; Eisenstein, R. A.; Essick, R. C.;
Etienne, Z. B.; Etzel, T.; Evans, M.; Evans, T. M.; Factourovich, M.;
Fafone, V.; Fair, H.; Fairhurst, S.; Fan, X.; Farinon, S.; Farr, B.;
Farr, W. M.; Fauchon-Jones, E. J.; Favata, M.; Fays, M.; Fehrmann,
H.; Feicht, J.; Fejer, M. M.; Fernandez-Galiana, A.; Ferrante, I.;
Ferreira, E. C.; Ferrini, F.; Fidecaro, F.; Fiori, I.; Fiorucci, D.;
Fisher, R. P.; Flaminio, R.; Fletcher, M.; Fong, H.; Forsyth, P. W. F.;
Forsyth, S. S.; Fournier, J. -D.; Frasca, S.; Frasconi, F.; Frei, Z.;
Freise, A.; Frey, R.; Frey, V.; Fries, E. M.; Fritschel, P.; Frolov,
V. V.; Fulda, P.; Fyffe, M.; Gabbard, H.; Gabel, M.; Gadre, B. U.;
Gaebel, S. M.; Gair, J. R.; Gammaitoni, L.; Ganija, M. R.; Gaonkar,
S. G.; Garufi, F.; Gaudio, S.; Gaur, G.; Gayathri, V.; Gehrels, N.;
Gemme, G.; Genin, E.; Gennai, A.; George, D.; George, J.; Gergely,
L.; Germain, V.; Ghonge, S.; Ghosh, Abhirup; Ghosh, Archisman; Ghosh,
S.; Giaime, J. A.; Giardina, K. D.; Giazotto, A.; Gill, K.; Glover,
L.; Goetz, E.; Goetz, R.; Gomes, S.; González, G.; Gonzalez Castro,
J. M.; Gopakumar, A.; Gorodetsky, M. L.; Gossan, S. E.; Gosselin, M.;
Gouaty, R.; Grado, A.; Graef, C.; Granata, M.; Grant, A.; Gras, S.;
Gray, C.; Greco, G.; Green, A. C.; Groot, P.; Grote, H.; Grunewald,
S.; Gruning, P.; Guidi, G. M.; Guo, X.; Gupta, A.; Gupta, M. K.;
Gushwa, K. E.; Gustafson, E. K.; Gustafson, R.; Hall, B. R.; Hall,
E. D.; Hammond, G.; Haney, M.; Hanke, M. M.; Hanks, J.; Hanna, C.;
Hannuksela, O. A.; Hanson, J.; Hardwick, T.; Harms, J.; Harry, G. M.;
Harry, I. W.; Hart, M. J.; Haster, C. -J.; Haughian, K.; Healy, J.;
Heidmann, A.; Heintze, M. C.; Heitmann, H.; Hello, P.; Hemming, G.;
Hendry, M.; Heng, I. S.; Hennig, J.; Henry, J.; Heptonstall, A. W.;
Heurs, M.; Hild, S.; Hoak, D.; Hofman, D.; Holt, K.; Holz, D. E.;
Hopkins, P.; Horst, C.; Hough, J.; Houston, E. A.; Howell, E. J.;
Hu, Y. M.; Huerta, E. A.; Huet, D.; Hughey, B.; Husa, S.; Huttner,
S. H.; Huynh-Dinh, T.; Indik, N.; Ingram, D. R.; Inta, R.; Intini, G.;
Isa, H. N.; Isac, J. -M.; Isi, M.; Iyer, B. R.; Izumi, K.; Jacqmin,
T.; Jani, K.; Jaranowski, P.; Jawahar, S.; Jiménez-Forteza, F.;
Johnson, W. W.; Jones, D. I.; Jones, R.; Jonker, R. J. G.; Ju,
L.; Junker, J.; Kalaghatgi, C. V.; Kalogera, V.; Kandhasamy, S.;
Kang, G.; Kanner, J. B.; Karki, S.; Karvinen, K. S.; Kasprzack, M.;
Katolik, M.; Katsavounidis, E.; Katzman, W.; Kaufer, S.; Kawabe, K.;
Kéfélian, F.; Keitel, D.; Kemball, A. J.; Kennedy, R.; Kent, C.;
Key, J. S.; Khalili, F. Y.; Khan, I.; Khan, S.; Khan, Z.; Khazanov,
E. A.; Kijbunchoo, N.; Kim, Chunglee; Kim, J. C.; Kim, W.; Kim, W. S.;
Kim, Y. -M.; Kimbrell, S. J.; King, E. J.; King, P. J.; Kirchhoff, R.;
Kissel, J. S.; Kleybolte, L.; Klimenko, S.; Koch, P.; Koehlenbeck,
S. M.; Koley, S.; Kondrashov, V.; Kontos, A.; Korobko, M.; Korth,
W. Z.; Kowalska, I.; Kozak, D. B.; Krämer, C.; Kringel, V.; Krishnan,
B.; Królak, A.; Kuehn, G.; Kumar, P.; Kumar, R.; Kumar, S.; Kuo,
L.; Kutynia, A.; Kwang, S.; Lackey, B. D.; Lai, K. H.; Landry, M.;
Lang, R. N.; Lange, J.; Lantz, B.; Lanza, R. K.; Lartaux-Vollard,
A.; Lasky, P. D.; Laxen, M.; Lazzarini, A.; Lazzaro, C.; Leaci, P.;
Leavey, S.; Lee, C. H.; Lee, H. K.; Lee, H. M.; Lee, H. W.; Lee, K.;
Lehmann, J.; Lenon, A.; Leonardi, M.; Leroy, N.; Letendre, N.; Levin,
Y.; Li, T. G. F.; Libson, A.; Littenberg, T. B.; Liu, J.; Liu, W.; Lo,
R. K. L.; Lockerbie, N. A.; London, L. T.; Lord, J. E.; Lorenzini,
M.; Loriette, V.; Lormand, M.; Losurdo, G.; Lough, J. D.; Lovelace,
G.; Lück, H.; Lumaca, D.; Lundgren, A. P.; Lynch, R.; Ma, Y.; Macfoy,
S.; Machenschalk, B.; MacInnis, M.; Macleod, D. M.; Magaña Hernandez,
I.; Magaña-Sandoval, F.; Magaña Zertuche, L.; Magee, R. M.; Majorana,
E.; Maksimovic, I.; Man, N.; Mandic, V.; Mangano, V.; Mansell, G. L.;
Manske, M.; Mantovani, M.; Marchesoni, F.; Marion, F.; Márka, S.;
Márka, Z.; Markakis, C.; Markosyan, A. S.; Maros, E.; Martelli, F.;
Martellini, L.; Martin, I. W.; Martynov, D. V.; Marx, J. N.; Mason,
K.; Masserot, A.; Massinger, T. J.; Masso-Reid, M.; Mastrogiovanni,
S.; Matas, A.; Matichard, F.; Matone, L.; Mavalvala, N.; Mayani,
R.; Mazumder, N.; McCarthy, R.; McClelland, D. E.; McCormick, S.;
McCuller, L.; McGuire, S. C.; McIntyre, G.; McIver, J.; McManus,
D. J.; McRae, T.; McWilliams, S. T.; Meacher, D.; Meadors, G. D.;
Meidam, J.; Mejuto-Villa, E.; Melatos, A.; Mendell, G.; Mercer, R. A.;
Merilh, E. L.; Merzougui, M.; Meshkov, S.; Messenger, C.; Messick,
C.; Metzdorff, R.; Meyers, P. M.; Mezzani, F.; Miao, H.; Michel,
C.; Middleton, H.; Mikhailov, E. E.; Milano, L.; Miller, A. L.;
Miller, A.; Miller, B. B.; Miller, J.; Millhouse, M.; Minazzoli, O.;
Minenkov, Y.; Ming, J.; Mishra, C.; Mitra, S.; Mitrofanov, V. P.;
Mitselmakher, G.; Mittleman, R.; Moggi, A.; Mohan, M.; Mohapatra,
S. R. P.; Montani, M.; Moore, B. C.; Moore, C. J.; Moraru, D.;
Moreno, G.; Morriss, S. R.; Mours, B.; Mow-Lowry, C. M.; Mueller,
G.; Muir, A. W.; Mukherjee, Arunava; Mukherjee, D.; Mukherjee, S.;
Mukund, N.; Mullavey, A.; Munch, J.; Muniz, E. A. M.; Murray, P. G.;
Napier, K.; Nardecchia, I.; Naticchioni, L.; Nayak, R. K.; Nelemans,
G.; Nelson, T. J. N.; Neri, M.; Nery, M.; Neunzert, A.; Newport,
J. M.; Newton, G.; Ng, K. K. Y.; Nguyen, T. T.; Nichols, D.; Nielsen,
A. B.; Nissanke, S.; Nitz, A.; Noack, A.; Nocera, F.; Nolting, D.;
Normandin, M. E. N.; Nuttall, L. K.; Oberling, J.; Ochsner, E.;
Oelker, E.; Ogin, G. H.; Oh, J. J.; Oh, S. H.; Ohme, F.; Oliver, M.;
Oppermann, P.; Oram, Richard J.; O'Reilly, B.; Ormiston, R.; Ortega,
L. F.; O'Shaughnessy, R.; Ottaway, D. J.; Overmier, H.; Owen, B. J.;
Pace, A. E.; Page, J.; Page, M. A.; Pai, A.; Pai, S. A.; Palamos,
J. R.; Palashov, O.; Palomba, C.; Pal-Singh, A.; Pan, H.; Pang, B.;
Pang, P. T. H.; Pankow, C.; Pannarale, F.; Pant, B. C.; Paoletti,
F.; Paoli, A.; Papa, M. A.; Paris, H. R.; Parker, W.; Pascucci, D.;
Pasqualetti, A.; Passaquieti, R.; Passuello, D.; Patricelli, B.;
Pearlstone, B. L.; Pedraza, M.; Pedurand, R.; Pekowsky, L.; Pele, A.;
Penn, S.; Perez, C. J.; Perreca, A.; Perri, L. M.; Pfeiffer, H. P.;
Phelps, M.; Piccinni, O. J.; Pichot, M.; Piergiovanni, F.; Pierro,
V.; Pillant, G.; Pinard, L.; Pinto, I. M.; Pisarski, A.; Pitkin, M.;
Poggiani, R.; Popolizio, P.; Porter, E. K.; Post, A.; Powell, J.;
Prasad, J.; Pratt, J. W. W.; Predoi, V.; Prestegard, T.; Prijatelj,
M.; Principe, M.; Privitera, S.; Prix, R.; Prodi, G. A.; Prokhorov,
L. G.; Puncken, O.; Punturo, M.; Puppo, P.; Pürrer, M.; Qi, H.; Qin,
J.; Qiu, S.; Quetschke, V.; Quintero, E. A.; Quitzow-James, R.; Raab,
F. J.; Rabeling, D. S.; Radkins, H.; Raffai, P.; Raja, S.; Rajan, C.;
Rakhmanov, M.; Ramirez, K. E.; Rapagnani, P.; Raymond, V.; Razzano,
M.; Read, J.; Regimbau, T.; Rei, L.; Reid, S.; Reitze, D. H.; Rew,
H.; Reyes, S. D.; Ricci, F.; Ricker, P. M.; Rieger, S.; Riles, K.;
Rizzo, M.; Robertson, N. A.; Robie, R.; Robinet, F.; Rocchi, A.;
Rolland, L.; Rollins, J. G.; Roma, V. J.; Romano, R.; Romel, C. L.;
Romie, J. H.; Rosińska, D.; Ross, M. P.; Rowan, S.; Rüdiger, A.;
Ruggi, P.; Ryan, K.; Rynge, M.; Sachdev, S.; Sadecki, T.; Sadeghian,
L.; Sakellariadou, M.; Salconi, L.; Saleem, M.; Salemi, F.; Samajdar,
A.; Sammut, L.; Sampson, L. M.; Sanchez, E. J.; Sandberg, V.; Sandeen,
B.; Sanders, J. R.; Sassolas, B.; Saulson, P. R.; Sauter, O.; Savage,
R. L.; Sawadsky, A.; Schale, P.; Scheuer, J.; Schmidt, E.; Schmidt,
J.; Schmidt, P.; Schnabel, R.; Schofield, R. M. S.; Schönbeck, A.;
Schreiber, E.; Schuette, D.; Schulte, B. W.; Schutz, B. F.; Schwalbe,
S. G.; Scott, J.; Scott, S. M.; Seidel, E.; Sellers, D.; Sengupta,
A. S.; Sentenac, D.; Sequino, V.; Sergeev, A.; Shaddock, D. A.;
Shaffer, T. J.; Shah, A. A.; Shahriar, M. S.; Shao, L.; Shapiro,
B.; Shawhan, P.; Sheperd, A.; Shoemaker, D. H.; Shoemaker, D. M.;
Siellez, K.; Siemens, X.; Sieniawska, M.; Sigg, D.; Silva, A. D.;
Singer, A.; Singer, L. P.; Singh, A.; Singh, R.; Singhal, A.; Sintes,
A. M.; Slagmolen, B. J. J.; Smith, B.; Smith, J. R.; Smith, R. J. E.;
Son, E. J.; Sonnenberg, J. A.; Sorazu, B.; Sorrentino, F.; Souradeep,
T.; Spencer, A. P.; Srivastava, A. K.; Staley, A.; Steinke, M.;
Steinlechner, J.; Steinlechner, S.; Steinmeyer, D.; Stephens, B. C.;
Stone, R.; Strain, K. A.; Stratta, G.; Strigin, S. E.; Sturani,
R.; Stuver, A. L.; Summerscales, T. Z.; Sun, L.; Sunil, S.; Sutton,
P. J.; Swinkels, B. L.; Szczepańczyk, M. J.; Tacca, M.; Talukder,
D.; Tanner, D. B.; Tao, D.; Tápai, M.; Taracchini, A.; Taylor, J. A.;
Taylor, R.; Theeg, T.; Thomas, E. G.; Thomas, M.; Thomas, P.; Thorne,
K. A.; Thorne, K. S.; Thrane, E.; Tiwari, S.; Tiwari, V.; Tokmakov,
K. V.; Toland, K.; Tonelli, M.; Tornasi, Z.; Torrie, C. I.; Töyrä,
D.; Travasso, F.; Traylor, G.; Trembath-Reichert, S.; Trifirò, D.;
Trinastic, J.; Tringali, M. C.; Trozzo, L.; Tsang, K. W.; Tse, M.; Tso,
R.; Tuyenbayev, D.; Ueno, K.; Ugolini, D.; Unnikrishnan, C. S.; Urban,
A. L.; Usman, S. A.; Vahi, K.; Vahlbruch, H.; Vajente, G.; Valdes,
G.; Vallisneri, M.; van Bakel, N.; van Beuzekom, M.; van den Brand,
J. F. J.; Van Den Broeck, C.; Vander-Hyde, D. C.; van der Schaaf,
L.; van Heijningen, J. V.; van Veggel, A. A.; Vardaro, M.; Varma, V.;
Vass, S.; Vasúth, M.; Vecchio, A.; Vedovato, G.; Veitch, J.; Veitch,
P. J.; Venkateswara, K.; Venugopalan, G.; Verkindt, D.; Vetrano,
F.; Viceré, A.; Viets, A. D.; Vinciguerra, S.; Vine, D. J.; Vinet,
J. -Y.; Vitale, S.; Vo, T.; Vocca, H.; Vorvick, C.; Voss, D. V.;
Vousden, W. D.; Vyatchanin, S. P.; Wade, A. R.; Wade, L. E.; Wade,
M.; Walet, R.; Walker, M.; Wallace, L.; Walsh, S.; Wang, G.; Wang, H.;
Wang, J. Z.; Wang, M.; Wang, Y. -F.; Wang, Y.; Ward, R. L.; Warner, J.;
Was, M.; Watchi, J.; Weaver, B.; Wei, L. -W.; Weinert, M.; Weinstein,
A. J.; Weiss, R.; Wen, L.; Wessel, E. K.; Weßels, P.; Westphal, T.;
Wette, K.; Whelan, J. T.; Whiting, B. F.; Whittle, C.; Williams, D.;
Williams, R. D.; Williamson, A. R.; Willis, J. L.; Willke, B.; Wimmer,
M. H.; Winkler, W.; Wipf, C. C.; Wittel, H.; Woan, G.; Woehler, J.;
Wofford, J.; Wong, K. W. K.; Worden, J.; Wright, J. L.; Wu, D. S.;
Wu, G.; Yam, W.; Yamamoto, H.; Yancey, C. C.; Yap, M. J.; Yu, Hang;
Yu, Haocun; Yvert, M.; ZadroŻny, A.; Zanolin, M.; Zelenova, T.;
Zendri, J. -P.; Zevin, M.; Zhang, L.; Zhang, M.; Zhang, T.; Zhang,
Y. -H.; Zhao, C.; Zhou, M.; Zhou, Z.; Zhu, S.; Zhu, X. J.; Zucker,
M. E.; Zweizig, J.; LIGO Scientific Collaboration; Virgo Collaboration
Bibcode: 2017PhRvD..96f2002A
Altcode: 2017arXiv170702667L
We report on an all-sky search for periodic gravitational waves in
the frequency band 20-475 Hz and with a frequency time derivative in
the range of [-1.0 ,+0.1 ] ×10-8 Hz /s . Such a signal
could be produced by a nearby spinning and slightly nonaxisymmetric
isolated neutron star in our galaxy. This search uses the data from
Advanced LIGO's first observational run, O1. No periodic gravitational
wave signals were observed, and upper limits were placed on their
strengths. The lowest upper limits on worst-case (linearly polarized)
strain amplitude h0 are ∼4 ×10-25 near 170
Hz. For a circularly polarized source (most favorable orientation), the
smallest upper limits obtained are ∼1.5 ×10-25. These
upper limits refer to all sky locations and the entire range of
frequency derivative values. For a population-averaged ensemble of sky
locations and stellar orientations, the lowest upper limits obtained
for the strain amplitude are ∼2.5 ×10-25.
Title: The Fate of Cool Material in the Hot Corona: Solar Prominences
and Coronal Rain
Authors: Liu, Wei; Antolin, Patrick; Sun, Xudong; Vial, Jean-Claude;
Berger, Thomas
Bibcode: 2017SPD....4810501L
Altcode:
As an important chain of the chromosphere-corona mass cycle,
some of the million-degree hot coronal mass undergoes a radiative
cooling instability and condenses into material at chromospheric or
transition-region temperatures in two distinct forms - prominences
and coronal rain (some of which eventually falls back to the
chromosphere). A quiescent prominence usually consists of numerous
long-lasting, filamentary downflow threads, while coronal rain consists
of transient mass blobs falling at comparably higher speeds along
well-defined paths. It remains puzzling why such material of similar
temperatures exhibit contrasting morphologies and behaviors. We report
recent SDO/AIA and IRIS observations that suggest different magnetic
environments being responsible for such distinctions. Specifically,
in a hybrid prominence-coronal rain complex structure, we found that
the prominence material is formed and resides near magnetic null points
that favor the radiative cooling process and provide possibly a high
plasma-beta environment suitable for the existence of meandering
prominence threads. As the cool material descends, it turns into
coronal rain tied onto low-lying coronal loops in a likely low-beta
environment. Such structures resemble to certain extent the so-called
coronal spiders or cloud prominences, but the observations reported
here provide critical new insights. We will discuss the broad physical
implications of these observations for fundamental questions, such as
coronal heating and beyond (e.g., in astrophysical and/or laboratory
plasma environments).
Title: Structure and Dynamics of Cool Flare Loops Observed by the
Interface Region Imaging Spectrograph
Authors: Mikuła, K.; Heinzel, P.; Liu, W.; Berlicki, A.
Bibcode: 2017ApJ...845...30M
Altcode:
Flare loops were well observed with the Interface Region Imaging
Spectrograph (IRIS) during the gradual phase of two solar flares
on 2014 March 29 and 2015 June 22. Cool flare loops are visible in
various spectral lines formed at chromospheric and transition-region
temperatures and exhibit large downflows which correspond to the
standard scenario. The principal aim of this work is to analyze
the structure and dynamics of cool flare loops observed in Mg II
lines. Synthetic profiles of the Mg II h line are computed using the
classical cloud model and assuming a uniform background intensity. In
this paper, we study novel IRIS NUV observations of such loops in Mg II
h and k lines and also show the behavior of hotter lines detected in
the FUV channel. We obtained the spatial evolution of the velocities:
near the loop top, the flow velocities are small and they are increasing
toward the loop legs. Moreover, from slit-jaw image (SJI) movies, we
observe some plasma upflows into the loops, which are also detectable
in Mg II spectra. The brightness of the loops systematically decreases
with increasing flow velocity, and we ascribe this to the effect of
Doppler dimming, which works for Mg II lines. Emission profiles of Mg
II were found to be extremely broad, and we explain this through the
large unresolved non-thermal motions.
Title: Data-driven Simulations of Magnetic Connectivity in
Behind-the-Limb Gamma-ray Flares and Associated Coronal Mass Ejections
Authors: Jin, Meng; Petrosian, Vahe; Liu, Wei; Omodei, Nicola
Bibcode: 2017SPD....48.0303J
Altcode:
Recent Fermi detection of high-energy gamma-ray emission from the
behind-the-limb (BTL) solar flares pose a puzzle on the particle
acceleration and transport mechanisms in such events. Due to
the large separation between the flare site and the location of
gamma-ray emission, it is believed that the associated coronal
mass ejections (CMEs) play an important role in accelerating and
subsequently transporting particles back to the Sun to produce obseved
gamma-rays. We explore this scenario by simulating the CME associated
with a well-observed flare on 2014 September 1 about 40 degrees behind
the east solar limb and by comparing the simulation and observational
results. We utilize a data-driven global magnetohydrodynamics model
(AWSoM: Alfven-wave Solar Model) to track the dynamical evolution of
the global magnetic field during the event and investigate the magnetic
connectivity between the CME/CME-driven shock and the Fermi emission
region. Moreover, we derive the time-varying shock parameters (e.g.,
compression ratio, Alfven Mach number, and ThetaBN) over the area
that is magnetically connected to the visible solar disk where Fermi
gamma-ray emission originates. Our simulation shows that the visible
solar disk develops connections both to the flare region and to the
CME-driven shock during the eruption, which indicate that the CME’s
interaction with the global solar corona is critical for understanding
such Fermi BTL events and gamma-ray flares in general. We discuss
the causes and implications of Fermi BTL events, in the framework
of a potential shift of paradigm on particle acceleration in solar
flares/CMEs.
Title: Fast-mode Coronal EUV Wave Trains Associated with Solar Flares
and CMEs
Authors: Liu, Wei; Ofman, Leon; Downs, Cooper; Karlicky, Marian;
Chen, Bin
Bibcode: 2017SPD....48.0401L
Altcode:
As a new observational phenomenon, Quasi-periodic, Fast Propagating EUV
wave trains (QFPs) are fast-mode magnetosonic waves closely related
to quasi-periodic pulsations commonly detected in solar flares
(traditionally with non-imaging observations). They can provide
critical clues to flare energy release and serve as new tools for
coronal seismology. We report recent advances in observing and modeling
QFPs, including evidence of heating and cooling cycles revealed with
differential emission measure (DEM) analysis that are consistent
with alternating compression and rarefaction expected for magnetosonic
waves. Through a statistical survey, we found a preferential association
of QFPs with eruptive flares (with CMEs) rather than confined flares
(without CMEs). We also identified some correlation with quasi-periodic
radio bursts observed at JVLA and Ondrejov observatories. We will
discuss the implications of these results and the potential roles of
QFPs in coronal heating and energy transport.
Title: Ten years of SLR production in Argentina
Authors: Pacheco, A.; Podestá, R.; Yin, Z.; Liu, W.; Actis, E.;
Adarvez, S.; Quinteros, J.; Podestá, F.
Bibcode: 2017RMxAC..49..143P
Altcode:
SLR technique is a proved astro-geodetic art with a significant power
to contribute to Earth and Space Sciences. Therefore, scientific
applications of SLR System are able to perform multiple tasks in
the fields of Astrometry, Geodesy and Geophysics. The results we
show here were obtained from satellite observations made at SLR 7406
Station of Observatorio Astronómico Félix Aguilar (OAFA) in San Juan,
Argentina. The telescope was installed early on 2006, in concordance
with an International Cooperation Agreement between Universidad
Nacional de San Juan, Argentina and Chinese Academy of Sciences. In this
abstract we show the current research being done with ILRS 7406 station:
Length of day (LOD) and Angular velocity of Earth Rotation, calculated
weekly; Pole Motion. ILRS7406 is daily surveying Pole coordinates x
and y; Tracking SLR to GNSS constellations. SLR System contributes
to the adjustment and validation of satellite GALILEO, GPS, GLONASS,
and BEIDOU orbits. Our station is nowadays member of the new ITRF 2014
frame, and these past years has been one of the 3 highest producing SLR
Stations on the ILRS net, composed of about 40 stations distributed all
around the world. The obtained results during this first 10 years of
experience are useful to enhance the traditional collaboration between
OAFA and international services such as ILRS, IERS and NASA.
Title: A Model-free CAF Fringe Search Algorithm with Wavelet Boosting
for VLBI Observation
Authors: Zhang, Tianyi; Meng, Qiao; Chen, Congyan; Zheng, Weimin;
Liu, Wei; Yu, Quantao; Tong, Li
Bibcode: 2017PASP..129g4501Z
Altcode:
Very-Long-Baseline interferometry (VLBI) is a powerful tool in radio
astronomy, geodesy, and deep space exploration. Priori predicted delay
models are needed to make interferometry fringes, but in some cases they
would be difficult to get. This paper proposes an effective algorithm
named CAF-W algorithm to search fringes from the raw data in a large
search range without priori predicted delay models. The cross-ambiguity
function (CAF) is used to make a time-frequency correlation in the
delay-delay rate plane. The wavelet boosting algorithm is used to
eliminate interference and enhance the CAF peak, whose position would
give the delay and delay rate estimations. Incoherent averaging and
sliding search window techniques are used to overcome the wide search
range and the poor signal-to-noise ratio in VLBI observations. The CAF-W
algorithm could be performed with fast algorithms so the computation
burden is affordable. This algorithm has successfully achieved VLBI
fringes from the raw data without priori predicted delay models in
VLBI observations.
Title: Double-coronal X-Ray and Microwave Sources Associated with
a Magnetic Breakout Solar Eruption
Authors: Chen, Yao; Wu, Zhao; Liu, Wei; Schwartz, Richard A.; Zhao,
Di; Wang, Bing; Du, Guohui
Bibcode: 2017ApJ...843....8C
Altcode: 2017arXiv170506074C
Double-coronal hard X-ray (HXR) sources are believed to be critical
observational evidence of bi-directional energy release through magnetic
reconnection in large-scale current sheets in solar flares. Here,
we present a study on double-coronal sources observed in both HXR
and microwave regimes, revealing new characteristics distinct from
earlier reports. This event is associated with a footpoint-occulted
X1.3-class flare (2014 April 25, starting at 00:17 UT) and a coronal
mass ejection that were likely triggered by the magnetic breakout
process, with the lower source extending upward from the top of the
partially occulted flare loops and the upper source co-incident with
rapidly squeezing-in side lobes (at a speed of ∼250 km s-1
on both sides). The upper source can be identified at energies as high
as 70-100 keV. The X-ray upper source is characterized by flux curves
that differ from those of the lower source, a weak energy dependence
of projected centroid altitude above 20 keV, a shorter duration,
and an HXR photon spectrum slightly harder than those of the lower
source. In addition, the microwave emission at 34 GHz also exhibits
a similar double-source structure and the microwave spectra at both
sources are in line with gyrosynchrotron emission given by non-thermal
energetic electrons. These observations, especially the co-incidence of
the very-fast squeezing-in motion of side lobes and the upper source,
indicate that the upper source is associated with (and possibly caused
by) this fast motion of arcades. This sheds new light on the origin of
the corona double-source structure observed in both HXRs and microwaves.
Title: Excesses of cosmic ray spectra from a single nearby source
Authors: Liu, Wei; Bi, Xiao-Jun; Lin, Su-Jie; Wang, Bing-Bing; Yin,
Peng-Fei
Bibcode: 2017PhRvD..96b3006L
Altcode: 2016arXiv161109118L
Growing evidence reveals universal hardening on various cosmic ray
spectra, e.g., proton, positron, as well as antiproton fractions. Such
universality may indicate they have a common origin. In this paper, we
argue that these widespread excesses can be accounted for by a nearby
supernova remnant surrounded by a giant molecular cloud. Secondary
cosmic rays (p , e+ ) are produced through the collisions
between the primary cosmic-ray nuclei from this supernova remnant and
the molecular gas. Different from the background, which is produced
by the ensemble of a large number of sources in the Milky Way, the
local injected spectrum can be harder. The time-dependent transport
of particles would make the propagated spectrum even harder. Under
this scenario, the anomalies of both primary (p , e-)
and secondary (e+, p ¯ /p ) cosmic rays can be properly
interpreted. We further show that the TeV to sub-PeV anisotropy of
the proton is consistent with the observations if the local source is
relatively young and lying at the anti-Galactic center direction.
Title: Explaining the rolling-pin distribution of suprathermal
electrons behind dipolarization fronts
Authors: Liu, C. M.; Fu, H. S.; Xu, Y.; Cao, J. B.; Liu, W. L.
Bibcode: 2017GeoRL..44.6492L
Altcode:
The rolling-pin distribution of suprathermal electrons (40-200 keV),
showing electron pitch angles primarily at 0°, 90°, and 180°,
has recently been reported behind dipolarization fronts (DFs)
both in observations and simulations. The formation of such type
of distribution, however, has been unclear so far. In this study,
we present an observation of such type of distribution by Cluster
in the magnetotail behind a DF. We interpret the formation of such
distribution using the global-scale Fermi acceleration together with
local-scale betatron acceleration. We quantitatively reproduce these two
processes and therefore the rolling-pin distribution of suprathermal
electrons using an analytical model. We further reveal that only at
energies higher than 26 keV can such distribution be formed. This study,
quantitatively explaining the formation of rolling-pin distribution,
can improve the understanding of electron dynamics behind DFs.
Title: Constraints on dark matter annihilation and decay from the
isotropic gamma-ray background
Authors: Liu, Wei; Bi, Xiao-Jun; Lin, Su-Jie; Yin, Peng-Fei
Bibcode: 2017ChPhC..41d5104L
Altcode: 2016arXiv160201012L
We study the constraints on dark matter (DM) annihilation/decay from
the Fermi-LAT Isotropic Gamma-Ray Background (IGRB) observation. We
consider the contributions from both extragalactic and galactic
DM components. For DM annihilation, the evolution of extragalactic
DM halos is taken into account. We find that the IGRB annihilation
constraints under some DM subhalo models can be comparable to those
derived from the observations of dwarf spheroidal galaxies and
CMB. We also use the IGRB results to constrain the parameter regions
accounting for the latest AMS-02 electron-positron anomaly. We find
that the majority of DM annihilation/decay channels are strongly
disfavored by the latest Fermi-LAT IGRB observation; only DM decays
to μ+μ- and 4μ channels may be valid. Supported by National Natural Science Foundation of China (11475189,
11475191, 11135009), 973 Program of China (2013CB837000), Strategic
Priority Research Program “The Emergence of Cosmological Structures”
of the Chinese Academy of Sciences (XDB09000000)
Title: Broadband high-frequency waves detected at dipolarization
fronts
Authors: Yang, J.; Cao, J. B.; Fu, H. S.; Wang, T. Y.; Liu, W. L.;
Yao, Z. H.
Bibcode: 2017JGRA..122.4299Y
Altcode:
Dipolarization front (DF) is a sharp boundary most probably separating
the reconnection jet from the background plasma sheet. So far at this
boundary, the observed waves are mainly in low-frequency range (e.g.,
magnetosonic waves and lower hybrid waves). Few high-frequency waves
are observed in this region. In this paper, we report the broadband
high-frequency wave emissions at the DF. These waves, having frequencies
extending from the electron cyclotron frequency fce, up to
the electron plasma frequency fpe, could contribute 10%
to the in situ measurement of intermittent energy conversion at the
DF layer. Their generation may be attributed to electron beams, which
are simultaneously observed at the DF as well.
Title: Lunar Water Spatial Distribution and Its Temporal Variations
Authors: Wang, H. Z.; Zhang, J.; Shi, Q. Q.; Tian, A. M.; Chen, J.;
Liu, J.; Ling, Z. C.; Fu, X. H.; Wei, Y.; Zhang, H.; Liu, W. L.; Fu,
S. Y.; Zong, Q. G.; Pu, Z. Y.
Bibcode: 2017LPI....48.1831W
Altcode:
We studied spatial distribution and temporal variations of lunar water
to investigate the influence of the Earth's magnetosphere in the lunar
surface hydration.
Title: Oxidative Alteration of Ferrous Smectites: A Formation Pathway
for Martian Nontronite?
Authors: Chemtob, S. M.; Catalano, J. G.; Nickerson, R. D.; Morris,
R. V.; Agresti, D. G.; Rivera-Banuchi, V.; Liu, W.; Yee, N.
Bibcode: 2017LPI....48.2520C
Altcode:
We show experimentally that martian ferric smectites can form by
oxidation of ferrous smectite precursors, suggesting reducing conditions
during the Noachian.
Title: Hard X-Ray Emission from Partially Occulted Solar Flares:
RHESSI Observations in Two Solar Cycles
Authors: Effenberger, Frederic; Rubio da Costa, Fatima; Oka, Mitsuo;
Saint-Hilaire, Pascal; Liu, Wei; Petrosian, Vahé; Glesener, Lindsay;
Krucker, Säm
Bibcode: 2017ApJ...835..124E
Altcode: 2016arXiv161202856E
Flares close to the solar limb, where the footpoints are occulted,
can reveal the spectrum and structure of the coronal looptop source
in X-rays. We aim at studying the properties of the corresponding
energetic electrons near their acceleration site, without footpoint
contamination. To this end, a statistical study of partially occulted
flares observed with Reuven Ramaty High-Energy Solar Spectroscopic
Imager is presented here, covering a large part of solar cycles
23 and 24. We perform detailed spectra, imaging, and light curve
analyses for 116 flares and include contextual observations from
SDO and STEREO when available, providing further insights into flare
emission that were previously not accessible. We find that most spectra
are fitted well with a thermal component plus a broken power-law,
non-thermal component. A thin-target kappa distribution model gives
satisfactory fits after the addition of a thermal component. X-ray
imaging reveals small spatial separation between the thermal and
non-thermal components, except for a few flares with a richer coronal
source structure. A comprehensive light curve analysis shows a very good
correlation between the derivative of the soft X-ray flux (from GOES)
and the hard X-rays for a substantial number of flares, indicative of
the Neupert effect. The results confirm that non-thermal particles
are accelerated in the corona and estimated timescales support the
validity of a thin-target scenario with similar magnitudes of thermal
and non-thermal energy fluxes.
Title: Fermi-LAT Observations of High-energy Behind-the-limb Solar
Flares
Authors: Ackermann, M.; Allafort, A.; Baldini, L.; Barbiellini, G.;
Bastieri, D.; Bellazzini, R.; Bissaldi, E.; Bonino, R.; Bottacini, E.;
Bregeon, J.; Bruel, P.; Buehler, R.; Cameron, R. A.; Caragiulo, M.;
Caraveo, P. A.; Cavazzuti, E.; Cecchi, C.; Charles, E.; Ciprini, S.;
Costanza, F.; Cutini, S.; D'Ammando, F.; de Palma, F.; Desiante, R.;
Digel, S. W.; Di Lalla, N.; Di Mauro, M.; Di Venere, L.; Drell, P. S.;
Favuzzi, C.; Fukazawa, Y.; Fusco, P.; Gargano, F.; Giglietto, N.;
Giordano, F.; Giroletti, M.; Grenier, I. A.; Guillemot, L.; Guiriec,
S.; Jogler, T.; Jóhannesson, G.; Kashapova, L.; Krucker, S.; Kuss,
M.; La Mura, G.; Larsson, S.; Latronico, L.; Li, J.; Liu, W.; Longo,
F.; Loparco, F.; Lubrano, P.; Magill, J. D.; Maldera, S.; Manfreda,
A.; Mazziotta, M. N.; Mitthumsiri, W.; Mizuno, T.; Monzani, M. E.;
Morselli, A.; Moskalenko, I. V.; Negro, M.; Nuss, E.; Ohsugi, T.;
Omodei, N.; Orlando, E.; Pal'shin, V.; Paneque, D.; Perkins, J. S.;
Pesce-Rollins, M.; Petrosian, V.; Piron, F.; Principe, G.; Rainò,
S.; Rando, R.; Razzano, M.; Reimer, O.; Rubio da Costa, F.; Sgrò,
C.; Simone, D.; Siskind, E. J.; Spada, F.; Spandre, G.; Spinelli,
P.; Tajima, H.; Thayer, J. B.; Torres, D. F.; Troja, E.; Vianello, G.
Bibcode: 2017ApJ...835..219A
Altcode: 2017arXiv170200577A
We report on the Fermi-LAT detection of high-energy emission from the
behind-the-limb (BTL) solar flares that occurred on 2013 October 11,
and 2014 January 6 and September 1. The Fermi-LAT observations are
associated with flares from active regions originating behind both
the eastern and western limbs, as determined by STEREO. All three
flares are associated with very fast coronal mass ejections (CMEs)
and strong solar energetic particle events. We present updated
localizations of the >100 MeV photon emission, hard X-ray (HXR)
and EUV images, and broadband spectra from 10 keV to 10 GeV, as well
as microwave spectra. We also provide a comparison of the BTL flares
detected by Fermi-LAT with three on-disk flares and present a study
of some of the significant quantities of these flares as an attempt
to better understand the acceleration mechanisms at work during these
occulted flares. We interpret the HXR emission to be due to electron
bremsstrahlung from a coronal thin-target loop top with the accelerated
electron spectra steepening at semirelativistic energies. The >100
MeV gamma-rays are best described by a pion-decay model resulting
from the interaction of protons (and other ions) in a thick-target
photospheric source. The protons are believed to have been accelerated
(to energies >10 GeV) in the CME environment and precipitate down to
the photosphere from the downstream side of the CME shock and landed
on the front side of the Sun, away from the original flare site and
the HXR emission.
Title: Enhancement of oxygen in the magnetic island associated with
dipolarization fronts
Authors: Wang, J.; Cao, J. B.; Fu, H. S.; Liu, W. L.; Lu, S.
Bibcode: 2017JGRA..122..185W
Altcode:
A significant enhancement of O+ is observed by Cluster inside
an earthward propagating magnetic island behind a dipolarization front
(DF). Such enhancement, from 0.005 to 0.03 cm-3, makes the
O+ flux inside the magnetic island 20 times larger than that
outside the magnetic island. In the meantime, the H+ density
is nearly a constant, 0.1 cm-3, during the magnetic-island
encounter. This results in a dramatic increase of the density ratio,
nO<mo form="prefix">+>/nH<mo form="prefix">+, from
0.05 to 0.3 (about 10 times as large as the average value in the
plasma sheet) and a dramatic decrease of the local Alfvén speed from
VA ≈ 770 km/s to VA ≈ 430 km/s inside the
magnetic island. The decrease of Alfvén speed indicates an asymmetric
reconnection and a slow magnetic reconnection rate near the secondary X
line. Since the reconnection rates at the primary X line and secondary
X line are imbalanced, the DFs and magnetic islands are pushed to
propagate earthward by the outflow of the primary reconnection, as
demonstrated in recent simulations.
Title: Fermi Large Area Telescope Observations of High-Energy
Gamma-ray Emission From Behind-the-limb Solar Flares
Authors: Omodei, Nicola; Pesce-Rollins, Melissa; Petrosian, Vahe;
Liu, Wei; Rubio da Costa, Fatima; Golenetskii, Sergei; Kashapova,
Larisa; Krucker, Sam; Palshin, Valentin; Fermi Large Area Telescope
Collaboration
Bibcode: 2017APS..APR.Y3005O
Altcode:
Fermi LAT >30 MeV observations of the active Sun have increased
the number of detected solar flares by almost a factor of 10 with
respect to previous space observations. Of particular interest are the
recent detections of three solar flares whose position behind the limb
was confirmed by the STEREO-B spacecraft. These observations sample
flares from active regions originating from behind both the eastern
and western limbs and include an event associated with the second
ground level enhancement event (GLE) of the 24th Solar Cycle. While
gamma-ray emission up to tens of MeV resulting from proton interactions
has been detected before from occulted solar flares, the significance
of these particular events lies in the fact that these are the first
detections of >100 MeV gamma-ray emission from footpoint-occulted
flares. These detections present an unique opportunity to diagnose
the mechanisms of high-energy emission and particle acceleration and
transport in solar flares. We will present the Fermi-LAT, RHESSI and
STEREO observations of these flares and discuss the various emission
scenarios for these sources.
Title: The Structure of the Local Hot Bubble
Authors: Liu, W.; Chiao, M.; Collier, M. R.; Cravens, T.; Galeazzi, M.;
Koutroumpa, D.; Kuntz, K. D.; Lallement, R.; Lepri, S. T.; McCammon,
D.; Morgan, K.; Porter, F. S.; Snowden, S. L.; Thomas, N. E.; Uprety,
Y.; Ursino, E.; Walsh, B. M.
Bibcode: 2017ApJ...834...33L
Altcode: 2016arXiv161105133L
Diffuse X-rays from the Local Galaxy (DXL) is a sounding rocket mission
designed to quantify and characterize the contribution of Solar Wind
Charge eXchange (SWCX) to the Diffuse X-ray Background and study the
properties of the Local Hot Bubble (LHB). Based on the results from
the DXL mission, we quantified and removed the contribution of SWCX to
the diffuse X-ray background measured by the ROSAT All Sky Survey. The
“cleaned” maps were used to investigate the physical properties of
the LHB. Assuming thermal ionization equilibrium, we measured a highly
uniform temperature distributed around kT = 0.097 keV ± 0.013 keV
(FWHM) ± 0.006 keV (systematic). We also generated a thermal emission
measure map and used it to characterize the three-dimensional (3D)
structure of the LHB, which we found to be in good agreement with the
structure of the local cavity measured from dust and gas.
Title: Underground Nuclear Astrophysics Experiment JUNA in China
Authors: Liu, W. P.
Bibcode: 2017nuco.confa1101L
Altcode:
Underground Nuclear Astrophysics Experiment in China (JUNA) will take
the advantage of the ultra-low background in Jinping underground
lab. A 400 kV high current accelerator with an ECR source and γ ,
neutron and charged particle detectors will be set up. We plan to study
directly a number of nuclear reactions important to hydrostatic stellar
evolution near their Gamow window energies such as 25Mg(p,
γ )26Al, 19F(p, α )16O,
13C(α , n)16O, and 12C(α , γ
)16O, by the end of 2019.
Title: Hard X-Ray Observations of Coronal Sources: Implications for
Particle Acceleration
Authors: Effenberger, F.; Rubio da Costa, F.; Oka, M.; Saint-Hilaire,
P.; Liu, W.; Krucker, S.; Glesener, L.; Petrosian, V.
Bibcode: 2016AGUFMSH51E2634E
Altcode:
The properties of hard X-ray emission from solar flares can provide
insight into particle acceleration and transport processes. Commonly,
at higher energies the bright footpoint emission from the flare loop
prevents a detailed analysis of the weaker loop-top source due to
the limited dynamic range. Thus, flares close to the solar limb,
where the footpoints are occulted, are interesting events to study
because they can reveal the coronal loop-top emission and thus the
electron properties at their acceleration site. We present results of
a survey study of partially occulted flares observed with the Reuven
Ramaty High-Energy Solar Spectroscopic Imager (RHESSI). We found that
most of the flare spectra allow a fit to a thermal plus non-thermal
component, either with a broken power-law or a kappa function. The
spatial separation between the thermal and non-thermal component,
as derived from imaging, is usually small. The light curve analysis
shows for many flares a very good correlation between the derivative
of the soft X-ray flux and the hard X-rays. We discuss implications
for particle acceleration models that result from our study.
Title: High resolution observations of prominence rotation by Hinode
and IRIS
Authors: Okamoto, J.; Liu, W.; Tsuneta, S.
Bibcode: 2016AGUFMSH41E..05O
Altcode:
Fine structures of prominences, especially threads, and their dynamics
provide physical information about the magnetic configuration and
property in the corona. Here we report two events of prominence rotation
observed by the Hinode and IRIS satellites. In the first event, we found
transverse motions of brightening threads at speeds up to 55 km/s seen
in the plane of the sky. Such motions appeared as sinusoidal space-time
trajectories with a typical period of 390 s, which is consistent
with plane-of-sky projections of rotational motions. At least 15
episodes of such motions occurred in two days, none associated with
any eruption. For these episodes, the plane-of-sky speed is linearly
correlated with the vertical travel distance, suggestive of a constant
angular speed. In the second event, spectral data taken by IRIS showed
strong blueshifts in the top portion of the prominence with a speed
of 30-40 km/s, while redshifts of similar speeds were detected at the
bottom. Line width of the bright threads were significantly larger
than those of stationary threads. These behaviors indicate rotations of
helical prominence threads. We interpreted the activations as evidence
of unwinding motions caused by magnetic reconnection between twisted
prominence fields and ambient coronal fields.
Title: Particle Acceleration in High-Energy Solar Flares Detected
by the Fermi Large Area Telescope
Authors: Omodei, N.; Pesce-Rollins, M.; Petrosian, V.; Liu, W.;
Rubio da Costa, F.
Bibcode: 2016AGUFMSH41D..02O
Altcode:
The Fermi Large Area Telescope (LAT) is the most sensitive instrument
ever deployed in space for observing gamma-ray emission above 100
MeV. LAT observations of the active Sun have increased the number of
detected solar flares by almost a factor of 10 with respect to previous
space observations. We will present an overview of these observations,
which include detections of impulsive and sustained emission, extending
up to 20 hours in the case of the X-class flare occurred on 2012
March 7. Of particular interest is the first detection of >100 MeV
gamma-ray emission from three solar flares whose positions behind the
limb were confirmed by the STEREO spacecrafts. These observations sample
flares from active regions originating from behind both the eastern
and western limbs and present a unique opportunity to diagnose the
mechanisms of high-energy emission and particle acceleration in solar
flares. We will present the Fermi-LAT, RHESSI and STEREO observations
of these flares and discuss how these observations provide constrains
on different emission mechanisms.
Title: Observations and Modeling of Plasma Waves in the Solar
Atmosphere
Authors: Liu, W.; Ofman, L.; Downs, C.
Bibcode: 2016AGUFMSH14B..01L
Altcode:
The solar atmosphere, especially the extended corona, provides rich
observations of magnetohydrodynamic (MHD) waves and plasma waves in
general. Such waves can be used as seismological tools to probe the
physical conditions of the medium in which they travel, such as the
coronal magnetic field and plasma parameters. Recent high-resolution
imaging and spectroscopic observations in extreme ultraviolet (EUV)
by the Atmospheric Imaging Assembly (AIA) onboard the Solar Dynamics
Observatory (SDO) and in UV by the Interface Region Imaging Spectrograph
(IRIS) have opened a new chapter in understanding these waves and
in utilizing them for coronal seismology. We will review such new
observations of two intimately related phenomena - global EUV waves
(so-called "EIT waves") associated with coronal mass ejections (CMEs)
and quasi-periodic, fast-mode magnetosonic wave trains associated with
flares. We will focus on the generation and propagation of global
EUV waves and their interaction with coronal structures, as well
as the correlation of AIA-detected fast-mode wave trains with flare
pulsations seen from radio to hard X-ray wavelengths. We will also
present recent MHD modeling efforts in reproducing these waves using
realistic, observationally-driven simulations. We will discuss the
roles of such waves in energy transport within the solar atmosphere
and in their associated CME/flare eruptions.
Title: Prompt GPS TEC Response to Magnetospheric Compression by
Interplanetary Shock
Authors: Hao, Y.; Liu, W. L.; Huang, J.; Zhang, D.; Xiao, Z.
Bibcode: 2016AGUFMSM13B2201H
Altcode:
A new type of total electron content (TEC) variation was observed in
prompt response to an interplanetary shock (IS) impact on the Earth's
magnetosphere. With hundreds of ground-based global positioning system
(GPS) receivers, simultaneous TEC impulses with amplitudes as large
as 0.3 TECU were detected in the signals of GPS satellites which were
cruising in the dayside equatorial magnetosphere. We suggest that the
TEC impulses result from shock-induced magnetospheric compression,
which drives plasma to move earthward via perturbed electric field
in the dayside magnetosphere. The observed TEC increase reflects the
radial motion of plasma from outside of the GPS orbit (4.2 RE) to
inside, showing an unprecedented ability of the GPS TEC technique to
capture small tremor of the magnetosphere and, with the dense receiver
network it can be a useful tool for investigating the plasma dynamics
around 4.2 RE.
Title: Curvature of the spectral energy distribution, the inverse
Compton component and the jet in Fermi 2LAC blazars
Authors: Xue, R.; Luo, D.; Du, L. M.; Wang, Z. R.; Xie, Z. H.; Yi,
T. F.; Xiong, D. R.; Xu, Y. B.; Liu, W. G.; Yu, X. L.
Bibcode: 2016MNRAS.463.3038X
Altcode: 2016arXiv160905697X
We fitted the spectral energy distributions (SEDs) of members of a
large sample of Fermi 2LAC blazars to synchrotron and inverse Compton
(IC) models. Our main results are as follows. (I) As suggested
by previous works, the correlation between the peak frequency and
curvature can be explained by statistical or stochastic particle
acceleration mechanisms. For BL Lacs, we found a linear correlation
between the synchrotron peak frequency and its curvature. The slope of
the correlation is consistent with stochastic acceleration mechanisms
and confirms the results of previous studies. For flat-spectrum radio
quasars (FSRQs), we also found a linear correlation, but in this case
the slope cannot be explained by previous theoretical models. (II) We
found a significant correlation between IC luminosity and synchrotron
luminosity. The slope of the correlation for FSRQs is consistent
with the external Compton (EC) process. The slope of the correlation
for BL Lacs is consistent with the synchrotron self-Compton (SSC)
process. (III) We found several significant correlations between IC
curvature and various basic parameters of blazars (black hole mass,
broad-line luminosity, the Lorentz factor of the jet). We also found
significant correlations between the bolometric luminosity and these
basic parameters of blazars, which suggests that the origin of jets
is a mixture of the mechanisms proposed by Blandford & Znajek and
by Blandford & Payne.
Title: The Contribution of Geomagnetic Activities to Polar Ozone
Changes in Upper Atmosphere
Authors: Huang, C.; Huang, F.; Zhang, X.; Liu, D.; Hao, Y.; Liu, W. L.
Bibcode: 2016AGUFMSM22A..08H
Altcode:
Energetic particle precipitation (EPP) plays an important role in
the catalytic process of ozone depletion due to the odd nitrogen and
odd hydrogen species produced by EPP in the polar middle atmosphere
during the geomagnetic activities. It is known that solar UV emission
variations have significant effects on ozone generation. So it
is interesting to compare the contributions of EPP and solar UV
emission to ozone change in the polar upper atmosphere. In this work,
we applied annual average Ap index to denote the annual mean magnitude
of geomagnetic activity which has good relationship with EPP flux and
annual average F10.7 index to denote annual mean magnitude of solar
radiation which has certain relevancy with solar UV emission. We adopted
latitude-average dataset of ozone measurements from SBUV instruments
on the POES satellites and studied the statistics characters between
ozone dataset and Ap,F10.7 index. The multiple regression analysis shows
that the contributions of geomagnetic activities are not negligible and
have the similar order of magnitude compared with solar UV emission
in polar upper atmosphere (above 30 km). The results also show that
HSSWS-Induced (HSSWS, High-Speed Solar Wind Stream) geomagnetic
activities and that of CME-Induced (CME, Coronal Mass Ejection) are
of the same order of magnitude. There exists differences between two
hemispheres according to the multiple regression analysis and we made
a discussion to interpret the causes of these differences.
Title: Calculation of electric radial diffusion coefficient of
radiation belt electrons with in situ electric field measurements
by THEMIS
Authors: Liu, W.; Tu, W.; Li, X.; Sarris, T. E.; Khotyaintsev, Y. V.;
Fu, H.; Zhang, H.; Shi, Q.
Bibcode: 2016AGUFMSM22B..03L
Altcode:
Based on seven years' observations from THEMIS, we investigate the
statistical distribution of electric field Pc5 ULF wave power under
different geomagnetic activities and calculate the radial diffusion
coefficient due to electric field, DLLE, for outer radiation belt
electrons. A simple empirical expression of DLLE[THEMIS] is also
derived. Subsequently we compare DLLE[THEMIS] to previous DLL models,
and find similar Kp dependence with the DLLE[CRRES] model, which is
also based on in-situ electric field measurements. The absolute value of
DLLE[THEMIS] is constantly higher than DLLE[CRRES], probably due to the
limited orbital coverage of CRRES. The differences between DLLE[THEMIS]
and the commonly-used DLLM[B-A] and DLLE[Ozeke] models are significant,
especially in Kp dependence and energy dependence. Possible reasons for
these differences and their implications are discussed. The diffusion
coefficient provided in this paper, which also has energy dependence,
will be an important contributor to quantify the radial diffusion
process of radiation belt electrons.
Title: Probing the Physical Connection between Solar Prominences
and Coronal Rain
Authors: Liu, W.; Antolin, P.; Sun, X.; Vial, J. C.; Guo, L.; Gibson,
S. E.; Berger, T. E.; Okamoto, J.; De Pontieu, B.
Bibcode: 2016AGUFMSH43C2587L
Altcode:
Solar prominences and coronal rain are intimately related phenomena,
both involving cool material at chromospheric temperatures within the
hot corona and both playing important roles as part of the return flow
of the chromosphere-corona mass cycle. At the same time, they exhibit
distinct morphologies and dynamics not yet well understood. Quiescent
prominences consist of numerous long-lasting, filamentary downflow
threads, while coronal rain is more transient and falls comparably
faster along well-defined curved paths. We report here a novel, hybrid
prominence-coronal rain complex in an arcade-fan geometry observed
by SDO/AIA and IRIS, which provides new insights to the underlying
physics of such contrasting behaviors. We found that the supra-arcade
fan region hosts a prominence sheet consisting of meandering threads
with broad line widths. As the prominence material descends to the
arcade, it turns into coronal rain sliding down coronal loops with
line widths 2-3 times narrower. This contrast suggests that distinct
local plasma and magnetic conditions determine the fate of the cool
material, a scenario supported by our magnetic field extrapolations
from SDO/HMI. Specifically, the supra-arcade fan (similar to those
in solar flares) is likely situated in a current sheet, where the
magnetic field is weak and the plasma-beta could be close to unity, thus
favoring turbulent flows like those prominence threads. In contrast,
the underlying arcade has a stronger magnetic field and most likely a
low-beta environment, such that the material is guided along magnetic
field lines to appear as coronal rain. We will discuss the physical
implications of these observations beyond the phenomena of prominences
and coronal rain.
Title: Observations of the Motion of X Line on the Dayside
Magnetopause
Authors: Zhu, C.; Zhang, H.; Ge, Y.; Pu, Z.; Liu, L.; Wan, W.; Liu,
W. L.; Chen, Y.; Le, H.
Bibcode: 2016AGUFMSM21A2425Z
Altcode:
Various observations from satellites have shown that reconnection X line
should be stable at a fixed position at low latitude of magnetosphere
during stable southward IMF conditions. On the contrary, there are also
events demonstrated that reconnection X line can move, which is rare
but particular important. The direction of the motion of X line has
been presumed along the electron diamagnetic drift direction on the
dayside magnetopause. However, we discovered a case that the X line
moved in the ion diamagnetic drift direction, which is opposite to
electron diamagnetic direction. The result is reasonable because the
fluid velocity that convect field lines is mainly determined by ions'
velocity instead of electrons' velocity, thus the direction of the
motion of X line is decided by ions. We analyzed the event of single
X line crossing Cluster 1 and Cluster 3 satellites sequentially on
the magnetopause, and found that the direction of the moving X line
is in the ion diamagnetic drift and the magnitude of that is the sum
of the ion and electron diamagnetic drift in the electron rest frame.
Title: Slipping reconnection in a solar flare observed in high
resolution with the GREGOR solar telescope
Authors: Sobotka, M.; Dudík, J.; Denker, C.; Balthasar, H.; Jurčák,
J.; Liu, W.; Berkefeld, T.; Collados Vera, M.; Feller, A.; Hofmann,
A.; Kneer, F.; Kuckein, C.; Lagg, A.; Louis, R. E.; von der Lühe, O.;
Nicklas, H.; Schlichenmaier, R.; Schmidt, D.; Schmidt, W.; Sigwarth,
M.; Solanki, S. K.; Soltau, D.; Staude, J.; Strassmeier, K. G.;
Volkmer, R.; Waldmann, T.
Bibcode: 2016A&A...596A...1S
Altcode: 2016arXiv160500464S
A small flare ribbon above a sunspot umbra in active region 12205 was
observed on November 7, 2014, at 12:00 UT in the blue imaging channel
of the 1.5 m GREGOR telescope, using a 1 Å Ca II H interference
filter. Context observations from the Atmospheric Imaging Assembly
(AIA) onboard the Solar Dynamics Observatory (SDO), the Solar Optical
Telescope (SOT) onboard Hinode, and the Interface Region Imaging
Spectrograph (IRIS) show that this ribbon is part of a larger one
that extends through the neighboring positive polarities and also
participates in several other flares within the active region. We
reconstructed a time series of 140 s of Ca II H images by means of the
multiframe blind deconvolution method, which resulted in spatial and
temporal resolutions of 0.1″ and 1 s. Light curves and horizontal
velocities of small-scale bright knots in the observed flare ribbon
were measured. Some knots are stationary, but three move along the
ribbon with speeds of 7-11 km s-1. Two of them move in the
opposite direction and exhibit highly correlated intensity changes,
which provides evidence of a slipping reconnection at small spatial
scales. Movies associated to Figs. 1 and 2 are available at http://www.aanda.org
Title: Physics of higher orbital bands in optical lattices: a review
Authors: Li, Xiaopeng; Liu, W. Vincent
Bibcode: 2016RPPh...79k6401L
Altcode: 2015arXiv150806285L
The orbital degree of freedom plays a fundamental role in understanding
the unconventional properties in solid state materials. Experimental
progress in quantum atomic gases has demonstrated that high orbitals
in optical lattices can be used to construct quantum emulators of
exotic models beyond natural crystals, where novel many-body states
such as complex Bose-Einstein condensates and topological semimetals
emerge. A brief introduction of orbital degrees of freedom in optical
lattices is given and a summary of exotic orbital models and resulting
many-body phases is provided. Experimental consequences of the novel
phases are also discussed.
Title: Helical Motions of Fine-structure Prominence Threads Observed
by Hinode and IRIS
Authors: Okamoto, Takenori J.; Liu, Wei; Tsuneta, Saku
Bibcode: 2016ApJ...831..126O
Altcode: 2016arXiv160800123O
Fine-structure dynamics in solar prominences holds critical clues
to understanding their physical nature of significant space-weather
implications. We report evidence of rotational motions of horizontal
helical threads in two active-region prominences observed by the
Hinode and/or Interface Region Imaging Spectrograph satellites at
high resolution. In the first event, we found transverse motions
of brightening threads at speeds up to 55 km s-1 seen in
the plane of the sky. Such motions appeared as sinusoidal space-time
trajectories with a typical period of ∼390 s, which is consistent
with plane-of-sky projections of rotational motions. Phase delays at
different locations suggest the propagation of twists along the threads
at phase speeds of 90-270 km s-1. At least 15 episodes of
such motions occurred in two days, none associated with an eruption. For
these episodes, the plane-of-sky speed is linearly correlated with the
vertical travel distance, suggestive of a constant angular speed. In the
second event, we found Doppler velocities of 30-40 km s-1 in
opposite directions in the top and bottom portions of the prominence,
comparable to the plane-of-sky speed. The moving threads have about
twice broader line widths than stationary threads. These observations,
when taken together, provide strong evidence for rotations of helical
prominence threads, which were likely driven by unwinding twists
triggered by magnetic reconnection between twisted prominence magnetic
fields and ambient coronal fields.
Title: Alfvén wings in the lunar wake: The role of pressure gradients
Authors: Zhang, H.; Khurana, K. K.; Kivelson, M. G.; Fatemi, S.;
Holmström, M.; Angelopoulos, V.; Jia, Y. D.; Wan, W. X.; Liu, L. B.;
Chen, Y. D.; Le, H. J.; Shi, Q. Q.; Liu, W. L.
Bibcode: 2016JGRA..12110698Z
Altcode:
Strongly conducting or magnetized obstacles in a flowing plasma generate
structures called Alfvén wings, which mediate momentum transfer between
the obstacle and the plasma. Nonconducting obstacles such as airless
planetary bodies can generate such structures, which, however, have so
far been seen only in sub-Alfvénic regime. A novel statistical analysis
of simultaneous measurements made by two ARTEMIS satellites, one in
the solar wind upstream of the Moon and one in the downstream wake, and
comparison of the data with results of a three-dimensional hybrid model
of the interaction reveal that the perturbed plasma downstream of the
Moon generates Alfvén wings in super-Alfvénic solar wind. In the wake
region, magnetic field lines bulge toward the Moon and the plasma flows
are significantly perturbed. We use the simulation to show that some of
the observed bends of the field result from field-aligned currents. The
perturbations in the wake thus arise from a combination of compressional
and Alfvénic perturbations. Because of the super-Alfvénic background
flow of the solar wind, the two Alfvén wings fold back to form a small
intersection angle. The currents that form the Alfvén wing in the wake
are driven by both plasma flow deceleration and a gradient of plasma
pressure, positive down the wake from the region just downstream of
the Moon. Such Alfvén wing structures, caused by pressure gradients
in the wake and the resulting plasma slowdown, should exist downstream
of any nonconducting body in a super-Alfvénic plasma flow.
Title: On the White Dwarf Mass Problem of Cataclysmic Variables
Authors: Liu, Wei-Min; Li, Xiang-Dong
Bibcode: 2016ApJ...832...80L
Altcode: 2016arXiv160906940L
Recent observations show that white dwarfs (WDs) in cataclysmic
variables (CVs) have an average mass significantly higher than
isolated WDs and WDs in post-common envelope binaries (PCEBs),
which are thought to be the progenitors of CVs. This suggests that
either the WDs have grown in mass during the PCEB/CV evolution or
the binaries with low-mass WDs are unable to evolve to be CVs. In
this paper, we calculate the evolution of accreting WD binaries with
updated hydrogen accumulation efficiency and angular momentum loss
(AML) prescriptions. We show that thermal-timescale mass transfer is
not effective in changing the average WD mass distribution. The WD
mass discrepancy is most likely related to unstable mass transfer in
WD binaries, in which an efficient mechanism of AML is required.
Title: Optical design study of the Wide Field Survey Telescope (WFST)
Authors: Lou, Zheng; Liang, Ming; Yao, Dazhi; Zheng, Xianzhong; Cheng,
Jingquan; Wang, Hairen; Liu, Wei; Qian, Yuan; Zhao, Haibin; Yang, Ji
Bibcode: 2016SPIE10154E..2AL
Altcode:
WFST is a proposed 2.5m wide field survey telescope intended for
dedicated wide field sciences. The telescope is to operate at
six wavelength bands (u, g, r, i, z, and w), spanning from 320
to 1028 nm. Designed with a field of view diameter of 3 degree
and an effective aperture diameter of 2.29 m, the WFST acquires a
total optical throughput over 29.3 m2deg2. With such a
large throughput, WFST will survey up to 6000deg2 of the
northern sky in multiple colors each night, reaching 23th magnitude
for high-precision photometry and astrometry. The optical design is
based on an advanced primary-focus system made up of a 2.5 m f/2.48
concave primary mirror and a primary-focus assembly (PFA) consisting of
five corrector lenses, atmospheric dispersion corrector (ADC), filters,
and the focal-plane instrument. For zenith angles from 0 to 60 degrees,
80% of the polychromatic diffracted energy falls within a 0.35 arcsec
diameter. The optical design also highlights an enhanced transmission in
the UV bands. The total optical transmission reaches 23.5% at 320 nm,
allowing unique science goals in the U band. Other features include
low distortion and ease of baffling against stray lights, etc. The
focal-plane instrument is a 0.9 gigapixel mosaic CCD camera comprising
9 pieces of 10K×10K CCD chips. An active optics system (AOS) is used
to maintain runtime image quality. Various design aspects of the WFST
including the optical design, active optics, mirror supports, and the
focal-plane instrument are discussed in detail.
Title: Flare-associated Fast-mode Coronal Wave Trains Detected by
SDO/AIA: Recent Observational Advances
Authors: Liu, Wei; Ofman, Leon; Downs, Cooper; Cheung, Mark; De
Pontieu, Bart
Bibcode: 2016usc..confE.107L
Altcode:
Quasi-periodic Fast Propagating wave trains (QFPs) are new observational
phenomena discovered by SDO/AIA in extreme ultraviolet (EUV). They
were interpreted as fast-mode magnetosonic waves using MHD modeling,
and also found to be closely related to quasi-periodic pulsations
in solar flare emission ranging from radio to X-ray wavelengths. The
significance of QFPs lies in their diagnostic potential (and possibly
in flare energy transport), because they can provide critical clues to
flare energy release and serve as new tools for coronal seismology. In
this presentation, we report recent advances in observing QFPs. In
particular, using differential emission measure (DEM) inversion,
we found clear evidence of heating and cooling cycles that are
consistent with alternating compression and rarefaction expected for
magnetosonic wave pulses. We also found that different local magnetic
and plasma environments can lead to two distinct types of QFPs located
in different spatial domains with respect to their accompanying coronal
mass ejections (CMEs). More interestingly, from a statistical survey of
over 100 QFP events, we found a preferential association with eruptive
flares rather than confined flares. We will discuss the implications
of these results and the potential roles of QFPs in coronal heating,
energy transport, and solar eruptions.
Title: Joint SDO and IRIS Observations of a Novel, Hybrid
Prominence-Coronal Rain Complex
Authors: Liu, Wei; Antolin, Patrick; Sun, Xudong; Gao, Lijia; Vial,
Jean-Claude; Gibson, Sarah; Okamoto, Takenori; Berger, Thomas;
Uitenbroek, Han; De Pontieu, Bart
Bibcode: 2016usc..confE..99L
Altcode:
Solar prominences and coronal rain are intimately related phenomena,
both involving cool material at chromospheric temperatures within the
hot corona and both playing important roles as part of the return flow
of the chromosphere-corona mass cycle. At the same time, they exhibit
distinct morphologies and dynamics not yet well understood. Quiescent
prominences consist of numerous long-lasting, filamentary downflow
threads, while coronal rain is more transient and falls comparably
faster along well-defined curved paths. We report here a novel, hybrid
prominence-coronal rain complex in an arcade-fan geometry observed
by SDO/AIA and IRIS, which provides new insights to the underlying
physics of such contrasting behaviors. We found that the supra-arcade
fan region hosts a prominence sheet consisting of meandering threads
with broad line widths. As the prominence material descends to the
arcade, it turns into coronal rain sliding down coronal loops with
line widths 2-3 times narrower. This contrast suggests that distinct
local plasma and magnetic conditions determine the fate of the cool
material, a scenario supported by our magnetic field extrapolations
from SDO/HMI. Specifically, the supra-arcade fan (similar to those
in solar flares; e.g., McKenzie 2013) is likely situated in a current
sheet, where the magnetic field is weak and the plasma-beta could be
close to unity, thus favoring turbulent flows like those prominence
threads. In contrast, the underlying arcade has a stronger magnetic
field and most likely a low-beta environment, such that the material
is guided along magnetic field lines to appear as coronal rain. We
will discuss the physical implications of these observations beyond
prominence and coronal rain.
Title: Solar Wind Charge Exchange Contribution to the ROSAT All Sky
Survey Maps
Authors: Uprety, Y.; Chiao, M.; Collier, M. R.; Cravens, T.; Galeazzi,
M.; Koutroumpa, D.; Kuntz, K. D.; Lallement, R.; Lepri, S. T.; Liu,
W.; McCammon, D.; Morgan, K.; Porter, F. S.; Prasai, K.; Snowden,
S. L.; Thomas, N. E.; Ursino, E.; Walsh, B. M.
Bibcode: 2016ApJ...829...83U
Altcode: 2016arXiv160303447U
DXL (Diffuse X-ray emission from the Local Galaxy) is a sounding
rocket mission designed to estimate the contribution of solar wind
charge eXchange (SWCX) to the diffuse X-ray background and to help
determine the properties of the Local Hot Bubble. The detectors are
large area thin-window proportional counters with a spectral response
that is similar to that of the PSPC used in the ROSAT All Sky Survey
(RASS). A direct comparison of DXL and RASS data for the same part of
the sky viewed from quite different vantage points in the solar system,
and the assumption of approximate isotropy for the solar wind, allowed
us to quantify the SWCX contribution to all six RASS bands (R1-R7,
excluding R3). We find that the SWCX contribution at l=140^\circ
,b=0^\circ , where the DXL path crosses the Galactic plane, is 33 %
+/- 6 % ({statistical})+/- 12 % ({systematic}) for R1, 44 % +/- 6 %
+/- 5 % for R2, 18 % +/- 12 % +/- 11 % for R4, 14 % +/- 11 % +/-
9 % for R5, and negligible for the R6 and R7 bands. Reliable models
for the distribution of neutral H and He in the solar system permit
estimation of the contribution of interplanetary SWCX emission over
the the whole sky and correction of the RASS maps. We find that the
average SWCX contribution in the whole sky is 26 % +/- 6 % +/- 13 %
for R1, 30 % +/- 4 % +/- 4 % for R2, 8 % +/- 5 % +/- 5 % for R4, 6 %
+/- 4 % +/- 4 % for R5, and negligible for R6 and R7.
Title: VizieR Online Data Catalog: Photometry and spectroscopy of
LS V+44 17 (Yan+, 2016)
Authors: Yan, J.; Zhang, P.; Liu, W.; Liu, Q.
Bibcode: 2016yCat..51510104Y
Altcode:
Most of our spectra of RX J0440.9+4431 were obtained with the
2.16m telescope at Xinglong Station of National Astronomical
Observatories. The optical spectroscopy with an intermediate resolution
was made with a CCD grating spectrograph at the Cassegrain focus
of the telescope. We took the red spectra covering from 5500 to
6700Å. Sometimes low-resolution spectra (covering from 4300 to
6700Å) were also obtained. In 2012 March and 2013 November, we also
carried out the spectroscopic observations with the Yunnan Faint
Object Spectrograph and Camera (YFOSC) instrument of the Lijiang
2.4m telescope in the Yunnan Astronomical Observatory. The Grism #8
was used with a resolution of 1.47Å/pixel, with a spectral range
from 5050 to 9750Å. The journal of our observations is summarized
in Table1. Since 2007, we performed systematic photometric
observations on a sample of X-ray binaries with the 100cm Education
and Science Telescope (EST) and the 80cm Tsinghua-NAOC Telescope (TNT)
at Xinglong Station of NAOC. The EST, manufactured by EOS Technologies,
is an altazimuth-mounted reflector with Nasmyth foci at a focal ratio
of f/8. TNT is an equatorial-mounted Cassegrain system with a focal
of f/10, made by AstroOptik, funded by Tsinghua University in 2002 and
jointly operated with NAOC. Both telescopes are equipped with the same
type of Princeton Instrument 1340*1300 thin back-illuminated CCD. The
CCD cameras use standard Johnson-Cousins UBVRI filters made by Custom
Scientific. The BVRI differential magnitudes and their errors are
listed in Table2. (2 data files).
Title: Coronal and Flare Diagnostic with SDO/AIA-discovered Fast
MHD Wave Trains in Active Regions
Authors: Ofman, Leon; Liu, Wei
Bibcode: 2016usc..confE.106O
Altcode:
Recently, SDO/AIA discovered quasi-periodic, fast-mode propagating
MHD wave trains (QFPs) that propagate at high speeds of more than 1000
km/s. The waves provide a new diagnostic tool for coronal seismology
that includes information on the flare energy release and the magnetic
structure of the active regions. Many events are now available in a
statistical study. However, for improved accuracy of coronal seismology,
3D MHD modeling is required and simple wave-mode analysis may be
insufficient. We present new results of observationally constrained
models of QFPs using our recently upgraded radiative, thermally
conductive, visco-resistive 3D MHD code. The waves are excited by
time-depended boundary conditions constrained by the spatial (localized)
and quasi-periodic temporal evolution of a C-class flare typically
associated with QFPs, and produce observable density and temperature
fluctuations. We investigate parametrically the excitation, propagation,
and damping of the waves for a range of key model parameters, such
as the background temperature, density, magnetic field structure,
and the location of the flaring site within the active region. We
synthesize EUV intensities in multiple AIA channels and then obtain the
model parameters that best reproduce the properties of observed QFPs,
such as the recent DEM analysis. We discuss the implications of our
modeling results for the seismological application of QFPs for the
diagnostic of the active region field and flare pulsations.
Title: Comparison and Analysis of BeiDou Satellite Single-system
Precise Orbit Determination
Authors: Liu, W. P.; Hao, J. M.; Deng, K.; Chen, Y. L.
Bibcode: 2016AcASn..57..534L
Altcode:
The method of double-difference dynamic precise orbit determination for
BeiDou satellites by using both carrier phase and smoothed pseudo-range
is presented. The data processing flows of zero-difference and
double-difference dynamic precise orbit determination for BeiDou
satellites are presented. And the two methods are analyzed. The
precision of two methods is compared based on the real data. The results
show that in the condition of stations layout and by using the two
methods, the three-dimension precision of GEO (Geostationary Earth
Orbit Satellite) can reach about 1 m, and those of IGSO (Inclined
Geosynchronous Earth Orbit Satellite) and MEO (Medium Earth Orbit
Satellite) can be better than 0.5 m. And the radial precision of the
three kinds of orbit satellites can be all better than 10 cm. Compared
with the zero-difference dynamic method, the orbit precision of GEO
is better with the double-difference dynamic method, and that of IGSO
is comparable, but that of MEO is worse.
Title: Data-driven Radiative Hydrodynamic Modeling of the 2014 March
29 X1.0 Solar Flare
Authors: Rubio da Costa, Fatima; Kleint, Lucia; Petrosian, Vahé;
Liu, Wei; Allred, Joel C.
Bibcode: 2016ApJ...827...38R
Altcode: 2016arXiv160304951R; 2016ApJ...827...38D
Spectroscopic observations of solar flares provide critical diagnostics
of the physical conditions in the flaring atmosphere. Some key
features in observed spectra have not yet been accounted for in
existing flare models. Here we report a data-driven simulation of
the well-observed X1.0 flare on 2014 March 29 that can reconcile some
well-known spectral discrepancies. We analyzed spectra of the flaring
region from the Interface Region Imaging Spectrograph (IRIS) in Mg
II h&k, the Interferometric BIdimensional Spectropolarimeter at
the Dunn Solar Telescope (DST/IBIS) in Hα 6563 Å and Ca II 8542 Å,
and the Reuven Ramaty High Energy Solar Spectroscope Imager (RHESSI)
in hard X-rays. We constructed a multithreaded flare loop model and
used the electron flux inferred from RHESSI data as the input to
the radiative hydrodynamic code RADYN to simulate the atmospheric
response. We then synthesized various chromospheric emission lines
and compared them with the IRIS and IBIS observations. In general, the
synthetic intensities agree with the observed ones, especially near the
northern footpoint of the flare. The simulated Mg II line profile has
narrower wings than the observed one. This discrepancy can be reduced
by using a higher microturbulent velocity (27 km s-1) in a
narrow chromospheric layer. In addition, we found that an increase of
electron density in the upper chromosphere within a narrow height range
of ≈800 km below the transition region can turn the simulated Mg II
line core into emission and thus reproduce the single peaked profile,
which is a common feature in all IRIS flares.
Title: Dynamics of a Prominence-horn Structure during Its Evaporation
in the Solar Corona
Authors: Wang, Bing; Chen, Yao; Fu, Jie; Li, Bo; Li, Xing; Liu, Wei
Bibcode: 2016ApJ...827L..33W
Altcode: 2016arXiv160804095W
The physical connections among and formation mechanisms of various
components of the prominence-horn cavity system remain elusive. Here
we present observations of such a system, focusing on a section
of the prominence that rises and separates gradually from the main
body. This forms a configuration sufficiently simple to yield clues
regarding the above issues. It is characterized by embedding horns,
oscillations, and a gradual disappearance of the separated material. The
prominence-horn structure exhibits a large-amplitude longitudinal
oscillation with a period of ∼150 minutes and an amplitude of ∼30
Mm along the trajectory defined by the concave horn structure. The
horns also experience a simultaneous transverse oscillation with a much
smaller amplitude (∼3 Mm) and a shorter period (∼10-15 minutes),
likely representative of a global mode of the large-scale magnetic
structure. The gradual disappearance of the structure indicates that the
horn, an observational manifestation of the field-aligned transition
region separating the cool and dense prominence from the hot and
tenuous corona, is formed due to the heating and diluting process of
the central prominence mass; most previous studies suggested that it
is the opposite process, I.e., the cooling and condensation of coronal
plasmas, that formed the horn. This study also demonstrates how the
prominence transports magnetic flux to the upper corona, a process
essential for the gradual build-up of pre-eruption magnetic energy.
Title: Measuring wind and stress under tropical cyclones with
scatterometer
Authors: Liu, W. Timothy
Bibcode: 2016cosp...41E1178L
Altcode:
Ocean surface stress, the turbulent transport of momentum, is largely
derived from wind through a drag coefficient. In tropical cyclones
(TC), scatterometers have difficulty in measuring strong wind and
there is large uncertainty in the drag coefficient. We postulate that
the microwave backscatter from ocean surface roughness, which is in
equilibrium with local stress, does not distinguish weather systems. The
reduced sensitivity of scatterometer wind retrieval algorithm under the
strong wind is an air-sea interaction problem that is caused by a change
in the behavior of the drag coefficient and not a sensor problem. Under
this assumption, we applied a stress retrieval algorithm developed
over a moderate wind range to retrieve stress under the strong winds
of TCs. Over a moderate wind range, the abundant wind measurements and
more established drag coefficient value allow sufficient stress data to
be computed from wind to develop a stress retrieval algorithm for the
scatterometer. Using unprecedented large amount of stress retrieved from
the scatterometer coincident with strong winds in TC, we showed that the
drag coefficient decreases with wind speed at a much steeper rate than
previously revealed, for wind speeds over 25 m/s. The result implies
that the ocean applies less drag to inhibit TC intensification and the
TC causes less ocean mixing and surface cooling than previous studies
indicated. With continuous and extensive coverage from constellations
of scatterometers for several decades, the impact of tropical cyclones
on the ocean and the feedback from the ocean are examined.
Title: The disk-jet connection of Fermi 2LAC blazars
Authors: Du, L. M.; Xie, Zh. H.; Yi, T. F.; Xue, R.; Xu, Y. B.; Liu,
W. G.; Wang, X. H.
Bibcode: 2016NewA...46....9D
Altcode:
In this article, an estimator of the radiative power for blazars is
proposed and is used in the study of the link between the accretion
disk power and jet power. The results lend support to the disk-jet
symbiosis. Since the blazars are strongly beamed sources, our results
suggest that the Doppler enhancement of the sources needs to be removed
to obtain physically reasonable results in the disk-jet connection
study. The results after de-beaming suggest that FSRQs are accreting in
the radiatively efficient regime, while the BL Lac population shows a
flatter dependence between jet power and disk power, possibly due to
a mixture of sources in the radiatively efficient (the broad lined BL
Lacs) and inefficient (the bulk of the BL Lac population) regimes.
Title: Propagation of small size magnetic holes in the magnetospheric
plasma sheet
Authors: Yao, S. T.; Shi, Q. Q.; Li, Z. Y.; Wang, X. G.; Tian, A. M.;
Sun, W. J.; Hamrin, M.; Wang, M. M.; Pitkänen, T.; Bai, S. C.; Shen,
X. C.; Ji, X. F.; Pokhotelov, D.; Yao, Z. H.; Xiao, T.; Pu, Z. Y.; Fu,
S. Y.; Zong, Q. G.; De Spiegeleer, A.; Liu, W.; Zhang, H.; Rème, H.
Bibcode: 2016JGRA..121.5510Y
Altcode:
Magnetic holes (MHs), characteristic structures where the magnetic
field magnitude decreases significantly, have been frequently observed
in space plasmas. Particularly, small size magnetic holes (SSMHs) which
the scale is less than or close to the proton gyroradius are recently
detected in the magnetospheric plasma sheet. In this study of Cluster
observations, by the timing method, the minimum directional difference
(MDD) method, and the spatiotemporal difference (STD) method, we obtain
the propagation velocity of SSMHs in the plasma flow frame. Furthermore,
based on electron magnetohydrodynamics (EMHD) theory we calculate the
velocity, width, and depth of the electron solitary wave and compare
it to SSMH observations. The result shows a good accord between the
theory and the observation.
Title: Understanding the formation of the Mg II h&k lines during
solar flares
Authors: Rubio Da Costa, Fatima; Kleint, Lucia; Petrosian, Vahe';
Liu, Wei; Allred, Joel C.
Bibcode: 2016SPD....4740304R
Altcode:
The Mg II h&k lines are useful diagnostics for physical processes
in the solar chromosphere. Understanding the line formation is
crucial for the correct interpretation of spectral observations
and characteristics such as line asymmetries or how their central
reversals in the line cores disappear and turn into emission during
flares are manifestations of various physical processes.Focusing on
the well-observed X1.0 flare on 2014 March 29, we carried out a joint
observational and modeling study to analyze the Mg II h&k spectra
observed by IRIS. We constructed a multi-threaded flare loop model and
used the time-dependent electron flux inferred from the RHESSI hard
X-ray data as the input to the radiative hydrodynamic code RADYN to
simulate the atmospheric response. Using the RH code we conducted a
detailed modeling on line shape and evolution to derive how different
atmospheric parameters may affect the MgII line emission.We successfully
simulated the single-peaked Mg II h&k line profiles by increasing
electron density in the upper chromosphere within a narrow height range
of ≈ 800 km below the transition region. To our knowledge, this is the
first successful attempt in reproducing such line-profile shapes under
flaring conditions. We will discuss the implications of this result for
diagnosing atmospheric dynamics and energy transport in solar flares.
Title: Fast-mode Coronal Wave Trains Detected by SDO/AIA: Recent
Observational Progress
Authors: Liu, Wei; Downs, Cooper; Ofman, Leon
Bibcode: 2016SPD....4730802L
Altcode:
Quasi-periodic Fast Propagating wave trains (QFPs) are a new
observational phenomenon discovered by SDO/AIA in extreme ultraviolet
(EUV). They are fast-mode magnetosonic waves, closely related to
quasi-periodic pulsations in solar flare emission ranging from
radio to X-ray wavelengths. The significance of QFPs lies in their
diagnostic potential, because they can provide critical clues to flare
energy release and serve as new tools for coronal seismology. In
this presentation, we report recent advances in observing QFPs. In
particular, using differential emission measure (DEM) inversion,
we found clear evidence of heating and cooling cycles that are
consistent with alternating compression and rarefaction expected for
magnetosonic wave pulses. We also found that different local magnetic
and plasma environments can lead to two distinct types of QFPs located
in different spatial domains with respect to their accompanying
coronal mass ejections (CMEs). Moreover, recent IRIS observations
of QFP source regions revealed sawtooth-like flare ribbon motions,
indicative of pulsed magnetic reconnection, that are correlated with
QFP excitation. More interestingly, from a statistical survey of over
100 QFP events, we found a preferential association with eruptive
flares rather than confined flares. We will discuss the implications
of these results and the potential roles of QFPs in coronal heating,
energy transport, and solar eruptions.
Title: IRIS Observations of a Novel, Hybrid Prominence-Coronal
Rain Complex
Authors: Liu, Wei; Antolin, Patrick; Sun, Xudong
Bibcode: 2016SPD....47.0402L
Altcode:
Solar prominences and coronal rain are intimately related phenomena,
both involving cool material at chromospheric temperatures within the
hot corona and both playing important roles as part of the return flow
of the chromosphere-corona mass cycle. At the same time, they exhibit
distinct morphologies and dynamics not yet well understood. Quiescent
prominences consist of numerous long-lasting, filamentary downflow
threads, while coronal rain is more transient and falls comparably
faster along well-defined curved paths. We report here a novel, hybrid
prominence-coronal rain complex in an arcade-fan geometry observed
by IRIS and SDO/AIA, which provides new insights to the underlying
physics of such contrasting behaviors. We found that the supra-arcade
fan region hosts a prominence sheet consisting of meandering threads
with broad Mg II k/h line widths. As the prominence material descends to
the arcade, it turns into coronal rain sliding down coronal loops with
line widths 2-3 times narrower. This contrast suggests that distinct
local plasma and magnetic conditions determine the fate of the cool
material, a scenario supported by our magnetic field extrapolations from
SDO/HMI. Specifically, the supra-arcade fan (similar to those in solar
flares; e.g., McKenzie 2013) is likely situated in a current sheet,
where the magnetic field is weak and the plasma-beta could be close to
unity, thus favoring turbulent flows like those prominence threads. In
contrast, the underlying arcade has a stronger magnetic field and
most likely a low-beta environment, such that the material is guided
along magnetic field lines to appear as coronal rain. We will discuss
the implications of these novel results for future observations e.g.,
with DKIST.
Title: Realistic Modeling of SDO/AIA-discovered Coronal Fast MHD
Wave Trains in Active Regions
Authors: Ofman, Leon; Liu, Wei
Bibcode: 2016SPD....47.0621O
Altcode:
High-resolution EUV observations by space telescopes have provided
plenty of evidence for coronal MHD waves in active regions. In
particular, SDO/AIA discovered quasi-periodic, fast-mode propagating
MHD wave trains (QFPs), which can propagate at speeds of ~1000 km/s
perpendicular to the magnetic field. Such waves can provide information
on the energy release of their associated flares and the magnetized
plasma structure of the active regions. Before we can use these waves
as tools for coronal seismology, 3D MHD modeling is required for
disentangling observational ambiguities and improving the diagnostic
accuracy. We present new results of observationally contained models
of QFPs using our recently upgraded radiative, thermally conductive,
visco-resistive 3D MHD code. The waves are excited by time-depended
boundary conditions constrained by the spatial (localized) and
quasi-periodic temporal evolution of a C-class flare typically
associated with QFPs. We investigate the excitation, propagation,
and damping of the waves for a range of key model parameters, such as
the background temperature, density, magnetic field structure, and the
location of the flaring site within the active region. We synthesize
EUV intensities in multiple AIA channels and then obtain the model
parameters that best reproduce the properties of observed QFPs. We
discuss the implications of our model results for the seismological
application of QFPs and for understanding the dynamics of their
associated flares.
Title: Microwave Imaging of a Hot Flux Rope Structure during the
Pre-impulsive Stage of an Eruptive M7.7 Solar Flare
Authors: Wu, Zhao; Chen, Yao; Huang, Guangli; Nakajima, Hiroshi;
Song, Hongqiang; Melnikov, Victor; Liu, Wei; Li, Gang; Chandrashekhar,
Kalugodu; Jiao, Fangran
Bibcode: 2016ApJ...820L..29W
Altcode: 2016arXiv160302777W
Corona structures and processes during the pre-impulsive stage of
solar eruption are crucial to understanding the physics leading
to the subsequent explosive energy release. Here we present the
first microwave imaging study of a hot flux rope structure during
the pre-impulsive stage of an eruptive M7.7 solar flare, with the
Nobeyama Radioheliograph at 17 GHz. The flux rope is also observed by
the SDO/AIA in its hot passbands of 94 and 131 Å. In the microwave
data, it is revealed as an overall arcade-like structure consisting of
several intensity enhancements bridged by generally weak emissions,
with brightness temperatures (T B) varying from ∼10,000
K to ∼20,000 K. Locations of microwave intensity enhancements along
the structure remain relatively fixed at certain specific parts of
the flux rope, indicating that the distribution of emitting electrons
is affected by the large-scale magnetic configuration of the twisted
flux rope. Wavelet analysis shows a pronounced 2 minute period of
the microwave T B variation during the pre-impulsive
stage of interest. The period agrees well with that reported for AIA
sunward-contracting loops and upward ejective plasmoids (suggested
to be reconnection outflows). This suggests that both periodicities
are controlled by the same reconnection process that takes place
intermittently at a 2 minute timescale. We infer that at least a part
of the emission is excited by non-thermal energetic electrons via the
gyro-synchrotron mechanism. The study demonstrates the potential of
microwave imaging in exploring the flux rope magnetic geometry and
relevant reconnection process during the onset of solar eruption.
Title: Analysis of a Limb Eruptive Event
Authors: Kotrč, P. Kupryakov, Yu. A.; Bárta, M.; Kashapova, K.,
L.; Liu, W.
Bibcode: 2016ASPC..504...51K
Altcode:
We present the analysis of an eruptive event that took place on the
eastern limb on April 21, 2015, which was observed by the Ondřejov
horizontal telescope and spectrograph. The eruption of the highly
twisted prominence was followed by the onset of soft X-ray sources. We
identified the structures observed in Hα spectra with the details on
the Hα filtergrams and analyzed the evolution of Doppler component
velocities. The timing and observed characteristics of the eruption
were compared with the prediction of the model based on the twisting
of the flux ropes and the kink/torus instability.
Title: The potential of crowdsourcing and mobile technology to
support flood disaster risk reduction
Authors: See, Linda; McCallum, Ian; Liu, Wei; Mechler, Reinhard;
Keating, Adriana; Hochrainer-Stigler, Stefan; Mochizuki, Junko;
Fritz, Steffen; Dugar, Sumit; Arestegui, Michael; Szoenyi, Michael;
Laso-Bayas, Juan-Carlos; Burek, Peter; French, Adam; Moorthy, Inian
Bibcode: 2016EGUGA..1811261S
Altcode:
The last decade has seen a rise in citizen science and crowdsourcing for
carrying out a variety of tasks across a number of different fields,
most notably the collection of data such as the identification of
species (e.g. eBird and iNaturalist) and the classification of images
(e.g. Galaxy Zoo and Geo-Wiki). Combining human computing with the
proliferation of mobile technology has resulted in vast amounts of
geo-located data that have considerable value across multiple domains
including flood disaster risk reduction. Crowdsourcing technologies,
in the form of online mapping, are now being utilized to great effect
in post-disaster mapping and relief efforts, e.g. the activities of
Humanitarian OpenStreetMap, complementing official channels of relief
(e.g. Haiti, Nepal and New York). Disaster event monitoring efforts have
been further complemented with the use of social media (e.g. twitter
for earthquakes, flood monitoring, and fire detection). Much of the
activity in this area has focused on ex-post emergency management while
there is considerable potential for utilizing crowdsourcing and mobile
technology for vulnerability assessment, early warning and to bolster
resilience to flood events. This paper examines the use of crowdsourcing
and mobile technology for measuring and monitoring flood hazards,
exposure to floods, and vulnerability, drawing upon examples from the
literature and ongoing projects on flooding and food security at IIASA.
Title: Long-term Optical Studies of the Be/X-Ray Binary RX
J0440.9+4431/LS V+44 17
Authors: Yan, Jingzhi; Zhang, Peng; Liu, Wei; Liu, Qingzhong
Bibcode: 2016AJ....151..104Y
Altcode: 2016arXiv160207778Y
We present the spectroscopic and photometric observations on the
Be/X-ray binary RX J0440.9+4431 from 2001 to 2014. The short-term and
long-term variability of the Hα line profile indicates that one-armed
global oscillations existed in the circumstellar disk. Several
positive and negative correlations between the V-band brightness
and the Hα intensity were found from the long-term photometric and
spectroscopic observations. We suggest that the monotonic increase
of the V-band brightness and the Hα brightness between our 2005 and
2007 observations might be the result of a continuous mass ejection
from the central Be star, while the negative correlation in 2007-2010
should be caused by the cessation of mass loss from the Be star
just before the decline in V-band brightness began (around our 2007
observations). With the extension of the ejection material, the largest
circumstellar disk during the last two decades has been observed in our
2010 observations with an equivalent width of approximately -12.88 Å,
which corresponds to a circumstellar disk with a size of 12.9 times
the radius of the central Be star. Three consecutive X-ray outbursts
peaking around MJD 55293, 55444, and 55591 might be connected with the
largest circumstellar disk around the Be star. We also use the orbital
motion of the neutron star as a probe to constrain the structure of
the circumstellar disk and estimate the eccentricity of the binary
system to be ≥0.4. After three years of the Hα intensity decline
after the X-ray outbursts, a new circumstellar disk was being formed
around the Be star after our 2013 observations.
Title: The composition and tail activity of Sun-grazing comets
Authors: Jia, Ying-Dong; Russell, Cristopher; Liu, Wei
Bibcode: 2016EGUGA..1810155J
Altcode:
Sun-grazing comets dive into the low corona to reveal the ambient
plasma and field conditions with its very active EUV and X-ray radiation
patterns. In this study we model the charging-balanced cometary plasma,
and its transportation in the solar magnetic field. We study the
comet C/2011 W3 (Lovejoy) event seen by SDO, Stereo and SOHO. Our model
provides line-of-sight integrated emission intensity calculated via each
emission lines of each charge state of O, and Fe ions. Such intensity is
then compared with the observed EUV and X-ray images. Typical structures
of the coronal magnetic field are studied to investigate their effects
on the comet tail, and to model the observed tail activity.
Title: Imaging a Magnetic-breakout Solar Eruption
Authors: Chen, Yao; Du, Guohui; Zhao, Di; Wu, Zhao; Liu, Wei; Wang,
Bing; Ruan, Guiping; Feng, Shiwei; Song, Hongqiang
Bibcode: 2016ApJ...820L..37C
Altcode:
The fundamental mechanism initiating coronal mass ejections (CMEs)
remains controversial. One of the leading theories is magnetic breakout,
in which magnetic reconnection occurring high in the corona removes the
confinement on an energized low-corona structure from the overlying
magnetic field, thus allowing it to erupt. Here, we report critical
observational evidence of this elusive breakout reconnection in a
multi-polar magnetic configuration that leads to a CME and an X-class,
long-duration flare. Its occurrence is supported by the presence of
pairs of heated cusp-shaped loops around an X-type null point and
signatures of reconnection inflows. Other peculiar features new to
the breakout picture include sequential loop brightening, coronal hard
X-rays at energies up to ∼100 keV, and extended high-corona X-rays
above the later restored multi-polar structure. These observations, from
a novel perspective with clarity never achieved before, present crucial
clues to understanding the initiation mechanism of solar eruptions.
Title: Quasi-periodic fast-mode magnetosonic wave trains within
coronal waveguides associated with flares and CMEs
Authors: Liu, Wei; Ofman, Leon; Broder, Brittany; Karlický, Marian;
Downs, Cooper
Bibcode: 2016AIPC.1720d0010L
Altcode: 2015arXiv151207930L
Quasi-periodic, fast-mode, propagating wave trains (QFPs) are a new
observational phenomenon recently discovered in the solar corona by
the Solar Dynamics Observatory with extreme ultraviolet (EUV) imaging
observations. They originate from flares and propagate at speeds up to
∼2000 km s-1 within funnel-shaped waveguides in the wakes
of coronal mass ejections (CMEs). QFPs can carry suffcient energy fluxes
required for coronal heating during their occurr ences. They can provide
new diagnostics for the solar corona and their associated flares. We
present recent observations of QFPs focusing on their spatio-temporal
properties, temperature dependence, and statistical correlation
with flares and CMEs. Of particular interest is the 2010-Aug-01 C3.2
flare with correlated QFPs and drifting zebra and fiber radio bursts,
which might be different manifestations of the same fast-mode wave
trains. We also discuss the potential roles of QFPs in accelerating
and/or modulating the solar wind.
Title: Reduced interdecadal variability of Atlantic Meridional
Overturning Circulation under global warming
Authors: Cheng, Jun; Liu, Zhengyu; Zhang, Shaoqing; Liu, Wei; Dong,
Lina; Liu, Peng; Li, Hongli
Bibcode: 2016PNAS..113.3175C
Altcode:
Interdecadal variability of the Atlantic Meridional Overturning
Circulation (AMOC-IV) plays an important role in climate variation and
has significant societal impacts. Past climate reconstruction indicates
that AMOC-IV has likely undergone significant changes. Despite some
previous studies, responses of AMOC-IV to global warming remain unclear,
in particular regarding its amplitude and time scale. In this study,
we analyze the responses of AMOC-IV under various scenarios of future
global warming in multiple models and find that AMOC-IV becomes weaker
and shorter with enhanced global warming. From the present climate
condition to the strongest future warming scenario, on average,
the major period of AMOC-IV is shortened from ∼50 y to ∼20 y,
and the amplitude is reduced by ∼60%. These reductions in period
and amplitude of AMOC-IV are suggested to be associated with increased
oceanic stratification under global warming and, in turn, the speedup
of oceanic baroclinic Rossby waves.
Title: Preface
Authors: Liu, W. -P.; Li, Z. -H.; Wang, Y. -B.; Guo, B.; Shen, Y. -P.
Bibcode: 2016EPJWC.10900001L
Altcode:
No abstract at ADS
Title: Astrophysical SE2 factor of the 12C(α,
γ)16O reaction through the 12C(11B,
7Li)16O transfer reaction
Authors: Guo, B.; Du, X. C.; Li, Z. H.; Li, Y. J.; Pang, D. Y.; Su,
J.; Yan, S. Q.; Fan, Q. W.; Gan, L.; Han, Z. Y.; Li, E. T.; Li, X. Y.;
Lian, G.; Liu, J. C.; Pei, C. J.; Qiao, L. H.; Shen, Y. P.; Su, Y.;
Wang, Y. B.; Zeng, S.; Zhou, Y.; Liu, W. P.
Bibcode: 2016EPJWC.10904003G
Altcode:
The 12C(α, γ)16O reaction plays a key role in
the evolution of stars with masses of M > 0.55 M⊙. At
the Gamow peak (Ec.m. = 300 ke V, T9 = 0.2),
the cross section of the 12C(α, γ)16O reaction
is so small (about 10-17 barn) that the direct measurement
in ground laboratory is not feasible with the existing technology. Up
to now, the cross sections at lower energies can only be extrapolated
from the data at higher energies. However, two subthreshold resonances,
locating at Ex = 7.117 MeV and Ex = 6.917 MeV,
make this extrapolation more complicated. In this work the 6.917 MeV
subthreshold resonance in the 12C(α, γ)16O
reaction was investigated via the 12C(11B,
7Li)16O reaction. The experiment was performed
using the Q3D magnetic spectrograph at HI-13 tandem accelerator. We
measured the angular distribution of the 12C(11B,
7Li)16O transfer reaction leading to the
6.917 MeV state. Based on DWBA analysis, we derived the square of
ANC of the 6.917 MeV level in 16O to be (2.45± 0.28)
×1010 fm-1, with which the reduced-α width can
be computed. Finally, we calculated the astrophysical SE2
factor of the 6.917 MeV resonance to be 67.6 ± 7.7 ke V b.
Title: Two measurements of the 22Na+p resonant scattering
via thick-target inverse-kinematics method
Authors: Wang, Y. B.; Jin, S. J.; Jing, L.; Han, Z. Y.; Bai, X. X.;
Guo, B.; Li, Y. J.; Li, Z. H.; Lian, G.; Su, J.; Sun, L. J.; Yan,
S. Q.; Zeng, S.; Liu, W. P.; Yamaguchi, H.; Kubono, S.; Hu, J.; Kahl,
D.; He, J. J.; Wang, J. S.; Tang, X. D.; Xu, S. W.; Ma, P.; Zhang,
N. T.; Bai, Z.; Huang, M. R.; Jia, B. L.; Jin, S. L.; Ma, J. B.;
Ma, S. B.; Ma, W. H.; Yang, Y. Y.; Zhang, L. Y.; Jung, H. S.; Moon,
J. Y.; Lee, C. S.; Teranishi, T.; Wang, H. W.; Ishiyama, H.; Iwasa,
N.; Komatsubara, T.; Brown, B. A.
Bibcode: 2016EPJWC.10904010W
Altcode:
22Na is an important isotope for the study of extinct
radioactivity, meanwhile its sufficiently long half life provides
the possibility to observe live 22Na in nearby nova
explosions. The 22Na(p,γ) 23Mg is one of
the key reactions that influence the 22Na abundance in
nova ejecta. To study the proton resonant states in 23Mg
relevant to the astrophysical 22Na(p,γ) 23Mg
reaction rates, two measurements have been carried out at the CRIB
separator of University of Tokyo, and the RIBLL secondary beamline
in Lanzhou, respectively. The 22Na secondary beam was
produced via the 1H(22Ne, 22Na)n
charge exchange reaction. Thick-target inverse-kinematics method
is applied to obtain the excitation function of 22Na+p
elastic scattering. Extended gas target and solid state polyethylene
foil were used in the two measurements, respectively, to map
the different excitation energy region of the compound nucleus
23Mg. Several new resonant levels are observed and their
contribution to the 22Na(p,γ) 23Mg reaction
rate is evaluated.
Title: Optical potential parameters from 12C + Zr elastic
scattering
Authors: Gan, L.; Li, Z. H.; Sun, H. B.; Su, J.; Li, Y. J.; Yan,
S. Q.; Wang, Y. B.; Zeng, S.; Bai, X. X.; Du, X. C.; Wu, Z. D.; Jin,
S. J.; Zhang, W. J.; Liu, W. P.; Li, E. T.
Bibcode: 2016EPJWC.10904002G
Altcode:
The angular distributions of 12C + 90,92,94,96Zr
elastic scattering were measured with the Q3D magnetic spectrometer
at the HI-13 tandem accelerator, Beijing. The real part of
optical potential were extracted by analysing these angular
distributions. The analysis enable us to avoid the influence of
Coulomb effect and to observe the dependence of optical potential
on the nuclear properties. With the deduced potential parameters,
the experimental elastic scattering angular distributions can be
reproduced very well. Formulas to infer global heavy-ion potential
parameters were obtained then by analyzing the extracted optical
potential parameters. The formulas can be used widely in heavy-ion
nuclear reactions.
Title: Identifying magnetic reconnection events using the FOTE method
Authors: Fu, H. S.; Cao, J. B.; Vaivads, A.; Khotyaintsev, Y. V.;
Andre, M.; Dunlop, M.; Liu, W. L.; Lu, H. Y.; Huang, S. Y.; Ma, Y. D.;
Eriksson, E.
Bibcode: 2016JGRA..121.1263F
Altcode:
A magnetic reconnection event detected by Cluster is analyzed using
three methods: Single-spacecraft Inference based on Flow-reversal
Sequence (SIFS), Multispacecraft Inference based on Timing a Structure
(MITS), and the First-Order Taylor Expansion (FOTE). Using the SIFS
method, we find that the reconnection structure is an X line; while
using the MITS and FOTE methods, we find it is a magnetic island (O
line). We compare the efficiency and accuracy of these three methods
and find that the most efficient and accurate approach to identify
a reconnection event is FOTE. In both the guide and nonguide field
reconnection regimes, the FOTE method is equally applicable. This study
for the first time demonstrates the capability of FOTE in identifying
magnetic reconnection events; it would be useful to the forthcoming
Magnetospheric Multiscale (MMS) mission.
Title: Fermi Large Area Telescope observation of high-energy solar
flares: constraining emission scenarios
Authors: Omodei, Nicola; Pesce-Rollins, Melissa; Petrosian, Vahè;
Liu, Wei; da Costa, Fatima Rubio; Allafort, Alice
Bibcode: 2016IAUS..320...51O
Altcode:
The Fermi Large Area Telescope (LAT) is the most sensitive instrument
ever deployed in space for observing gamma-ray emission >100
MeV. This has also been demonstrated by its detection of quiescent
gamma-ray emission from pions produced by cosmic-ray protons
interacting in the solar atmosphere, and from cosmic-ray electron
interactions with solar optical photons. The Fermi-LAT has also
detected high-energy gamma-ray emission associated with GOES M-class
and X-class solar flares, each accompanied by a coronal mass ejection
and a solar energetic particle event, increasing the number of detected
solar flares by almost a factor of 10 with respect to previous space
observations. During the impulsive phase, gamma rays with energies up
to several hundreds of MeV have been recorded by the LAT. Emission up
to GeV energies lasting several hours after the flare has also been
detected by the LAT. Of particular interest are the recent detections
of three solar flares whose position behind the limb was confirmed
by the STEREO satellites. While gamma-ray emission up to tens of
MeV resulting from proton interactions has been detected before from
occulted solar flares, the significance of these particular events
lies in the fact that these are the first detections of >100 MeV
gamma-ray emission from footpoint-occulted flares. We will present the
Fermi-LAT, RHESSI and STEREO observations of these flares and discuss
the various emission scenarios for these sources.
Title: GREGOR observations of a small flare above a sunspot
Authors: Sobotka, M.; Dudík, J.; Denker, C.; Balthasar, H.; Jurčák,
J.; Liu, W.
Bibcode: 2016IAUS..320...68S
Altcode:
A small flare ribbon above a sunspot umbra in active region 12205 was
observed on November 7, 2014, at 12:00 UT in the blue imaging channel
of the 1.5-m GREGOR telescope, using a 0.1 nm Ca II H interference
filter. Context observations from SDO/AIA, Hinode/SOT, and IRIS show
that the ribbon is a part of a larger one that extends through the
neighboring positive polarities and also participates in several
other flares within the active region. A 140 second long time series
of Ca II H images was reconstructed by means of the Multi-Frame
Blind Deconvolution method, giving the respective spatial and
temporal resolutions of 0''.1 and 1 s. Light curves and horizontal
velocities of small-scale bright knots in the observed flare ribbon
were measured. Some knots are stationary but three move along the
ribbon with speeds of 7-11 km s-1. Two of them move in the
opposite direction and exhibit highly correlated intensity changes,
providing evidence for the presence of slipping reconnection at small
spatial scales.
Title: Evidence for a Very Low-column Density Hole in the Galactic
Halo in the Direction of the High Latitude Molecular Cloud MBM 16
Authors: Liu, W.; Galeazzi, M.; Ursino, E.
Bibcode: 2016ApJ...816...82L
Altcode: 2015arXiv151200043L
Shadow observations are the only way to observe emission from the
galactic halo (GH) and/or the circumgalactic medium (CGM) free of any
foreground contamination from local hot bubble (LHB) and solar wind
charge exchange (SWCX). We analyzed data from a shadow observation in
the direction of the high latitude, neutral hydrogen cloud MBM 16 with
Suzaku. We found that all emission can be accounted for by foreground
emission from LHB and SWCX, plus power-law emission associated with
unresolved point sources. The GH/CGM in the direction of MBM 16 is
negligible or inexistent in our observation, with upper limits on
the emission measure of 9× {10}-4 pc cm-6
(90% C.L.-solar metallicity), at the lowest end of current estimates.
Title: Studying the Interstellar Medium and the Inner Region of
NPS/LOOP 1 with Shadow Observations toward MBM36
Authors: Ursino, E.; Galeazzi, M.; Liu, W.
Bibcode: 2016ApJ...816...33U
Altcode: 2015arXiv151200024U
We analyzed data from a shadow observation of the high density
molecular cloud MBM36 (l ∼ 4°, b ∼ 35°) with Suzaku. MBM36 is
located in a region that emits relatively weakly in the 3/4 keV band
compared to the surrounding North Polar Spur (NPS)/Loop 1 structure
and the Galactic Bulge (GB). The contrast between high and low density
targets in the MBM36 area allows one to separate the local and distant
contributors to the soft diffuse X-ray background, providing a much
better characterization of the individual components compared to single
pointing observations. We identify two non-local thermal components,
one at kT ≈ 0.12 keV and one at kT ≈ 0.29 keV. The colder component
matches well with models of emission from the higher latitude region
of the GB. The emission of the warmer component is in agreement with
models predicting that the NPS is due to a hypershell from the center
of the Milky Way. Geometrical and pressure calculations rule out a
nearby bubble as responsible for the emission associated with the
NPS. Any Galactic Halo/circumgalactic halo emission, if present, is
outshined by the other components. We also report an excess emission
around 0.9 keV, likely due to an overabundance of Ne ix.
Title: Flare-associated Fast-mode Coronal Wave Trains Discovered by
SDO/AIA: Physical Properties and Implications
Authors: Liu, W.; Ofman, L.; Downs, C.; Cheung, C. M. M.; Broder,
B.; De Pontieu, B.
Bibcode: 2015AGUFMSH54B..02L
Altcode:
Quasi-periodic Fast Propagating wave trains (QFPs) are a new
observational phenomenon discovered in extreme ultraviolet (EUV) by
the Atmospheric Imaging Assembly (AIA) onboard the Solar Dynamics
Observatory (SDO). They are fast-mode magnetosonic waves, closely
related to quasi-periodic pulsations in solar flare emission ranging
from radio to X-ray wavelengths. The significance of QFPs lies in their
diagnostic potential, because they can provide critical clues to flare
energy release and serve as new tools for coronal seismology. In
this presentation, we report recent advances in observing and
modeling QFPs. For example, using differential emission measure (DEM)
inversion, we found clear evidence of heating and cooling cycles that
are consistent with alternating compression and rarefaction expected
for magnetosonic wave pulses. Moreover, recent IRIS observations
of QFP source regions revealed sawtooth-like flare ribbon motions,
indicative of pulsed magnetic reconnection, that are correlated with QFP
excitation. More interestingly, from a survey of over 100 QFP events,
we found a preferential association with eruptive flares rather than
confined flares. We will discuss the implications of these results
and the potential roles of QFPs in coronal heating, energy transport,
and solar eruptions.
Title: Fast Wave Trains Associated with Solar Eruptions: Insights
from 3D Thermodynamic MHD Simulations
Authors: Downs, C.; Liu, W.; Torok, T.; Linker, J.; Mikic, Z.;
Ofman, L.
Bibcode: 2015AGUFMSH22A..06D
Altcode:
EUV imaging observations during the SDO/AIA era have provided new
insights into a variety of wave phenomena occurring in the low
solar corona. One example is the observation of quasi-periodic,
fast-propagating wave trains that are associated with solar eruptions,
including flares and CMEs. While there has been considerable
progress in understanding such waves from both an observational
and theoretical perspective, it remains a challenge to pin down
their physical origin. In this work, we detail our results from
a case-study 3D thermodynamic MHD simulation of a coronal mass
ejection where quasi-periodic wave trains are generated during the
simulated eruption. We find a direct correlation between the onset of
non-steady reconnection in the flare current sheet and the generation
of quasi-periodic wave train signatures when patchy, collimated
downflows interact with the flare arcade. Via forward modeling of
SDO/AIA observables, we explore how the appearance of the wave trains
is affected by line-of-sight integration and the multi-thermal nature
of the coronal medium. We also examine how the wave trains themselves
are channeled by natural waveguides formed in 3D by the non-uniform
background magnetic field. While the physical association of the
reconnection dynamics to the generation of quasi-periodic wave trains
appears to be a compelling result, unanswered questions posed from
recent observations as well as future prospects will be discussed.
Title: Dynamic plasmapause model based on THEMIS measurements
Authors: Liu, X.; Liu, W.; Cao, J. B.; Fu, H. S.; Yu, J.; Li, X.
Bibcode: 2015JGRA..12010543L
Altcode:
This paper presents a dynamic plasmapause location model established
based on 5 years of Time History of Events and Macroscale Interactions
during Substorms (THEMIS) measurements from 2009 to 2013. In total,
5878 plasmapause crossing events are identified, sufficiently covering
all 24 magnetic local time (MLT) sectors. Based on this plasmapause
crossing database, we investigate the correlations between plasmapause
locations with solar wind parameters and geomagnetic indices. Input
parameters for the best fits are obtained for different MLT sectors,
and finally, we choose five input parameters to build a plasmapause
location model, including 5 min-averaged SYM-H, AL, and AU indices
as well as hourly-averaged AE and Kp indices. two out-of-sample
comparisons on the evolution of the plasmapause is shown during two
magnetic storms, demonstrating good agreement between model results and
observations. Two major advantages are achieved by this model. First,
this model provides plasmapause locations at 24 MLT sectors, still
providing good consistency with observations. Second, this model is
able to reproduce dynamic variations of the plasmapause on timescales
as short as 5 min.
Title: Mg II Lines Observed During the X-class Flare on 29 March
2014 by the Interface Region Imaging Spectrograph
Authors: Liu, W.; Heinzel, P.; Kleint, L.; Kašparová, J.
Bibcode: 2015SoPh..290.3525L
Altcode: 2015SoPh..tmp..166L; 2015arXiv151100480L
Mg II lines represent one of the strongest emissions from the
chromospheric plasma during solar flares. In this article, we
studied the Mg II lines observed during the X1 flare on 29 March 2014
(SOL2014-03-29T17:48) by the Interface Region Imaging Spectrograph
(IRIS). IRIS detected large intensity enhancements of the Mg II h and
k lines, subordinate triplet lines, and several other metallic lines
at the flare footpoints during this flare. We have used the advantage
of the slit-scanning mode (rastering) of IRIS and performed, for the
first time, a detailed analysis of spatial and temporal variations
of the spectra. Moreover, we were also able to identify positions
of strongest hard X-ray (HXR) emissions using the Reuven Ramaty
High Energy Solar Spectroscopic Imager (RHESSI) observations and to
correlate them with the spatial and temporal evolution of IRIS Mg
II spectra. The light curves of the Mg II lines increase and peak
contemporarily with the HXR emissions but decay more gradually. There
are large red asymmetries in the Mg IIh and k lines after the flare
peak. We see two spatially well-separated groups of Mg II line profiles,
non-reversed and reversed. In some cases, the Mg II footpoints with
reversed profiles are correlated with HXR sources. We show the spatial
and temporal behavior of several other line parameters (line metrics)
and briefly discuss them. Finally, we have synthesized the Mg IIk line
using our non-LTE code with the Multilevel Accelerated Lambda Iteration
(MALI) technique. Two kinds of models are considered, the flare model
F2 of Machado et al. (Astrophys. J.242, 336, 1980) and the models of
Ricchiazzi and Canfield (Astrophys. J.272, 739, 1983, RC models). Model
F2 reproduces the peak intensity of the non-reversed Mg IIk profile
at flare maximum, but does not account for high wing intensities. On
the other hand, the RC models show the sensitivity of Mg II line
intensities to various electron-beam parameters. Our simulations also
show that the microturbulence produces a broader line core, while the
intense line wings are caused by an enhanced line source function.
Title: A self-consistent combined radiative transfer hydrodynamic and
particle acceleration model for the X1.0 class flare on March 29, 2014
Authors: Rubio da Costa, F.; Kleint, L.; Sainz Dalda, A.; Petrosian,
V.; Liu, W.
Bibcode: 2015AGUFMSH31B2419R
Altcode:
The X1.0 flare on March 29, 2014 was well observed, covering its
emission at several wavelengths from the photosphere to the corona. The
RHESSI spectra images allow us to estimate the temporal variation of
the electron spectra using regularized inversion techniques. Using
this as input for a combined particle acceleration and transport
(Stanford-Flare) and radiative transfer hydrodynamic (Radyn) code, we
calculate the response of the atmosphere to the electron heating. We
will present the evolution of the thermal continuum and several line
emissions. Comparing them with GOES soft X-ray and high resolution
observations from IRIS, SDO and DST/IBIS allows us to test the basic
mechanism(s) of acceleration and to constrain its characteristics. We
will also present perspectives on how to apply this methodology and
related diagnostics to other flares.
Title: Controls of Earth's dipole tilt angle and background
magnetosheath flow to the locations of reconnection sites on the
magnetopasue
Authors: Zhu, C.; Zhang, H.; Ge, Y.; Pu, Z.; Liu, W. L.; Liu, L.;
Wan, W.; Le, H.; Chen, Y.; Wang, Y. F.
Bibcode: 2015AGUFMSM13C2523Z
Altcode:
Plasma energy-dispersion properties inside reconnection jet flows
observed in the low latitude boundary layer are used to determine
the distances of the observing satellites to reconnection sites. The
locations of the reconnection sites are then retrieved by tracing the
modeled field lines by those distances. The controlling effects of
the dipole tilt angle to the location of X-lines or reconnection sites
are investigated. Our results show that the Earth's dipole tilt angles
strongly modify the location of X-lines predicted by Cooling et al's
model, which is thought to be the result of magnetopause reshaping due
to finite dipole tilt angles. By investigating the magnetosheath flow
outside the reconnection sites, we found that besides the dipole tilt
angle the magnetosheath background flows also play a significant role
in determining the locations of the reconnection sites.
Title: Dynamic plasmapause model based on THEMIS measurements
Authors: Liu, W.; Liu, X.
Bibcode: 2015AGUFMSM41G2565L
Altcode:
We will present a dynamic plasmapause location model established based
on five years of THEMIS measurements from 2009 to 2013. In total,
5878 plasmapause crossing events are identified, sufficiently covering
all 24 Magnetic Local Time (MLT) sectors. Based on this plasmapause
crossing database, we investigate the correlations between plasmapause
locations with solar wind parameters and geomagnetic indices. Input
parameters for the best fits are obtained for different MLT sectors
and finally we choose five input parameters to build a plasmapause
location model, including five-minute-averaged SYM-H, AL and AU
indices as well as hourly-averaged AE and Kp indices. An out-of-sample
comparison on the evolution of the plasmapause is shown during April
2001 magnetic storm, demonstrating good agreement between model
results and observations. Two major advantages are achieved by this
model. First, this model provides plasmapause locations at 24 MLT
sectors, still providing good consistency with observations. Second,
this model is able to reproduce dynamic variations of plasmapause in
the time scale as short as five minutes.
Title: Flexible Filter Bank Based on an Improved Weighted Overlap-Add
Algorithm for Processing Wide Bandwidth Radio Astronomy Signals
Authors: Wang, Xianhai; Meng, Qiao; Han, J. L.; Liu, Wei; Zhang,
Jianwei
Bibcode: 2015PASP..127.1263W
Altcode:
No abstract at ADS
Title: Combined Modeling of Acceleration, Transport, and Hydrodynamic
Response in Solar Flares. II. Inclusion of Radiative Transfer
with RADYN
Authors: Rubio da Costa, Fatima; Liu, Wei; Petrosian, Vahé; Carlsson,
Mats
Bibcode: 2015ApJ...813..133R
Altcode: 2015arXiv150501549R
Solar flares involve complex processes that are coupled and span a
wide range of temporal, spatial, and energy scales. Modeling such
processes self-consistently has been a challenge in the past. Here we
present results from simulations that couple particle kinetics with
hydrodynamics (HD) of the atmospheric plasma. We combine the Stanford
unified Fokker-Planck code that models particle acceleration and
transport with the RADYN HD code that models the atmospheric response
to collisional heating by accelerated electrons through detailed
radiative transfer calculations. We perform simulations using two
different electron spectra, one an ad hoc power law and the other
predicted by the model of stochastic acceleration by turbulence or
plasma waves. Surprisingly, the later model, even with energy flux \ll
{10}10 {erg} {{{s}}}-1 {{cm}}-2, can
cause “explosive” chromospheric evaporation and drive stronger
up- and downflows (and HD shocks). This is partly because our
acceleration model, like many others, produces a spectrum consisting
of a quasi-thermal component plus a power-law tail. We synthesize
emission-line profiles covering different heights in the lower
atmosphere, including Hα 6563 Å, He ii 304 Å, Ca ii K 3934 Å, and
Si iv 1393 Å. One interesting result is the unusual high temperature
(up to a few times 105 K) of the formation site of He ii
304 Å, which is expected owing to photoionization-recombination under
flare conditions, compared to those in the quiet Sun dominated by
collisional excitation. When compared with observations, our results
can constrain the properties of nonthermal electrons and thus the
poorly understood particle acceleration mechanism.
Title: Temporal Evolution of Chromospheric Evaporation: Case
Studies of the M1.1 Flare on 2014 September 6 and X1.6 Flare on 2014
September 10
Authors: Tian, Hui; Young, Peter R.; Reeves, Katharine K.; Chen, Bin;
Liu, Wei; McKillop, Sean
Bibcode: 2015ApJ...811..139T
Altcode: 2015arXiv150502736T
With observations from the Interface Region Imaging Spectrograph, we
track the complete evolution of ∼11 MK evaporation flows in an M1.1
flare on 2014 September 6 and an X1.6 flare on 2014 September 10. These
hot flows, as indicated by the blueshifted Fe xxi 1354.08 Å line,
evolve smoothly with a velocity decreasing exponentially from ∼200
km s-1 to almost stationary within a few minutes. We find a
good correlation between the flow velocity and energy deposition rate
as represented by the hard X-ray flux observed with the Reuven Ramaty
High Energy Solar Spectroscopic Imager, or time derivative of the soft
X-ray flux observed with the Geostationary Operational Environmental
Satellites and the HINODE X-ray Telescope, which is in general agreement
with models of nonthermal electron heating. The maximum blueshift of
Fe xxi appears approximately at the same time as or slightly after
the impulsive enhancement of the ultraviolet continuum and the Mg ii
2798.8 Å line emission, demonstrating that the evaporation flow is
closely related to heating of the lower chromosphere. Finally, while
the hot Fe xxi 1354.08 Å line is entirely blueshifted with no obvious
rest component, cool chromospheric and transition region lines like
Si iv 1402.77 Å are often not entirely redshifted but just reveal an
obvious red wing enhancement at the ribbons, suggesting that the speed
of chromospheric condensation might be larger than previously thought.
Title: LOD First Estimates In 7406 SLR San Juan Argentina Station
Authors: Pacheco, A.; Podestá, R.; Yin, Z.; Adarvez, S.; Liu, W.;
Zhao, L.; Alvis Rojas, H.; Actis, E.; Quinteros, J.; Alacoria, J.
Bibcode: 2015RMxAC..46...29P
Altcode:
In this paper we show results derived from satellite observations at
the San Juan SLR station of Felix Aguilar Astronomical Observatory
(OAFA). The Satellite Laser Ranging (SLR) telescope was installed in
early 2006, in accordance with an international cooperation agreement
between the San Juan National University (UNSJ) and the Chinese Academy
of Sciences (CAS). The SLR has been in successful operation since
2011 using NAOC SLR software for the data processing. This program
was designed to calculate satellite orbits and station coordinates,
however it was used in this work for the determination of LOD (Length
Of Day) time series and Earth Rotation speed.
Title: Measurement of the 14O(α ,p ) 17F
cross section at Ec .m .≈2.1 -5.3 MeV
Authors: Kim, A.; Lee, N. H.; Han, M. H.; Yoo, J. S.; Hahn, K. I.;
Yamaguchi, H.; Binh, D. N.; Hashimoto, T.; Hayakawa, S.; Kahl, D.;
Kawabata, T.; Kurihara, Y.; Wakabayashi, Y.; Kubono, S.; Choi, S.;
Kwon, Y. K.; Moon, J. Y.; Jung, H. S.; Lee, C. S.; Teranishi, T.;
Kato, S.; Komatsubara, T.; Guo, B.; Liu, W. P.; Wang, B.; Wang, Y.
Bibcode: 2015PhRvC..92c5801K
Altcode:
Background: The 14O(α ,p ) 17F reaction
plays an important role as the trigger reaction for the x-ray
burst. Purpose: The direct measurement of 14O(α
,p ) 17F was made for studying the resonant states in
18Ne and determining the reaction rate of 14O(α
,p ) 17F at astrophysical temperatures. Methods: The
differential cross section of the 14O(α ,p ) 17F
reaction was measured using a 2.5-MeV/u 14O radioactive
beam and the thick target method in inverse kinematics. Three sets
of Δ E -E Si telescopes were installed and coincidence measurements
were performed. We analyzed single-proton decay events using the
time-of-flight (TOF) information of the recoiling protons. Results:
The excitation function of 14O(α ,p ) 17F
was acquired for excitation energies between 7.2 and 10.4 MeV in
18Ne by considering the two channels which decay to the
ground state and first excited state of 17F . Several new,
as well as previously known, states in 18Ne were observed and
their resonance parameters were extracted from R -matrix analysis. The
contributions of four resonances over the excitation energy range,
7 <Ex<8.2 MeV , to the 14O(α ,p )
17F reaction rate were calculated. Conclusions:
We observed very strong single-proton decay events, but did not
observe strong double-proton decay events as in a previous study
by Fu et al. The reaction rates contributed by the 7.35-, 7.58-,
and 7.72-MeV states were estimated to be dominant at temperatures
T9>2 . Among these three states, the 7.35-MeV state was
found to enhance the reaction rate by a factor of 10 greater than the
other two resonance states.
Title: Rapid Large Scale Reprocessing of the ODI Archive using the
QuickReduce Pipeline
Authors: Gopu, A.; Kotulla, R.; Young, M. D.; Hayashi, S.; Harbeck,
D.; Liu, W.; Henschel, R.
Bibcode: 2015ASPC..495...53G
Altcode: 2015adass..24...53G
The traditional model of astronomers collecting their observations
as raw instrument data is being increasingly replaced by astronomical
observatories serving standard calibrated data products to observers and
to the public at large once proprietary restrictions are lifted. For
this model to be effective, observatories need the ability to
periodically re-calibrate archival data products as improved master
calibration products or pipeline improvements become available, and also
to allow users to rapidly calibrate their data on-the-fly. Traditional
astronomy pipelines are heavily I/O dependent and do not scale with
increasing data volumes. In this paper, we present the One Degree Imager
- Portal, Pipeline and Archive (ODI-PPA) calibration pipeline framework
which integrates the efficient and parallelized QuickReduce pipeline
to enable a large number of simultaneous, parallel data reduction jobs
- initiated by operators AND/OR users - while also ensuring rapid
processing times and full data provenance. Our integrated pipeline
system allows re-processing of the entire ODI archive (∼15,000 raw
science frames, ∼3.0 TB compressed) within ∼18 hours using twelve
32-core compute nodes on the Big Red II supercomputer. Our flexible,
fast, easy to operate, and highly scalable framework improves access to
ODI data, in particular when data rates double with an upgraded focal
plane (scheduled for 2015), and also serve as a template for future data
processing infrastructure across the astronomical community and beyond.
Title: Operational Support for Instrument Stability through ODI-PPA
Metadata Visualization and Analysis
Authors: Young, M. D.; Hayashi, S.; Gopu, A.; Kotulla, R.; Harbeck,
D.; Liu, W.
Bibcode: 2015ASPC..495..181Y
Altcode: 2015adass..24..181Y
Over long time scales, quality assurance metrics taken from calibration
and calibrated data products can aid observatory operations in
quantifying the performance and stability of the instrument, and
identify potential areas of concern or guide troubleshooting and
engineering efforts. Such methods traditionally require manual SQL
entries, assuming the requisite metadata has even been ingested
into a database. With the ODI-PPA system, QA metadata has been
harvested and indexed for all data products produced over the life
of the instrument. In this paper we will describe how, utilizing
the industry standard Highcharts Javascript charting package with a
customized AngularJS-driven user interface, we have made the process
of visualizing the long-term behavior of these QA metadata simple and
easily replicated. Operators can easily craft a custom query using
the powerful and flexible ODI-PPA search interface and visualize
the associated metadata in a variety of ways. These customized
visualizations can be bookmarked, shared, or embedded externally,
and will be dynamically updated as new data products enter the system,
enabling operators to monitor the long-term health of their instrument
with ease.
Title: Fermi Large Area Telescope observation of high-energy solar
flares: constraining emission scenarios
Authors: Omodei, Nicola; Pesce-Rollins, Melissa; Petrosian, Vahe;
Liu, Wei; Rubio da Costa, Fatima
Bibcode: 2015IAUGA..2255415O
Altcode:
The Fermi Large Area Telescope (LAT) is the most sensitive instrument
ever deployed in space for observing gamma-ray emission >100
MeV. This has also been demonstrated by its detection of quiescent
gamma-ray emission from pions produced by cosmic-ray protons
interacting in the solar atmosphere, and from cosmic-ray electron
interactions with solar optical photons. The Fermi LAT has also
detected high-energy gamma-ray emission associated with GOES M-class
and X-class X-ray flares, each accompanied by a coronal mass ejection
and a solar energetic particle event increasing the number of detected
solar flares by almost a factor of 10 with respect to previous space
observations. During the impulsive phase, gamma rays with energies up
to several hundreds of MeV have been recorded by the LAT. Emission up
to GeV energies lasting several hours after the flare has also been
recorded by the LAT. Of particular interest are the recent detections
of two solar flares whose position behind the limb was confirmed by
the STEREO-B satellite. While gamma-ray emission up to tens of MeV
resulting from proton interactions has been detected before from
occulted solar flares, the significance of these particular events
lies in the fact that these are the first detections of >100 MeV
gamma-ray emission from footpoint-occulted flares. We will present the
Fermi-LAT, RHESSI and STEREO observations of these flares and discuss
the various emission scenarios for these sources.
Title: Dipole tilt angle effect on magnetic reconnection locations
on the magnetopause
Authors: Zhu, C. B.; Zhang, H.; Ge, Y. S.; Pu, Z. Y.; Liu, W. L.;
Wan, W. X.; Liu, L. B.; Chen, Y. D.; Le, H. J.; Wang, Y. F.
Bibcode: 2015JGRA..120.5344Z
Altcode:
Plasma energy dispersion properties inside reconnection jet flows
observed inside the low-latitude boundary layer are used to determine
the distances of observing satellites to reconnection sites. The
locations of the reconnection sites are then retrieved by tracing
the modeled field lines by those distances. The controlling effects
of the dipole tilt angle to the location of X lines or reconnection
sites are investigated. Our results show that the Earth's dipole tilt
angles strongly modify the location of X lines predicted by Cooling et
al's model, which is thought to be the result of magnetopause reshaping
due to finite dipole tilt angles.
Title: Fermi Large Area Telescope observations of high-energy
gamma-ray emission from behind-the-limb solar flares
Authors: Pesce-Rollins, M.; Omodei, N.; Petrosian, V.; Liu, W.;
Rubio da Costa, F.; Allafort, A.; Fermi-LAT Collaboration
Bibcode: 2015ICRC...34..128P
Altcode: 2015arXiv150704303P; 2015PoS...236..128P
Fermi-LAT >30 MeV observations have increased the number of detected
solar flares by almost a factor of 10 with respect to previous space
observations. These sample both the impulsive and long duration phases
of GOES M and X class flares. Of particular interest is the recent
detections of three solar flares whose position behind the limb was
confirmed by the STEREO-B spacecraft. While gamma-ray emission up to
tens of MeV resulting from proton interactions has been detected before
from occulted solar flares, the significance of these particular events
lies in the fact that these are the first detections of >100 MeV
gamma-ray emission from footpoint-occulted flares. We will present the
Fermi-LAT, RHESSI and STEREO observations of these flares and discuss
the various emission scenarios for these sources and implications for
the particle acceleration mechanisms.
Title: First Detection of >100 MeV Gamma Rays Associated with
a Behind-the-limb Solar Flare
Authors: Pesce-Rollins, M.; Omodei, N.; Petrosian, V.; Liu, Wei;
Rubio da Costa, Fatima; Allafort, A.; Chen, Qingrong
Bibcode: 2015ApJ...805L..15P
Altcode: 2015arXiv150503480P
We report the first detection of >100 MeV gamma-rays associated with
a behind-the-limb solar flare, which presents a unique opportunity to
probe the underlying physics of high-energy flare emission and particle
acceleration. On 2013 October 11 a GOES M1.5 class solar flare occurred
∼9.°9 behind the solar limb as observed by STEREO-B. RHESSI observed
hard X-ray (HXR) emission above the limb, most likely from the flare
loop-top, as the footpoints were occulted. Surprisingly, the Fermi Large
Area Telescope (LAT) detected >100 MeV gamma-rays for ∼30 minutes
with energies up to 3 GeV. The LAT emission centroid is consistent
with the RHESSI HXR source, but its uncertainty does not constrain the
source to be located there. The gamma-ray spectra can be adequately
described by bremsstrahlung radiation from relativistic electrons having
a relatively hard power-law (PL) spectrum with a high-energy exponential
cutoff, or by the decay of pions produced by accelerated protons and
ions with an isotropic pitch-angle distribution and a PL spectrum with
a number index of ∼3.8. We show that high optical depths rule out
the gamma-rays originating from the flare site and a high-corona trap
model requires very unusual conditions, so a scenario in which some
of the particles accelerated by the CME shock travel to the visible
side of the Sun to produce the observed gamma-rays may be at work.
Title: Numerical simulation of radio signal from extended air showers
Authors: Liu, Wei; Chen, Xuelei
Bibcode: 2015RAA....15..623L
Altcode: 2014arXiv1408.2234L
The burst of radio emission by an extensive air shower provides a
promising alternative for detecting ultra-high energy cosmic rays. We
have developed an independent numerical program to simulate these
radio signals. Our code is based on a microscopic treatment, with
both the geosynchrotron radiation and charge included. Here we give
the first presentation of our basic program and its results. When
the time-domain signals for different polarizations are computed,
we find that the pulses take on a bipolar pattern and the spectrum is
suppressed towards the lower frequencies. We investigate how showers at
different heights in the atmosphere contribute to the total signal, and
examine the signal strength and distribution at sites with different
elevations. We also study the signal from showers with different
inclination angles and azimuth directions. In all these cases we find
the charge excess effect is important. Supported by the National
Natural Science Foundation of China.
Title: Solar Flare Chromospheric Line Emission: Comparison Between
IBIS High-resolution Observations and Radiative Hydrodynamic
Simulations
Authors: Rubio da Costa, Fatima; Kleint, Lucia; Petrosian, Vahé;
Sainz Dalda, Alberto; Liu, Wei
Bibcode: 2015ApJ...804...56R
Altcode: 2015ApJ...804...56D; 2014arXiv1412.1815R
Solar flares involve impulsive energy release, which results in enhanced
radiation over a broad spectral range and a wide range of heights. In
particular, line emission from the chromosphere can provide critical
diagnostics of plasma heating processes. Thus, a direct comparison
between high-resolution spectroscopic observations and advanced
numerical modeling results could be extremely valuable, but has not
yet been attempted. In this paper, we present such a self-consistent
investigation of an M3.0 flare observed by the Dunn Solar Telescope’s
Interferometric Bi-dimensional Spectrometer (IBIS) on 2011 September 24
which we have modeled using the radiative hydrodynamic code RADYN. We
obtained images and spectra of the flaring region with IBIS in Hα
6563 Å and Ca ii 8542 Å, and with RHESSI in X-rays. The latter
observations were used to infer the non-thermal electron population,
which was passed to RADYN to simulate the atmospheric response to
electron collisional heating. We then synthesized spectral lines and
compared their shapes and intensities to those observed by IBIS and
found a general agreement. In particular, the synthetic Ca ii 8542
Å profile fits well to the observed profile, while the synthetic Hα
profile is fainter in the core than for the observation. This indicates
that Hα emission is more responsive to the non-thermal electron flux
than the Ca ii 8542 Å emission. We suggest that it is necessary to
refine the energy input and other processes to resolve this discrepancy.
Title: Simultaneous field-aligned currents at Swarm and Cluster
satellites
Authors: Dunlop, M. W.; Yang, J. -Y.; Yang, Y. -Y.; Xiong, C.; Lühr,
H.; Bogdanova, Y. V.; Shen, C.; Olsen, N.; Zhang, Q. -H.; Cao,
J. -B.; Fu, H. -S.; Liu, W. -L.; Carr, C. M.; Ritter, P.; Masson,
A.; Haagmans, R.
Bibcode: 2015GeoRL..42.3683D
Altcode:
We show for the first time, with direct, multispacecraft calculations
of electric current density, and other methods, matched signatures
of field-aligned currents (FACs) sampled simultaneously near the
ionosphere at low (~500 km altitude) orbit and in the magnetosphere at
medium (~2.5 RE altitude) orbits using a particular Swarm
and Cluster conjunction. The Cluster signatures are interpreted and
ordered through joint mapping of the ground/magnetospheric footprints
and estimation of the auroral zone boundaries (taken as indication
of the boundaries of Region 1 and Region 2 currents). We find clear
evidence of both small-scale and large-scale FACs and clear matching of
the behavior and structure of the large-scale currents at both Cluster
and Swarm. The methodology is made possible through the joint operations
of Cluster and Swarm, which contain, in the first several months of
Swarm operations, a number of close three-spacecraft configurations.
Title: Connecting the evolution and properties of CMEs to their low
coronal signatures. A modeling case study of the ‘simple’ Feb
13 2009 event
Authors: Downs, Cooper; Török, Tibor; Titov, Viacheslav; Liu, Wei;
Linker, Jon; Mikić, Zoran
Bibcode: 2015TESS....130401D
Altcode:
The early onset and and evolution of a CME is a process that features
an intimate coupling between the erupting flux-system and the
ambient corona. For this reason low coronal signatures that we often
observe in the EUV can be used to infer information on the physical
nature and evolution of CMEs. In this presentation we will discuss
a 3D thermodynamic MHD simulation of the Feb 13 2009 eruption,
which occurred from an isolated region during solar minimum and
produced well characterized EUV wave and transient coronal dimming
features. Using observations as a guide, we simulate the entire
evolution of the eruption and global corona, starting from the initial
stable configuration through onset and evolution to the post-eruptive
reconfiguration. With a particular focus on coronal dimmings, we
track how the connectivity of the erupting flux-rope evolves with
time and how this relates to corresponding dimmings in synthetic EUV
observables. We find that the appearance of the core dimming regions
and their migration over time can be related to when and where the
erupting rope reconnects with itself and the adjacent arcade. Other
aspects related to CME evolution, such as the generation of an EUV
wave and quasi-periodic fast-propagating waves are also discussed.
Title: Observations and Interpretation of Behind the Limb Solar
Flares Detected by Fermi-LAT and Other Instruments
Authors: Petrosian, Vahe; Omodei, Nicola; Pesce-Rollins, Melissa;
Rubio da Costa, Fatima; Liu, Wei
Bibcode: 2015TESS....120505P
Altcode:
The Fermi Large Area Telescope (LAT) is the most sensitive instrument
ever deployed in space for observing > 30 MeV gamma-rays. During the
past active period of the Sun the LAT has detected more than 40 flares
up to GeV energies some of which occur behind the limb as determined
by STEREO observations. We will present the observations on two such
flares with significant flux of > 100 MeV (and some indication of
1 to 10 MeV detected by Fermi-GBM) gamma-rays coming from the visible
disk while the flare and associated CMEs are initiated in active regions
tens of degrees behind the visible limb of the Sun. We will consider
acceleration of particles, their transport and radiative signatures, and
the transfer of these radiation in the solar atmosphere to distinguish
between (i) acceleration in the low corona, in a high corona trap,
and/or in the CME driven shock; (ii) between continuous and prompt
acceleration; and (iii) between electron bremsstrahlung and decay of
pions produced by accelerated ions.
Title: First High-resolution Spectroscopic Observations of an Erupting
Prominence Within a Coronal Mass Ejection by the Interface Region
Imaging Spectrograph (IRIS)
Authors: Liu, Wei; De Pontieu, Bart; Vial, Jean-Claude; Title, Alan
M.; Carlsson, Mats; Uitenbroek, Han; Okamoto, Takenori J.; Berger,
Thomas E.; Antolin, Patrick
Bibcode: 2015ApJ...803...85L
Altcode: 2015arXiv150204738L
Spectroscopic observations of prominence eruptions associated with
coronal mass ejections (CMEs), although relatively rare, can provide
valuable plasma and three-dimensional geometry diagnostics. We report
the first observations by the Interface Region Imaging Spectrograph
mission of a spectacular fast CME/prominence eruption associated with
an equivalent X1.6 flare on 2014 May 9. The maximum plane-of-sky and
Doppler velocities of the eruption are 1200 and 460 km s-1,
respectively. There are two eruption components separated by ∼200
km s-1 in Doppler velocity: a primary, bright component
and a secondary, faint component, suggesting a hollow, rather than
solid, cone-shaped distribution of material. The eruption involves
a left-handed helical structure undergoing counterclockwise (viewed
top-down) unwinding motion. There is a temporal evolution from upward
eruption to downward fallback with less-than-free-fall speeds and
decreasing nonthermal line widths. We find a wide range of Mg ii k/h
line intensity ratios (less than ∼2 expected for optically-thin
thermal emission): the lowest ever reported median value of 1.17
found in the fallback material, a comparably high value of 1.63 in
nearby coronal rain, and intermediate values of 1.53 and 1.41 in
the two eruption components. The fallback material exhibits a strong
(\gt 5σ ) linear correlation between the k/h ratio and the Doppler
velocity as well as the line intensity. We demonstrate that Doppler
dimming of scattered chromospheric emission by the erupted material
can potentially explain such characteristics.
Title: VizieR Online Data Catalog: HeI* in broad absorption line QSOs
(Liu+, 2015)
Authors: Liu, W. -J.; Zhou, H.; Ji, T.; Yuan, W.; Wang, T. -G.; Jian,
G.; Shi, X.; Zhang, S.; Jiang, P.; Shu, X.; Wang, H.; Wang, S. -F.;
Sun, L.; Yang, C.; Liu, B.; Zhao, W.
Bibcode: 2015yCat..22170011L
Altcode:
Neutral helium multiplets, HeI*λλ3189, 3889, 10830, are very
useful diagnostics for the geometry and physical conditions of the
absorbing gas in quasars. So far only a handful of HeI* detections
have been reported. Using a newly developed method, we detected the
HeI*λ3889 absorption line in 101 sources of a well-defined sample
of 285 MgII broad absorption line (BAL) quasars selected from SDSS
DR5. This has increased the number of HeI* BAL quasars by more than
one order of magnitude. We further detected HeI*λ3189 in 50% (52/101)
of the quasars in the sample. The detection fraction of HeI* BALs in
MgII BAL quasars is ~35% as a whole, and it increases dramatically
with increasing spectral signal-to-noise ratio (S/N), from ~18% at
S/N<=10 to ~93% at S/N>=35. This suggests that HeI* BALs could
be detected in most MgII LoBAL quasars, provided the spectra S/N is
high enough. Such a surprisingly high HeI* BAL fraction is actually
predicted from photoionization calculations based on a simple BAL
model. The result indicates that HeI* absorption lines can be used
to search for BAL quasars at low z, which cannot be identified by
ground-based optical spectroscopic surveys with commonly seen UV
absorption lines. Using HeI*λ3889, we discovered 19 BAL quasars at
z<0.3 from the available SDSS spectral database. The fraction of HeI*
BAL quasars is similar to that of LoBAL objects. (7 data files).
Title: Shedding new light on the Sun with the Fermi LAT
Authors: Omodei, N.; Petrosian, V.; Liu, W.; Rubio da Costa, F.;
Chen, Q.; Pesce-Rollins, M.; Grove, E.; Longo, F.
Bibcode: 2015arXiv150203895O
Altcode:
During its first six years of operation, the Fermi Large Area Telescope
(LAT) has detected >30 MeV gamma-ray emission from more than
40 solar flares, nearly a factor of 10 more than those detected by
EGRET. These include detections of impulsive and sustained emissions,
extending up to 20 hours in the case of the 2012 March 7 X-class
flares. We will present an overview of solar flare detections with
LAT, highlighting recent results and surprising features, including
the detection of >100 MeV emission associated with flares located
behind the limb. Such flares may shed new light on the relationship
between the sites of particle acceleration and gamma-ray emission.
Title: An Unobscured Type II Quasar Candidate: SDSS
J012032.19-005501.9
Authors: Li, Y.; Yuan, W.; Zhou, H. Y.; Komossa, S.; Ai, Y. L.; Liu,
W. J.; Boisvert, J. H.
Bibcode: 2015AJ....149...75L
Altcode: 2014arXiv1412.2776L
We report the finding of an unobscured type II active galactic nucleus
(AGN) candidate, SDSS J012032.19-005501.9, at a relatively high
redshift of 0.601, which shows a number of unusual properties. It
varies significantly on timescales of years, typical of type I AGNs,
and marginally on timescales of weeks. The color-magnitude relation
and the structure function are also consistent with that of type I
AGNs, which implies that its variability likely originates from the
black hole accretion system. However, no broad emission line (BEL) is
detected in the Sloan Digital Sky Survey spectrum, and the upper limit
of the equivalent width of the Hβ BEL is much less than that of type I
AGNs. These properties suggest that SDSS J012032.19-005501.9 may be an
unobscured quasar without intrinsically broad emission lines, namely,
an unobscured type II AGN or “true” type II AGN. Furthermore,
its continuum luminosity is at least one order of magnitude fainter
than the average value over the past century from the [O iii] emission
line. This indicates that SDSS J012032.19-005501.9 may be switching
off. Additional possible scenarios to explain this intriguing source
are also discussed. Future deep observations at multiwavelengths are
needed to reveal the nature of this peculiar and intriguing AGN.
Title: TeV cosmic-ray proton and helium spectra in the myriad model II
Authors: Liu, Wei; Salati, Pierre; Chen, Xuelei
Bibcode: 2015RAA....15...15L
Altcode: 2014arXiv1405.2835L
Recent observations show that the spectra of cosmic ray nuclei start to
harden above ~ 102 GeV, which contradicts the conventional
steady-state cosmic ray model. We had suggested that this anomaly
is due to the propagation effect of cosmic rays released from local
young cosmic ray sources; the total flux of cosmic rays should be
computed with the Myriad Model, where a contribution from sources
in the local catalog is added to the background. However, although
the hardening could be elegantly explained in this model, the model
parameters obtained from the fit are skewed toward a region with fast
diffusion and a low supernova rate in the Galaxy, in disagreement with
other observations. We further explore this model in order to set up
a concordant picture. Two possible improvements related to cosmic ray
sources are considered. First, instead of the usual axisymmetric disk
model, we examine a spiral model for the source distribution. Second,
for nearby and young sources which are necessary to explain the
hardening, we allow for an energy-dependent escape. We find that a
major improvement comes from incorporating an energy-dependent escape
time for local sources, and with both modifications not only are the
cosmic ray proton and helium anomalies resolved, but also the parameters
attain values in a reasonable range compatible with other analyses.
Title: Instant: An Innovative L5 Small Mission Concept for Coordinated
Science with Solar Orbiter and Solar Probe Plus
Authors: Lavraud, B.; Liu, Y. D.; Harrison, R. A.; Liu, W.;
Auchere, F.; Gan, W.; Lamy, P. L.; Xia, L.; Eastwood, J. P.;
Wimmer-Schweingruber, R. F.; Zong, Q.; Rochus, P.; Maksimovic, M.;
Temmer, M.; Escoubet, C. P.; Kilpua, E.; Rouillard, A. P.; Davies,
J. A.; Vial, J. C.; Gopalswamy, N.; Bale, S. D.; Li, G.; Howard,
T. A.; DeForest, C. E.
Bibcode: 2014AGUFMSH21B4109L
Altcode:
We will present both the science objectives and related instrumentation
of a small solar and heliospheric mission concept, INSTANT:
INvestigation of Solar-Terrestrial Activity aNd Transients. It will be
submitted as an opportunity to the upcoming ESA-China S-class mission
call later this year. This concept was conceived to allow innovative
measurements and unprecedented, early determination of key properties
of Earthbound CMEs from the L5 vantage point. Innovative measurements
will include magnetic field determination in the corona thanks to
Hanle measurement in Lyman-α and polarized heliospheric imaging
for accurate determination of CME trajectories. With complementary
in situ measurements, it will uniquely permit solar storm science,
solar storm surveillance, and synergy with Solar Orbiter and Solar
Probe Plus (the ESA-China S2 mission launch is planned in 2021).
Title: The Relation Between Large-Scale Coronal Propagating Fronts
and Type II Radio Bursts
Authors: Nitta, Nariaki V.; Liu, Wei; Gopalswamy, Nat; Yashiro, Seiji
Bibcode: 2014SoPh..289.4589N
Altcode: 2014arXiv1409.4754N
Large-scale, wave-like disturbances in extreme-ultraviolet (EUV) and
type II radio bursts are often associated with coronal mass ejections
(CMEs). Both phenomena may signify shock waves driven by CMEs. Taking
EUV full-disk images at an unprecedented cadence, the Atmospheric
Imaging Assembly (AIA) onboard the Solar Dynamics Observatory has
observed the so-called EIT waves or large-scale coronal propagating
fronts (LCPFs) from their early evolution, which coincides with the
period when most metric type II bursts occur. This article discusses the
relation of LCPFs as captured by AIA with metric type II bursts. We show
examples of type II bursts without a clear LCPF and fast LCPFs without
a type II burst. Part of the disconnect between the two phenomena may
be due to the difficulty in identifying them objectively. Furthermore,
it is possible that the individual LCPFs and type II bursts may reflect
different physical processes and external factors. In particular,
the type II bursts that start at low frequencies and high altitudes
tend to accompany an extended arc-shaped feature, which probably
represents the 3D structure of the CME and the shock wave around it,
and not just its near-surface track, which has usually been identified
with EIT waves. This feature expands and propagates toward and beyond
the limb. These events may be characterized by stretching of field
lines in the radial direction and may be distinct from other LCPFs,
which may be explained in terms of sudden lateral expansion of the
coronal volume. Neither LCPFs nor type II bursts by themselves serve
as necessary conditions for coronal shock waves, but these phenomena
may provide useful information on the early evolution of the shock
waves in 3D when both are clearly identified in eruptive events.
Title: Imaging and Spectroscopic Observations of Magnetic Reconnection
and Chromospheric Evaporation in a Solar Flare
Authors: Tian, Hui; Li, Gang; Reeves, Katharine K.; Raymond, John C.;
Guo, Fan; Liu, Wei; Chen, Bin; Murphy, Nicholas A.
Bibcode: 2014ApJ...797L..14T
Altcode: 2014arXiv1411.2301T
Magnetic reconnection is believed to be the dominant energy release
mechanism in solar flares. The standard flare model predicts both
downward and upward outflow plasmas with speeds close to the coronal
Alfvén speed. Yet, spectroscopic observations of such outflows,
especially the downflows, are extremely rare. With observations of
the newly launched Interface Region Imaging Spectrograph (IRIS), we
report the detection of a greatly redshifted (~125 km s-1
along the line of sight) Fe XXI 1354.08 Å emission line with a ~100 km
s-1 nonthermal width at the reconnection site of a flare. The
redshifted Fe XXI feature coincides spatially with the loop-top
X-ray source observed by RHESSI. We interpret this large redshift as
the signature of downward-moving reconnection outflow/hot retracting
loops. Imaging observations from both IRIS and the Atmospheric Imaging
Assembly (AIA) on board the Solar Dynamics Observatory also reveal
the eruption and reconnection processes. Fast downward-propagating
blobs along these loops are also found from cool emission lines (e.g.,
Si IV, O IV, C II, Mg II) and images of AIA and IRIS. Furthermore,
the entire Fe XXI line is blueshifted by ~260 km s-1 at
the loop footpoints, where the cool lines mentioned above all exhibit
obvious redshift, a result that is consistent with the scenario of
chromospheric evaporation induced by downward-propagating nonthermal
electrons from the reconnection site.
Title: Comparison between IBIS Observations and Radiative Transfer
Hydrodynamic Simulations of a Solar Flare
Authors: Rubio da Costa, F.; Kleint, L.; Liu, W.; Sainz Dalda, A.;
Petrosian, V.
Bibcode: 2014AGUFMSH13B4104R
Altcode:
High-resolution spectroscopic observations of solar flares are
rare but can provide valuable diagnostics. On September 24, 2011 an
M3.0 class flare was observed by the Interferometric BIdimensional
Spectropolarimeter (IBIS) in chromospheric Hα and CaII 8542 Å
lines and by the Reuven Ramaty High Energy Solar Spectroscopic Imager
(RHESSI) in X-rays. We fitted the RHESSI spectra at different times
with a power-law plus isothermal component. We then used the fitted
real-time spectral parameters of nonthermal electrons as the input to
the RADYN radiative hydrodynamic code (Carlsson et al, 1992, 1996;
Allred et al, 2005) to simulate the low-chromospheric response to
collisional heating by energetic electrons. We synthesized both the
Hα and CaII 8542 Å lines from the simulation results and compare
them with the IBIS observations. We discuss the constraints from this
comparison on particle acceleration mechanisms in solar flares.
Title: Coronal Extreme Ultraviolet (EUV) Waves and Their Seismological
Applications
Authors: Liu, W.; Ofman, L.
Bibcode: 2014AGUFMSH23C..01L
Altcode:
Magnetohydrodynamic (MHD) waves can be used as seismological tools
to probe the physical conditions of the solar corona, including its
magnetic field and plasma parameters. Recent high cadence and full-disk
imaging observations in extreme ultraviolet (EUV) by the Atmospheric
Imaging Assembly (AIA) onboard the Solar Dynamics Observatory (SDO)
have opened a new chapter in understanding these waves and utilizing
them for coronal seismology. We will review such new observations,
focusing on two intimately related phenomena - global EUV waves
(so-called "EIT waves") associated with coronal mass ejections (CMEs)
and quasi-periodic, fast-mode magnetosonic wave trains associated
with flares: (1) The generation and propagation of global EUV waves
and their interaction with coronal structures, e.g., reflection and
refraction, can provide diagnostics for the global corona in which they
propagate, such as mapping the spatial distribution of the wave phase
speed and thus the magnetic field strength. (2) AIA-detected fast-mode
wave trains are closely correlated with flare pulsations seen from
radio to hard X-rays and propagate at typically 500-2000 km/s along
funnel-shaped waveguides often located within CME bubbles. They can
provide diagnostics for flare energy release mechanisms and the local
corona around the flaring active region. We will discuss the roles
of such waves in energy transport within the solar atmosphere and in
their associated CME/flare eruptions.
Title: First High-resolution Spectroscopic Observations by IRIS
of a Fast, Helical Prominence Eruption Associated with a Coronal
Mass Ejection
Authors: Liu, W.; De Pontieu, B.; Okamoto, T. J.; Vial, J. C.; Title,
A. M.; Antolin, P.; Berger, T. E.; Uitenbroek, H.
Bibcode: 2014AGUFMSH11D..04L
Altcode:
High-resolution spectroscopic observations of prominence eruptions and
associated coronal mass ejections (CMEs) are rare but can provide
valuable plasma and energy diagnostics. New opportunities have
recently become available with the advent of the Interface Region
Imaging Spectrograph (IRIS) mission equipped with high resolution of
0.33-0.4 arcsec in space and 1 km/s in velocity, together with the
Hinode Solar Optical Telescope of 0.2 arcsec spatial resolution. We
report the first result of joint IRIS-Hinode observations of a
spectacular prominence eruption occurring on 2014-May-09. IRIS
detected a maximum redshift of 450 km/s, which, combined with the
plane-of-sky speed of 800 km/s, gives a large velocity vector of 920
km/s at 30 degrees from the sky plane. This direction agrees with the
source location at 30 degrees behind the limb observed by STEREO-A
and indicates a nearly vertical ejection. We found two branches of
redshifts separated by 200 km/s appearing in all strong lines at
chromospheric to transition-region temperatures, including Mg II k/h,
C II, and Si IV, suggesting a hollow, rather than solid, cone in the
velocity space of the ejected material. Opposite blue- and redshifts
on the two sides of the prominence exhibit corkscrew variations both
in space and time, suggestive of unwinding rotations of a left-handed
helical flux rope. Some erupted material returns as nearly streamline
flows, exhibiting distinctly narrow line widths (~10 km/s), about
50% of those of the nearby coronal rain at the apexes of coronal
loops, where the rain material is initially formed out of cooling
condensation. We estimate the mass and kinetic energy of the ejected
and returning material and compare them with those of the associated
CME. We will discuss the implications of these observations for CME
initiation mechanisms.
Title: Whistler-mode waves inside flux pileup region: Structured
or unstructured?
Authors: Fu, H. S.; Cao, J. B.; Cully, C. M.; Khotyaintsev,
Y. V.; Vaivads, A.; Angelopoulos, V.; Zong, Q. -G.; Santolík, O.;
Macúšová, E.; André, M.; Liu, W. L.; Lu, H. Y.; Zhou, M.; Huang,
S. Y.; Zhima, Z.
Bibcode: 2014JGRA..119.9089F
Altcode:
During reconnection, a flux pileup region (FPR) is formed behind a
dipolarization front in an outflow jet. Inside the FPR, the magnetic
field magnitude and Bz component increase and the whistler-mode waves
are observed frequently. As the FPR convects toward the Earth during
substorms, it is obstructed by the dipolar geomagnetic field to form
a near-Earth FPR. Unlike the structureless emissions inside the tail
FPR, we find that the whistler-mode waves inside the near-Earth FPR
can exhibit a discrete structure similar to chorus. Both upper band
and lower band chorus are observed, with the upper band having a
larger propagation angle (and smaller wave amplitude) than the lower
band. Most chorus elements we observed are "rising-tone" type, but
some are "falling-tone" type. We notice that the rising-tone chorus
can evolve into falling-tone chorus within <3 s. One of the factors
that may explain why the waves are unstructured inside the tail FPR but
become discrete inside the near-Earth FPR is the spatial inhomogeneity
of magnetic field: we find that such inhomogeneity is small inside
the near-Earth FPR but large inside the tail FPR.
Title: Multi-fluid Model of a Sun-grazing Comet in the Rapidly
Ionizing, Magnetized Low Corona
Authors: Jia, Y. -D.; Russell, C. T.; Liu, W.; Shou, Y. S.
Bibcode: 2014ApJ...796...42J
Altcode:
Two Sun-grazing comets were recently imaged in the low solar corona
by space telescopes in unprecedented detail, revealing a wide range
of new phenomena. This sparked growing interest in the interaction of
comets with the coronal plasma and magnetic field and their diagnostic
potential as solar probes. However, interpretation of such rich
observational data requires profound understanding of relevant physical
processes in an unexplored regime. Here advanced numerical modeling
can provide critical clues. To this end, we present a prototype,
multi-fluid, magnetohydrodynamic model of a steady-state comet in
the low solar corona. These simulation results are compared with
previously modeled comets in the solar wind environment. By inspecting
their projection and column densities, we find a dominance of O6
+ ions in the cometary tail, which can explain the observed
extreme ultraviolet emission. The tail is found to be comparable to
recent EUV images of these comets. In addition, the comet tail appears
wider when the observer's line of sight is perpendicular rather than
parallel to the local magnetic field. This is opposite to the trend
in the interplanetary space permeated in the solar wind, because the
ratio between dynamic pressure and magnetic pressure is an order of
magnitude smaller than at 1 AU. On the other hand, we find that iron
ions in the comet head build up to a density comparable to that of
oxygen ions, but are unlikely to form a visible tail because of the
shorter mean free paths of the neutrals.
Title: Evidence of nonthermal particles in coronal loops heated
impulsively by nanoflares
Authors: Testa, P.; De Pontieu, B.; Allred, J.; Carlsson, M.; Reale,
F.; Daw, A.; Hansteen, V.; Martinez-Sykora, J.; Liu, W.; DeLuca, E. E.;
Golub, L.; McKillop, S.; Reeves, K.; Saar, S.; Tian, H.; Lemen, J.;
Title, A.; Boerner, P.; Hurlburt, N.; Tarbell, T. D.; Wuelser, J. P.;
Kleint, L.; Kankelborg, C.; Jaeggli, S.
Bibcode: 2014Sci...346B.315T
Altcode: 2014arXiv1410.6130T
The physical processes causing energy exchange between the Sun’s
hot corona and its cool lower atmosphere remain poorly understood. The
chromosphere and transition region (TR) form an interface region between
the surface and the corona that is highly sensitive to the coronal
heating mechanism. High-resolution observations with the Interface
Region Imaging Spectrograph (IRIS) reveal rapid variability (~20 to
60 seconds) of intensity and velocity on small spatial scales (≲500
kilometers) at the footpoints of hot and dynamic coronal loops. The
observations are consistent with numerical simulations of heating by
beams of nonthermal electrons, which are generated in small impulsive
(≲30 seconds) heating events called “coronal nanoflares.” The
accelerated electrons deposit a sizable fraction of their energy
(≲1025 erg) in the chromosphere and TR. Our analysis
provides tight constraints on the properties of such electron beams
and new diagnostics for their presence in the nonflaring corona.
Title: Linear weakening of the AMOC in response to receding glacial
ice sheets in CCSM3
Authors: Zhu, Jiang; Liu, Zhengyu; Zhang, Xu; Eisenman, Ian; Liu, Wei
Bibcode: 2014GeoRL..41.6252Z
Altcode:
The transient response of the Atlantic Meridional Overturning
Circulation (AMOC) to a deglacial ice sheet retreat is studied using
the Community Climate System Model version 3 (CCSM3), with a focus on
orographic effects rather than meltwater discharge. It is found that
the AMOC weakens significantly (41%) in response to the deglacial
ice sheet retreat. The AMOC weakening follows the decrease of the
Northern Hemisphere ice sheet volume linearly, with no evidence of
abrupt thresholds. A wind-driven mechanism is proposed to explain the
weakening of the AMOC: lowering the Northern Hemisphere ice sheets
induces a northward shift of the westerlies, which causes a rapid
eastward sea ice transport and expanded sea ice cover over the subpolar
North Atlantic; this expanded sea ice insulates the ocean from heat
loss and leads to suppressed deep convection and a weakened AMOC. A
sea ice-ocean positive feedback could be further established between
the AMOC decrease and sea ice expansion.
Title: Hawking Radiations from an Arbitrarily Accelerating Kerr
Black Hole
Authors: Yang, Xue-Jun; Zhang, Yan-Nv; Liu, Wei
Bibcode: 2014JApA...35..559Y
Altcode: 2014JApA..tmp...38Y
The Hawking radiation from an arbitrarily accelerating Kerr black hole
is calculated by using a new tortoise coordinate transformation and
the improved Damour-Ruffini method.
Title: γ-Rays Radiation of High Redshift Fermi Blazars
Authors: Liu, W. G.; Fu, S. H.; Zhang, X.; Ma, L.; Li, Y. B.; Xiong,
D. R.
Bibcode: 2014JApA...35..349L
Altcode: 2014JApA..tmp...65L
Based on the 31 high redshift ( z > 2) Flat Spectral Radio Quasars
(FSRQs), which is from the second Fermi-LAT AGNs catalogue (2LAC),
we studied the correlation between flux densities ( F R,
F K, F γ) in the radio, infrared and γ-ray wave bands. We
found that there is a significant positive correlation between F
γ and F R, and a weak anticorrelation between F
γ and FK in the average state. For high redshift
blazars, we argue that the seed photon of γ-ray emission mainly comes
from the jet itself and partially from the dusty torus.
Title: Hawking Temperature of an Arbitrarily Accelerating Black Hole
Authors: Pan, Wei-Zhen; Liu, Wei
Bibcode: 2014JApA...35..533P
Altcode: 2014JApA..tmp...94P
Hawking temperature of an arbitrarily accelerating black hole
with electric and magnetic charges are obtained based on the
Klein-Gordon equation with a correct-dimension new tortoise coordinate
transformation.
Title: Advances in Observing Various Coronal EUV Waves in the SDO
Era and Their Seismological Applications (Invited Review)
Authors: Liu, Wei; Ofman, Leon
Bibcode: 2014SoPh..289.3233L
Altcode: 2014SoPh..tmp...67L; 2014arXiv1404.0670L
Global extreme-ultraviolet (EUV) waves are spectacular traveling
disturbances in the solar corona associated with energetic eruptions
such as coronal mass ejections (CMEs) and flares. Over the past
15 years, observations from three generations of space-borne EUV
telescopes have shaped our understanding of this phenomenon and at
the same time led to controversy about its physical nature. Since its
launch in 2010, the Atmospheric Imaging Assembly (AIA) onboard the
Solar Dynamics Observatory (SDO) has observed more than 210 global
EUV waves in exquisite detail, thanks to its high spatio-temporal
resolution and full-disk, wide-temperature coverage. A combination of
statistical analysis of this large sample, more than 30 detailed case
studies, and data-driven MHD modeling, has been leading their physical
interpretations to a convergence, favoring a bimodal composition
of an outer, fast-mode magnetosonic wave component and an inner,
non-wave CME component. Adding to this multifaceted picture, AIA has
also discovered new EUV wave and wave-like phenomena associated with
various eruptions, including quasi-periodic fast propagating (QFP)
wave trains, magnetic Kelvin-Helmholtz instabilities (KHI) in the
corona and associated nonlinear waves, and a variety of mini-EUV
waves. Seismological applications using such waves are now being
actively pursued, especially for the global corona. We review such
advances in EUV wave research focusing on recent SDO/AIA observations,
their seismological applications, related data-analysis techniques,
and numerical and analytical models.
Title: Three-dimensional lunar wake reconstructed from ARTEMIS data
Authors: Zhang, H.; Khurana, K. K.; Kivelson, M. G.; Angelopoulos, V.;
Wan, W. X.; Liu, L. B.; Zong, Q. -G.; Pu, Z. Y.; Shi, Q. Q.; Liu, W. L.
Bibcode: 2014JGRA..119.5220Z
Altcode:
Data from the two-spacecraft Acceleration, Reconnection, Turbulence
and Electrodynamics of the Moon's Interaction with the Sun mission
to the Moon have been exploited to characterize the lunar wake
with unprecedented fidelity. The differences between measurements
made by a spacecraft in the solar wind very near the Moon and
concurrent measurements made by a second spacecraft in the near
lunar wake are small but systematic. They enabled us to establish the
perturbations of plasma density, temperature, thermal, magnetic and
total pressure, field, and flow downstream of the Moon to distances of
12 lunar radii (RM). The wake disturbances are initiated
immediately behind the Moon by the diamagnetic currents at the lunar
terminator. Rarefaction waves propagate outward at fast MHD wave
velocities. Beyond ~6.5 RM, all plasma and field parameters
are poorly structured which suggests the presence of instabilities
excited by counter-streaming particles. Inward flowing plasma
accelerated through pressure gradient force and ambipolar electric
field compresses the magnetic field and leads to continuous increase in
magnitude of magnetic perturbations. Besides the downstream distance,
the field perturbation magnitude is also a function of the solar wind
ion beta and the angle between the solar wind and the interplanetary
magnetic field (IMF). Both ion and electron temperatures increase
as a consequence of an energy dispersion effect, whose explanation
requires fully kinetic models. Downstream of the Moon, the IMF field
lines are observed to bulge toward the Moon, which is unexpected and
may be caused by a plasma pressure gradient force or/and the pickup
of heavy charged dust grains behind the Moon.
Title: Thermochemical sulphate reduction (TSR) versus maturation
and their effects on hydrogen stable isotopes of very dry alkane gases
Authors: Liu, Q. Y.; Worden, R. H.; Jin, Z. J.; Liu, W. H.; Li, J.;
Gao, B.; Zhang, D. W.; Hu, A. P.; Yang, C.
Bibcode: 2014GeCoA.137..208L
Altcode:
Here we report the first study of the effect of thermochemical sulphate
reduction (TSR) on the hydrogen isotopes of natural gas. Variably sour
(H2S-bearing) and very dry (>97% methane) gas samples from
Lower Triassic, Permian and Carboniferous marine carbonate reservoirs
in the Sichuan Basin, China, have been analysed. All gases seem to have
been sourced from mature marine kerogen and contain H2S that
resulted from TSR. The Carboniferous samples are largely unaffected by
TSR and were used to assess the effects of normal thermal maturation
processes on the carbon and hydrogen isotopes of methane and ethane as
a function of gas dryness (a proxy for thermal maturity). Maturation
led to heavier carbon isotopes of methane and ethane and hydrogen
isotopes of ethane; in contrast methane hydrogen isotopes seem to have
little systematic variation with increasing maturity. TSR did not have
a systematic effect on the hydrogen isotopes of methane, although
the spread of values diminished (ending up at a constant -120‰)
as TSR proceeded. This was possibly due to the partial thermochemical
sulphate reduction of ethane adding isotopically light methane and thus
offsetting the Rayleigh fractionation effects of TSR of methane. In
contrast, hydrogen isotopes of ethane became much heavier as TSR
proceeded, to values greater than those for samples only influenced
by maturation. Under some circumstances, the effects of TSR can be
identified and discerned from the effects of normal thermal maturation
by plotting the difference between the carbon isotope compositions of
methane and ethane and the difference between the hydrogen isotope
compositions of methane and ethane. Do the hydrogen isotope
ratios of alkane gases systematically vary as a function of dryness
or sourness? Do the hydrogen isotope ratios of alkane gases from
the Carboniferous, Permian and Lower Triassic dry gas reservoirs help
reveal the maturity and/or extent of TSR in the Sichuan Basin? Is it possible to separate and discriminate the effects of TSR and
non-TSR processes on alkane hydrogen isotopes in dry gas accumulations?
Title: Magnetic braking of Ap/Bp stars: an alternative formation
mechanism of compact intermediate-mass binary pulsars
Authors: Liu, Wei-Min; Chen, Wen-Cong
Bibcode: 2014MNRAS.441.3615L
Altcode: 2014arXiv1405.0691L
It is difficult for the intermediate-mass X-ray binaries (IMXBs)
evolutionary channel to form intermediate-mass binary pulsars
(IMBPs) with a short orbital period (less than 3 d) via stable mass
transfer. The main reason is that the magnetic braking mechanisms
are generally thought not to work for donor stars with a mass of
greater than 1.5 M⊙ in the canonical model. However,
some intermediate-mass stars have anomalously strong magnetic fields
(about 100-10 000 G), i.e. so-called Ap or Bp stars. With the coupling
between the magnetic field and the irradiation-driven wind from the
surface of Ap/Bp stars, a plausible magnetic braking mechanism should
be expected. In this work, we attempt to investigate if IMXBs with
Ap/Bp stars can produce IMBPs with a short orbital period (less than
3 d) by such an anomalous magnetic braking mechanism. Using a stellar
evolution code, we have simulated the evolution of a large number of
IMXBs consisting of a neutron star (NS) and an Ap/Bp star. For the spin
evolution of the NS, we consider the accretion torque, the propeller
torque and the spin-down torque caused by the interaction between the
magnetic field and the accretion disc. The calculated results show that,
employing anomalous magnetic braking of Ap/Bp stars, IMXBs can evolve
into compact IMBPs with short orbital periods of less than 3 d. However,
there exists significant discrepancy between the spin periods of IMBPs
in our simulated results and those observed.
Title: The Rayleigh-Taylor Instability and the role of Prominences
in the Chromosphere-Corona Mass Cycle
Authors: Berger, Thomas; Liu, Wei; Hillier, Andrew; Scullion, Eamon;
Low, Boon Chye
Bibcode: 2014AAS...22421201B
Altcode:
We review recent results in the study of so-called "prominence
bubbles", a buoyant instability discovered in quiescent solar
prominences by the Hinode/SOT instrument in 2007. Analysis of the
plasma flows along the boundary of the bubbles indicates that shear
flows leading to Kelvin-Helmholtz instability waves can develop into
the seed perturbations triggering the Rayleigh-Taylor instability. The
non-linear phase of the RT instability leads to the formation of large
turbulent plumes that transport the bubble plasma (and presumably
magnetic flux) into the overlying coronal flux rope. We propose that
the upward turbulent transport of hot bubble plasma and the downflows
of cooler chromospheric plasma in the prominence are related aspects
of a large-scale "chromosphere-corona mass cycle" in which hot plasma
and magnetic flux and helicity from the chromosphere are transported
upwards while the cooler prominence plasma downflows, which decouple
from the magnetic field they are originally frozen-into, represent
the condensation return flows of the cycle. This cycling enables a
mechanism by which magnetic flux and helicity build up in the coronal
flux rope while mass drains out of the flux rope, eventually triggering
a "loss of confinement" eruption in the form of a CME.
Title: Fermi Detection of Gamma-ray Emission from a Behind-the-limb
M1.5 Flare on 2013 October 11
Authors: Pesce-Rollins, Melissa; Omodei, Nicola; Petrosian, Vahe;
Liu, Wei; Chen, Qingrong; Rubio Da Costa, Fatima
Bibcode: 2014shin.confE..91P
Altcode:
On 2013 October 11 an M1.5 class solar flare erupted from the NOAA
active region 11868, which was then behind the solar limb. RHESSI images
reveal hard X-ray emission well above the limb, most likely from the
top of the flare loop whose footpoints were occulted. Surprisingly the
Fermi Large Area Telescope (LAT) detected gamma-rays up to 3 GeV for
30 minutes from this flare, making it the first behind-the-limb flare
observed by Fermi. The LAT gamma-ray emission centroid is consistent
with the vicinity of the RHESSI hard X-ray source. The gamma-ray
spectra can be adequately described by a power law with a high-energy
exponential cutoff, or as a result of the decay of pions produced by
accelerated protons and ions with an isotropic pitch angle distribution
and a power-law energy spectrum. The required proton spectrum would
have a number index of 3.8. STEREO-B detected enhanced electron,
proton, and other ion fluxes from this flare. We present the Fermi and
RHESSI observations together with STEREO and SDO data to explore the
various emission scenarios of this behind-the-limb flare, as well as
the possible correlation with the SEPs.
Title: Evidence of Magnetic Reconnection Involving Partially Ionized
Coronal Rain near Null Points Observed by SDO/AIA and IRIS
Authors: Liu, Wei; Antolin, Patrick; Sun, Xudong; Berger, Thomas E.
Bibcode: 2014shin.confE..50L
Altcode:
Coronal rain is cool, partially ionized material formed in the hot,
fully ionized corona. We report a newly discovered class of coronal
rain formed near cusp-shaped portions of coronal loops, indicative
of topological null points. We present evidence of cross-field flows
associated with magnetic reconnection near such null points from
SDO/AIA and IRIS observations, investigate the responsible magnetic
environment, and infer clues to where and when catastrophic cooling
take place to produce coronal rain. We also discuss the implications
of such a cooling process for the enigmatic coronal heating mechanisms
(e.g., Antolin et al. 2010) and compare transient coronal rain and
persistent prominence downflows.
Title: IRIS Observations of Coronal Rain and Prominences: Return
Flows of the Chromosphere-Corona Mass Cycle
Authors: Liu, Wei; Berger, Thomas; Antolin, Patrick; Schrijver, Karel
Bibcode: 2014AAS...22431303L
Altcode:
It has recently been recognized that a mass cycle (e.g., Berger
et al. 2011; McIntosh et al. 2012) between the hot, tenuous solar
corona and the cool, dense chromosphere underneath it plays an
important role in the mass budget and dynamic evolution of the solar
atmosphere. Although the corona ultimately loses mass through the solar
wind and coronal mass ejections, a fraction of its mass returns to the
chromosphere in coronal rain, downflows of prominences, and other as-yet
unidentified processes. We present here analysis of joint observations
of IRIS, SDO/AIA, and Hinode/SOT of such phenomena. By utilizing the
wide temperature coverage (logT: 4 - 7) provided by these instruments
combined, we track the coronal cooling sequence (e.g., Schrijver 2001;
Liu et al. 2012; Berger et al. 2012) leading to the formation of such
material at transition region or chromospheric temperatures (logT: 4 -
5) in the million-degree corona. We compare the cooling times with those
expected from the radiative cooling instability. We also measure the
kinematics and densities of such downflows and infer their mass fluxes,
which are compared to the upward mass fluxes into the corona, e.g.,
those associated with spicules and flux emergence. Special attention is
paid to coronal rain formed near cusp-shaped portions of coronal loops,
funnel-shaped prominences at dips of coronal loops, and their respective
magnetic environments. With the information about where and when such
catastrophic cooling events take place, we discuss the implications for
the enigmatic coronal heating mechanisms (e.g., Antolin et al. 2010).
Title: Solar wind pressure pulse-driven magnetospheric vortices and
their global consequences
Authors: Shi, Q. Q.; Hartinger, M. D.; Angelopoulos, V.; Tian, A. M.;
Fu, S. Y.; Zong, Q. -G.; Weygand, J. M.; Raeder, J.; Pu, Z. Y.; Zhou,
X. Z.; Dunlop, M. W.; Liu, W. L.; Zhang, H.; Yao, Z. H.; Shen, X. C.
Bibcode: 2014JGRA..119.4274S
Altcode:
We report the in situ observation of a plasma vortex induced by a solar
wind dynamic pressure enhancement in the nightside plasma sheet using
multipoint measurements from Time History of Events and Macroscale
Interactions during Substorms (THEMIS) satellites. The vortex has
a scale of 5-10 Re and propagates several Re downtail, expanding
while propagating. The features of the vortex are consistent with the
prediction of the Sibeck (1990) model, and the vortex can penetrate
deep ( 8 Re) in the dawn-dusk direction and couple to field line
oscillations. Global magnetohydrodynamics simulations are carried out,
and it is found that the simulation and observations are consistent with
each other. Data from THEMIS ground magnetometer stations indicate a
poleward propagating vortex in the ionosphere, with a rotational sense
consistent with the existence of the vortex observed in the magnetotail.
Title: Height-dependent Refraction of A Global EUV Wave and Its
Associated Sympathetic Eruptions
Authors: Liu, Wei; Ofman, Leon; Downs, Cooper; Schrijver, Karel
Bibcode: 2014AAS...22421814L
Altcode:
The height dependence of global extreme-ultraviolet (EUV) waves in
the solar corona, especially of their wave-like behaviors such as
transmission and reflection, is critical to understanding their physical
nature. Prior observations of such behaviors, when detected on the solar
disk, were compromised because height-dependent information is lost
due to the line-of-sight projection from a top-down view. We report a
global EUV wave on the limb observed by SDO/AIA from a side-view that
evidently shows height-dependent transmission and refraction. As the
wave travels through an active region, the orientation of the low-corona
wave front changes from a forward inclination toward the solar surface
to a backward inclination. This indicates that the EUV wave speed
is lower at higher altitudes, which is expected because of the rapid
drop with height of the Alfven and fast-mode speeds in active regions,
as predicted by MHD models. When traveling into the active region,
the EUV wave speed in the low corona increases from ~600 km/s to ~900
km/s. In addition, in the neighborhood of the active region, sympathetic
eruptions of local coronal structures take place sequentially upon
the wave impact and may appear as wave reflection. Understanding
propagation behaviors of global EUV waves brings us one step closer
to fully utilizing them for seismological diagnostics of the global
corona, such as mapping the spatial distribution of the Alfven speed
and magnetic field strength.
Title: Fermi Detection of Gamma-ray Emission from a Behind-the-limb
M1.5 Flare on 2013 October 11
Authors: Pesce-Rollins, Melissa; Omodei, Nicola; Petrosian, Vahe;
Liu, Wei; Chen, Qingrong; Rubio Da Costa, Fatima
Bibcode: 2014AAS...22441404P
Altcode:
On 2013 October 11 an M1.5 class solar flare erupted from the NOAA
active region 11868, which was then behind the solar limb. RHESSI images
reveal hard X-ray emission well above the limb, most likely from the
top of the flare loop whose footpoints were occulted. Surprisingly
the Fermi Large Area Telescope (LAT) detected gamma-rays up to 3 GeV
for ~30 minutes from this flare, making it the first behind-the-limb
flare observed by Fermi. The LAT gamma-ray emission centroid is
consistent with the vicinity of the RHESSI hard X-ray source. The
gamma-ray spectra can be adequately described by a power law with a
high-energy exponential cutoff, or as a result of the decay of pions
produced by accelerated protons and ions with an isotropic pitch angle
distribution and a power-law energy spectrum. The required proton
spectrum would have a number index of ~3.8. We present the Fermi and
RHESSI observations together with STEREO and SDO data to explore the
various emission scenarios of this behind-the-limb flare.
Title: Quasi-periodic Fast-mode Magnetosonic Wave Trains Detected
by SDO/AIA and Their Correlation with Quasi-period Flare Pulsations
Authors: Liu, Wei; Ofman, Leon; Fleishman, Gregory; Downs, Cooper
Bibcode: 2014shin.confE.157L
Altcode:
Quasi-periodic fast propagating wave trains (QFPs; Liu et al. 2011,
2012) are a new phenomenon recently discovered in extreme ultraviolet
(EUV) by the Atmospheric Imaging Assembly (AIA) onboard the Solar
Dynamics Observatory (SDO). They are fast-mode magnetosonic waves,
closely related to quasi-periodic pulsations of solar flares observed
from radio to hard X-rays. QFPs usually originate from a flare and
propagate at typically 500-2000 km/s within a funnel-shaped waveguide
located inside a CME bubble. QFPs can potentially be used for coronal
seismological diagnostics and provide critical clues to flare energy
release and particle acceleration processes. We will present recent
observational and numerical results of QFPs and compare them with
quasi-periodic flare pulsations.
Title: Hybrid Kinetic and Radiative Hydrodynamic Simulations of
Solar Flares and Comparison With Multiwavelength Observations
Authors: Rubio Da Costa, Fatima; Petrosian, Vahe; Liu, Wei; Carlsson,
Mats; Kleint, Lucia
Bibcode: 2014AAS...22440906R
Altcode:
We present a unified simulation which combines two physical processes:
how the particles are accelerated and the energy is transported along
a coronal loop, and how the atmosphere responds. The “flare”
code from Stanford University (Petrosian et al, 2001) models the
stochastic acceleration and transport of particles and radiation of
solar flares. It includes pitch angle diffusion and energy loss, and
computes collisional heating to the background plasma and bremsstrahlung
emission along the loop. The radiative hydrodynamic RADYN Code
(Carlsson et al, 1992, 1996; Allred et al, 2005) computes the energy
transport by the injected non-thermal electrons at the top of a 1D
coronal loop. Recently, we have combined the two codes by updating the
non-thermal heating in the RADYN code from the "flare" code, allowing us
to develop a self-consistent simulation. In addition, we can now model
more realistically the multi-wavelength emission of solar flares and
compare it with observations, e.g., at optical wavelengths from IBIS at
the Dunn Solar Telescope and in X-rays from RHESSI. The high resolution
UV observations from the recently launched IRIS imaging spectrograph
will be particularly useful in this regard. These will allow us to
compare numerically modeled and observed emissions of solar flares in
several lines using more robust simulations than possible before.
Title: Phase transition and elasticity of enstatite under pressure
from experiments and first-principles studies
Authors: Li, Baosheng; Kung, Jennifer; Liu, Wei; Liebermann, Robert C.
Bibcode: 2014PEPI..228...63L
Altcode:
We have investigated the thermodynamic stability, crystal structure,
elastic constants, and sound velocities of MgSiO3-enstatite
using data from X-ray diffraction and ultrasonic measurements up to
16.8 GPa and first-principles calculations up to 30 GPa. The calculated
enthalpies provide theoretical support for the phase transition from
Pbca to P21/c between 9 and 14 GPa previously observed
in natural orthoensatite and MgSiO3 enstatite. A density
increase of 1.4-1.5% for the Pbca → P21/c transition is
obtained from both first-principles and experimental studies. Elastic
constants of Pbca, P21/c, C2/c, P21ca and Pbca-II
are all calculated, and a softening in the shear constant C55
is predicted for Pbca and Pbca-II phases. C55 of Pbca
is found to be closely correlated with the A-site SiO4
tetrahedra chain angle while C44 and C66 are
correlated with the B-site chain angle. Pbca, P21/c and C2/c
all exhibit similar volumetric compressibilities at all pressures. The
calculated velocities of the P21/c phase at 12 GPa are equal
to those of Pbca for P and 1.3% higher for S waves. The experimentally
observed P and S wave velocity anomalies can be qualitatively described
by the transformation from Pbca to P21/c; however, the
magnitudes of the velocity decreases between 10 and 14 GPa remain to be
verified by future single crystal data or polycrystalline measurements
at high pressures. The predicted velocity jumps of 2.8% and 4.5% for P
and S waves, respectively, between Pbca and C2/c in the pressure range
of 5-12 GPa are in excellent agreement with the values of ∼3(1)%
and ∼5(1)% obtained from the directly measured data, thereby making
it a plausible candidate for the seismic X-discontinuity at depths of
250-300 km in the Earth’s upper mantle.
Title: Mysterious abrupt carbon-14 increase in coral contributed by
a comet
Authors: Liu, Yi; Zhang, Zhao-Feng; Peng, Zi-Cheng; Ling, Ming-Xing;
Shen, Chuan-Chou; Liu, Wei-Guo; Sun, Xiao-Chun; Shen, Cheng-De; Liu,
Ke-Xin; Sun, Weidong
Bibcode: 2014NatSR...4E3728L
Altcode:
A large and sudden increase in radiocarbon (14C) around AD
773 are documented in coral skeletons from the South China Sea. The
14C increased by ~ 15‰ during winter, and remain elevated
for more than 4 months, then increased and dropped down within two
months, forming a spike of 45‰ high in late spring, followed by two
smaller spikes. The 14C anomalies coincide with an historic
comet collision with the Earth's atmosphere on 17 January AD 773. Comas
are known to have percent-levels of nitrogen by weight, and are exposed
to cosmic radiation in space. Hence they may be expected to contain
highly elevated 14C/12C ratios, as compared to
the Earth's atmosphere. The significant input of 14C by
comets may have contributed to the fluctuation of 14C in the
atmosphere throughout the Earth's history, which should be considered
carefully to better constrain the cosmic ray fluctuation.
Title: Spectroscopic factors for low-lying N16 levels and the
astrophysical N15(n ,γ)N16 reaction rate
Authors: Guo, B.; Li, Z. H.; Li, Y. J.; Su, J.; Pang, D. Y.; Yan,
S. Q.; Wu, Z. D.; Li, E. T.; Bai, X. X.; Du, X. C.; Fan, Q. W.; Gan,
L.; He, J. J.; Jin, S. J.; Jing, L.; Li, L.; Li, Z. C.; Lian, G.;
Liu, J. C.; Shen, Y. P.; Wang, Y. B.; Yu, X. Q.; Zeng, S.; Zhang,
L. Y.; Zhang, W. J.; Liu, W. P.
Bibcode: 2014PhRvC..89a2801G
Altcode: 2014arXiv1401.0067G
Background: Fluorine is a key element for nucleosynthetic studies
since it is extremely sensitive to the physical conditions within
stars. The astrophysical site to produce fluorine is suggested to
be asymptotic giant branch stars. In these stars the N15(n,γ)N16
reaction could affect the abundance of fluorine by competing with
N15(α ,γ)F19. Purpose: The N15(n ,γ)N16 reaction rate depends
directly on the neutron spectroscopic factors of the low-lying states
in N16. Shell model calculations and two previous measurements of the
(d ,p) reaction yielded the spectroscopic factors with a discrepancy
by a factor of ∼2. The present work aims to explore these neutron
spectroscopic factors through an independent transfer reaction
and to determine the stellar rate of the N15(n,γ)N16 reaction. Methods: The angular distributions of the N15(Li7,Li6)N16 reaction
populating the ground state and the first three excited states in N16
are measured using a Q3D magnetic spectrograph and are used to derive
the spectroscopic factors of these states based on distorted wave Born
approximation analysis. Results: The spectroscopic factors of
these four states are extracted to be 0.96 ± 0.09, 0.69 ± 0.09, 0.84
± 0.08, and 0.65 ± 0.08, respectively. Based on the new spectroscopic
factors we derive the N15(n ,γ)N16 reaction rate. Conclusions:
The accuracy and precision of the spectroscopic factors are enhanced
due to the first application of high-precision magnetic spectrograph
for resolving the closely spaced N16 levels which cannot be achieved
in most recent measurements. The present result demonstrates that two
levels corresponding to neutron transfers to the 2s1/2
orbit in N16 are not good single-particle levels although N15 is a
closed neutron-shell nucleus. This finding is contrary to the shell
model expectation. The present work also provides an independent
examination to shed some light on the existing discrepancies in the
spectroscopic factors and the N15(n ,γ)N16 rate.
Title: Mixture steering law design for control moment gyroscopes
Authors: Zhang, JingRui; Luo, Yang; Liu, Wei; Zhang, Yao
Bibcode: 2014SCPMA..57..138Z
Altcode: 2014ScChG..57..138Z
Focusing on the singularities of a spacecraft using control moment
gyros (CMGs) to do the large angle maneuvers, a new mixture steering
law is proposed to avoid the singularities. According to this method,
if the CMGs are far away from the singularity, the Moore-Penrose
pseudo-inverse steering law (MP) is used directly. If the CMGs are
close to the singularity, instead of solving the inverse matrix, a
set of optimal gimbal angles are sought for the singular measurement
to reach the maximum, which can avoid the singularities. Simulations
show that the designed steering law enables the spacecraft to carry
out the large angle maneuver and avoid the singularities simultaneously.
Title: Hubble Space Telescope STIS Coronagraphy of WISE Debris
Disk Candidates
Authors: Padgett, Deborah; Stapelfeldt, K. R.; Krist, J. E.; Liu,
W. M.; Leisawitz, D.; Fajardo-Acosta, S.; Debes, J. H.
Bibcode: 2014AAS...22340907P
Altcode:
We report on an HST imaging program to search for debris disks in
scattered light using the STIS coronagraph. The targets are 13 Hipparcos
stars selected for robust levels of WISE 22 micron emission in excess
of photospheric levels. These sources represent some of the closest
and brightest of the large set of new WISE debris disk candidates
(Padgett et al. 2013). Many of the sources appear as bare point spread
functions with no extended nebulosity; two others are revealed as blends
of bright stars with adjacent background star-forming galaxies. Debris
disks were directly imaged in 5/13 targets, one of which is a marginal
detection. Among these is an outstanding new edge-on system with
diameter of 1000 AU and clear structural asymmetries suggestive of
perturbations from planetary-mass companions. In this talk we will
present HST images of these five new debris disk systems and discuss
their characteristics.
Title: Analysis of Satellite Drag Coefficient Based on Wavelet
Transform
Authors: Liu, Wei; Wang, Ronglan; Liu, Siqing
Bibcode: 2014cosp...40E1855L
Altcode:
Abstract: Drag coefficient sequence was obtained by solving Tiangong1
continuous 55days GPS orbit data with different arc length. The same
period solar flux f10.7 and geomagnetic index Ap ap series were high and
low frequency multi-wavelet decomposition. Statistical analysis results
of the layers sliding correlation between space environmental parameters
and decomposition of Cd, showed that the satellite drag coefficient
sequence after wavelet decomposition and the corresponding level of
f10.7 Ap sequence with good lag correlation. It also verified that the
Cd prediction is feasible. Prediction residuals of Cd with different
regression models and different sample length were analysed. The results
showed that the case was best when setting sample length 20 days and
f10.7 regression model were used. It also showed that NRLMSIS-00
model's response in the region of 350km (Tiangong's altitude) and
low-middle latitude (Tiangong's inclination) is excessive in ascent
stage of geomagnetic activity Ap and is inadequate during fall off
segment. Additionally, the low-frequency decomposition components
NRLMSIS-00 model's response is appropriate in f10.7 rising segment. High
frequency decomposition section, Showed NRLMSIS-00 model's response is
small-scale inadequate during f10.7 ascent segment and is reverse in
decline of f10.7. Finally, the potential use of a summary and outlook
were listed; This method has an important reference value to improve
the spacecraft orbit prediction accuracy. Key words: wavelet transform;
drag coefficient; lag correlation; Tiangong1;space environment
Title: Coronal Condensation in Funnel Prominences as Return Flows
of the Chromosphere-Corona Mass Cycle
Authors: Liu, Wei; Berger, Thomas E.; Low, B. C.
Bibcode: 2014IAUS..300..441L
Altcode:
We present SDO/AIA observations of a potentially novel type of
prominence, called ``funnel prominence'', that forms out of coronal
condensation at magnetic dips. They can drain a large amount
of mass (up to ~1015 g day-1) and may play an
important role as return flows of the chromosphere-corona mass cycle.
Title: The WIYN One Degree Imager: Upgrading for the Future
Authors: Harbeck, Daniel R.; Liu, W. M.; Rajagopal, J.; ODI Team
Bibcode: 2014AAS...22314819H
Altcode:
The WIYN One Degree Imager has been in shared risk operations since
February 2013. At this time, the focal plane is populated with 13
out of 64 possible Orthogonal Transfer Array (OTA) CCD detectors,
yielding a science field of view of 24’ x 24’. In this poster we
first report on the performance of the instrument during its first year
of operations. Then we will update on the progress towards improving
ODI for the future: As of this writing, WIYN is acquiring a new
batch of OTA detectors with a better low light level charge transfer
efficiency. With the new detectors in a 6x6 detector configuration,
the field of view will be increased to 48x48 arcminutes. Other ODI
improvements will focus on observing efficiency, including a redesign
of the filter drive mechanism and an improvement on WIYN’s pointing
accuracy. Commissioning of upgraded 6x6 ODI is scheduled for late 2014.
Title: The Perihelion Passage of Comet ISON as seen by SDO
Authors: Pesnell, W. D.; Schrijver, C. J.; Boerner, P.; DeRosa, M. L.;
Liu, W.; Thompson, B. J.
Bibcode: 2013AGUFM.P24A..10P
Altcode:
Comet ISON will fly through perihelion on November 28, 2013. It is one
of the largest sungrazing comets to be seen in the Space Age. The Solar
Dynamics Observatory (SDO) has seen two previous sungrazing comets in
the extreme ultraviolet channels of the Atmospheric Imaging Assembly
(AIA). Comet ISON will fly farther from the Sun (perihelion distance
of 2.7 Rsun compared to 1.15 for Comet Lovejoy), meaning it probes
a different part of the solar corona, but its larger size should
provide enough mass to illuminate the path of the nucleus. Based on
the latest ephemeris, SDO will be able to track Comet ISON through
the entire perihelion passage by a series of off-point maneuvers. We
will present the AIA data obtained from the Comet ISON perihelion,
discussing the differences between Comets ISON and Lovejoy. We will
then summarize what we have learned from the observations and offer
some thoughts on what sungrazing comets may reveal about comets,
the Sun, and their interaction.
Title: Distribution of thermal oxygen ions in the near earth
magnetosphere
Authors: Liu, W.; Cao, J.
Bibcode: 2013AGUFMSM51B2172L
Altcode:
Based on eleven years of Cluster particle observations, we investigate
the distribution of thermal oxygen ions in the near earth magnetosphere
with full spatial coverage between 4 to 20 Re. Averaged oxygen ion
fluxes are calculated for three energy ranges (E1: 25-136eV; E2:
136eV-3keV; E3 3-35keV) based on measurements from CIS instrument. In
a preliminary analysis, we found that oxygen ions of E1 energy are
observed mostly in the Polar Regions flowing toward the nightside with
average speed of ~20 km/s at 5 Re. They are accelerated to E2 energy
range before they arrive at plasmasheet. Clear dawn-dusk asymmetry is
observed in the plasmasheet for oxygen ions of the E1 and E2 energy
that they are distributed beyond 10 Re on the duskside and beyond 15
Re on the dawnside, suggesting the transportation from ionosphere to
plasmasheet is asymmetric for dawn and dusk sides. These oxygen ions
are further accelerated in the plasmasheet to E3 energy range and are
transported toward the Earth, while they drift westward. These oxygen
ions finally reach the dayside, and then either return to the ionosphere
or escape from the dayside magnetopause to magnetosheeth. This study
provides background knowledge on complete distribution of thermal
oxygen ions in the near earth magnetosphere for the modelling and
simulation studies on ionosphere-magnetosphere coupling.
Title: Nonlinear fluid equations for fully toroidal electromagnetic
waves for the core tokamak plasma
Authors: Weiland, J.; Liu, C. S.; Liu
Bibcode: 2013JPlPh..79.1015W
Altcode:
The rather general set of fluid equations with full curvature effects
(Shukla and Weiland, Phys. Rev. A 40, 341 (1989)) has been modified
to apply to the core and generalized to include also microtearing modes.
Title: Estimating the Power per Mode Number and Power vs L-shell of
Broadband, Storm-time ULF Waves
Authors: Sarris, T. E.; Li, X.; Liu, W.; Argyriadis, E.
Bibcode: 2013AGUFMSM53D2258S
Altcode:
In studies of particles' radial diffusion processes in the magnetosphere
it is well known that Ultra-Low Frequency (ULF) waves of frequency m*ωd
can resonantly interact with particles of drift frequency ωd, where m
is the azimuthal mode number of the waves; however due to difficulties
in estimating m an over-simplifying assumption is often made in radial
diffusion simulations, namely that all ULF wave power is located at
m=1 or, in some cases, m=2. In another assumption that is commonly
made, power measured from geosynchronous satellites is assumed to be
uniform across L-shells. In the present work, a technique is presented
for extracting information on the distribution of ULF wave power in a
range of azimuthal mode numbers, through calculations of the cross-power
and phase differences between a number of azimuthally aligned pairs
of magnetometers, either in space or on the ground. We find that the
temporal evolution of power at each mode number gives unique insight
into the temporal evolution of ULF waves during a storm as well as a
more accurate characterization of broadband ULF waves. Furthermore,
using multi-spacecraft measurements during a particular storm, we
calculate the L-dependence of ULF wave power. These measurements and
calculations can be used in more accurate ULF wave representation in
radial diffusion simulations.
Title: Turbulence in the Earth's cusp region: k-filtering analysis
Authors: Wang, T.; Cao, J.; Fu, H.; Liu, W.
Bibcode: 2013AGUFMSM53B2228W
Altcode:
On April 13 2002, four Cluster spacecraft with separation up to 127 km
measured similar turbulence in the Earth's mid-altitude cusp region
during southward IMF Bz. Using the k-filtering technique, we obtain
the propagation angle and dispersion relation of the turbulence. The
propagation angle is quite large and ranges from 80° to 92°, meaning
that the turbulence propagates perpendicularly to the background
magnetic field. By comparing the dispersion relationship with the
linear solution of the Vlasov kinetic theory obtained by WHAMP,
we conclude that the turbulence is Kinetic Alfvén mode (KAWs). The
regions of KAWs are located within an inhomogeneous high density plasma
background, suggesting that it is the ion drift, not field aligned ion
beam that plays an important role in the wave generation. The magnetic
flied fluctuation spectrum resembles the classical Kolmogorov power law
under the proton gyrofrequency ωci, but breaks and steepens near ωci,
indicating that the KAW may be powered by a turbulent cascade transverse
to the magnetic field from large MHD scales to proton gyroradius scales.
Title: An electromagnetic gamma-ray free electron laser*
Authors: Eliasson, Bengt; Liu, Chuan Sheng; Liu
Bibcode: 2013JPlPh..79..995E
Altcode:
We present a theoretical model for the generation of coherent gamma
rays by a free electron laser, where a high-energy electron beam
interacts with an electromagnetic wiggler. By replacing the static
undulator with a 1-μm laser wiggler, the resulting radiation would go
from X-rays currently observed in experiments, to gamma rays. Coherent
light in the gamma-ray range would have wide-ranging applications in
the probing of matter on sub-atomic scales.
Title: Observations of chorus at sun-synchronous orbit
Authors: zhima, Z.; Cao, J.; Liu, W.; Fu, H.
Bibcode: 2013AGUFMSM41A2214Z
Altcode:
Using the data of the DEMTER satellite during the magnetic storm on
14 April 2006, we study the storm time VLF electromagnetic waves, and
find the first observational evidence of chorus waves propagating to
high latitude and entering the plasmasphere. During this geomagnetic
storm, ';banded' emissions of a few hertz to 20 kHz are observed to be
intensified and to be organized in the frequency range of 0.1-0.5fce
(equatorial electron cyclotron frequency) in high latitude region
of magnetic latitude between ~40°to ~60°. The signatures in the
wave power spectra suggest these emissions are likely lower-band
chorus. We also investigate the spatial coverage and temporal variation
of the observed high-latitude chorus emissions and their relation to
plasmapause locations. It is convincing that the plasmapause location
obtained from the observations by DEMETER and the one from the empirical
model are consistent. The observed chorus waves are generally outside
the plasmasphere. However, interestingly, these waves are frequently
observed inside the plasmasphere at regions with low L value during the
main phase and early recover phase, which has never been reported in
previous studies of chorus in low latitude regions. The present study
gives observational supports for the theory and simulations suggesting
that chorus waves propagate into the plasmasphere and evolve into
hiss waves.
Title: Mode number calculations of ULF field-line resonances using
ground magnetometers and THEMIS measurements
Authors: Sarris, T. E.; Li, X.; Liu, W.; Argyriadis, E.; Boudouridis,
A.; Ergun, R.
Bibcode: 2013JGRA..118.6986S
Altcode:
multiple pairs of International Monitor for Auroral Geomagnetic Effects
ground magnetometers together with simultaneous measurements from two of
the Time History of Events and Macroscale Interactions during Substorms
(THEMIS) spacecraft constellation, when they were flying over the
magnetometers in magnetic conjunction and in close azimuthal separation,
we are able to calculate the phase differences of Ultra Low Frequency
Field-Line Resonances, and, through that, their azimuthal mode number,
wavelength and propagation characteristics. A cross-wavelet technique is
applied, that exposes the times and frequencies of common power between
time series from azimuthally aligned magnetometers in space or on the
ground, yielding their relative phase. Using the amplitude ratio and
phase differences between ground stations with similar longitudes that
are separated in latitude, a correction to the mode number calculation
is demonstrated, accounting for the phase differences that arise from
the L shell separation of the THEMIS probes.
Title: Constraining nova observables: Direct measurements of resonance
strengths in 33S(p,γ)34Cl
Authors: Fallis, J.; Parikh, A.; Bertone, P. F.; Bishop, S.; Buchmann,
L.; Chen, A. A.; Christian, G.; Clark, J. A.; D'Auria, J. M.; Davids,
B.; Deibel, C. M.; Fulton, B. R.; Greife, U.; Guo, B.; Hager, U.;
Herlitzius, C.; Hutcheon, D. A.; José, J.; Laird, A. M.; Li, E. T.;
Li, Z. H.; Lian, G.; Liu, W. P.; Martin, L.; Nelson, K.; Ottewell,
D.; Parker, P. D.; Reeve, S.; Rojas, A.; Ruiz, C.; Setoodehnia, K.;
Sjue, S.; Vockenhuber, C.; Wang, Y. B.; Wrede, C.
Bibcode: 2013PhRvC..88d5801F
Altcode: 2013arXiv1309.3543F
The 33S(p,γ)34Cl reaction is important for
constraining predictions of certain isotopic abundances in oxygen-neon
novae. Models currently predict as much as 150 times the solar abundance
of 33S in oxygen-neon nova ejecta. This overproduction
factor may vary by orders of magnitude due to uncertainties in
the 33S(p,γ)34Cl reaction rate at nova peak
temperatures. Depending on this rate, 33S could potentially
be used as a diagnostic tool for classifying certain types of presolar
grains. Better knowledge of the 33S(p,γ)34Cl
rate would also aid in interpreting nova observations over the S-Ca
mass region and contribute to the firm establishment of the maximum
endpoint of nova nucleosynthesis. Additionally, the total S elemental
abundance which is affected by this reaction has been proposed as
a thermometer to study the peak temperatures of novae. Previously,
the 33S(p,γ)34Cl reaction rate had only been
studied directly down to resonance energies of 432 keV. However, for
nova peak temperatures of 0.2-0.4 GK there are seven known states
in 34Cl both below the 432-keV resonance and within the
Gamow window that could play a dominant role. Direct measurements
of the resonance strengths of these states were performed using
the DRAGON (Detector of Recoils And Gammas of Nuclear reactions)
recoil separator at TRIUMF. Additionally two new states within this
energy region are reported. Several hydrodynamic simulations have
been performed, using all available experimental information for the
33S(p,γ)34Cl rate, to explore the impact of
the remaining uncertainty in this rate on nucleosynthesis in nova
explosions. These calculations give a range of ≈20-150 for the
expected 33S overproduction factor, and a range of ≈100-450
for the 32S/33S ratio expected in ONe novae.
Title: Large-scale Coronal Propagating Fronts in Solar Eruptions
as Observed by the Atmospheric Imaging Assembly on Board the Solar
Dynamics Observatory—an Ensemble Study
Authors: Nitta, Nariaki V.; Schrijver, Carolus J.; Title, Alan M.;
Liu, Wei
Bibcode: 2013ApJ...776...58N
Altcode: 2013arXiv1308.3544N
This paper presents a study of a large sample of global disturbances
in the solar corona with characteristic propagating fronts as
intensity enhancement, similar to the phenomena that have often
been referred to as Extreme Ultraviolet Imaging Telescope (EIT)
waves or extreme-ultraviolet (EUV) waves. Now EUV images obtained by
the Atmospheric Imaging Assembly (AIA) on board the Solar Dynamics
Observatory provide a significantly improved view of these large-scale
coronal propagating fronts (LCPFs). Between 2010 April and 2013 January,
a total of 171 LCPFs have been identified through visual inspection of
AIA images in the 193 Å channel. Here we focus on the 138 LCPFs that
are seen to propagate across the solar disk, first studying how they
are associated with flares, coronal mass ejections (CMEs), and type II
radio bursts. We measure the speed of the LCPF in various directions
until it is clearly altered by active regions or coronal holes. The
highest speed is extracted for each LCPF. It is often considerably
higher than EIT waves. We do not find a pattern where faster LCPFs
decelerate and slow LCPFs accelerate. Furthermore, the speeds are
not strongly correlated with the flare intensity or CME magnitude,
nor do they show an association with type II bursts. We do not find
a good correlation either between the speeds of LCPFs and CMEs in a
subset of 86 LCPFs observed by one or both of the Solar and Terrestrial
Relations Observatory spacecraft as limb events.
Title: Multi-fluid MHD model for Sun-grazing comets
Authors: Jia, Y. -D.; Russell, C. T.; Liu, W.; Gombosi, T. I.
Bibcode: 2013EPSC....8..760J
Altcode:
Sun-grazing comets are comets that dive into the lower corona. Recent
advances in spacecraft capabilities have enabled us to observe
these comets with high resolution both in time and space. These
comets exhibit rich tail activity, even multiple tails. This study
investigates a collection of these activities, models the cometary
plasma with model-generated coronal conditions.
Title: Resonant scattering of 22Na + p studied by the
thick-target inverse-kinematic method
Authors: Jin, S. J.; Wang, Y. B.; Su, J.; Yan, S. Q.; Li, Y. J.; Guo,
B.; Li, Z. H.; Zeng, S.; Lian, G.; Bai, X. X.; Liu, W. P.; Yamaguchi,
H.; Kubono, S.; Hu, J.; Kahl, D.; Jung, H. S.; Moon, J. Y.; Lee, C. S.;
Teranishi, T.; Wang, H. W.; Ishiyama, H.; Iwasa, N.; Komatsubara,
T.; Brown, B. A.
Bibcode: 2013PhRvC..88c5801J
Altcode:
Background: In presolar low-density graphite grains, an extraordinarily
large 22Ne/20Ne ratio or even nearly pure
22Ne is found, pointing to the condensation of radioactive
22Na in grains. Supernovae and neon-rich novae are the
main events that produce 22Na via the explosive hydrogen
burning process. The 22Na(p, γ)23Mg reaction
is one of the key reactions that influences the 22Na
abundance in ejecta.Purpose:The present work aims to explore
the proton resonant states in 23Mg relevant to the
astrophysical 22Na(p, γ)23Mg reaction. The
determined 23Mg resonant parameters can be used to
evaluate the 22Na(p, γ)23Mg reaction
rate.Method:A low-energy 22Na radioactive ion beam is
produced via the 1H(22Ne, 22Na)n
reaction, and used to measure the experimental excitation function
of the 22Na + p resonant scattering with a conventional
thick-target inverse kinematic method. R-matrix analysis is applied to
deduce the 23Mg resonance parameters from the experimental
excitation function.Results: Three proton resonance states in
23Mg are observed. Spins/parities and the proton partial
widths are determined. The deduced excitation energies agree with
the compiled values.Conclusions: The new spin and parity assignments
allow us to perform a shell-model calculation of the γ widths
of the 23Mg resonant states for the evaluation of the
22Na(p, γ)23Mg astrophysical reaction rate. The
two s-wave resonant states established in this work at 8.793 and 8.916
MeV in 23Mg, respectively, increase the total reaction rate
by about 5% at a temperature greater than 2 GK.
Title: SDO/AIA and Hinode/EIS Observations of Interaction between
an EUV Wave and Active Region Loops
Authors: Yang, Liheng; Zhang, Jun; Liu, Wei; Li, Ting; Shen, Yuandeng
Bibcode: 2013ApJ...775...39Y
Altcode: 2013arXiv1308.1821Y
We present detailed analysis of an extreme-ultraviolet (EUV) wave
and its interaction with active region (AR) loops observed by the
Solar Dynamics Observatory/Atmospheric Imaging Assembly and the
Hinode EUV Imaging Spectrometer (EIS). This wave was initiated from
AR 11261 on 2011 August 4 and propagated at velocities of 430-910
km s-1. It was observed to traverse another AR and
cross over a filament channel on its path. The EUV wave perturbed
neighboring AR loops and excited a disturbance that propagated toward
the footpoints of these loops. EIS observations of AR loops revealed
that at the time of the wave transit, the original redshift increased
by about 3 km s-1, while the original blueshift decreased
slightly. After the wave transit, these changes were reversed. When
the EUV wave arrived at the boundary of a polar coronal hole, two
reflected waves were successively produced and part of them propagated
above the solar limb. The first reflected wave above the solar limb
encountered a large-scale loop system on its path, and a secondary wave
rapidly emerged 144 Mm ahead of it at a higher speed. These findings
can be explained in the framework of a fast-mode magnetosonic wave
interpretation for EUV waves, in which observed EUV waves are generated
by expanding coronal mass ejections.
Title: Observation of a Moreton Wave and Wave-Filament Interactions
Associated with the Renowned X9 Flare on 1990 May 24
Authors: Liu, Rui; Liu, Chang; Xu, Yan; Liu, Wei; Kliem, Bernhard;
Wang, Haimin
Bibcode: 2013ApJ...773..166L
Altcode:
Using Big Bear Solar Observatory film data recently digitized at
NJIT, we investigate a Moreton wave associated with an X9 flare
on 1990 May 24, as well as its interactions with four filaments
F1-F4 located close to the flaring region. The interaction yields
interesting insight into physical properties of both the wave and
the filaments. The first clear Moreton wavefront appears at the
flaring-region periphery at approximately the same time as the peak
of a microwave burst and the first of two γ-ray peaks. The wavefront
propagates at different speeds ranging from 1500-2600 km s-1
in different directions, reaching as far as 600 Mm away from the flaring
site. Sequential chromospheric brightenings are observed ahead of the
Moreton wavefront. A slower diffuse front at 300-600 km s-1
is observed to trail the fast Moreton wavefront about one minute after
the onset. The Moreton wave decelerates to ~550 km s-1 as it
sweeps through F1. The wave passage results in F1's oscillation which
is featured by ~1 mHz signals with coherent Fourier phases over the
filament, the activation of F3 and F4 followed by gradual recovery,
but no disturbance in F2. Different height and magnetic environment
together may account for the distinct responses of the filaments to
the wave passage. The wavefront bulges at F4, whose spine is oriented
perpendicular to the upcoming wavefront. The deformation of the
wavefront is suggested to be due to both the forward inclination of
the wavefront and the enhancement of the local Alfvén speed within
the filament channel.
Title: Thinking Problems of the Present Collision Warning Work by
Analyzing the Intersection Between Cosmos 2251 and Iridium 33
Authors: Wang, R. L.; Liu, W.; Yan, R. D.; Gong, J. C.
Bibcode: 2013ESASP.723E.156W
Altcode:
After Cosmos 2251 and Iridium 33 collision breakup event, the
institutions at home and abroad began the collision warning analysis for
the event. This paper compared the results from the different research
units and discussed the problems of the current collision warning work,
then gave the suggestions of further study.
Title: TeV cosmic-ray proton and helium spectra in the myriad model
Authors: Bernard, G.; Delahaye, T.; Keum, Y. -Y.; Liu, W.; Salati,
P.; Taillet, R.
Bibcode: 2013A&A...555A..48B
Altcode: 2012arXiv1207.4670B
Context. Recent measurements of cosmic ray proton and helium spectra
show a hardening above a few hundred GeV. This excess is hard to
understand in the framework of the conventional models of Galactic
cosmic ray production and propagation.
Aims: We propose here
to explain this anomaly by the presence of local sources (myriad
model).
Methods: Cosmic ray propagation is described as a
diffusion process taking place inside a two-zone magnetic halo. We
calculate the proton and helium fluxes at the Earth between 50 GeV and
100 TeV. As an improvement over a similar analysis, we consistently
derive these fluxes by taking both local and remote sources for which a
unique injection rate is assumed into account.
Results: We find
cosmic ray propagation parameters compatible with B/C measurements for
which the proton and helium spectra agree remarkably with the PAMELA
and CREAM measurements over four decades in energy.
Title: Evidence of Particle Acceleration and Plasma Heating in
Magnetic Reconnection Outflows in an Eruptive Solar Flare
Authors: Liu, Wei; Chen, Q.; Petrosian, V.
Bibcode: 2013SPD....44...89L
Altcode:
Where particle acceleration and plasma heating take place in relation
to magnetic reconnection is a fundamental question for solar flares. We
present here analysis of an M7.7 flare on 2012 July 19 observed by
SDO/AIA and RHESSI that sheds new light on this question (Liu, Chen,
& Petrosian, 2013, ApJ). Bi-directional outflows in forms of
plasmoid ejections and contracting cusp-shaped loops originate between
an erupting flux rope (Patsourakos et al. 2013, ApJ) and underlying
flare loops at speeds of typically 200-300 km/s up to 1050 km/s. These
outflows are associated with spatially separated double coronal X-ray
sources with their centroid separation decreasing with energy. The
highest temperature is located near the nonthermal X-ray loop-top
source, well below the original heights of contracting cusps near the
inferred reconnection site. These observations suggest that the primary
loci of particle acceleration and plasma heating are in the reconnection
outflow regions, rather than the reconnection site itself. We stress
that models with this ingredient were proposed long ago (e.g., Forbes
& Priest 1983) and backed by recent numerical simulations (e.g.,
Drake & Swisdak 2012), but solid observational evidence as presented
here has been lacking. In addition, there is an initial ascent of the
X-ray and EUV loop-top source prior to its recently recognized descent,
which we ascribe to the interplay among multiple processes including
the upward development of reconnection and the downward contractions of
reconnected loops. The impulsive phase onset coincides with the rapid
speed increases of the upward plasmoids, the individual loop shrinkages,
and the overall loop-top descent, suggestive of an intimate relation
of the energy release rate and the reconnection outflow speed.Abstract
(2,250 Maximum Characters): Where particle acceleration and plasma
heating take place in relation to magnetic reconnection is a fundamental
question for solar flares. We present here analysis of an M7.7 flare
on 2012 July 19 observed by SDO/AIA and RHESSI that sheds new light on
this question (Liu, Chen, & Petrosian, 2013, ApJ). Bi-directional
outflows in forms of plasmoid ejections and contracting cusp-shaped
loops originate between an erupting flux rope (Patsourakos et al. 2013,
ApJ) and underlying flare loops at speeds of typically 200-300 km/s up
to 1050 km/s. These outflows are associated with spatially separated
double coronal X-ray sources with their centroid separation decreasing
with energy. The highest temperature is located near the nonthermal
X-ray loop-top source, well below the original heights of contracting
cusps near the inferred reconnection site. These observations suggest
that the primary loci of particle acceleration and plasma heating are
in the reconnection outflow regions, rather than the reconnection site
itself. We stress that models with this ingredient were proposed long
ago (e.g., Forbes & Priest 1983) and backed by recent numerical
simulations (e.g., Drake & Swisdak 2012), but solid observational
evidence as presented here has been lacking. In addition, there is
an initial ascent of the X-ray and EUV loop-top source prior to its
recently recognized descent, which we ascribe to the interplay among
multiple processes including the upward development of reconnection
and the downward contractions of reconnected loops. The impulsive phase
onset coincides with the rapid speed increases of the upward plasmoids,
the individual loop shrinkages, and the overall loop-top descent,
suggestive of an intimate relation of the energy release rate and the
reconnection outflow speed.
Title: Quasi-periodic Fast-mode Magnetosonic Wave Trains Inside and
Outside CME Bubbles Detected by SDO/AIA
Authors: Liu, Wei; Ofman, L.; Downs, C.; Title, A. M.
Bibcode: 2013SPD....44...50L
Altcode:
Quasi-periodic fast-mode magnetosonic wave trains both inside and
outside expanding CME bubbles have recently been discovered by
SDO/AIA (Liu et al. 2011, 2012; Shen & Liu 2012). In general,
a wave train inside a CME bubble originates from a flare site and
propagates along a funnel of coronal loops at typically 1000-2000 km/s
(Ofman et al. 2011). A wave train outside a CME usually originates
from a CME flank and propagates in the low corona along the solar
surface following the leading front of a global EUV wave at typically
500-1000 km/s. The former is primarily seen in the cooler 171 Angstrom
channel with a characteristic temperature of 0.8 MK, while the latter
is pronounced in the hotter 193 and 211 Angstrom channels of typically
1.6-2.0 MK. What is the relationship between the two types of wave
trains? Why do they appear differently in location and wavelength
(temperature)? To answer these questions, we report here for the
first time the evidence that the wave train beyond the CME bubble is
the continuation of the same wave train along the funnel within the
CME. The continuous deceleration of the waves is consistent with the
expected decrease of the local fast-mode speed with distance from the
active region (e.g., Ofman et al. 2011; Downs et al. 2012). There is
an abrupt change of the wave speed at the topological interface where
the expanding CME flank is located, indicative of contrasting magnetic
and plasma conditions, which can give rise to different (fast-mode)
speeds and wavelength (temperature) dependent appearances of these wave
trains.Abstract (2,250 Maximum Characters): Quasi-periodic fast-mode
magnetosonic wave trains both inside and outside expanding CME bubbles
have recently been discovered by SDO/AIA (Liu et al. 2011, 2012;
Shen & Liu 2012). In general, a wave train inside a CME bubble
originates from a flare site and propagates along a funnel of coronal
loops at typically 1000-2000 km/s (Ofman et al. 2011). A wave train
outside a CME usually originates from a CME flank and propagates in
the low corona along the solar surface following the leading front of a
global EUV wave at typically 500-1000 km/s. The former is primarily seen
in the cooler 171 Angstrom channel with a characteristic temperature
of 0.8 MK, while the latter is pronounced in the hotter 193 and 211
Angstrom channels of typically 1.6-2.0 MK. What is the relationship
between the two types of wave trains? Why do they appear differently
in location and wavelength (temperature)? To answer these questions,
we report here for the first time the evidence that the wave train
beyond the CME bubble is the continuation of the same wave train
along the funnel within the CME. The continuous deceleration of the
waves is consistent with the expected decrease of the local fast-mode
speed with distance from the active region (e.g., Ofman et al. 2011;
Downs et al. 2012). There is an abrupt change of the wave speed at
the topological interface where the expanding CME flank is located,
indicative of contrasting magnetic and plasma conditions, which can
give rise to different (fast-mode) speeds and wavelength (temperature)
dependent appearances of these wave trains.
Title: Observation of a Moreton Wave and Wave-Filament Interactions
Using Digitized Film Data at BBSO
Authors: Wang, Haimin; Liu, R.; Liu, C.; Xu, Y.; Liu, W.
Bibcode: 2013SPD....4410402W
Altcode:
We have finished digitizing all full disk and a fraction of high
resolution films obtained by Big Bear Solar Observatory (BBSO) from
1969 to 1997. Using high-cadence (10s) digitized data we investigate
a Moreton wave associated with an X9 flare on 1990 May 24, as well
as its interactions with four filaments F1-F4 located close to the
flaring active region. The interaction yields interesting insight
into physical properties of both the wave and the filaments. The
first Moreton wavefront appears at the active-region periphery at
21UT, about the same time as the peak of the microwave burst and the
first of the double-peak gamma-ray burst. The wavefront propagates at
2 Mm/s within five minutes of its initiation, reaching as far as 600
Mm away from the flaring site. Sequential chromospheric brightenings
(SCBs) are observed ahead of the Moreton wavefront, with similar
appearance as the subsequent sequential brightenings due to the wave
passage. A slower diffuse moving front at 300 o 600 km/s is observed
to trail the fast Moreton wavefront about 1 min after the onset. The
Moreton wave decelerates to 550 km/s as it sweeps through F1. The
wave passage results in oscillations throughout the entire filament,
predominantly perpendicular to F1’s spine, a temporary disappearance
of F3 and F4 followed by a gradual recovery, but no disturbance in
F2. Different height and magnetic configuration together may account
for the distinct responses of the filaments to the wave passage. The
wavefront bulges at F4 whose spine is oriented perpendicular to the
upcoming wavefront. The deformation of the wavefront is suggested to
be due both to the forward inclination of the wavefront and to the
enhancement of the local Alfven speed within the filament channel.
Title: SDO/AIA and Hinode/EIS observations of interaction between
an EUV wave and active region loops
Authors: Yang, Liheng; Zhang, Jun; Li, Ting; Liu, Wei
Bibcode: 2013IAUS..294..567Y
Altcode:
We study an EUV wave initiated in active region (AR) 11261 on 2011
August 4 by using the SDO/AIA and the Hinode/EIS. We found that: (1)
the EUV wave interacted with AR loops between AR 11261 and AR 11263,
and exited mass flows in these loops. (2) EIS observations of AR loops
in AR 11263 revealed that at the time of the wave transit, the original
red-shifted feature had an increase of about 3 km s-1, and
the original blue-shifted feature slightly weakened. These findings
could be explained in the framework of a fast-mode magnetosonic wave
interpretation for EUV waves.
Title: UV and EUV Emissions at the Flare Foot-points Observed by AIA
Authors: Qiu, Jiong; Sturrock, Z.; Longcope, D.; Klimchuk, J. A.;
Liu, W.
Bibcode: 2013SPD....44...53Q
Altcode:
A solar flare is composed of impulsive energy release events by magnetic
reconnection, which forms and heats flare loops. Recent studies have
revealed a two-phase evolution pattern of UV 1600A emission at the
feet of these loops: a rapid pulse lasting for a few seconds to a
few minutes, followed by a gradual decay on timescales of a few tens
of minutes. Multiple band EUV observations by AIA further reveal
very similar signatures. These two phases represent different but
related signatures of an impulsive energy release in the corona. The
rapid pulse is an immediate response of the lower atmosphere to an
intense thermal conduction flux resulting from the sudden heating of
the corona to high temperatures (we rule out energetic particles due
to a lack of significant hard X-ray emission). The gradual phase is
associated with the cooling of hot plasma that has been evaporated
into the corona. The observed footpoint emission is again powered
by thermal conduction (and enthalpy), but now during a period when
approximate steady state conditions are established in the loop. UV
and EUV light curves of individual pixels may therefore be separated
into contributions from two distinct physical mechanisms to shed
light on the nature of energy transport in a flare. We demonstrate
this technique using coordinated, spatially resolved observations of
UV and EUV emission from the footpoints of a C3.2 thermal flare.
Title: An interferometric study of the Fomalhaut inner debris
disk. III. Detailed models of the exozodiacal disk and its origin
Authors: Lebreton, J.; van Lieshout, R.; Augereau, J. -C.; Absil,
O.; Mennesson, B.; Kama, M.; Dominik, C.; Bonsor, A.; Vandeportal,
J.; Beust, H.; Defrère, D.; Ertel, S.; Faramaz, V.; Hinz, P.; Kral,
Q.; Lagrange, A. -M.; Liu, W.; Thébault, P.
Bibcode: 2013A&A...555A.146L
Altcode: 2013arXiv1306.0956L
Context. Debris disks are thought to be extrasolar analogs to the
solar system planetesimal belts. The star Fomalhaut harbors a cold
debris belt at 140 AU comparable to the Edgeworth-Kuiper belt, as
well as evidence of a warm dust component, unresolved by single-dish
telescopes, which is suspected of being a bright analog to the solar
system's zodiacal dust.
Aims: Interferometric observations
obtained with the VLTI/VINCI instrument and the Keck Interferometer
Nuller have identified near- and mid-infrared excesses attributed
respectively to hot and warm exozodiacal dust residing in the inner few
AU of the Fomalhaut environment. We aim to characterize the properties
of this double inner dust belt and to unveil its origin.
Methods: We performed parametric modeling of the exozodiacal disk
("exozodi") using the GRaTeR radiative transfer code to reproduce the
interferometric data, complemented by mid- to far-infrared photometric
measurements from Spitzer and Herschel. A detailed treatment of
sublimation temperatures was introduced to explore the hot population
at the size-dependent sublimation rim. We then used an analytical
approach to successively testing several source mechanisms for the
dust and suspected parent bodies.
Results: A good fit to the
multiwavelength data is found by two distinct dust populations: (1)
a population of very small (0.01 to 0.5 μm), hence unbound, hot dust
grains confined in a narrow region (~0.1-0.3 AU) at the sublimation
rim of carbonaceous material; (2) a population of bound grains at ~2
AU that is protected from sublimation and has a higher mass despite
its fainter flux level. We propose that the hot dust is produced by
the release of small carbon grains following the disruption of dust
aggregates that originate in the warm component. A mechanism, such
as gas braking, is required to further confine the small grains for
a long enough time. In situ dust production could hardly be ensured
for the age of the star, so we conclude that the observed amount of
dust is triggered by intense dynamical activity.
Conclusions:
Fomalhaut may be representative of exozodis that are currently being
surveyed at near and mid-infrared wavelengths worldwide. We propose a
framework for reconciling the "hot exozodi phenomenon" with theoretical
constraints: the hot component of Fomalhaut is likely the "tip of the
iceberg" since it could originate in the more massive, but fainter,
warm dust component residing near the ice line. This inner disk exhibits
interesting morphology and can be considered a prime target for future
exoplanet research. Appendices are available in electronic form
at http://www.aanda.org
Title: Poloidal ULF wave observed in the plasmasphere boundary layer
Authors: Liu, W.; Cao, J. B.; Li, X.; Sarris, T. E.; Zong, Q. -G.;
Hartinger, M.; Takahashi, K.; Zhang, H.; Shi, Q. Q.; Angelopoulos, V.
Bibcode: 2013JGRA..118.4298L
Altcode:
report on a rare ultra-low-frequency (ULF) wave generation event
associated with the formation of a plasmasphere boundary layer (PBL),
which was well observed by one of the THEMIS satellites, TH-D, during
subsequent outbound passes. On 13 September 2011, TH-D observed a sharp
plasmapause at L = 3.4. The plasmasphere started to expand and continued
to be refilled on 14 September. On 15 September, a PBL was formed with
two density gradients at L = 4.4 and 6.5, respectively. Within the two
density gradients, strong radial magnetic field and azimuthal electric
field oscillations were observed, suggesting poloidal ULF waves. Based
on the phase delay between magnetic and electric field signals, as well
as the comparison between the observed wave frequency and predicted
harmonic eigenfrequency, we find that the observed oscillations are
second harmonic poloidal waves. Further investigation shows that the
observed waves are likely generated by drift-bounce resonance with
"bump-on-tail" plasma distributions at ~10 keV. We demonstrate that
the waves are excited within the PBL where the eigenfrequency is close
to the bounce frequency of these hot protons, but not outside the PBL
where the eigenfrequency deviates from the bounce frequency. Finally,
we suggest that cold plasma density seems to be a controlling factor
for ULF wave generation as well, in addition to the bump-on-tail energy
source, by altering eigenfrequency of the local field lines.
Title: Funnel Prominences as Return Flows of the Chromosphere-Corona
Mass Cycle: SDO/AIA Observations of Coronal Condensation
Authors: Liu, Wei; Berger, T.; Low, B. C.
Bibcode: 2013SPD....44...42L
Altcode:
It has recently been proposed that prominences play an important role
as return flows of the chromosphere-corona mass cycle, in which hot
plasma is transported upward in forms of spicules and prominence bubbles
(likely due to flux emergence), while cool plasma drains downward in
forms of vertical prominence threads (Berger et al. 2011 Nature). A
critical step in this cycle is the condensation of the million-degree
coronal plasma into T<10,000 K prominence material by a radiative
cooling instability (i.e., thermal non-equilibrium), as numerically
simulated (Karpen & Antiochos 2008; Xia et al. 2012) and first
evidenced in recent SDO/AIA observations (Liu et al. 2012; Berger et
al. 2012 ApJL). Such a runaway cooling process occurs in coronal loops
of various sizes and generally leads to condensation at magnetic dips
and formation of funnel-shaped prominences. A moderate-sized prominence
can drain a significant mass of typically 10^15 gram/day, which is
comparable to the mass of a CME or a fraction of the entire corona. Here
we present a survey of funnel prominences that appear to be common
in AIA observations at various locations and times. We find longer
cooling times in longer/taller coronal loops whose densities are lower,
consistent with the expected quadratic dependence on density of the
optically-thin radiative loss. We propose that such funnel prominences,
usually small in size, can constitute a new type of prominences, and
similar processes can produce elementary building blocks of large-scale
quiescent prominences in filament channels. This picture is supported
by the recent theoretical development on spontaneous formation of
current sheets and condensations manifested as prominence threads
(Low et al. 2012a, b, ApJ).Abstract (2,250 Maximum Characters): It
has recently been proposed that prominences play an important role
as return flows of the chromosphere-corona mass cycle, in which hot
plasma is transported upward in forms of spicules and prominence bubbles
(likely due to flux emergence), while cool plasma drains downward in
forms of vertical prominence threads (Berger et al. 2011 Nature). A
critical step in this cycle is the condensation of the million-degree
coronal plasma into T<10,000 K prominence material by a radiative
cooling instability (i.e., thermal non-equilibrium), as numerically
simulated (Karpen & Antiochos 2008; Xia et al. 2012) and first
evidenced in recent SDO/AIA observations (Liu et al. 2012; Berger et
al. 2012 ApJL). Such a runaway cooling process occurs in coronal loops
of various sizes and generally leads to condensation at magnetic dips
and formation of funnel-shaped prominences. A moderate-sized prominence
can drain a significant mass of typically 10^15 gram/day, which is
comparable to the mass of a CME or a fraction of the entire corona. Here
we present a survey of funnel prominences that appear to be common
in AIA observations at various locations and times. We find longer
cooling times in longer/taller coronal loops whose densities are lower,
consistent with the expected quadratic dependence on density of the
optically-thin radiative loss. We propose that such funnel prominences,
usually small in size, can constitute a new type of prominences, and
similar processes can produce elementary building blocks of large-scale
quiescent prominences in filament channels. This picture is supported
by the recent theoretical development on spontaneous formation of
current sheets and condensations manifested as prominence threads
(Low et al. 2012a, b, ApJ).
Title: A new approach to model particle acceleration and energy
transfer in solar flares
Authors: Rubio Da Costa, Fatima; Zuccarello, F.; Fletcher, L.;
Labrosse, N.; Kasparova, J.; Prosecký, T.; Carlsson, M.; Petrosian,
V.; Liu, W.
Bibcode: 2013SPD....4440401R
Altcode:
Motivated by available observations of two different flares in Lyα and
Hα, we model the conditions of the solar atmosphere using a radiation
hydrodynamics code (RADYN, Carlsson & Stein, 1992) and analyze the
energy transport carried by a beam of non-thermal electrons injected
at the top of a 1D coronal loop. The numerical Lyα and Hα intensities
match with the observations. The electron energy distribution is assumed
to follow a power law of the form (E/Ec )-δ for
energies greater than a cutoff value of Ec. Abbett &
Hawley (1999) and Allred et al. (2005) assumed that the non-thermal
electrons flux injected at the top of a flaring loop, the cut-off energy
and the power law index are constant over time. An improvement was
achieved by Allred & Hawley (2006), who modified the RADYN code
in such a way that the input parameters were time dependent. Their
inputs were based on observations of a flare obtained with RHESSI. By
combining RADYN with the “flare” code from Stanford University
which models the acceleration and transport of particles and radiation
of solar flares in non-LTE regime, we can calculate the non-thermal
electrons flux, the cut-off energy and the power law index at every
simulated time step. The atmospheric parameters calculated by RADYN
could in turn be used as updated inputs for "flare", providing several
advantages over the results from Liu et al. (2009), who combined the
particle acceleration code with a 1-D hydrodynamic code, improving
the atmospheric conditions.
Title: SDO AIA Observations of Large-Scale Coronal Propagating Fronts
Authors: Nitta, Nariaki; Schrijver, C. J.; Title, A. M.; Liu, W.
Bibcode: 2013SPD....44...40N
Altcode:
The discovery of "EIT waves" rekindled interests in what used to be
called flare waves, which had been typically observed in H-alpha. In
addition to Moreton waves, first observed at the Lockheed Solar
Observatory, other manifestations of shock waves propagating in the
corona include type II radio bursts and filament oscillations away from
flare sites. Identification of EIT waves with the postulated fast-mode
MHD shock waves in the corona has been questioned, however, largely
because of their low speeds (e.g., 200-400 km/s). EIT's 10-20 minute
cadence could be a contributing factor for this, and we need to find how
fast large-scale coronal propagating fronts are in higher-cadence EUV
images. It is clear that AIA on SDO is the best instrument at the moment
for this type of work. With the availability of high-cadence full-disk
images, we now can compare propagating fronts in different directions,
and determine the highest speed of each event on AIA images more
objectively and accurately than on EIT (and STEREO EUVI) images. In a
large number of EIT wave events, we have measured speeds of propagating
fronts using AIA's 193 A images. Before the fronts are deflected by the
discontinuities, e.g., active regions and coronal holes, the mean and
median speeds are 620 km/s and 600 km/s, respectively, and many exceed
800 km/s. Higher speeds are often seen in events that accompany a type
II burst, strong flare or energetic CME, but the distribution of the
speed with these attributes is broad. We also find that the speeds of
the large-scale coronal propagating fronts are not well correlated
with those of the associated CMEs. Given that large-scale coronal
propagating fronts at large distances represent freely propagating MHD
waves, we discuss how to understand their nature close to their origins.
Title: Asteroid Rotation Studies
Authors: Han, Xianming L.; Liu, W.; Sun, L.; Gao, S.; Shi, J.; Wang,
S.; Pan, X.; Jiang, P.; Zhou, H.; Li, B.; Zhao, H.
Bibcode: 2013AAS...22231502H
Altcode:
During winter of 2012-2013, we measured the rotation periods of seven
asteroids using the 0.9-m SARA North telescope located at the Kitt
Peak National Observatory in Arizona and at the 0.6-m SARA South
telescope located at the Cerro Tololo Inter-American Observatory in
Chile. The asteroids that we carried out photometry studies include:
1614 Goldschmidt, 1727 Mette, 2207 Antenor, 2616 Lesya, 2972 Niilo,
4387 Tanaka, 34898 (2622 P-L). We will present their rotation periods,
and compare with previous results where available.
Title: Broad line and multi-wave luminosity relations in Fermi FSRQs
Authors: Xiong, D. R.; Zhang, H. J.; Zhang, X.; Zheng, Y. G.; Yi,
T. F.; Liu, W. G.; Cha, Y. J.; Li, B. J.
Bibcode: 2013Ap&SS.345..345X
Altcode: 2013Ap&SS.tmp...70X; 2013Ap&SS.tmp...59X
We study broad line and multi-wave luminosity relations for 80
flat-spectrum radio quasars (FSRQs) detected by Fermi LAT. Our results
are as follows: for FSRQs, the correlations between log L γ
and log L BLR, between log L X and log L
BLR, between log L O and log L BLR,
between log L R and log L BLR are significant;
the correlation between log L IR and log L BLR
( P=0.08) is not significant, but might be refereed as a "trend"
of significant correlation. These results support a close link
between jet formation and accretion disk, and the L γ -
L BLR correlation suggests that the radiation mechanism of
the γ-ray emission in FSRQs is likely to be inverse Compton scattering
of seed photons from BLR or outflowing BLR.
Title: Evolution of neutron star + He star binaries: an alternative
evolutionary channel to intermediate-mass binary pulsars.
Authors: Chen, W. -C.; Liu, W. -M.
Bibcode: 2013MNRAS.432L..75C
Altcode: 2013MNRAS.tmpL..93C; 2013arXiv1303.6155C
It is difficult for intermediate-mass X-ray binaries to form compact
intermediate-mass binary pulsars (IMBPs) with a short orbital-period
( ≲ 3 d), which have heavy ( ≳ 0.4 M⊙) CO or ONeMg
white dwarf (WD) companions. Since neutron star + He star binaries
may experience common-envelope evolution, they have some advantage
to account for the formation of short orbital-period IMBPs. In this
work, we explore the probability of IMBPs formed by this evolutionary
channel. Using Eggleton's stellar evolution code, considering that
the dead pulsars were spun up by the accreting material and angular
momentum from the He star companions, we have calculated the evolution
of a large number of neutron star + He star binaries. Our simulated
results indicate that the NS + He star evolutionary channel can produce
IMBPs with a WD of ∼ 0.5-1.1 M⊙ and an orbital period of
0.03-20 d, in which pulsars have a spin period of 1.4-200 ms. Comparing
the calculated results with the observational parameters (spin period
and orbital period) of nine compact IMBPs, the NS + He star evolutionary
channel can account for the formation of four sources. Therefore,
NS + He star binaries offer an alternative evolutionary channel to
compact IMBPs.
Title: Plasmoid Ejections and Loop Contractions in an Eruptive M7.7
Solar Flare: Evidence of Particle Acceleration and Heating in Magnetic
Reconnection Outflows
Authors: Liu, Wei; Chen, Qingrong; Petrosian, Vahé
Bibcode: 2013ApJ...767..168L
Altcode: 2013arXiv1303.3321L
Where particle acceleration and plasma heating take place in relation
to magnetic reconnection is a fundamental question for solar flares. We
report analysis of an M7.7 flare on 2012 July 19 observed by SDO/AIA
and RHESSI. Bi-directional outflows in forms of plasmoid ejections
and contracting cusp-shaped loops originate between an erupting
flux rope and underlying flare loops at speeds of typically 200-300
km s-1 up to 1050 km s-1. These outflows are
associated with spatially separated double coronal X-ray sources with
centroid separation decreasing with energy. The highest temperature
is located near the nonthermal X-ray loop-top source well below the
original heights of contracting cusps near the inferred reconnection
site. These observations suggest that the primary loci of particle
acceleration and plasma heating are in the reconnection outflow regions,
rather than the reconnection site itself. In addition, there is an
initial ascent of the X-ray and EUV loop-top source prior to its
recently recognized descent, which we ascribe to the interplay among
multiple processes including the upward development of reconnection
and the downward contractions of reconnected loops. The impulsive
phase onset is delayed by 10 minutes from the start of the descent,
but coincides with the rapid speed increases of the upward plasmoids,
the individual loop shrinkages, and the overall loop-top descent,
suggestive of an intimate relation of the energy release rate and
reconnection outflow speed.
Title: The stability of an evolving Atlantic meridional overturning
circulation
Authors: Liu, Wei; Liu, Zhengyu; Hu, Aixue
Bibcode: 2013GeoRL..40.1562L
Altcode:
In this study, we propose a generalized stability indicator, L, for
a slowly evolving and quasi-steady Atlantic meridional overturning
circulation (AMOC), which represents a feedback related to the AMOC
and its associated freshwater transport within the Atlantic basin. As
an improvement from previous indicators for the AMOC in equilibrium,
this generalized indicator does not require a divergence-free freshwater
transport in the Atlantic for a collapsed AMOC, which enables it to
correctly monitor the AMOC stability through the AMOC hysteresis loop
in the coupled atmosphere-ocean general circulation models. From the
simulation, the indicator L suggests that the AMOC is in a stable
regime, with single equilibrium under the present-day and the Last
Glacial Maximum (LGM) climates. However, under the present-day climate,
a Bering Strait (BS) closure will diminish the freshwater outflow from
the North Atlantic into the Arctic as the AMOC collapses, resulting in a
freshwater convergence in the Atlantic basin and making the AMOC reside
in a stable collapsed state, i.e., the AMOC exhibits characteristics
of multiple equilibria. Further analysis shows that the BS effect
is much reduced under the LGM climate. This generalized indicator L
has great implications for paleoclimate studies in understanding the
abrupt climate change due to the instability of the AMOC.
Title: A multi-fluid MHD Model for Sun-grazing comets
Authors: Jia, Ying-Dong; Russell, Christopher; Liu, Wei; Gombosi, Tamas
Bibcode: 2013EGUGA..15.6348J
Altcode:
Cometary plasma has been modeled with numerical codes for decades,
to study its shock, contact surface and tail under nominal solar wind
conditions. Recently, comets have been observed under very different
conditions, the lower corona. This region contains plasma, orders of
magnitude denser, and much stronger field. The cometary molecules are
ionized much faster as well. Tail activity has been observed, providing
a new way to study the plasma in coronal loops. In this study we model
the charging-balanced cometary plasma, and its interaction with the
lower corona. We simulate the momentum exchange between solar corona
plasma and the cometary ions. Typical structures of the coronal field
are studied to observe their effects on the tail, and to model the
observed tail activity.
Title: Recent Advances in Observations of Coronal EUV Waves
Authors: Liu, Wei; Ofman, Leon; Aschwanden, Markus J.; Nitta, Nariaki;
Zhao, Junwei; Title, Alan M.
Bibcode: 2013enss.confE..67L
Altcode:
MHD waves can be used as seismological tools to decipher otherwise
elusive physical parameters of the solar corona, such as the magnetic
field strength and plasma density. Recent high cadence, high resolution,
full-disk imaging observations from SDO/AIA have opened a new chapter
in understanding these waves. Various types of EUV waves associated with
flares/CMEs have been discovered or observed in unprecedented detail. In
this talk, we will review such new observations, focusing on the
following topics and their interrelationships: (1) quasi-periodic fast
waves traveling along coronal funnels within CME bubbles at speeds up
to 2000 km/s, associated with flare pulsations at similar frequencies;
(2) quasi-periodic wave trains within broad, diffuse pulses of global
EUV waves (so-called "EIT waves") running ahead of CME fronts; (3)
interactions of global EUV waves with local coronal structures on
their paths, such as flux-rope coronal cavities and their embedded
filaments (kink oscillations) and coronal holes or active regions
(deflections). We will discuss the implications of these observations
on coronal seismology, on their roles in transporting energy through
different parts of the solar atmosphere, and on understanding their
associated eruptive flares/CMEs.
Title: Heating of Flare Loops During a Two-ribbon Flare on 2011
March 07 Observed by AIA and EVE
Authors: Liu, W. -J.; O'Hara, J.; Peck, C.; Qiu, J.; Longcope, D. W.
Bibcode: 2013enss.confE.109L
Altcode:
Recent high-resolution EUV observations have revealed that flare
loops are formed and heated by reconnection events taking place
successively. Our recent work shows that the rapidly rising phase of
the UV emission at the foot-points of the flare loops could be used to
infer the time profile of the impulsive heating rate. In this study,
we analyze an M-class flare observed by AIA and EVE. We utilize the
spatially resolved UV brightness time profiles to infer heating rates of
a few thousand flux tubes anchored at the UV foot-points, and compute
plasma evolution in each flux tube using the EBTEL model (Klimchuk
et al. 2008, Cargrill et al. 2012). The coronal radiation is then
calculated and compared with soft X-ray and EUV light curves observed
by GOES and AIA. With a steady-state assumption, we also compute the
transition-region DEM for each flux tube during its decay phase, and
compare the predicted optically-thin transition-region emission in
UV and EUV with AIA foot-points observations. The EUV emissions from
both loops and foot points are also compared with irradiance observed
by EVE. This study presents a method to infer heating functions of
reconnection formed flare loops and how they affect evolution of the
overlying corona as well as the lower-atmosphere dynamics coherently.
Title: SDO AIA Observations of Large-Scale Coronal Disturbances in
the Form of Propagating Fronts
Authors: Nitta, Nariaki V.; Schrijver, Carolus J.; Title, Alan M.;
Liu, Wei
Bibcode: 2013enss.confE.111N
Altcode:
One of the most spectacular phenomena detected by SOHO EIT
was the large-scale propagating fronts associated with solar
eruptions. Initially these 'EIT' waves were thought to be coronal
counterparts of chromospheric Moreton waves. However, different
spatial and kinematic properties of the fronts seen in H-alpha and
EUV images, and far more frequent occurrences of the latter have
led to various interpretations that are still actively debated by
a number of researchers. A major factor for the lack of closure was
the various limitation in EIT data, including the cadence that was
typically every 12 minutes. Now we have significantly improved data
from SDO AIA, which have revealed some very interesting phenomena
associated with EIT waves. However, the studies so far conducted
using AIA data have primarily dealt with single or a small number of
events, where selection bias and particular observational conditions
may prevent us from discovering the general and true nature of EIT
waves. Although automated detection of EIT waves was promised for
AIA images some time ago, it is still not actually implemented in the
data pipeline. Therefore we have manually found nearly 200 examples
of large-scale propagating fronts, going through movies of difference
images from the AIA 193 A channel up to January 2013. We present our
study of the kinematic properties of the fronts in a subset of about
150 well-observed events in relation with other phenomena that can
accompany EIT waves. Our emphasis is on the relation of the fronts
with the associated coronal eruptions often but not always taking
the form of full-blown CMEs, utilizing STEREO data for a subset of
more than 80 events that have occurred near the limb as viewed from
one of the STEREO spacecraft. In these events, the availability of
data from the STEREO inner coronagraph (COR1) as well as from the EUVI
allows us to trace eruptions off the solar disk during the times of our
propagating fronts. The representative relations between the fronts and
CMEs will be discussed in terms of the evolution of EIT waves observed
in different channels of AIA, which provide information of the thermal
properties of the fronts. Our study will further clarify the variety
of solar eruptions and their associated manifestations in the corona.
Title: Bi-directional Ejections and Loop Contractions in an Eruptive
M7.7 Solar Flare: Evidence of Particle Acceleration and Heating in
Magnetic Reconnection Outflows
Authors: Liu, Wei; Chen, Qingrong; Petrosian, Vahe
Bibcode: 2013enss.confE.119L
Altcode:
Where particle acceleration and plasma heating take place in relation
to magnetic reconnection is a fundamental question for solar flares. We
report analysis of an M7.7 flare on 2012 July 19 observed by SDO/AIA
and RHESSI. Bi-directional ejections in forms of plasmoids and
contracting cusp-shaped loops originate between an erupting flux rope
and underlying flare loops at speeds of typically 200-300 km/s up to
1050 km/s. These ejections are associated with spatially separated
double coronal X-ray sources with centroid separation decreasing with
energy. The highest temperature is located near the nonthermal X-ray
loop-top source well below the original heights of contracting cusps
near the inferred reconnection site. These observations suggest that
the primary loci of particle acceleration and plasma heating are in
the reconnection outflow regions, rather than the reconnection site
itself. This supports particle acceleration by turbulence, shocks,
and/or collapsing traps associated with reconnection outflows, not by
a DC electric field within the reconnection region. In addition, there
is an initial ascent of the X-ray and EUV loop-top source prior to its
recently recognized descent. The impulsive phase onset is delayed by
10 minutes from the start of the descent, but coincides with the rapid
speed increases of the upward plasmoids, the individual loop shrinkages,
and the overall loop-top descent, suggestive of an intimate relation
of the energy release rate and reconnection outflow speed.
Title: An Interferometric Study of the Fomalhaut Inner Debris
Disk. II. Keck Nuller Mid-infrared Observations
Authors: Mennesson, B.; Absil, O.; Lebreton, J.; Augereau, J. -C.;
Serabyn, E.; Colavita, M. M.; Millan-Gabet, R.; Liu, W.; Hinz, P.;
Thébault, P.
Bibcode: 2013ApJ...763..119M
Altcode: 2012arXiv1211.7143M
We report on high-contrast mid-infrared observations of Fomalhaut
obtained with the Keck Interferometer Nuller (KIN) showing a
small resolved excess over the level expected from the stellar
photosphere. The measured null excess has a mean value of 0.35% ± 0.10%
between 8 and 11 μm and increases from 8 to 13 μm. Given the small
field of view of the instrument, the source of this marginal excess
must be contained within 2 AU of Fomalhaut. This result is reminiscent
of previous VLTI K-band (sime2μm) observations, which implied the
presence of a ~0.88% excess, and argued that thermal emission from hot
dusty grains located within 6 AU from Fomalhaut was the most plausible
explanation. Using a parametric two-dimensional radiative transfer code
and a Bayesian analysis, we examine different dust disk structures to
reproduce both the near- and mid-infrared data simultaneously. While
not a definitive explanation of the hot excess of Fomalhaut, our model
suggests that the most likely inner few AU disk geometry consists of
a two-component structure, with two different and spatially distinct
grain populations. The 2-11 μm data are consistent with an inner hot
ring of very small (sime10-300 nm) carbon-rich grains concentrating
around 0.1 AU. The second dust population—inferred from the KIN
data at longer mid-infrared wavelengths—consists of larger grains
(size of a few microns to a few tens of microns) located further out
in a colder region where regular astronomical silicates could survive,
with an inner edge around 0.4 AU-1 AU. From a dynamical point of view,
the presence of the inner concentration of submicron-sized grains is
surprising, as such grains should be expelled from the inner planetary
system by radiation pressure within only a few years. This could either
point to some inordinate replenishment rates (e.g., many grazing comets
coming from an outer reservoir) or to the existence of some braking
mechanism preventing the grains from moving out.
Title: Reexamining the β decay of 53,54Ni,
52,53Co, 51Fe, and 50Mn
Authors: Su, J.; Liu, W. P.; Shu, N. C.; Yan, S. Q.; Li, Z. H.; Guo,
B.; Huang, W. Z.; Zeng, S.; Li, E. T.; Jin, S. J.; Liu, X.; Wang,
Y. B.; Lian, G.; Li, Y. J.; Chen, Y. S.; Bai, X. X.; Wang, J. S.;
Yang, Y. Y.; Chen, R. F.; Xu, S. W.; Hu, J.; Chen, S. Z.; Ma, S. B.;
Han, J. L.; Ma, P.; Hu, Q.; Ma, J. B.; Cao, X. G.; Jin, S. L.; Bai, Z.;
Yang, K.; Shi, F. D.; Zhang, W.; Chen, Z.; Liu, L. X.; Lin, Q. Y.; Yan,
X. S.; Zhang, X. H.; Fu, F.; He, J. J.; Li, X. Q.; He, C.; Smith, M. S.
Bibcode: 2013PhRvC..87b4312S
Altcode:
The β decay of 53,54Ni, 52,53Co, 51Fe,
and 50Mn was investigated via the fragmentation of a
58Ni primary beam with an energy of 68.6 MeV/u. The proton-γ
coincidences of 53Ni β-delayed proton emission were
observed. Based on the analysis of the proton-γ coincidence events,
it was inferred that the previous assignment of the excitation energy
for the isobaric analog state in 53Co may be problematic. The
half-lives of these nuclei were obtained, in which the uncertainty of
52Co half-life was reduced by a factor of 3. The half-lives
were evaluated and used as inputs of nucleosynthesis calculations of
the rapid proton-capture process in an x-ray burst.
Title: Discovery of an unusual radio galaxy with a hybrid
double-double and X-shaped morphology
Authors: Wang, C. C.; Zhou, H. Yan.; Ji, T.; Liu, W. J.; Jiang, N.
Bibcode: 2013IAUS..290..323W
Altcode:
We report the discovery of the first `X'-shaped double-double radio
galaxy (DDRG), MRC0929+164 (J0932+1611), from FIRST radio survey. The
intersection angle of the lines of two pairs of radio lobes is around
20.6° for this object, much larger than other DDRGs. This unusual
morphology may be a hint that the growth of its central super-massive
black hole suffered a violent galaxy merger once.
Title: TeV Cosmic-ray Proton and Helium Spectra in the Myriad Model
Authors: Bernard, Guilhem; Delahaye, Timur; Keum, Y. -Y.; Liu, Wei;
Salati, Pierre; Taillet, Richard
Bibcode: 2013ICRC...33..750B
Altcode:
Recent measurements of cosmic ray proton and helium spectra show a
hardening above a few hundred GeV. This excess is hard to understand
in the framework of the conventional models of Galactic cosmic ray
production and propagation. We propose to explain this anomaly by the
presence of local sources (myriad model). We consistently derive the
proton and helium fluxes between 50 GeV and 100 TeV by taking both local
and remote sources for which a unique injection rate is assumed into
account. We find cosmic ray propagation parameters compatible with B/C
measurements for which the proton and helium spectra agree remarkably
with the PAMELA and CREAM measurements over four decades in energy.
Title: TSR versus non-TSR processes and their impact on gas
geochemistry and carbon stable isotopes in Carboniferous, Permian
and Lower Triassic marine carbonate gas reservoirs in the Eastern
Sichuan Basin, China
Authors: Liu, Q. Y.; Worden, R. H.; Jin, Z. J.; Liu, W. H.; Li, J.;
Gao, B.; Zhang, D. W.; Hu, A. P.; Yang, C.
Bibcode: 2013GeCoA.100...96L
Altcode:
The Palaeozoic and lowermost Mesozoic marine carbonate reservoirs of
the Sichuan Basin in China contain variably sour and very dry gas. The
source of the gas in the Carboniferous, Permian and Lower Triassic
reservoirs is not known for certain and it has proved difficult to
discriminate and differentiate the effects of thermal cracking- and
TSR-related processes for these gases. Sixty-three gas samples were
collected and analysed for their composition and carbon stable isotope
values. The gases are all typically very dry (alkane gases being
>97.5% methane), with low (<1%) nitrogen and highly variable
H2S and CO2. Carboniferous gas is negligibly
sour while the Lower Triassic gas tends to be most sour. The elevated
H2S (up to 62%) is due to thermochemical sulphate reduction
with the most sour Triassic and Permian reservoirs being deeper than
4800 m. The non-TSR affected Carboniferous gas is a secondary gas that
was derived from the cracking of sapropelic kerogen-derived oil and
primary gas and is highly mature. Carboniferous (and non-sour Triassic
and Permian) gas has unusual carbon isotopes with methane and propane
being isotopically heavier than ethane (a reversal of typical low-
to moderate-maturity patterns). The gas in the non-sour Triassic and
Permian reservoirs has the same geochemical and isotopic characteristics
(and therefore the same source) as the Carboniferous gas. TSR in the
deepest Triassic reservoirs altered the gas composition reaching 100%
dryness in the deepest, most sour reservoirs showing that ethane and
propane react faster than methane during TSR. Ethane evolves to heavier
carbon isotope values than methane during TSR leading to removal
of the reversed alkane gas isotope trend found in the Carboniferous
and non-sour Triassic and Permian reservoirs. However, methane was
directly involved in TSR as shown by the progressive increase in its
carbon isotope ratio as gas souring proceeded. CO2 increased
in concentration as gas souring proceeded, but typical CO2
carbon isotope ratios in sour gases remained about -4‰ V-PDB showing
that it was not solely derived from the oxidation of alkanes. Instead
CO2 may partly result from reaction of sour gas with
carbonate reservoir minerals, such as Fe-rich dolomite or calcite,
resulting in pyrite growth as well as CO2-generation.
Title: Determination of the astrophysical
12N(p,γ)13O reaction rate from the
2H(12N,13O)n reaction and its
astrophysical implications
Authors: Guo, B.; Su, J.; Li, Z. H.; Wang, Y. B.; Yan, S. Q.; Li,
Y. J.; Shu, N. C.; Han, Y. L.; Bai, X. X.; Chen, Y. S.; Liu, W. P.;
Yamaguchi, H.; Binh, D. N.; Hashimoto, T.; Hayakawa, S.; Kahl, D.;
Kubono, S.; He, J. J.; Hu, J.; Xu, S. W.; Iwasa, N.; Kume, N.; Li,
Z. H.
Bibcode: 2013PhRvC..87a5803G
Altcode: 2012arXiv1211.4972G
The evolution of massive stars with very low-metallicities depends
critically on the amount of CNO nuclides which they produce. The
12N(p,γ)13O reaction is an important branching
point in the rap processes, which are believed to be alternative paths
to the slow 3α process for producing CNO seed nuclei and thus could
change the fate of massive stars. In the present work, the angular
distribution of the 2H(12N, 13O)n
proton transfer reaction at Ec.m.=8.4 MeV has been measured
for the first time. Based on the Johnson-Soper approach, the square
of the asymptotic normalization coefficient (ANC) for the virtual
decay of 13Og.s. → 12N+p was
extracted to be 3.92±1.47 fm-1 from the measured angular
distribution and utilized to compute the direct component in the
12N(p,γ)13O reaction. The direct astrophysical
S factor at zero energy was then found to be 0.39±0.15 keV b. By
considering the direct capture into the ground state of 13O,
the resonant capture via the first excited state of 13O and
their interference, we determined the total astrophysical S factors
and rates of the 12N(p,γ)13O reaction. The new
rate is two orders of magnitude slower than that from the REACLIB
compilation. Our reaction network calculations with the present
rate imply that 12N(p,γ)13O will only compete
successfully with the β+ decay of 12N at higher
(∼2 orders of magnitude) densities than initially predicted.
Title: Warm Debris Disks from WISE
Authors: Padgett, Deborah; Stapelfeldt, K. R.; Liu, W. M.; Leisawitz,
D.; Krist, J. E.; Debes, J. H.; Fajardo-Acosta, S.; WISE Science Team
Bibcode: 2013AAS...22140303P
Altcode:
We report on an all-sky survey for warm debris disks in the solar
neighborhood using data from the Wide-field Infrared Survey Explorer
(WISE). Cross-correlation of robustly-detected WISE 22 micron
sources with the Hipparcos 2 catalog yields 25,964 stars within
120 pc of the Sun and 47,204 Tycho stars whose proper motions are
suggestive of the same distance horizon. After careful vetting to
exclude sources compromised by image artifacts, source confusion,
and astronomical contaminants, a total of 508 Hipparcos and 296 Tycho
high-confidence disk candidates emerge from the samples. Three hundred
forty-six Hipparcos and 277 Tycho stars are newly-identified infrared
excess stars. We have observed a subsample of the new FGK debris disk
candidates with Herschel at 70 and 160 microns and find a mixture of
warm and cold debris disks. In this talk, we will discuss the new WISE
debris disks and their ongoing characterization.
Title: Photometry Studies of Asteroids and Variable Stars
Authors: Han, Xianming; Li, B.; Zhao, H.; Liu, W.; Sun, L.; Gao, S.;
Shi, J.; Wang, S.; Pan, X.; Jiang, P.; Zhou, H.
Bibcode: 2013AAS...22144503H
Altcode:
During the fall semester of 2012, we carried out extensive photometry
studies of asteroids to obtain their rotation periods using the 0.9-m
SARA North telescope located at the Kitt Peak National Observatory in
Arizona and at the 0.6-m SARA South telescope located at the Cerro
Tololo Inter-American Observatory in Chile. The asteroids that we
carried out photometry studies include: 782 Montefiore, 3024 Hainan,
3842 Harlansmith, 3920 Aubignan, 5542 Moffatt, 5951 AliceMone,
6720 Gifu, 19978 1989VJ. We will present their rotation periods,
and compare with previous results where available. During the course
of photometry studies, we also discovered several variable stars. We
will also present these new variable stars and their periods.
Title: Numerical study of collisionless q = 1 double tearing
instability in a cylindrical plasma
Authors: Wei, Lai; Yang, Xuefeng; Zheng, Shu; Liu, Yue; Liu
Bibcode: 2012JPlPh..78..663W
Altcode:
The double tearing mode (DTM) instability with two q s
= 1 rational surfaces is investigated by taking into account the
collisionless effects, including electron inertia and electron
viscosity in a cylindrical geometry. The calculations show that for
q-profile with a small distance between two rational surfaces, Δr
s, there exists a broad linear spectrum of collisionless
DTMs. The collisionless effects not only can significantly increase the
linear growth rate of DTMs but can also enlarge the width of spectrum
of unstable modes. For the q-profile with fixed Δr s
and fixed magnetic shears at two rational surfaces, the high-order
harmonics with smaller wavelength, such as the m/n = 2/2, 3/3 and 4/4
modes, can be easily excited to have larger growth rates than the m/n
= 1/1 mode by `lifting' the safety factor value between two rational
surfaces. The characteristics of eigenmode structures of the most
unstable and secondly unstable DTMs with various mode numbers are
analyzed in detail and the corresponding collisionless scalings are
numerically obtained and verified theoretically based on the previous
relevant analytical theories. In addition, the synergetic effects of
plasma resistivity, electron inertia and electron viscosity on the
linear growth rates of DTMs are analyzed.
Title: Quantifying Coronal Dimming as Observed in EUV and X-ray
Images in Eruptive Events
Authors: Nitta, N. V.; Aschwanden, M. J.; Boerner, P.; Hill, S. M.;
Lemen, J. R.; Liu, W.; Schrijver, C.; Wuelser, J.
Bibcode: 2012AGUFMSH41A2097N
Altcode:
Data from SOHO have shown that coronal dimming is closely related
with coronal mass ejections (CMEs). In particular, dimming areas in
EIT 195 A images often match the lateral extension of the associated
CMEs. In this presentation, we summarize how CMEs compare with dimming
as identified at different wavelengths and by other instruments, such as
Yohkoh SXT, TRACE, GOES (12-15) SXI, STEREO EUVI and SDO AIA. Emphasis
is placed on recent data, since the combination of AIA and STEREO
data can lead us to better characterize CMEs and to more accurately
estimate how much mass is ejected. We discuss technical issues that
arise when quantifying dimming as a proxy for a CME. The issues include
instrument calibration, effects of heating and cooling and integration
along the line of sight. We also touch on the relation of dimming with
globally propagating coronal fronts, which are routinely isolated in
running difference images, and its implications on the magnitudes of
the associated CMEs.
Title: Observation and Theoretical Interpretation of Fermi Detected
Solar Flares with Gamma-ray Emission >100 MeV
Authors: Petrosian, V.; Chen, Q.; Liu, W.; Omodei, N.; Allafort, A.
Bibcode: 2012AGUFMSH51C..06P
Altcode:
With solar activity ramping up Fermi Space Telescope is accumulating
data from increasing number of solar flares with some having
substantial flux above 100 MeV, as detected by Fermi-Large Area
Telescope. Unlike previous such detection by EGRET on board Compton
Gamma-ray Observatory, some of the Fermi detections are not from
powerful GOES X-class flares. We will review the observations of
these flares by Fermi and other instruments, notably RHESSI, GOES,
SDO and ground based observations. As examples of an impulsive and
a long duration gamma-ray flare we will focus on the 2010 June 12
and 2011 March 7-8 with 12 hours of gamma-ray emission. Based on the
temporal and spectral characteristics of these flares we will discuss
the competing processes (i) for production of the gamma-ray and other
radiation (leptonic vs hadronic), (ii) affecting the transport of
the accelerated particle (turbulence and field geometry), and (iii)
those involved in determining the site (CME shock or flaring loop)
and mechanism of the acceleration of particles into the GeV range
(first or second order Fermi). This paper is presented on behalf of
Fermi Collaboration.
Title: Poloidal ULF wave observed in the plasmasphere boundary layer
Authors: Liu, W.; Cao, J.; Zong, Q.; Li, X.; Sarris, T. E.;
Angelopoulos, V.
Bibcode: 2012AGUFMSM33A..01L
Altcode:
We investigate an event on the formation of a plasmasphere boundary
layer and its effect on ULF wave generation observed by THEMIS
satellites during three consecutive outbound passes. On September 13
2011, TH-D observed a sharp plasmapause at L=3.4. The plasmasphere
starts to expand and to be refilled on September 14th. On September
15th, a plasmasphere boundary layer is formed with two density drops
at L=4.5 and 6.5, respectively. Strong radial magnetic field and
azimuthal electric field oscillations are observed within the two
density gradients, suggesting poloidal ULF wave. Even mode signature
and bump-on-tail plasma distribution at ~10keV observed in this event
favour the mechanism of drift-bounce resonance. We suggest that
the plasma density structures in plasmasphere boundary layers can
provide conditions for resonances that could generate ULF waves. All
the above features suggest that plasmasphere boundary layer may have
impact on the generation of ULF wave and potential impact on radiation
belt acceleration.
Title: Three Dimensional Lunar Wake Reconstructed by the ARTEMIS Data
Authors: Zhang, H.; Khurana, K. K.; Kivelson, M. G.; Angelopoulos,
V.; Zong, Q.; Pu, Z.; Hsu, T.; Wan, W.; Shi, Q.; Liu, W.
Bibcode: 2012AGUFM.P43D1942Z
Altcode:
Thanks to large data coverage of the ARTEMIS mission within the lunar
wake, we reconstructed the lunar wake in a three dimensional manner
by presenting distributions of key plasma and field parameters: the
ion density, parallel and perpendicular temperatures, ion thermal
pressure, magnetic pressure (field magnitude), total pressure, and
field and flow perturbations. Our observations suggest that the wake
is confined within a rarefaction front, which propagates at fast mode
velocities in the rest frame of solar wind. When solar wind plasma is
absorbed by the dayside lunar surface, a diamagnetic current system
with thickness of ~2 ri forms on the surface of the Moon and initiates
field disturbances there (bend and compression). These disturbances are
controlled by the solar wind ion beta. In the wake behind the Moon, due
to force unbalance, plasma reenters into the wake through perpendicular
and parallel ways. In the perpendicular way, the inward flowing plasma
continues to squeeze flux tubes in the wake, and thus enhances field
magnitude there. In the parallel way, the refilling process presents
more kinetic features, and leads to higher perpendicular temperature
inside the wake. The refilling plasma from opposite sides of the
wake may mix with each other significantly at ~6 RM downstream from
the Moon, and the lunar wake is found to have fine structure within
that distance. In addition, our data also shows that plasma may be
decelerated by a total pressure gradient force in the direction against
the background solar wind. Our observations thus establish a global
lunar wake picture to be tested by theories or simulations.
Title: Interaction of Cometary Material With the Solar Corona:
EUV Observations and MHD Simulations
Authors: Liu, W.; Jia, Y.; Downs, C.; Schrijver, C.; Saint-Hilaire,
P.; Battams, K.; Tarbell, T. D.; Shine, R. A.
Bibcode: 2012AGUFMSH13B2254L
Altcode:
Extreme ultraviolet (EUV) emission from two recent sun-grazing comets,
C/2011 N3 and C/2011 W3 (Lovejoy), has been observed in the solar corona
for the first time by the SDO/AIA and STEREO/EUVI instruments (Schrijver
et al. 2011). These observations provided a unique opportunity to
investigate the interaction of the cometary material with the solar
corona and probe their physical conditions. We present here EUV
observations and MHD simulations on this subject, focusing on the
deceleration of the cometary tail material within the corona. We found
that despite their different local coronal environments, the two comets
exhibited quite similar characteristics. The initial EUV emitting tail
had a projected velocity of 100-200 km/s, which was much lower than the
orbital velocity of 500-600 km/s in the plane-of-sky. This indicates
that significant deceleration had taken place while the tail material
was heated to coronal temperatures on the order of 1 MK before it
started to emit in EUV (Bryans & Pesnell 2012). After its initial
appearance, the tail further experienced a projected deceleration
of ~1 km/s^2 (or 4 g_Sun). In particular, in the Lovejoy case, the
tail appeared as clusters of bright parallel striations roughly at
right angles to the orbit direction, suggestive of magnetic field
lines illuminated by the plasma frozen onto them. These striations
came to a stop and then accelerated in an opposite direction (seen
in projection), approaching a constant velocity of ~50 km/s. These
observations suggest that a Lorentz force from the coronal magnetic
field was operating on the newly ionized cometary plasma. To test this
hypothesis and understand tail deceleration mechanisms, we adopted a
multi-fluid MHD model (Jia et al. 2012) to simulate the interaction
between charged particles and the magnetized coronal plasma. We used
potential extrapolation (Schrijver & DeRosa 2003) and a more
sophisticated global MHD model (Lionello et al. 2009) to infer the
magnetic field and plasma conditions of the corona along the comet's
orbit as inputs to the simulations. We will compare the observations and
simulation results, and discuss the implications for using sun-grazing
comets as probes to the solar corona in the context of NASA's future
Solar Probe Plus mission.
Title: Next Generation Auroral Imaging From Space
Authors: Spanswick, E. L.; Donovan, E.; Liu, W.; Unick, C.; Uritsky,
V. M.
Bibcode: 2012AGUFMSA13D..05S
Altcode:
Geospace multi-scale dynamics are projected (albeit imperfectly)
onto the upper atmosphere via the aurora, and consequently auroral
observations provide us with our best way of observing geospace at the
system-level. Over the last 40 years, there have been great successes
in auroral imaging from space. Still, we must acknowledge that there
are shortcomings. For example, true daylight suppression has eluded us,
and the dynamic range of past auroral imagers has not been sufficient
to allow for reliable determination of the open-closed boundary (OCB)
from auroral images. As well, the spatial resolution of satellite-borne
imagers to date has not been sufficient to enable tracking of dynamic
auroral features such as arcs. Finally, all auroral imaging missions
to date have been single satellite, so that we have never imaged
complete sequences spanning long-duration processes such as storms and
SMC events. Much more importantly, the inability to specify the OCB
means we have never reliably measured the time series of open flux,
and so the fundamental driver of all geospace dynamics has never been
quantified. In terms of the underlying dynamics of geospace, we have
yet to specify the space/time distribution of auroral structures
across all relevant scales, so transients and the non-equilibrium
cascade cannot be studied within the context of the overall system
dynamics. In this talk, we present the results of a decade of planning
for the "next generation" of auroral imaging. We discuss how new imaging
technologies, flown on three-axis stabilized satellites will allow for
accurate specification of the OCB at all local times, for near-perfect
suppression of daylight and thus excellent dayside auroral imaging, and
spatial resolution allowing for identification and tracking of arcs,
patches, and other features that have never been imaged globally. We
present the significant advantages of a two-satellite imaging mission
as envisaged for the concepts of Canada's Ravens and PCW missions,
and China's Kuafu B satellite pair. Finally, we argue that 24/7 "next
generation" auroral imaging, complimented by equally innovative ENA
and X-ray imaging, will form the cornerstone of what we call the Great
Geospace Observatory.
Title: If substorm onset triggers tail reconnection, what triggers
substorm onset?
Authors: Liu, W. W.; Liang, J.; Donovan, E. F.; Spanswick, E.
Bibcode: 2012JGRA..11711220L
Altcode:
Despite the claim that tail reconnection triggers substorm onset,
there is an abundance of cases wherein substorm onset triggers tail
reconnection. In such cases, the first observable precursor to onset
is a periodic rippling (beads) along an equatorward auroral arc. In
this study, through an example, we show that substorms arising out
of arcs of this type have the classical “inside-out” evolution,
including the triggering of tail reconnection as a possible result. We
then investigate what the magnetospheric mode underlying the ripples
along the arcs might be. The classical MHD ballooning invoked by some
substorm theories is inconsistent with the observation, which exhibits
a finite azimuthal wavelength comparable to the local ion gyroradius
and the propensity of onset to occur under moderately high (1-10)
rather than extremely high plasma β. We show that the onset is due
to a modified ballooning mode, subject to corrections by the General
Ohm's Law and ion heat flux. The net result is that the necessary
condition for the instability remains unchanged from the classical
MHD, but the growth rate of the instability is heavily attenuated or
quenched in the high β and short azimuthal wavelength limits. In
the actual magnetosphere, the mode has a wavelength ∼1,500 km,
growth timescale ∼10 s, and critical plasma beta in the 3-13 range,
all consistent with observations.
Title: Indirect measurements of reactions in hot p-p chain and
CNO cycles
Authors: Wang, Y. B.; Guo, B.; Jin, S. J.; Li, Z. H.; Binh, D. N.;
Hashimoto, H.; Hayakawa, S.; He, J. J.; Hu, J.; Iwasa, N.; Kahl,
D. M.; Kubono, S.; Kume, N.; Li, E. T.; Li, Y. J.; Liu, X.; Su, J.;
Xu, S. W.; Yamaguchi, H.; Yan, S. Q.; Zeng, S.; Bai, X. X.; Lian,
G.; Wang, B. X.; Liu, W. P.
Bibcode: 2012AIPC.1484...19W
Altcode:
Several reactions have been experimentally studied, including
the 12N(d,n)13O and the ones induced by
the 3He+12C entrance channel. The former
was carried out at the CRIB facility of University of Tokyo,
aiming to indirectly determine the astrophysical reaction rates
of the 12N(p,γ)13O reaction. For the
3He+12C entrance channel, many excited states
of several nuclei are populated and the angular distribution of each
state is being analyzed.
Title: SDO/AIA Detection of Solar Prominence Formation within a
Coronal Cavity
Authors: Berger, Thomas E.; Liu, Wei; Low, B. C.
Bibcode: 2012ApJ...758L..37B
Altcode: 2012arXiv1208.3431B
We report the first analyses of SDO/AIA observations of the formation of
a quiescent polar crown prominence in a coronal cavity. The He II 304 Å
(log T max ~ 4.8 K) data show both the gradual disappearance
of the prominence due to vertical drainage and lateral transport of
plasma followed by the formation of a new prominence 12 hr later. The
formation is preceded by the appearance of a bright emission "cloud"
in the central region of the coronal cavity. The peak brightness of
the cloud progressively shifts in time from the Fe XIV 211 Å channel,
through the Fe XII 193 Å channel, to the Fe IX 171 Å channel (log T
max ~ 6.2, 6.1, 5.8 K, respectively) while simultaneously
decreasing in altitude. Filter ratio analysis estimates the initial
temperature of the cloud to be approximately log T ~ 6.25 K with
evidence of cooling over time. The subsequent growth of the prominence
is accompanied by darkening of the cavity in the 211 Å channel. The
observations imply prominence formation via in situ condensation of hot
plasma from the coronal cavity, in support of our previously proposed
process of magnetothermal convection in coronal magnetic flux ropes.
Title: Resistive wall mode in cylindrical plasmas in the presence
of surface currents
Authors: Cui, Shaoyan; Lu, Gaimin; Liu, Yue; Liu
Bibcode: 2012JPlPh..78..501C
Altcode:
Stability of the resistive wall mode in cylindrical plasmas confined by
surface currents is investigated for the δ-function and step-function
equilibrium surface-current profiles. For the former, it is shown that
the perturbations oscillate and even decay for all locations of the
initial perturbation. The entire system is stable and the plasma flow
has little effect. For the step-function surface-current distribution,
it is found that the thicker the surface current layer, the more stable
is the system even if the largest initial perturbation is located on
the rational surface, but the plasma flow also has little effect on
the system.
Title: The Black Hole Mass and Radio Characteristics of Radio Quasars
Authors: Xiong, D. R.; Zhang, X.; Zheng, Y. G.; Huang, B. R.; Mao,
L. S.; Liu, W. G.
Bibcode: 2012AcASn..53..369X
Altcode:
In this paper, we collect the redshift, bolometric luminosity,
full-width at half maximum (FWHM), monochromatic luminosity at
5100&:Aring;, radio loudness of 117 quasars, including 20 radio
quiet quasars and 97 radio loud quasars. Then we calculate the black
hole mass and Eddington ratio with the reverberation mapping method,
and calculate the radio luminosity using total 5 GHz flux density. By
analyzing the relations among them, our conclusions are as follows:
(1) there are weak correlations between black hole mass and bolometric
luminosity, between black hole mass and radio loudness, and between
black hole mass and radio luminosity for radio quiet quasars (RQQs),
while there are strong correlations between black hole mass and
bolometric luminosity, between black hole mass and radio loudness,
and between black hole mass and radio luminosity for radio loud
quasars (RLQs); (2) there are weak correlations between bolometric
luminosity and radio luminosity, and between bolometric luminosity and
monochromatic luminosity at 5100Å for RQQs, while there are strong
correlations between bolometric luminosity and radio luminosity, and
between bolometric luminosity and monochromatic luminosity at 5100Å for
RLQs; (3) the distributions of black hole mass, FWHM and Eddington ratio
between RQQs and RLQs are different. From these results we suggest that
the difference in black hole mass between RQQs and RLQs is predominantly
due to the difference in FWHM between RQQs and RLQs; the difference
between RQQs and RLQs is not due to the difference in orientation,
but due to the difference in intrinsic property; the black hole mass,
spin of black hole, Eddington ratio and morphology of host galaxy play
an important role in explaining the origin of radio loudness and the
radio loudness "bimodality"; there is a close link between the disk
accretion rate and the generation of the relativistic radio jet.
Title: Outward expansion of the lunar wake: ARTEMIS observations
Authors: Zhang, H.; Khurana, K. K.; Zong, Q. -G.; Kivelson, M. G.;
Hsu, T. -S.; Wan, W. X.; Pu, Z. Y.; Angelopoulos, V.; Cao, X.; Wang,
Y. F.; Shi, Q. Q.; Liu, W. L.; Tian, A. M.; Tang, C. L.
Bibcode: 2012GeoRL..3918104Z
Altcode:
Magnetohydrodynamics (MHD) predicts that lunar wake expands outward at
magnetosonic velocities in all directions perpendicular to background
solar wind; however, fluid theories emphasize that lunar wake expands
outward at sound speeds mainly along the interplanetary magnetic field
(IMF). Early observations supported the MHD predictions in the near-moon
region despite lack of solar wind and IMF observations. Thanks to the
special orbit design of the ARTEMIS mission, the solar wind conditions
are well determined at the time of concurrent observations in the
lunar wake. 164 wake crossings made by ARTEMIS are statistically
studied in this paper. Observations indicated that, in either distant
or near-Moon regions, the lunar wake expands outward at the fast
MHD wave velocities. This simple model provides a powerful way to
determine wake boundaries, particularly at large distances where the
boundary signatures are indistinct, thus allowing further studies on
the Moon-solar wind/crustal field-solar wind interactions.
Title: New Determination of the 13C(α, n)16O
Reaction Rate and its Influence on the s-process Nucleosynthesis in
AGB Stars
Authors: Guo, B.; Li, Z. H.; Lugaro, M.; Buntain, J.; Pang, D. Y.; Li,
Y. J.; Su, J.; Yan, S. Q.; Bai, X. X.; Chen, Y. S.; Fan, Q. W.; Jin,
S. J.; Karakas, A. I.; Li, E. T.; Li, Z. C.; Lian, G.; Liu, J. C.;
Liu, X.; Shi, J. R.; Shu, N. C.; Wang, B. X.; Wang, Y. B.; Zeng, S.;
Liu, W. P.
Bibcode: 2012ApJ...756..193G
Altcode: 2012arXiv1208.0714G
We present a new measurement of the α-spectroscopic factor (S
α) and the asymptotic normalization coefficient for the
6.356 MeV 1/2+ subthreshold state of 17O through
the 13C(11B, 7Li)17O
transfer reaction and we determine the α-width of this state. This is
believed to have a strong effect on the rate of the 13C(α,
n)16O reaction, the main neutron source for slow
neutron captures (the s-process) in asymptotic giant branch (AGB)
stars. Based on the new width we derive the astrophysical S-factor
and the stellar rate of the 13C(α, n)16O
reaction. At a temperature of 100 MK, our rate is roughly two times
larger than that by Caughlan & Fowler and two times smaller than
that recommended by the NACRE compilation. We use the new rate and
different rates available in the literature as input in simulations
of AGB stars to study their influence on the abundances of selected
s-process elements and isotopic ratios. There are no changes in the
final results using the different rates for the 13C(α,
n)16O reaction when the 13C burns completely
in radiative conditions. When the 13C burns in convective
conditions, as in stars of initial mass lower than ~2 M ⊙
and in post-AGB stars, some changes are to be expected, e.g., of up to
25% for Pb in our models. These variations will have to be carefully
analyzed when more accurate stellar mixing models and more precise
observational constraints are available.
Title: Discovery of Kangite, (Sc,Ti,Al,Zr,Mg,Ca,□)2O3, a New
Ultra-Refractory Mineral in Allende
Authors: Ma, C.; Tschauner, O.; Beckett, J. R.; Rossman, G. R.; Liu, W.
Bibcode: 2012M&PSA..75.5004M
Altcode:
Here we report the first occurrence of kangite in nature, as a new
ultra-refractory mineral among the earliest solids formed in the solar
system, and discuss its origin and significance for nebular processes.
Title: The Hydromagnetic Interior of a Solar Quiescent
Prominence. II. Magnetic Discontinuities and Cross-field Mass
Transport
Authors: Low, B. C.; Liu, W.; Berger, T.; Casini, R.
Bibcode: 2012ApJ...757...21L
Altcode:
This second paper of the series investigates the transverse response
of a magnetic field to the independent relaxation of its flux tubes
of fluid seeking hydrostatic and energy balance, under the frozen-in
condition and suppression of cross-field thermal conduction. The
temperature, density, and pressure naturally develop discontinuities
across the magnetic flux surfaces separating the tubes, requiring the
finite pressure jumps to be compensated by magnetic-pressure jumps in
cross-field force balance. The tangentially discontinuous fields are
due to discrete currents in these surfaces, δ-function singularities
in the current density that are fully admissible under the rigorous
frozen-in condition but must dissipate resistively if the electrical
conductivity is high but finite. The magnetic field and fluid must
thus endlessly evolve by this spontaneous formation and resistive
dissipation of discrete currents taking place intermittently in
spacetime, even in a low-β environment. This is a multi-dimensional
effect in which the field plays a central role suppressed in the
one-dimensional (1D) slab model of the first paper. The study begins
with an order-of-magnitude demonstration that of the weak resistive
and cross-field thermal diffusivities in the corona, the latter is
significantly weaker for small β. This case for spontaneous discrete
currents, as an important example of the general theory of Parker, is
illustrated with an analysis of singularity formation in three families
of two-dimensional generalizations of the 1D slab model. The physical
picture emerging completes the hypothesis formulated in Paper I that
this intermittent process is the origin of the dynamic interiors of
a class of quiescent prominences revealed by recent Hinode/SOT and
SDO/AIA high-resolution observations.
Title: A dipole pattern of the sea surface height anomaly in the
North Atlantic: 1990s-2000s
Authors: Li, Feili; Jo, Young-Heon; Liu, W. Timothy; Yan, Xiao-Hai
Bibcode: 2012GeoRL..3915604L
Altcode:
Despite a long-term trend of sea level rise continuing into the 2000s
in the subpolar North Atlantic, variations in the sea surface height
have behaved differently in both spatial and temporal domains. A dipole
pattern, centered between the Northern Atlantic subpolar region and
the region near the Gulf Stream, was observed in the linear trends
of the sea surface height anomaly (SSHA). By applying the Ensemble
Empirical Mode Decomposition (EEMD), we found that this dipole pattern
is mainly associated with the interannual to decadal SSHA oscillations
of the two regions, which are 180° out of phase with each other over
the time span of this study. The low-frequency variations of the
SSHA in the subpolar region are strongly inversely correlated with
the cumulative North Atlantic Oscillation (NAO) index (r = -0.84), in
contrast with the Gulf Stream region, which is positively correlated (r
= 0.22). This therefore reveals an asymmetric response of the regional
SSHA to the cumulative NAO-forcing, in which the subpolar variability
leads that of the Gulf Stream region by 29 months. Moreover, there is
a remarkable reversal of the SSHA trends from the 1990s to the 2000s,
which is unexpected given a weak and fluctuating NAO behavior since
mid-1990s. Such SSHA variations in the 2000s might be related to the
lagged variations of the Atlantic meridional overturning circulation
(AMOC).
Title: Interaction of solar wind pressure pulses with the
magnetosphere: IMF modulation and cavity mode
Authors: Liu, W. W.
Bibcode: 2012JGRA..117.8234L
Altcode: 2012JGRA..11708234L
Energy transfer through the magnetopause involves an interplay of
two processes. On one hand, microphysics of reconnection determines
how easily the magnetopause can be opened. On the other hand, the
global state of the solar wind and magnetosphere determines how much
energy is available for transfer and whether there exist "resonant"
interactions whereby the transfer is particularly efficient. In
the case of solar wind pressure pulses, empirical evidence has
suggested that the solar wind-magnetosphere interaction can become
unusually intense, leading to large-scale global auroral response and
occasionally geomagnetic storms. In this study, for the first time,
magnetic reconnection and global magnetospheric oscillation known as
the cavity mode are integrated to give a comprehensive description of
energy transfer through the dayside magnetopause. Using a heuristic
model in which the inflow into the magnetopause is proportional to the
magnitude of pressure pulse and an IMF proxy, we derive the fractions
of energy converted to reconnection and field-line resonance per unit
incident compressional energy in a pressure pulse. It is found that the
magnitude of energy transfer is modulated by the IMF proxy, whereas
the frequency spectrum of the transfer is modulated by the cavity
mode. Under extreme conditions, reconnection can transfer almost 100%
of incident compressional energy at the maximum absorption bands. Even
under the typical value reconnection rate (∼0.1), approximately 30%
of the incident energy can be absorbed in these bands. The frequency
response of reconnection transfer has pulse-like peaks in the >3 mHz
range and rather insensitive to the solar wind and wave parameters. In
contrast, the frequency response of the shear-Alfvénic transfer
centers in the 1-4 mHz range and has a more broadband shape that is
significantly influenced by the solar wind density.
Title: The Hydromagnetic Interior of a Solar Quiescent
Prominence. I. Coupling between Force Balance and Steady Energy
Transport
Authors: Low, B. C.; Berger, T.; Casini, R.; Liu, W.
Bibcode: 2012ApJ...755...34L
Altcode: 2012arXiv1203.1056L
This series of papers investigates the dynamic interiors of quiescent
prominences revealed by recent Hinode and SDO/AIA high-resolution
observations. This first paper is a study of the static equilibrium
of the Kippenhahn-Schlüter diffuse plasma slab, suspended vertically
in a bowed magnetic field, under the frozen-in condition and subject
to a theoretical thermal balance among an optically thin radiation,
heating, and field-aligned thermal conduction. The everywhere-analytical
solutions to this nonlinear problem are an extremely restricted subset
of the physically admissible states of the system. For most values
of the total mass frozen into a given bowed field, force balance
and steady energy transport cannot both be met without a finite
fraction of the total mass having collapsed into a cold sheet of zero
thickness, within which the frozen-in condition must break down. An
exact, resistive hydromagnetic extension of the Kippenhahn-Schlüter
slab is also presented, resolving the mass-sheet singularity into
a finite-thickness layer of steadily falling dense fluid. Our
hydromagnetic result suggests that the narrow, vertical prominence
Hα threads may be falling across magnetic fields, with
optically thick cores much denser and ionized to much lower degrees than
conventionally considered. This implication is discussed in relation
to (1) the recent SDO/AIA observations of quiescent prominences that
are massive and yet draining mass everywhere in their interiors, (2)
the canonical range of 5-60 G determined from spectral polarimetric
observations of prominence magnetic fields over the years, and (3)
the need for a more realistic multi-fluid treatment.
Title: Quasi-periodic Fast-mode Wave Trains within a Global EUV Wave
and Sequential Transverse Oscillations Detected by SDO/AIA
Authors: Liu, Wei; Ofman, Leon; Nitta, Nariaki V.; Aschwanden, Markus
J.; Schrijver, Carolus J.; Title, Alan M.; Tarbell, Theodore D.
Bibcode: 2012ApJ...753...52L
Altcode: 2012arXiv1204.5470L
We present the first unambiguous detection of quasi-periodic wave
trains within the broad pulse of a global EUV wave (so-called EIT wave)
occurring on the limb. These wave trains, running ahead of the lateral
coronal mass ejection (CME) front of 2-4 times slower, coherently
travel to distances >~ R ⊙/2 along the solar surface,
with initial velocities up to 1400 km s-1 decelerating to
~650 km s-1. The rapid expansion of the CME initiated at
an elevated height of 110 Mm produces a strong downward and lateral
compression, which may play an important role in driving the primary
EUV wave and shaping its front forwardly inclined toward the solar
surface. The wave trains have a dominant 2 minute periodicity that
matches the X-ray flare pulsations, suggesting a causal connection. The
arrival of the leading EUV wave front at increasing distances produces
an uninterrupted chain sequence of deflections and/or transverse (likely
fast kink mode) oscillations of local structures, including a flux-rope
coronal cavity and its embedded filament with delayed onsets consistent
with the wave travel time at an elevated (by ~50%) velocity within
it. This suggests that the EUV wave penetrates through a topological
separatrix surface into the cavity, unexpected from CME-caused magnetic
reconfiguration. These observations, when taken together, provide
compelling evidence of the fast-mode MHD wave nature of the primary
(outer) fast component of a global EUV wave, running ahead of the
secondary (inner) slow component of CME-caused restructuring.
Title: Keck Interferometer Nuller science highlights
Authors: Mennesson, Bertrand; Millan-Gabet, Rafael; Colavita, M. M.;
Serabyn, E.; Hinz, P.; Kuchner, M.; Liu, W.; Barry, R.; Stark, C.;
Ragland, S.; Woillez, J.; Traub, W.; Absil, O.; Defrère, Denis;
Augereau, J. C.; Lebreton, J.
Bibcode: 2012SPIE.8445E..07M
Altcode:
We report here on some of the major astronomical observations obtained
by the Keck Interferometer Nuller (KIN), the high dynamic range
instrument recombining the Keck Telescopes at wavelengths of 8 to 13
microns. A few science targets were observed during the commissioning
phase (2004-2007). These early observations aimed at demonstrating the
KIN’s ability to spatially resolve and characterize circumstellar
dust emission around a variety of targets, ranging from evolved stars
to young debris disks. Science operations started then in 2008 with
the more demanding KIN exozodi key science programs, augmented by
observations of YSOs and hot debris disks between 2009 and 2011. The
last KIN observations were gathered in 2011B, and the interpretation
of some of the results depicted here is still preliminary (exo-zodi
survey) or pending (complicated behavior observed in YSOs). We discuss
in particular the initial results of the KIN’s exo-zodi observations,
which targeted a total of 40 nearby main sequence single stars. We look
for trends in this sample, searching for possible correlations between
the measured KIN excesses and basic stellar properties such as spectral
type or the presence of dust inferred from separate observations.
Title: Large-Scale Coronal Disturbances as Observed by SDO AIA
Authors: Nitta, Nariaki; Schrijver, Carolus; Title, Alan; Lemen,
James; Liu, Wei
Bibcode: 2012cosp...39.1378N
Altcode: 2012cosp.meet.1378N
With increasing solar activity, the Atmospheric Imaging Assembly
(AIA) on the Solar Dynamics Observatory (SDO) has observed a number
of large-scale coronal disturbances, which may correspond to what we
have generally known as "EIT waves." Although their nature is still
actively debated, these disturbances usually accompany CMEs. In certain
cases, the fronts of the disturbances may signify CME-related shock
waves important for particle acceleration. Using the unprecedented
temporal resolution and broad temperature coverage of the AIA, we have
studied more than 100 such events. Here we discuss their kinematics
characterized by faster fronts than EIT waves in Solar Cycle 23, and
spatial relations with CMEs using STEREO data that provide triangulation
of the fronts. We also try plasma diagnostic using images in different
filters. Association of these disturbances with CMEs, flares and type
II bursts is discussed on a statistical basis. Lastly, we explore the
possible relation of the larger-scale coronal disturbances with SEP
events observed at widely separate longitudes and their onset times.
Title: Slow-Mode Oscillations of Hot Loops Excited at Flaring
Footpoints
Authors: Wang, T.; Liu, W.; Ofman, L.; Davila, J.
Bibcode: 2012ASPC..456..127W
Altcode: 2017arXiv170605427W
The analysis of a hot loop oscillation event using SOHO/SUMER,
GOES SXI, and RHESSI observations is presented. Damped Doppler shift
oscillations were detected in the Fe xix line by SUMER, and interpreted
as a fundamental standing slow mode. The evolution of soft X-ray
emission from GOES/SXI and hard X-ray sources from RHESSI suggests
that the oscillations of a large loop are triggered by a small flare,
which may be produced by interaction (local reconnection) of this
large loop with a small loop at its footpoint. This study provides
clear evidence supporting our early conjecture that the slow-mode
standing waves in hot coronal loops are excited by impulsive heating
(small or microflares) at the loop's footpoint.
Title: The Journey of Sungrazing Comet Lovejoy
Authors: Bryans, Paul; A'Hearn, M.; Battams, K.; Biesecker, D.;
Bodewits, D.; Boice, D.; Brown, J.; Caspi, A.; Chodas, P.; Hudson,
H.; Jia, Y.; Jones, G.; Keller, H. U.; Knight, M.; Linker, J.; Lisse,
C.; Liu, W.; McIntosh, S.; Pesnell, W. D.; Raymond, J.; Saar, S.;
Saint-Hilaire, P.; Schrijver, C.; Snow, M.; Tarbell, T.; Thompson,
W.; Weissman, P.; Comet Lovejoy Collaboration Team
Bibcode: 2012AAS...22052507B
Altcode:
Comet Lovejoy (C/2011 W3) was the first sungrazing comet, observed
by space-based instruments, to survive perihelion passage. First
observed by ground-based telescopes several weeks prior to perihelion,
its journey towards the Sun was subsequently recorded by several solar
observatories, before being observed in the weeks after perihelion by
a further array of space- and ground-based instruments. Such a surfeit
of wide-ranging observations provides an unprecedented insight into
both sungrazing comets themselves, and the solar atmosphere through
which they pass. This paper will summarize what we have learnt from the
observations thus far and offer some thoughts on what future sungrazing
comets may reveal about comets, the Sun, and their interaction.
Title: SDO/AIA Detection of Quasi-periodic Wave Trains Within Global
EUV ("EIT") Waves and Their Coronal Seismology Implications
Authors: Liu, Wei; Ofman, L.; Aschwanden, M. J.; Nitta, N.; Schrijver,
C. J.; Title, A. M.; Tarbell, T. D.
Bibcode: 2012AAS...22051501L
Altcode:
The nature of global EUV waves (so-called "EIT waves") has long
been under debate because of instrumental limitations and projection
effects when viewed on the solar disk. We present here high cadence
SDO/AIA observations of global EUV waves occurring on the limb. We
report newly discovered quasi-periodic wave trains located in the low
corona within a broad, diffuse pulse of the global EUV wave ahead of
the lateral CME front/flank. These waves coherently travel to large
distances on the order of 1 solar radii with initial velocities up
to 1400 km/s. They have dominant 1-3 minute periodicities that often
match the X-ray pulsations of the accompanying flare, suggestive of
a causal connection. In addition, recently discovered quasi-periodic
fast propagating (QFP) waves of 1000-2000 km/s (Liu, Title, Zhao et
al. 2011 ApJL) are found in the funnel of coronal loops rooted at the
flare kernel. These waves are spatially confined within the CME bubble
and rapidly disappear while approaching the CME front, suggestive
of strong damping and/or dispersion. These observations provide new
evidence of the fast-mode wave nature of the primary, fast component
of a global EUV wave, running ahead of a secondary, slow component
of CME-caused restructuring of the coronal magnetic field. We suggest
that the two types of quasi-periodic waves are both integral parts of
global coronal dynamics manifested as a CME/flare eruption, and they
have important implications for global and local coronal seismology.
Title: WISE Photometry of Young Stellar Object Candidates in the
Canis Major Star-Forming Region
Authors: Padgett, Deborah; Liu, W.; Rebull, L.; Leisawitz, D.
Bibcode: 2012AAS...22033403P
Altcode:
We present WISE (Wide-field Infrared Survey Explorer) photometry
of young stellar object candidates in the Canis Major clouds at a
distance of 1 kpc. WISE has identified 682 objects with apparent 12
and 22 micron excess emission in a 7 deg x 10 deg field around the
the CMa R1 cloud. While a substantial fraction of these candidates
are likely galaxies, AGB stars, and artifacts from confusion along
the galactic plane, others are part of a spectacular cluster of
YSOs imaged by WISE along a dark filament in the R1 cloud. Palomar
Double Spectrograph observations of several sources in this cluster
confirm their identity as young A and B stars with strong emission
lines. In this contribution,we plot the optical - mid-infrared spectral
energy distribution for the WISE YSO candidates and discuss potential
contaminants to the sample. The data demonstrate the utility of WISE
in performing wide-area surveys for young stellar objects.
Title: SDO/AIA Observations of Sustained Coronal Condensation in
Prominences as Return Flows of the Chromosphere-Corona Mass Cycle
Authors: Liu, Wei; Berger, T.; Low, B. C.
Bibcode: 2012AAS...22020708L
Altcode:
It has recently been proposed that prominences are manifestations
of a magneto-thermal convection process that involves ever-present
dynamic descents of cool material threads and upflows of hot bubbles
(Berger et al. 2011 Nature). On global scales, prominences may play
an important role as the return flows of the chromosphere-corona
mass cycle, in which hot mass is originally transported upward
through spicules. A critical step in this cycle is the condensation of
million-degree coronal plasma into T<10,000 K prominence material by
radiative cooling instability. However, direct observation of coronal
condensation has been difficult in the past, a situation recently
changed. We present here the first example observed with SDO/AIA,
in which hours of gradual cooling through multiple EUV channels (from
2 MK to 80,000 K) in large-scale loops leads to eventual condensation
at magnetic dips, where we find evidence of magnetic reconnection and
subsequent outflows. A moderate-size prominence of 10^14 gram is then
formed. Its mass is not static but maintained by a continual supply
through condensation at a high rate of 10^10 gram/s against a comparable
drainage through numerous vertical threads at less than free-fall
speeds. Most of the total condensation of 10^15 gram, comparable
to a CME mass and an order of magnitude more than the instantaneous
mass of the prominence itself, is drained in merely one day. These
new observations show that a macroscopically quiescent prominence is
microscopically dynamic (Liu, Berger, Low 2012 ApJL), involving the
passage of a significant mass that bears important implications for
the chromosphere-corona mass cycle. This interpretation is further
supported by the recent theoretical development on spontaneous formation
of current sheets and cool condensations (Low, Berger, Casini, &
Liu, 2012 submitted to ApJ).
Title: Coupling of Particle Acceleration and Atmospheric Dynamic
Response to Impulsive Energy Release in Solar Flares
Authors: Liu, Wei; Petrosian, V.; Chen, Q.; Mariska, J.
Bibcode: 2012AAS...22020419L
Altcode:
In solar flares, acceleration and transport of high-energy particles
and fluid dynamics of the atmospheric plasma are interrelated
processes coupled in a circular chain. Chromospheric evaporation,
for example, can alter the density and temperature distribution
along the flare loop, in particular in the acceleration site near
the loop-top source. This produces a feedback on particle collisional
heating, and more importantly on the energy release and acceleration
process. This in turn will change the heating of the chromosphere and
mass flows in the corona. In recent years, there have been increasing
theoretical and observational motivations to investigate these coupled
processes together in a self-consistent manner. We present here combined
Fokker-Planck modeling of particles and hydrodynamic simulation of
flare plasma. We extended our earlier hybrid simulation (Liu, Petrosian,
Mariska 2009) by feeding the updated plasma density and temperature at
the loop-top source to the stochastic acceleration process. We find
that the density enhancement causes the ratio of the electron plasma
frequency to gyro-frequency to increase. This can lead to the reduction
of the efficiency of electron acceleration and thus the quenching
or spectral softening of nonthermal hard X-ray tails observed during
the late stages of flares. This also affects the relative production
of energetic electrons vs. protons (Petrosian and Liu 2004). We will
compare our results with recent observations from RHESSI, SDO, and
Hinode. We will also discuss their implications for cyclic spectral
hardening, quasi-periodic flare pulsations, and recently imaged
super-fast quasi-periodic coronal waves originating from flare kernels.
Title: Impulsively Driven Waves And Flows In Coronal Active Regions
Authors: Ofman, Leon; Wang, T.; Davila, J. M.; Liu, W.
Bibcode: 2012AAS...22032204O
Altcode:
Recent SDO/AIA and Hinode EIS observations indicate that both (super)
fast and slow magnetosonic waves are present in active region (AR)
magnetic structures. Evidence for fast (100-300 km/s) impulsive flows
is found in spectroscopic and imaging observations of AR loops. The
super-fast waves were observed in magnetic funnels of ARs. The
observations suggest that waves and flow are produced by impulsive
events, such as (micro) flares. We have performed three-dimensional
magnetohydrodynamic (3D MHD) simulations of impulsively generated
flows and waves in coronal loops of a model bi-polar active region
(AR). The model AR is initiated with a dipole magnetic field and
gravitationally stratified density, with impulsively driven flow at
the coronal base of the AR in localized magnetic field structures. We
model the excitation of the flows in hot (6MK) and cold (1MK) active
region plasma, and find slow and fast magnetosonic waves produced by
these events. We also find that high-density (compared to surrounding
corona) loops are produced as a result of the upflows. We investigate
the parametric dependence between the properties of the impulsive
flows and the waves. The results of the 3D MHD modeling study supports
the conjecture that slow magnetosonic waves are often produced by
impulsive upflows along the magnetic field, and fast magnetosonic
waves can result from impulsive transverse field line perturbations
associated with reconnection events. The waves and flows can be used
for diagnostic of AR structure and dynamics.
Title: Some Like it Hot: the Trajectory of Sungrazing Comet C/2011 W3
(Lovejoy) in the Solar Neighborhood.
Authors: Saint-Hilaire, Pascal; Chodas, P. W.; Battams, K.; Tarbell,
T. D.; Shine, R. A.; Liu, W.; Thompson, W. T.; Comet Lovejoy
Collaboration Team
Bibcode: 2012AAS...22052107S
Altcode:
Sungrazing comet Lovejoy (C/2011 W3) was a recent spectacle in the sky,
observed from the ground and by a host of space-based instruments,
including several solar observatories. It is the first sungrazing comet
in recent memory to have survived perihelion (q 1.2 Rs). It is only
the second sungrazer to have been observed in the Sun's low corona in
the extreme ultra-violet (EUV), where a plethora of EUV observations
were obtained by the SDO and STEREO spacecraft. Such an occurrence
can be used to probe the solar corona and test our understanding
of plasma and cometary physics. In this work, we use the best orbit
elements currently available to plot the path of the comet's nucleus on
solar EUV images from SDO/AIA, both STEREO/EUVIs, and yellow continuum
(near the Na D lines) images from Hinode/SOT. We compare the predicted
positions and timing of the comet's nucleus to the latter, while the
SDO and STEREO EUV observations are used to estimate the distance at
which the EUV tail appears behind the comet's nucleus.
Title: Large-scale Coronal Disturbances As Observed By SDO AIA
Authors: Nitta, Nariaki; Schrijver, C.; title, A.; Liu, W.; Lemen, J.
Bibcode: 2012AAS...22051502N
Altcode:
With increasing solar activity, the Atmospheric Imaging Assembly
(AIA) on the Solar Dynamics Observatory (SDO) has observed a number
of large-scale coronal disturbances, which may correspond to what
we have generally known as "EIT waves." Their nature is still
actively debated. In certain cases, the fronts of the disturbances
may signify CME-related shock waves that are important for particle
acceleration. Using the unprecedented temporal resolution and broad
temperature coverage of the AIA, we have studied more than 100 such
events. Here we discuss their kinematics characterized by faster fronts
than EIT waves in Solar Cycle 23, and spatial relations with CMEs
using STEREO data that provide triangulation of the fronts. We also
try plasma diagnostic using images in different filters. Association
of these disturbances with other phenomena such as CMEs, flares and
type II bursts, is discussed on a statistical basis.
Title: Period doubling in magnetospheric convection cycle
Authors: Liu, W. William
Bibcode: 2012JGRA..117.4206L
Altcode: 2012JGRA..11704206L
A gedanken investigation is performed on magnetospheric complexity. In
an attempt to separate complexities due to external (solar wind) and
internal (magnetospheric) dynamics, we hold the solar wind condition
constant and investigate how the open flux in the magnetosphere
changes from one convection cycle to the next. The change of open
flux is related to the time integral of the tail electric field. This
field, in turn, is proportional to the product of the normal (x)
and tangential (z) components of the tail magnetic field. As the
magnetosphere evolves, the magnetic components typically vary
in opposite directions. We show that this competition leads to a
magnetic flux cycle described by the classical logistic equation
xn+1 = r(1 - xn)xn, where x is a
linear function of open flux, the much researched route to chaos through
period-doubling. The result could provide a possible explanation of the
steady magnetospheric convection, sawtooth events, and other observed
manifestations of nonlinearity.
Title: Explanatory Supplement to the WISE All-Sky Data Release
Products
Authors: Cutri, R. M.; Wright, E. L.; Conrow, T.; Bauer, J.; Benford,
D.; Brandenburg, H.; Dailey, J.; Eisenhardt, P. R. M.; Evans, T.;
Fajardo-Acosta, S.; Fowler, J.; Gelino, C.; Grillmair, C.; Harbut,
M.; Hoffman, D.; Jarrett, T.; Kirkpatrick, J. D.; Leisawitz, D.;
Liu, W.; Mainzer, A.; Marsh, K.; Masci, F.; McCallon, H.; Padgett,
D.; Ressler, M. E.; Royer, D.; Skrutskie, M. F.; Stanford, S. A.;
Wyatt, P. L.; Tholen, D.; Tsai, C. W.; Wachter, S.; Wheelock, S. L.;
Yan, L.; Alles, R.; Beck, R.; Grav, T.; Masiero, J.; McCollum, B.;
McGehee, P.; Papin, M.; Wittman, M.
Bibcode: 2012wise.rept....1C
Altcode:
The Wide-field Infrared Survey Explorer (WISE; Wright et al. 2010)
surveyed the entire sky at 3.4, 4.6, 12 and 22 microns in 2010,
achieving 5-sigma point source sensitivities per band better than
0.08, 0.11, 1 and 6 mJy in unconfused regions on the ecliptic. The
WISE All-Sky Data Release, conducted on March 14, 2012, incorporates
all data taken during the full cryogenic mission phase, 7 January 2010
to 6 August 2010, that were processed with improved calibrations and
reduction algorithms. Release data products include: (1) an Atlas
of 18,240 match-filtered, calibrated and coadded image sets; (2)
a Source Catalog containing positions and four-band photometry for
over 563 million objects, and (3) an Explanatory Supplement. Ancillary
products include a Reject Table that contains 284 million detections
that were not selected for the Source Catalog because they are low
signal-to-noise ratio or spurious detections of image artifacts, an
archive of over 1.5 million sets of calibrated WISE Single-exposure
images, and a database of 9.4 billion source extractions from those
single-images, and moving object tracklets identified by the NEOWISE
program (Mainzer et al. 2011). The WISE All-Sky Data Release products
supersede those from the WISE Preliminary Data Release (Cutri et
al. 2011). The Explanatory Supplement to the WISE All-Sky Data
Release Products is a general guide for users of the WISE data. The
Supplement contains an overview of the WISE mission, facilities, and
operations, a detailed description of WISE data processing algorithms,
a guide to the content and formats of the image and tabular data
products, and cautionary notes that describe known limitations of the
All-Sky Release products. Instructions for accessing the WISE data
products via the services of the NASA/IPAC Infrared Science Archive
are provided. The Supplement also provides analyses of the achieved sky
coverage, photometric and astrometric characteristics and completeness
and reliability of the All-Sky Release data products. The WISE
All-Sky Release Explanatory Supplement is an on-line document that is
updated frequently to provide the most current information for users of
the WISE data products. The Explanatory Supplement is maintained at: http://wise2.ipac.caltech.edu/docs/release/allsky/expsup/index.html WISE is a joint project of the University of California, Los Angeles
and the Jet Propulsion Laboratory/California Institute of Technology,
funded by the National Aeronautics and Space Administration. NEOWISE
is a project of the Jet Propulsion Laboratory/California Institute of
Technology, funded by the Planetary Science Division of the National
Aeronautics and Space Administration.
Title: The Hydromagnetic Nature of Quiescent Prominences
Authors: Low, B. C.; Berger, T.; Casini, R.; Liu, W.
Bibcode: 2012decs.confE..84L
Altcode:
High-resolution observations of quiescent prominences with Hinode
and SDO have revealed within their interiors the ever-¬present
descent at less than free-fall speeds of cool, vertical dense
filaments interspersed among upward, narrow streams at comparable
speeds of heated, low-density plasma. We address the physical nature
of this dynamical state. Despite the high magnetic Reynolds numbers
characterizing this hydromagnetic environment, magnetic reconnection
takes place via spontaneous formation and dissipation of current sheets
by the coupled effects of highly-anisotropic thermal conduction,
gravity, optically-thin radiation, heating, and high electrical
conductivity. In this interesting new version of the theory of Parker
(1994, Spontaneous current sheets in magnetic fields, Cambridge U
Press), pervasive reconnections produce a perennial local descent of
dense condensations under gravity along newly reconnected magnetic field
lines and a concurrent turbulent rise of buoyant pockets of heated
magnetized plasma through the large-scale magnetic structure. This
mechanism may explain the massive downward drainage through a quiescent
prominence observed recently (Liu et al. 2012 ApJ 745, L21) and, in
the broader context, relate the quiescent prominence to the surrounding
chromosphere/corona as a novel, large-scale, magneto-thermal convective
phenomenon (Berger et al. 2011, Nature 472, 197).
Title: SDO/AIA Observations of Sustained Coronal Condensation and Mass
Drainage in Prominences as Return Flows of the Chromosphere-Corona
Mass Cycle
Authors: Liu, Wei; Berger, Thomas; Low, B. C.
Bibcode: 2012decs.confE..90L
Altcode:
It has recently been proposed that prominences are manifestations
of a magneto-thermal convection process that involves ever-present
dynamic descents of cool material threads and upflows of hot bubbles
(Berger et al. 2011 Nature). On global scales, prominences may play
an important role as the return flows of the chromosphere-corona mass
cycle, in which hot mass is originally transported upward through
spicules. A critical step in this cycle is the condensation of
million-degree coronal plasma into T<10,000 K prominence material
by radiative cooling instability. However, direct observation of
coronal condensation has been difficult in the past, a situation
recently changed with the launch of the Hinode/SOT and SDO/AIA. We
present here the first example observed with SDO/AIA, in which hours of
gradual cooling through multiple EUV channels (from 2 MK to 80,000 K)
in large-scale loops leads to eventual condensation at magnetic dips,
forming a moderate-size prominence of 10^14 gram. The prominence
mass is not static but maintained by a continual supply through
condensation at a high rate of 10^10 gram/s against a comparable
drainage through numerous vertical threads at less than free-fall
speeds. Most of the total condensation of 10^15 gram, comparable
to a CME mass and an order of magnitude more than the instantaneous
mass of the prominence itself, is drained in merely one day. These
new observations show that a macroscopically quiescent prominence
is microscopically dynamic, involving the passage of a significant
mass that bears important implications for the chromosphere-corona
mass cycle. This interpretation is further supported by the recent
theoretical development on spontaneous formation of current sheets
and cool condensations (Low, Berger, Casini, & Liu, this meeting).
Title: Modeling waves, flows, and instabilities produced by impulsive
events in coronal active regions
Authors: Ofman, L.; Liu, W.; Wang, T. J.; Davila, J. M.; Thompson,
B. J.
Bibcode: 2012decs.confE..73O
Altcode:
Recent high-resolution observations by SDO/AIA combined with spectral
data from Hinode provide insights into the properties of MHD waves,
flows, and instabilities in coronal active region plasma and
their connection with impulsive energy release. Shear flow driven
instabilities, such as the Kelvin-Helmholtz (KH) instability were
only recently detected in detail in the corona. I will present recent
results of 3D MHD models of slow and fast magnetosonic waves in active
regions excited by jets and quasi-periodic flows driven by micro-flares
at loops' footpoints. I will discuss models of super-fast magnetosonic
waves detected recently by SDO/AIA. I will also discuss models of global
(EIT) waves, and KH instabilities driven by CMEs. The relations between
waves, flows, instabilities, and impulsive events such as flares and
CMEs are becoming apparent thanks to the combination of observational
data analysis and the 3D MHD modeling. Understanding these relations
is useful for coronal seismology and for tracing the flow of energy
from the transition region to the corona.
Title: Herschel Observations of Debris Disks from WISE
Authors: Padgett, D. L.; Stapelfeldt, K. R.; Liu, W.; Leisawitz,
D. T.; Fajardo-Acosta, S.
Bibcode: 2012faph.confE..44P
Altcode:
The Wide Field Infrared Survey Explorer (WISE) has just completed a
sensitive all-sky survey in photometric bands at 3.4, 4.6, 12, and 22
microns. We report on a study of main sequence Hipparcos and Tycho
catalog stars within 120 pc with WISE 22 micron emission in excess
of photospheric levels. This warm excess emission traces material in
the circumstellar region likely to host terrestrial planets and is
preferentially found in young systems with ages < 1 Gyr. Nearly a
hundred of the WISE new warm debris disk candidates detected among FGK
stars are being observed by Herschel/PACS to characterize circumstellar
dust. Preliminary results indicate 70 micron detection rates in excess
of 80% for these targets, suggesting that most of these systems have
both warm and cool dust in analogy to our asteroid and Kuiper belts. In
this contribution, we will discuss the WISE debris disk survey and
latest results from Herschel observations of these sources.
Title: SDO/AIA Observations of Various Coronal EUV Waves Associated
with Flares/CMEs and Their Coronal Seismology Implications
Authors: Liu, Wei; Ofman, Leon; Aschwanden, Markus J.; Nitta, Nariaki;
Zhao, Junwei; Title, Alan M.
Bibcode: 2012decs.confE..87L
Altcode:
MHD waves can be used as diagnostic tools of coronal seismology to
decipher otherwise elusive critical physical parameters of the solar
corona, such as the magnetic field strength and plasma density. They
are analogous to acoustic waves used in helioseismology, but with
complexities arising from the magnetic field and nonlinearity. Recent
high cadence, high resolution, full-disk imaging observations from
SDO/AIA have opened a new chapter in understanding these waves. Various
types of EUV waves associated with flares/CMEs have been discovered
or observed in unprecedented detail. In this presentation, we will
review such new AIA observations, focusing on the following topics and
their interrelationships: (1) quasi-periodic fast waves traveling along
coronal funnels within CME bubbles at speeds up to 2000 km/s, associated
with flare pulsations at similar frequencies; (2) quasi-periodic wave
trains within broad, diffuse pulses of global EUV waves (so-called
EIT waves) running ahead of CME fronts; (3) interactions of global EUV
waves with local coronal structures on their paths, such as flux-rope
coronal cavities and their embedded filaments (kink oscillations)
and coronal holes/active regions (deflections). We will discuss the
implications of these observations on coronal seismology, on their roles
in transporting energy through different parts of the solar atmosphere,
and on understanding their associated eruptive flares/CMEs.
Title: SDO/AIA Observations of Secondary Waves Generated by
Interaction of the 2011 June 7 Global EUV Wave with Solar Coronal
Structures
Authors: Li, Ting; Zhang, Jun; Yang, Shuhong; Liu, Wei
Bibcode: 2012ApJ...746...13L
Altcode: 2011arXiv1111.5202L
We present Solar Dynamics Observatory/Atmospheric Imaging Assembly
observations of the interaction of a global EUV wave on 2011 June
7 with active regions (ARs), coronal holes (CHs), and coronal bright
structures. The primary global wave has a three-dimensional dome shape,
with propagation speeds ranging from 430 to 780 km s-1 in
different directions. The primary coronal wave runs in front of the
expanding loops involved in the coronal mass ejection (CME) and its
propagation speeds are approximately constant within 10-20 minutes. Upon
arrival at an AR on its path, the primary EUV wave apparently disappears
and a secondary wave rapidly reemerges within 75 Mm of the AR boundary
at a similar speed. When the EUV wave encounters a coronal bright
structure, an additional wave front appears there and propagates in
front of it at a velocity nearly a factor of two faster. Reflected
waves from a polar CH and a coronal bright structure are observed and
propagate fractionally slower than the primary waves. Some of these
phenomena can be equally explained by either a wave or a non-wave
model alone. However, taken together, these observations provide new
evidence for the multitudes of global EUV waves, in which a true MHD
fast-mode wave or shock propagates in front of an expanding CME bubble.
Title: First SDO/AIA Observation of Solar Prominence Formation
Following an Eruption: Magnetic Dips and Sustained Condensation
and Drainage
Authors: Liu, Wei; Berger, Thomas E.; Low, B. C.
Bibcode: 2012ApJ...745L..21L
Altcode:
Imaging solar coronal condensation forming prominences was difficult
in the past, a situation recently changed by Hinode and the Solar
Dynamics Observatory (SDO). We present the first example observed with
the SDO/Atmospheric Imaging Assembly, in which material gradually cools
through multiple EUV channels in a transequatorial loop system that
confines an earlier eruption. Nine hours later, this leads to eventual
condensation at the dips of these loops, forming a moderate-size
prominence of ~1014 g, to be compared to the characteristic
1015 g mass of a coronal mass ejection (CME). The prominence
mass is not static but maintained by condensation at a high estimated
rate of 1010 g s-1 against a comparable, sustained
drainage through numerous vertical downflow threads, such that 96% of
the total condensation (~1015 g) is drained in approximately
one day. The mass condensation and drainage rates temporally correlate
with the total prominence mass. The downflow velocity has a narrow
Gaussian distribution with a mean of 30 km s-1, while the
downward acceleration distribution has an exponential drop with a
mean of ~1/6 g ⊙, indicating a significant canceling of
gravity, possibly by the Lorentz force. Our observations show that
a macroscopically quiescent prominence is microscopically dynamic,
involving the passage of a significant mass through it, maintained
by a continual mass supply against a comparable mass drainage, which
bears important implications for CME initiation mechanisms in which
mass unloading is important.
Title: New determination of the astrophysical 13C(
p, γ) 14N S(E) factors and reaction rates via the
13C(7Li, 6He) 14N reaction
Authors: Li, Y. J.; Li, Z. H.; Li, E. T.; Bai, X. X.; Su, J.; Guo,
B.; Wang, B. X.; Yan, S. Q.; Zeng, S.; Li, Z. C.; Liu, J. C.; Liu,
X.; Jin, S. J.; Wang, Y. B.; Zhang, L. Y.; Yu, X. Q.; Li, L.; Lian,
G.; Fan, Q. W.; Liu, W. P.
Bibcode: 2012EPJA...48...13L
Altcode:
The 13C(7Li, 6He) 14
N0,1 reactions were measured at E (7Li) = 34 MeV
with the Q3D magnetic spectrometer of the HI-13 tandem accelerator, and
the first peaks of the angular distributions were obtained for the first
time. The 14N0,1 proton spectroscopic factors were
extracted to be 0.67±0.09 and 0.73±0.10 , respectively. Using the
13C( p, γ) 14N direct capture S dc(
E) factors derived by the spectroscopic factors, the direct measurement
data for both 1- and 0- resonances were well
fitted via updating the resonance parameters, and then the total
astrophysical 13C( p, γ) 14N S( E) factors
and reaction rates were determined at stellar energies. The present
work offers an independent examination to the existing results of the
13 C( p, γ) 14N reaction.
Title: Measurement of reaction, decay of astrophysical interest and
progress of RI beam facilities
Authors: Liu, W.; BRIF Collaboration; Nuclear Astrophysics
Collaboration
Bibcode: 2012nuco.confE.170L
Altcode: 2012PoS...146E.170L
No abstract at ADS
Title: Kinematics and amplitude evolution of global coronal extreme
ultraviolet waves
Authors: Li, Ting; Zhang, Jun; Yang, Shu-Hong; Liu, Wei
Bibcode: 2012RAA....12..104L
Altcode:
With the observations of the Solar-Terrestrial Relations Observatory
(STEREO) and the Solar Dynamics Observatory (SDO), we analyze in
detail the kinematics of global coronal waves together with their
intensity amplitudes (so-called “perturbation profiles"). We use
a semi-automatic method to investigate the perturbation profiles of
coronal waves. The location and amplitude of the coronal waves are
calculated over a 30° sector on the sphere, where the wave signal is
strongest. The position with the strongest perturbation at each time
is considered as the location of the wave front. In all four events,
the wave velocities vary with time for most of their lifetime, up to 15
min, while in the event observed by the Atmospheric Imaging Assembly
there is an additional early phase with a much higher velocity. The
velocity varies greatly between different waves from 216 to 440 km
s-1. The velocity of the two waves initially increases,
subsequently decreases, and then increases again. Two other waves show a
deceleration followed by an acceleration. Three categories of amplitude
evolution of global coronal waves are found for the four events. The
first is that the amplitude only shows a decrease. The second is
that the amplitude initially increases and then decreases, and the
third is that the amplitude shows an orderly increase, a decrease,
an increase again and then a decrease. All the extreme ultraviolet
waves show a decrease in amplitude while propagating farther away,
probably because the driver of the global coronal wave (coronal mass
ejection) is moving farther away from the solar surface.
Title: Study of the primordial Lithium abundance at CIAE
Authors: Li, Z. H.; Li, E. T.; Su, J.; Guo, B.; Liu, W. P.; Li, Y. J.;
Chen, Y. S.; Hou, S. Q.; Bai, X. X.; Yan, S. Q.; Want, Y. B.; Want,
B. X.; Zeng, S.; Lian, G.; Liu, X.; Jin, S. J.
Bibcode: 2012nuco.confE.209L
Altcode: 2012PoS...146E.209L
No abstract at ADS
Title: New Young Star Candidates in the Taurus-Auriga Region as
Selected from WISE
Authors: Rebull, Luisa M.; Koenig, X.; Padgett, D.; Terebey, S.;
McGehee, P.; Hillenbrand, L.; Knapp, G.; Leisawitz, D.; Liu, W.;
Noriega-Crespo, A.; Ressler, M.; Stapelfeldt, K.; Fajardo-Acosta,
S.; Mainzer, A.
Bibcode: 2012AAS...21942505R
Altcode:
The Taurus Molecular Cloud subtends a large solid angle on the sky, in
excess of 250 square degrees. The search for legitimate Taurus members
to date has been limited by sky coverage as well as the challenge
of distinguishing members from field interlopers. The Wide-field
Infrared Survey Explorer (WISE) has recently observed the entire sky,
and we take advantage of the opportunity to search for young stellar
object (YSO) candidate Taurus members from a 260 square degree region
designed to encompass previously-identified Taurus members. We use
near- and mid-infrared colors to select objects with apparent infrared
excesses and incorporate other catalogs of ancillary data to present:
a list of rediscovered Taurus YSOs with infrared excesses (taken to
be due to circumstellar disks), a list of rejected YSO candidates
(largely galaxies), and a list of 94 surviving candidate new YSO-like
Taurus members. There is likely to be contamination lingering in this
candidate list, and follow-up spectra are warranted.
Title: A Risk Assessment Model and Method of Major Aerospace Projects
Authors: Jin, B.; Liu, W.; Chen, F.; Li, F.
Bibcode: 2012ESASP.699E..35J
Altcode:
A "five-claw" model which is based on the idea of risk profile in NASA,
common risk sources of equipment development in GJB 5852-2006 and
"nine-new" analysis method in CASC is put forward. The "five-claw"
risk assessment model uses design & test, manufacturing, basic
parts & general parts to describe aerospace projects' risk. In
order to assess the extent of a risk described by this new model,
a semi-quantitative method is put forward. It could avoid lacking
objectivity of qualitative method and the difficulty in data-obtaining
of quantitative method. Although the model and method present in
this paper may not be fully practical in major aerospace projects,
it just provides a new idea for risk assessment during the development
of major aerospace projects
Title: Destruction of Sun-Grazing Comet C/2011 N3 (SOHO) Within the
Low Solar Corona
Authors: Schrijver, C. J.; Brown, J. C.; Battams, K.; Saint-Hilaire,
P.; Liu, W.; Hudson, H.; Pesnell, W. D.
Bibcode: 2012Sci...335..324S
Altcode:
Observations of comets in Sun-grazing orbits that survive solar
insolation long enough to penetrate into the Sun's inner corona provide
information on the solar atmosphere and magnetic field as well as on
the makeup of the comet. On 6 July 2011, the Solar Dynamics Observatory
(SDO) observed the demise of comet C/2011 N3 (SOHO) within the low solar
corona in five wavelength bands in the extreme ultraviolet (EUV). The
comet penetrated to within 0.146 solar radius (~100,000 kilometers)
of the solar surface before its EUV signal disappeared. Before that,
material released into the coma - at first seen in absorption - formed
a variable EUV-bright tail. During the final 10 minutes of observation
by SDO's Atmospheric Imaging Assembly, ~6 × 10^8 to 6 × 10^10 grams
of total mass was lost (corresponding to an effective nucleus diameter
of ~10 to 50 meters), as estimated from the tail's deceleration due to
interaction with the surrounding coronal material; the EUV absorption
by the comet and the brightness of the tail suggest that the mass was
at the high end of this range. These observations provide evidence
that the nucleus had broken up into a family of fragments, resulting
in accelerated sublimation in the Sun's intense radiation field.
Title: SDO/AIA Observations of Quasi-periodic Fast (~1000 km/s)
Propagating (QFP) Waves as Evidence of Fast-mode Magnetosonic Waves
in the Low Corona: Statistics and Implications
Authors: Liu, W.; Ofman, L.; Title, A. M.; Zhao, J.; Aschwanden, M. J.
Bibcode: 2011AGUFMSH33A2043L
Altcode:
Recent EUV imaging observations from SDO/AIA led to the discovery of
quasi-periodic fast (~2000 km/s) propagating (QFP) waves in active
regions (Liu et al. 2011). They were interpreted as fast-mode
magnetosonic waves and reproduced in 3D MHD simulations (Ofman
et al. 2011). Since then, we have extended our study to a sample
of more than a dozen such waves observed during the SDO mission
(2010/04-now). We will present the statistical properties of these waves
including: (1) Their projected speeds measured in the plane of the sky
are about 400-2200 km/s, which, as the lower limits of their true speeds
in 3D space, fall in the expected range of coronal Alfven or fast-mode
speeds. (2) They usually originate near flare kernels, often in the wake
of a coronal mass ejection, and propagate in narrow funnels of coronal
loops that serve as waveguides. (3) These waves are launched repeatedly
with quasi-periodicities in the 30-200 seconds range, often lasting
for more than one hour; some frequencies coincide with those of the
quasi-periodic pulsations (QPPs) in the accompanying flare, suggestive
a common excitation mechanism. We obtained the k-omega diagrams and
dispersion relations of these waves using Fourier analysis. We estimate
their energy fluxes and discuss their contribution to coronal heating
as well as their diagnostic potential for coronal seismology.
Title: The EUV Emission in Comet-Solar Corona Interactions
Authors: Bryans, P.; Pesnell, W. D.; Schrijver, C. J.; Brown, J. C.;
Battams, K.; Saint-Hilaire, P.; Liu, W.; Hudson, H. S.
Bibcode: 2011AGUFMSH34B..05B
Altcode:
The Atmospheric Imaging Assembly (AIA) on the Solar Dynamics Observatory
(SDO) viewed a comet as it passed through the solar corona on 2011 July
5. This was the first sighting of a comet by a EUV telescope. For 20
minutes, enhanced emission in several of the AIA wavelength bands marked
the path of the comet. We explain this EUV emission by considering
the evolution of the cometary atmosphere as it interacts with the
ambient solar atmosphere. Water ice in the comet rapidly sublimates
as it approaches the Sun. This water vapor is then photodissociated,
primarily by Ly-α, by the solar radiation field to create atomic H and
O. Other molecules present in the comet also evaporate and dissociate
to give atomic Fe and other metals. Subsequent ionization of these
atoms can be achieved by a number of means, including photoionization,
electron impact, and charge exchange with coronal protons and other
highly-charged species. Finally, particles from the cometary atmosphere
are thermalized to the background temperature of the corona. Each step
could cause emission in the AIA bandpasses. We will report here on
their relative contribution to the emission seen in the AIA telescopes.
Title: Investigation of ULF waves in space and on the ground
Authors: Sarris, T. E.; Liu, W.; Li, X.; Argyriadis, E.
Bibcode: 2011AGUFMSM51B2080S
Altcode:
In this study we compare features of magnetospheric Ultra-Low
Frequency waves as they are observed on the ground and in space. In
particular, the characteristics that we investigate include the waves'
azimuthal mode number, using spacecraft conjunctions and azimuthally
aligned magnetometer stations; the wave amplitudes and their spatial
variations in space and on the ground; their occurence distribution
in terms of latitudinal and local time extent, as they are seen by
ground magnetometer chains and by multiple spacecraft in different
locations in the magnetosphere; and their polarization. We comment
on the characteristics that are mostly altered by the ionosphere
and on the implications in using ground measurements in models of
radial diffusion, which require the above inputs to approximate the
drift-resonant interraction of high-energy particles with ULF waves.
Title: Measurable realistic image-based 3D mapping
Authors: Liu, W.; Wang, J.; Wang, J. J.; Ding, W.; Almagbile, A.
Bibcode: 2011ArFKT..22..297L
Altcode:
Maps with 3D visual models are becoming a remarkable feature of 3D map
services. High-resolution image data is obtained for the construction
of 3D visualized models.The3D map not only provides the capabilities
of 3D measurements and knowledge mining, but also provides the
virtual experienceof places of interest, such as demonstrated in
the Google Earth. Applications of 3D maps are expanding into the
areas of architecture, property management, and urban environment
monitoring. However, the reconstruction of high quality 3D models is
time consuming, and requires robust hardware and powerful software to
handle the enormous amount of data. This is especially for automatic
implementation of 3D models and the representation of complicated
surfacesthat still need improvements with in the visualisation
techniques. The shortcoming of 3D model-based maps is the limitation of
detailed coverage since a user can only view and measure objects that
are already modelled in the virtual environment. This paper proposes and
demonstrates a 3D map concept that is realistic and image-based, that
enables geometric measurements and geo-location services. Additionally,
image-based 3D maps provide more detailed information of the real world
than 3D model-based maps. The image-based 3D maps use geo-referenced
stereo images or panoramic images. The geometric relationships between
objects in the images can be resolved from the geometric model of stereo
images. The panoramic function makes 3D maps more interactive with
users but also creates an interesting immersive circumstance. Actually,
unmeasurable image-based 3D maps already exist, such as Google street
view, but only provide virtual experiences in terms of photos. The
topographic and terrain attributes, such as shapes and heights though
are omitted. This paper also discusses the potential for using a low
cost land Mobile Mapping System (MMS) to implement realistic image
3D mapping, and evaluates the positioning accuracy that a measureable
realistic image-based (MRI) system can produce. The major contribution
here is the implementation of measurable images on 3D maps to obtain
various measurements from real scenes.
Title: Investigation on a dayside poloidal ULF wave event on 29
May 2007
Authors: Liu, W.; Sarris, T. E.; Li, X.; Zong, Q.; Ergun, R. E.;
Angelopoulos, V.; Glassmeier, K.
Bibcode: 2011AGUFMSM13B2070L
Altcode:
We investigate a strong poloidal ultralow frequency wave event in
the noon sector observed by THEMIS and LANL satellites on 29 May
2007. From 07:00 to 10:00 UT, five THEMIS satellites that were lined up
in similar outbound orbits consecutively observed narrow-band poloidal
pulsations from 10 to 4 mHz. The wave activity covered a broad region
from 09:00 to 13:30 LT azimuthally and 5 to 9.5 RE radially with an
azimuthal mode number around 8. The radial extent and power of the wave
decreased with time from 07:00 to 08:30 UT, suggesting a decay process
with a time scale of hours. In the region outside the plasmapause,
the wave power was observed to decrease then increase from 08:00 to
09:00 UT with a rapid temporal variation. The decrease in wave power,
which suggests fast decay (within one hour), might be related to the
evolution of the plasmasphere. The increase could be related to the
regeneration by the surface wave at the plasmapause. We suggest that
a coupling between the surface wave and the resonance of the field
line around the plasmapause takes place when the density inside the
plasmapause is twice of the density outside the plasmapause.
Title: Large-scale Coronal Propagating Fronts During the Rising
Phase of Solar Cycle 24
Authors: Nitta, N. V.; Liu, W.; Schrijver, C. J.; Title, A. M.; Lemen,
J. R.
Bibcode: 2011AGUFMSH23A1941N
Altcode:
With increasing solar activity, the AIA on SDO has observed a number
of large-scale coronal propagating fronts, which are often called
"EIT waves." Although their nature is still actively debated,
these propagating fronts usually accompany CMEs, and, in certain
cases, may signify CME-related shock waves important for particle
acceleration. Using the unprecedented temporal resolution and broad
temperature coverage of the AIA, it is possible to characterize
the propagating fronts in the corona far better than before, as
demonstrated in the literature for a yet small number of cases. We
study the properties of more than 40 propagating fronts as observed
by AIA, and discuss the key properties for them to be associated with
other phenomena such as type II radio bursts, flares, CMEs, ICMEs,
and SEP events. We make use of data, both remote-sensing and in-situ,
from STEREO which provides two additional vantage points, to make the
associations more solid. For the associated phenomena, their basic
properties are correlated with those of the propagating fronts. We
also revisit the association of EIT waves with other phenomena during
the similar phase of Solar Cycle 23 and discuss possible differences
in terms of global magnetic field. Understanding their relation with
other phenomena, we can have a more complete picture of the coronal
propagating fronts in the context of CME acceleration and deceleration.
Title: Quantifying Radial Diffusion of Radiation Belt Electrons Based
on Global MHD Simulation Validated by GOES and THEMIS Measurements
Authors: Tu, W.; Elkington, S. R.; Li, X.; Liu, W.
Bibcode: 2011AGUFMSM21C..08T
Altcode:
Radial diffusion is one of the most important acceleration mechanisms
for radiation belt electrons, which is due to the drift-resonant
interactions with large-scale fluctuations of the magnetosphere's
magnetic and electric fields (Pc4 and Pc5 ranges of ULF waves). A key
step in radial diffusion simulations is to quantify the radial diffusion
coefficient, which is related to the power spectral density and global
mode structure of the ULF waves. However, difficulties in determining
the global properties of ULF waves have guided researchers towards
specifying empirical forms of the diffusion coefficient, introducing
additional uncertainties in the radiation belt studies. In order to
quantify the radial diffusion, we run the global MHD simulations
to obtain the mode structure and power spectrum of the ULF waves
and validate the simulation results with available satellite
measurements, such as GOES and THEMIS measurements. The calculated
diffusion coefficient is shown to be dominated by the contribution
from magnetic field perturbations, and much less from the electric
field perturbations. Fast diffusion is found to generally occur when
solar wind dynamic pressure is high or nightside geomagnetic activity
is strong and with faster diffusion at higher L regions.
Title: VizieR Online Data Catalog: New young star candidates in
Taurus-Auriga (Rebull+, 2011)
Authors: Rebull, L. M.; Koenig, X. P.; Padgett, D. L.; Terebey, S.;
McGehee, P. M.; Hillenbrand, L. A.; Knapp, G. R.; Leisawitz, D.;
Liu, W.; Noriega-Crespo, A.; Ressler, M. E.; Stapelfeldt, K. R.;
Fajardo-Acosta, S.; Mainzer, A.
Bibcode: 2011yCat..21960004R
Altcode:
In the context of Rebull et al. (2010ApJS..186..259R), we assembled
a substantial multi-wavelength database, spanning Sloan u through
Spitzer/MIPS 160um (with some X-rays) for point sources throughout
the Taurus region. We use that catalog as the core for our analysis
here, updating it with confirmed Taurus members from, e.g., Kenyon
et al. (2008hsf1.book..405K) and Luhman et al. (2010ApJS..186..111L)
outside of our original Spitzer map. We have also searched SIMBAD (and
literature references therein) for known galaxies and other contaminants
in this vicinity. Our Taurus Spitzer Survey spanned ~44deg2
(figure 1). WISE data acquisition and reduction are discussed in Wright
et al. (2010AJ....140.1868W), Jarrett et al. (2011, ApJ, submitted),
and in the Explanatory Supplement to the WISE Preliminary Data Release
Products. There are four WISE bands, with central wavelengths at 3.4,
4.6, 12, and 22um, and a spatial resolution of 6" (12" at 22um). (3 data files).
Title: Modeling Super-fast Magnetosonic Waves Observed by SDO in
Active Region Funnels
Authors: Ofman, L.; Liu, W.; Title, A.; Aschwanden, M.
Bibcode: 2011ApJ...740L..33O
Altcode:
Recently, quasi-periodic, rapidly propagating waves have been observed
in extreme ultraviolet by the Solar Dynamics Observatory/Atmospheric
Imaging Assembly (AIA) instrument in about 10 flare/coronal mass
ejection (CME) events thus far. A typical example is the 2010 August 1
C3.2 flare/CME event that exhibited arc-shaped wave trains propagating
in an active region (AR) magnetic funnel with ~5% intensity variations
at speeds in the range of 1000-2000 km s-1. The fast
temporal cadence and high sensitivity of AIA enabled the detection
of these waves. We identify them as fast magnetosonic waves driven
quasi-periodically at the base of the flaring region and develop
a three-dimensional MHD model of the event. For the initial state
we utilize the dipole magnetic field to model the AR and include
gravitationally stratified density at coronal temperature. At the
coronal base of the AR, we excite the fast magnetosonic wave by
periodic velocity pulsations in the photospheric plane confined to a
funnel of magnetic field lines. The excited fast magnetosonic waves
have similar amplitude, wavelength, and propagation speeds as the
observed wave trains. Based on the simulation results, we discuss the
possible excitation mechanism of the waves, their dynamical properties,
and the use of the observations for coronal MHD seismology.
Title: Spatial structure and temporal evolution of a dayside poloidal
ULF wave event
Authors: Liu, W.; Sarris, T. E.; Li, X.; Zong, Q. -G.; Ergun, R.;
Angelopoulos, V.; Glassmeier, K. H.
Bibcode: 2011GeoRL..3819104L
Altcode:
We investigate a strong poloidal ultralow frequency wave event in
the noon sector observed by THEMIS and LANL satellites on 29 May
2007. From 07:00 to 10:00 UT, the five THEMIS satellites that were
lined up in similar outbound orbits consecutively observed narrow-band
poloidal pulsations from 10 to 4 mHz. The wave activity covered a broad
region from 09:00 to 13:30 LT azimuthally and 5 to 9.5 RE
radially. The radial extent and power of the wave decreased with
time from 07:00 to 08:30 UT, suggesting a decay process with a time
scale of hours. In the region outside the plasmapause, the wave power
was observed to decrease then increase from 08:00 to 09:00 UT with a
rapid temporal variation. The decrease in wave power, which suggests
fast decay (within one hour), might be related to the evolution of
the plasmasphere. The subsequent increase could possibly be related
to a regeneration process by a surface wave at the plasmapause. We
suggest that a coupling between the surface wave and the resonance
of the field line around the plasmapause takes place when the density
inside the plasmapause is twice the density outside the plasmapause.
Title: Coronal Seismology in the SDO Era: AIA Observations of Various
Coronal Waves Associated with CMEs/Flares
Authors: Liu, Wei; Ofman, Leon; Aschwanden, Markus J.; Nitta, Nariaki;
Zhao, Junwei; Title, Alan M.
Bibcode: 2011sdmi.confE..49L
Altcode:
MHD waves, as critical diagnostic tools of coronal seismology, can be
used to decipher otherwise elusive physical parameters of the solar
corona, such as the magnetic field strength and plasma density. They
are analogous to acoustic waves used in helioseismology. Recent high
cadence, high resolution, full-disk imaging observations from SDO/AIA
have opened a new chapter in understanding these waves. Various types
of waves associated with flares and/or CMEs have been discovered. In
this presentation, we will review such new AIA observations, focusing
on the following topics: (1) fine structures in CME-related global EUV
waves (so-called EIT waves), including a diffuse pulse superimposed
with multiple sharp fronts or "ripples" (Liu et al. 2010, ApJL); (2)
quasi-periodic fast waves traveling in coronal funnels at speeds up to
2000 km/s and associated with flares pulsating at similar frequencies
(Liu et al. 2011, ApJL); (3) interaction of global EUV waves with local
coronal structures on their paths, such as flux-rope coronal cavities
(triggered kink oscillations, Liu et al. in preparation) and coronal
holes/active regions (deflection). We will discuss the implications
of these observations on coronal seismology and on understanding their
associated flares and CMEs. We also anticipate to exchange ideas with
helioseismologists at this workshop, in a hope to bring together coronal
seismology and helioseismology techniques to advance our understanding
of solar oscillations from the interior to the upper atmosphere.
Title: Analysis of Land Water Storage in Southwest China Based on
GRACE Data
Authors: Liu, Wei; Miao, Yuan-Xing
Bibcode: 2011ChA&A..35..421L
Altcode:
The inversion of the variation in the land water storage in Southwest
China is carried out by taking advantage of the data obtained by the
earth gravity satellite GRACE (Gravity Recovery and Climate Experiment)
for 64 months from January 2005 to April 2010. The result shows that
by selecting an appropriate Gauss radius ( R = 600 km) and taking the
average gravitational field of the adopted data as the back-ground
gravitational field, the land water storage in Southwest China inverted
on the basis of the GRACE data reflects the drought in Southwest China
at the beginning of 2010 very well.
Title: Improving the 33S(p,γ)34Cl Reaction
Rate for Models of Classical Nova Explosions
Authors: Parikh, A.; Faestermann, Th.; Krücken, R.; Bildstein, V.;
Bishop, S.; Eppinger, K.; Herlitzius, C.; Lepyoshkina, O.; Maierbeck,
P.; Seiler, D.; Wimmer, K.; Hertenberger, R.; Wirth, H. -F.; Fallis,
J.; Hager, U.; Hutcheon, D.; Ruiz, Ch.; Buchmann, L.; Ottewell, D.;
Freeman, B.; Wrede, Ch.; García, A.; Delbridge, B.; Knecht, A.;
Sallaska, A.; Chen, A. A.; Clark, J. A.; Deibel, C. M.; Fulton, B.;
Laird, A.; Greife, U.; Guo, B.; Li, E.; Li, Z.; Lian, G.; Wang, Y.;
Liu, W.; Parker, P. D.; Setoodehnia, K.
Bibcode: 2011AIPC.1377..188P
Altcode:
Reduced uncertainty in the thermonuclear rate of the
33S(p,γ)34Cl reaction would help to improve
our understanding of nucleosynthesis in classical nova explosions. At
present, models are generally in concordance with observations that
nuclei up to roughly the calcium region may be produced in these
explosive phenomena; better knowledge of this rate would help with
the quantitative interpretation of nova observations over the S-Ca
mass region, and contribute towards the firm establishment of a
nucleosynthetic endpoint. As well, models find that the ejecta of
nova explosions on massive oxygen-neon white dwarfs may contain
as much as 150 times the solar abundance of 33S. This
characteristic isotopic signature of a nova explosion could possibly
be observed through the analysis of microscopic grains formed in the
environment surrounding a nova and later embedded within primitive
meteorites. An improved 33S(p,γ)34Cl rate
(the principal destruction mechanism for 33S in novae)
would help to ensure a robust model prediction for the amount of
33S that may be produced. Finally, constraining this
rate could confirm or rule out the decay of an isomeric state of
34Cl (Ex = 146 keV, t1/2 = 32 m) as a source
for observable gamma-rays from novae. We have performed several
complementary experiments dedicated to improving our knowledge of the
33S(p,γ)34Cl rate, using both indirect methods
(measurement of the 34S(3He,t)34Cl
and 33S(3He,d)34Cl reactions with the
Munich Q3D spectrograph) and direct methods (in normal kinematics at
CENPA, University of Washington, and in inverse kinematics with the
DRAGON recoil mass separator at TRIUMF). Our results will be used
with nova models to facilitate comparisons of model predictions with
present and future nova observables.
Title: On the progenitors of millisecond pulsars by the recycling
evolutionary channel
Authors: Liu, Wei-Min; Chen, Wen-Cong
Bibcode: 2011MNRAS.416.2285L
Altcode: 2011arXiv1106.1567L; 2011MNRAS.tmp.1198L
The recycling model suggested that low-mass X-ray binaries (LMXBs)
could evolve into binary millisecond pulsars (BMSPs). In this work,
we attempt to investigate the progenitor properties of BMSPs formed by
the recycling evolutionary channel, and if submillisecond pulsars can
be produced by this channel. Using Eggleton's stellar evolution code,
considering that the dead pulsars can be spun up to a short spin period
by the accreting material and angular momentum from the donor star,
we have calculated the evolution of close binaries consisting of a
neutron star (NS) and a low-mass main-sequence donor star, and the
spin evolution of NSs. In the calculation, some physical processes,
such as the thermal and viscous instability of an accretion disc,
propeller effect and magnetic braking, are included. Our calculated
results indicate that all LMXBs with a low-mass donor star of 1.0-2.0
M⊙ and a short orbital period (≲ 3-4 d) can form
millisecond pulsars with a spin period less than 10 ms. However, it
is difficult to produce submillisecond pulsars by this evolutionary
channel. In addition, our evolutionary scenario cannot account for
the existence of BMSPs with a long orbital period (Porb≳
70-80 d).
Title: Implications of X-ray Observations for Electron Acceleration
and Propagation in Solar Flares
Authors: Holman, G. D.; Aschwanden, M. J.; Aurass, H.; Battaglia, M.;
Grigis, P. C.; Kontar, E. P.; Liu, W.; Saint-Hilaire, P.; Zharkova,
V. V.
Bibcode: 2011SSRv..159..107H
Altcode: 2011SSRv..tmp..162H; 2011SSRv..tmp..242H; 2011SSRv..tmp..260H;
2011SSRv..tmp...86H; 2011arXiv1109.6496H
High-energy X-rays and γ-rays from solar flares were discovered
just over fifty years ago. Since that time, the standard for
the interpretation of spatially integrated flare X-ray spectra
at energies above several tens of keV has been the collisional
thick-target model. After the launch of the Reuven Ramaty High
Energy Solar Spectroscopic Imager ( RHESSI) in early 2002, X-ray
spectra and images have been of sufficient quality to allow a greater
focus on the energetic electrons responsible for the X-ray emission,
including their origin and their interactions with the flare plasma
and magnetic field. The result has been new insights into the flaring
process, as well as more quantitative models for both electron
acceleration and propagation, and for the flare environment with
which the electrons interact. In this article we review our current
understanding of electron acceleration, energy loss, and propagation
in flares. Implications of these new results for the collisional
thick-target model, for general flare models, and for future flare
studies are discussed.
Title: An Observational Overview of Solar Flares
Authors: Fletcher, L.; Dennis, B. R.; Hudson, H. S.; Krucker, S.;
Phillips, K.; Veronig, A.; Battaglia, M.; Bone, L.; Caspi, A.; Chen,
Q.; Gallagher, P.; Grigis, P. T.; Ji, H.; Liu, W.; Milligan, R. O.;
Temmer, M.
Bibcode: 2011SSRv..159...19F
Altcode: 2011SSRv..tmp..261F; 2011arXiv1109.5932F
We present an overview of solar flares and associated phenomena,
drawing upon a wide range of observational data primarily from the
RHESSI era. Following an introductory discussion and overview of
the status of observational capabilities, the article is split into
topical sections which deal with different areas of flare phenomena
(footpoints and ribbons, coronal sources, relationship to coronal mass
ejections) and their interconnections. We also discuss flare soft X-ray
spectroscopy and the energetics of the process. The emphasis is to
describe the observations from multiple points of view, while bearing
in mind the models that link them to each other and to theory. The
present theoretical and observational understanding of solar flares is
far from complete, so we conclude with a brief discussion of models,
and a list of missing but important observations.
Title: Current progress of nuclear astrophysical reaction and decay
study at CIAE
Authors: Liu, W. P.; Li, Z. H.; Guo, B.; Wang, Y. B.; Su, J.; Bai,
X. X.; Lian, G.; Wang, B. X.; Yan, S. Q.; Zeng, S.; Li, Y. J.; Li,
E. T.; Jin, S. J.; Liu, X.
Bibcode: 2011JPhCS.312d2013L
Altcode:
Presented here was current progress of the study of nuclear
astrophysical reaction and decay at CIAE. We studied astrophysical
12N(p,γ)13O reaction through the measurement
of the 12N(d,n)13O angular distribution
in inverse kinematics. Our result is in agreement with that from
the 14N(12N,13O)13C
reaction and two shell model calculations. We also measured
the angular distributions of single neutron transfer reaction of
7Li(6Li,7Li)6Li, and derived
the reaction cross section for 6Li(n,γ)7Li by
using the present spectroscopic factor. The astrophysical reaction
rate is found to be higher by a factor of 1.7 than the value adopted
in previous reaction network calculations. In addition, half-life of
147Sm in metal samarium and Sm2O3
was measured. No significant change has been observed within the
experimental uncertainty.
Title: New Young Star Candidates in the Taurus-Auriga Region as
Selected from the Wide-Field Infrared Survey Explorer
Authors: Rebull, L. M.; Koenig, X. P.; Padgett, D. L.; Terebey, S.;
McGehee, P. M.; Hillenbrand, L. A.; Knapp, G. R.; Leisawitz, D.;
Liu, W.; Noriega-Crespo, A.; Ressler, M. E.; Stapelfeldt, K. R.;
Fajardo-Acosta, S.; Mainzer, A.
Bibcode: 2011ApJS..196....4R
Altcode: 2011arXiv1106.5080R
The Taurus Molecular Cloud subtends a large solid angle on the sky, in
excess of 250 deg2. The search for legitimate Taurus members
to date has been limited by sky coverage as well as the challenge
of distinguishing members from field interlopers. The Wide-field
Infrared Survey Explorer has recently observed the entire sky, and we
take advantage of the opportunity to search for young stellar object
(YSO) candidate Taurus members from a ~260 deg2 region
designed to encompass previously identified Taurus members. We use
near- and mid-infrared colors to select objects with apparent infrared
excesses and incorporate other catalogs of ancillary data to present
a list of rediscovered Taurus YSOs with infrared excesses (taken to
be due to circumstellar disks), a list of rejected YSO candidates
(largely galaxies), and a list of 94 surviving candidate new YSO-like
Taurus members. There is likely to be contamination lingering in this
candidate list, and follow-up spectra are warranted.
Title: Direct Imaging of Quasi-periodic Fast Propagating Waves of
~2000 km s-1 in the Low Solar Corona by the Solar Dynamics
Observatory Atmospheric Imaging Assembly
Authors: Liu, Wei; Title, Alan M.; Zhao, Junwei; Ofman, Leon;
Schrijver, Carolus J.; Aschwanden, Markus J.; De Pontieu, Bart;
Tarbell, Theodore D.
Bibcode: 2011ApJ...736L..13L
Altcode: 2011arXiv1106.3150L
Quasi-periodic propagating fast mode magnetosonic waves in the solar
corona were difficult to observe in the past due to relatively low
instrument cadences. We report here evidence of such waves directly
imaged in EUV by the new Atmospheric Imaging Assembly instrument
on board the Solar Dynamics Observatory. In the 2010 August 1 C3.2
flare/coronal mass ejection event, we find arc-shaped wave trains of
1%-5% intensity variations (lifetime ~200 s) that emanate near the
flare kernel and propagate outward up to ~400 Mm along a funnel of
coronal loops. Sinusoidal fits to a typical wave train indicate a phase
velocity of 2200 ± 130 km s-1. Similar waves propagating
in opposite directions are observed in closed loops between two flare
ribbons. In the k-ω diagram of the Fourier wave power, we find a
bright ridge that represents the dispersion relation and can be well
fitted with a straight line passing through the origin. This k-ω
ridge shows a broad frequency distribution with power peaks at 5.5,
14.5, and 25.1 mHz. The strongest signal at 5.5 mHz (period 181 s)
temporally coincides with quasi-periodic pulsations of the flare,
suggesting a common origin. The instantaneous wave energy flux
of (0.1-2.6) × 107 erg cm-2 s-1
estimated at the coronal base is comparable to the steady-state heating
requirement of active region loops.
Title: Multi-instrument observations of soft electron precipitation
and its association with magnetospheric flows
Authors: Liang, Jun; Spanswick, E.; Nicolls, M. J.; Donovan, E. F.;
Lummerzheim, D.; Liu, W. W.
Bibcode: 2011JGRA..116.6201L
Altcode:
We present a multi-instrument study on the variations of optical
auroras and ionospheric electron densities during an interval of a
series of fast earthward flows in the magnetotail on 3 March 2009. The
flow-related auroral signatures include intermittent higher-latitude
(>68° magnetic latitude) intensifications manifested in green and
blue line auroras and more latitudinally extended red line auroral
intensifications and expansions. During the same interval the Poker
Flat incoherent scatter radar (PFISR) detected F region ionospheric
electron density enhancements which, together with the red line
auroral intensifications, give evidence for soft electron (<1 keV)
precipitation associated with fast magnetospheric flow activity. We
demonstrated the southward motion of ionospheric electron density
patches in correspondence to individual earthward flow bursts and
auroral activations. By virtue of the multibeam technique of PFISR we
construct the altitudinal profile of the density patches and estimate
that the characteristic energies of the precipitating electrons were
on order of a few hundred eV, comparable to the observed electron
temperature in the near-Earth central plasma sheet (CPS). We propose
that the fast flows give rise to enhanced ELF wave activity, which
causes strong pitch angle diffusion of the soft electron population
in the CPS via wave-particle interactions. The precipitation may be
further aided with a moderate field-aligned potential drop comparable
to or smaller than the CPS electron temperature. When the flows
penetrate into the inner plasma sheet, the adiabatic drift motion of
soft electrons may lead to a decreasing trend of electron energy with
decreasing radial distance, which is manifested in PFISR observations
as an ascending trend of the altitude range of the density patches
toward the equatorward auroral border.
Title: SDO/AIA Observations of a Global EUV Disturbance Traveling
into a Coronal Cavity and Its Subsequent Oscillations: New Evidence
of Fast Mode MHD Waves
Authors: Liu, Wei; Aschwanden, M. J.; Ofman, L.; Nitta, N. V.; Tarbell,
T. D.
Bibcode: 2011SPD....42.0906L
Altcode: 2011BAAS..43S.0906L
We report new SDO/AIA observations of a global EUV disturbance
that propagates at 600 km/s and sweeps through a coronal cavity,
instigating its bodily transverse oscillations. The high temporal
resolution and large FOV of AIA allow us to clearly see, for the first
time, the timing coincidence between the onsets of the oscillations
and the arrival of the disturbance at increasing distances covering
300 Mm in the neighborhood of the cavity. There is a time delay of
the oscillations from the near side to the far side of the cavity,
which is consistent with the travel time of the global perturbation. In
addition, we find a fine structure consisting of evenly spaced pulses
of periods 100-120 s within the global disturbance. In contrast, the
CME loop expansion falls behind the global disturbance at a smaller
velocity of 200 km/s. These observations suggests that this global
disturbance is a real fast mode MHD wave that continues propagating
into the cavity, rather than an apparent wave caused by CME expulsion
that is not expected to penetrate through a topological separatrix,
including the flux rope cavity boundary here. The cavity and its
hosted prominence have oscillation amplitudes of 20 km/s and periods
of 20-30 minutes. Such unusually long periods, compared with a few
minutes commonly observed in coronal loops, likely reflect kink mode
oscillations of the long cavity flux rope of a large length (a fraction
of the solar radius).
Title: Particle energization in 3D magnetic reconnection of
relativistic pair plasmas
Authors: Liu, Wei; Li, Hui; Yin, Lin; Albright, B. J.; Bowers, K. J.;
Liang, Edison P.
Bibcode: 2011PhPl...18e2105L
Altcode: 2010arXiv1005.2435L
We present large scale 3D particle-in-cell simulations to examine
particle energization in magnetic reconnection of relativistic
electron-positron (pair) plasmas. The initial configuration is set
up as a relativistic Harris equilibrium without a guide field. These
simulations are large enough to accommodate a sufficient number of
tearing and kink modes. Contrary to the non-relativistic limit, the
linear tearing instability is faster than the linear kink instability,
at least in our specific parameters. We find that the magnetic
energy dissipation is first facilitated by the tearing instability
and followed by the secondary kink instability. Particles are mostly
energized inside the magnetic islands during the tearing stage due
to the spatially varying electric fields produced by the outflows
from reconnection. Secondary kink instability leads to additional
particle acceleration. Accelerated particles are, however, observed to
be thermalized quickly. The large amplitude of the vertical magnetic
field resulting from the tearing modes by the secondary kink modes
further help thermalizing the non-thermal particles generated from
the secondary kink instability. Implications of these results for
astrophysics are briefly discussed.
Title: SDO/AIA Observations of Coronal Condensation Leading to
Prominence Formation
Authors: Liu, Wei; Berger, T.; Low, B. C.; Casini, R.
Bibcode: 2011SPD....42.2119L
Altcode: 2011BAAS..43S.2119L
Coronal condensation takes place when million degree coronal plasma
undergoes radiative cooling instability. Direct observation of coronal
condensation in prominences has been difficult in the past, but with the
launch of the Hinode/SOT and SDO/AIA instruments, numerous observations
of plasma condensing "out of nowhere" high up in quiescent prominences
have been captured. We present here one such event seen with SDO/AIA. On
25-Nov-2010, a prominence above the southwest limb is swept away by
a nearby eruption, and for next a few hours there is no visible 304
A material in the local corona. Then, a portion of the coronal loops
at the same location progressively sags and forms a local dip, where
the first sign of new, cool material appears, 7.5 hours after the
eruption. This is a clear indication of coronal condensation, and the
gradual sag of the loops is likely a result of increasing weight of
the condensed material that has been accumulated at the dip. Similar
condensation occurs nearby at a larger rate and leads to the formation
of a moderate-size prominence. The estimated prominence mass increases
linearly for about 7 hours at a rate of 2.6e10 grams/sec and reaches
approximately 6e14 grams. Simultaneously, the prominence drains through
vertical flows of approximately 32 km/s, bringing the mass back to the
chromosphere. We estimate the mass drain rate to be 2.7e10 grams/sec,
which, together with the estimated mass accumulation rate, implies a
coronal condensation rate of approximately 5.3e10 grams/sec. This study
can provide critical information about the coupling between condensation
energetics and MHD, prominence mass cycles, and coronal mass ejections
initiated by loss of anchoring prominence mass (e.g., Low 2001).
Title: Heating of Flare Loops During a Two-ribbon Flare on 2005 May 13
Authors: Qiu, Jiong; Liu, W.; Longcope, D. W.
Bibcode: 2011SPD....42.1205Q
Altcode: 2011BAAS..43S.1205Q
Many eruptive flares exhibit two extended ribbons in the
lower-atmosphere outlining the feet of the post-flare coronal
arcade. High-cadence high-resolution UV observations by TRACE reveal
that a flare ribbon consists of small patches sequentially brightened
along the ribbon, suggesting that reconnection takes place sequentially
forming individual post-flare loops along the arcade, as often seen in
coronal observations in the EUV wavelengths. These reconnection events
and formation of new loops continue into the decay phase. Our recent
study (Qiu et al. 2010) further shows that the spatially resolved UV
brightness at the foot-points of individual loops grows rapidly on
timescales of 1 minute, followed by a long decay on timescales of more
than 10 minutes. The rapid rise of UV radiation is correlated with
the hard X-ray light curve during the impulsive phase, hence is most
likely a direct response of instantaneous heating in the reconnection
formed flux tubes. In this study, we utilize the spatially resolved UV
brightness time profiles to reconstruct instantaneous heating functions
of individual flux tubes, and compute evolution of each flux tube using
the EBTEL model (Klimchuk et al. 2008). To build the heating function,
we take into account the scaling between the total UV peak count rate,
the hard X-ray energy flux derived from RHESSI spectral analysis during
the impulsive phase, and as well the reconnection rate that persists
from the pre-impulsive phase to the decay phase. The sum of the computed
coronal radiation in all the flux tubes compares favorably with the
gross coronal radiation observed by GOES. This study presents the
first effort to constrain heating functions of flare loops directly
using all available observables, and provides a method to examine
physics of heating discrete flux tubes formed by reconnection events
throughout the flare. The work is supported by NSF grant ATM-0748428.
Title: Astrophysical Rates for the 6He(p, γ)7Li
Reaction
Authors: Li, Er-Tao; Li, Zhi-Hong; Su, Jun; Guo, Bing; Li, Yun-Ju;
Yan, Sheng-Quan; Bai, Xi-Xiang; Wang, You-Bao; Wang, Bao-Xiang; Lian,
Gang; Zeng, Sheng; Fang, Xiao; Zhao, Wei-Juan; Liu, Wei-Ping
Bibcode: 2011ChPhL..28e2102L
Altcode:
Angular distribution of the 6He(d,n)7Li reaction
at Ec.m.=9.1 MeV is measured in inverse kinematics for
the first time. The proton spectroscopic factors for the ground
and first excited states of 7Li are derived by using the
distorted wave Born approximation analysis. The astrophysical rates
of 6He(p, γ)7Li reaction are then deduced and
fitted with an expression of REACLIB.
Title: Preliminary Experimental Result of Magnetic Reconnection in
Laboratory Plasma
Authors: Zhang, S. B.; Xie, J. L.; Hu, G. H.; Li, H.; Huang, G. L.;
Liu, W. D.
Bibcode: 2011AcASn..52..199Z
Altcode:
Magnetic reconnection is one of the most important physical processes
in astrophysical plasmas. Lots of theoretical works, numerical
simulations and observations have been done. Some experimental
programs have been activated to investigate the basic mechanisms of
magnetic reconnection. In order to investigate the electron dynamic
near the electron diffusion region in magnetic reconnection process,
an upgrade is accomplished in the LMP (Linear magnetic plasmas) device
at University of Science and Technology of China. The magnetic field
of reconnection is produced by passing two identical currents axially
through two copper plates. Magnetic field and parallel electric field
are measured by magnetic probes and emissive probes, respectively. The
existence of a large electric field related to the reconnection process
is verified. The plasma is driven by electric field and magnetic
field, so the magnetic reconnection appears. The magnitude of axial
current is found to scale with the number of passing particles. In
the configuration of current bars, passing particles are even more and
our measured axial current is about 10 A. Magnetic flux doesn't pile
up because of the parameter region in our case, which is consistent
with the result of numerical simulation.
Title: Direct Imaging by SDO/AIA of Quasi-periodic Propagating Fast
Mode Magnetosonic Waves of 2000 km/s in the Solar Corona
Authors: Liu, Wei; Title, A. M.; Zhao, J.; Ofman, L.; Schrijver,
C. J.; Aschwanden, M. J.; De Pontieu, B.; Tarbell, T. D.
Bibcode: 2011SPD....42.2114L
Altcode: 2011BAAS..43S.2114L
Quasi-periodic, propagating fast mode magnetosonic waves in the
corona were difficult to observe in the past due to relatively low
instrument cadences. We report here unprecedented evidence of such
waves directly imaged in EUV by the new SDO/AIA instrument. In the 2010
August 1 C3.2 flare/CME event, we find arc-shaped wave trains of 1-5%
intensity variations emanating near the flare kernel and propagating
outward along a funnel of coronal loops. Sinusoidal fits to a typical
wave train indicate a phase velocity of 2350 +/- 210 km/s. Similar
waves propagating in opposite directions are observed in closed loops
between two flare ribbons. In the k-omega diagram of the Fourier wave
power, we find a bright ridge that represents the dispersion relation
and can be well fitted with a straight line passing through the
origin, giving an equal phase and group velocity of 1630 +/- 760 km/s
averaged over the event. This k-omega ridge shows a broad frequency
distribution with prominent power at four non-harmonic frequencies,
5.5, 14.5, 25.1, and 37.9 mHz, among which the 14.5 mHz (period:
69 s) signal is the strongest. The signal at 5.5 mHz (period: 181 s,
same as chromospheric 3-minute oscillations) temporally coincides with
flare pulsations, suggesting a common origin of possibly quasi-periodic
magnetic reconnection. The instantaneous wave energy flux of (0.1-2.6)e7
ergs/cm2/s estimated at the coronal base is comparable to
the steady-state heating requirement of active region loops.
Title: Modeling Fast Magnetosonic Waves Observed by SDO in Active
region Funnels
Authors: Ofman, Leon; Liu, W.; Title, A.; Aschwanden, M.
Bibcode: 2011SPD....42.2104O
Altcode: 2011BAAS..43S.2104O
Recently, quasi-periodic, propagating waves have been observed in EUV by
the SDO/AIA instrument in about 10 flare/CME events thus far. A typical
example is the waves associated with the 2010 August 1 C3.2 flare/CME
that exhibited arc-shaped wave trains propagating in an active region
magnetic funnel with 5% intensity variations at speeds in the range
of 1000-2000 km/s. The fast temporal cadence and high sensitivity of
AIA enabled the detection of these waves. We identify them as fast
magnetosonic waves driven quasi-periodically at the base of the flaring
region, and develop a three-dimensional MHD model of the event. For
the initial state we utilize the dipole magnetic field to model the
active region, and include gravitationally stratified density at coronal
temperature. At the coronal base of the active region we excite the fast
magnetosonic wave by periodic velocity pulsations in the photospheric
plane confined to the funnel of magnetic field line. The excited fast
magnetosonic waves have similar amplitude, wavelength and propagation
speeds as the observed wave trains. Based on the simulation results, we
discuss the possible excitation mechanism of the waves, their dynamical
properties, and the use of the event for coronal MHD seismology.
Title: Heating of Flare Loops During a Two-ribbon Flare
Authors: Qiu, Jiong; Liu, W.; Longcope, D. W.
Bibcode: 2011SPD....42.2221Q
Altcode: 2011BAAS..43S.2221Q
Many eruptive flares exhibit two extended ribbons in the
lower-atmosphere outlining the feet of the post-flare coronal
arcade. High-cadence high-resolution UV observations by TRACE reveal
that the flare ribbon consists of small patches sequentially brightened
along the ribbon, suggesting that reconnection takes place sequentially
forming individual post-flare loops along the arcade, as often seen in
coronal observations in the EUV wavelengths. These reconnection events
and formation of new loops continue well into the decay phase. Our
recent study (Qiu et al. 2010) further shows that the spatially resolved
UV brightness at the foot-points of individual loops grows rapidly
on timescales of 1 minutes, followed by a long decay on timescales of
more than 10 minutes. The rapid rise of UV radiation is correlated with
the hard X-ray light curve during the impulsive phase, hence is most
likely a direct response of instantaneous heating in the reconnection
formed flux tubes. In this study, we utilize the spatially resolved UV
brightness time profiles to reconstruct instantaneous heating functions
of individual flux tubes, and compute evolution of each flux tube using
the EBTEL model (Klimchuk et al. 2008). To build the heating function,
we take into account the scaling between the total UV peak count rate,
the hard X-ray energy flux derived from RHESSI spectral analysis during
the impulsive phase, and as well the reconnection rate that persists
from the pre-impulsive phase to the decay phase. The sum of the computed
coronal radiation in all the flux tubes compares favorably with the
gross coronal radiation observed by GOES. This study presents the
first effort to constrain heating functions of flare loops directly
using all available observables, and provides a method to examine
physics of heating discrete flux tubes formed by reconnection events
throughout the flare. This work is supported by NSF grant ATM-0748428.
Title: RHESSI and SDO Observation Of HXR and UV/EUV Emissions in
the 2011 March 7 Solar Flare
Authors: Chen, Qingrong; Petrosian, V.; Liu, W.
Bibcode: 2011SPD....42.2231C
Altcode: 2011BAAS..43S.2231C
We present analysis of the RHESSI and SDO observation of a very unusual
M3.7 class solar flare on 2011 March 7 from the active region 11164,
which was also detected by the Fermi Large Area Telescope above 100 MeV
at gamma-rays and NoRP at microwaves. This flare was accompanied by a
relatively strong CME and solar energetic particles. During the
flare, hard X-ray emission up to 300 keV was detected by RHESSI. The
HXR images at 12-300 keV in the impulsive phase exhibit two footpoint
sources with an unusually large separation of more than 120 arcsec and
a thermal loop below 18 keV connecting the two footpoints. On the other
hand, the SDO/AIA UV and EUV images indicate that the spatial structure
of the flare is much more complicated than the above HXR picture. The UV
continuum images at 1600 and 1700 angstrom show three elongated ribbons,
the outer two being brightest and coincident with the HXR footpoints and
the middle one without any detectable cospatial HXR source. Furthermore,
the EUV images show a few arcade systems successively developing during
the flare, while there are no clear EUV loops seen to connect the two
HXR footpoints. We will examine the magnetic configuration within
the flaring regions using the RHESSI, SDO/AIA and SDO/HMI magnetogram
data, and investigate the relation between UV ribbon brightening and
electron heating in this flare. The relation between the HXR and EUV
emission and other observations will be analyzed and described.
Title: Slow-Mode Oscillations of Hot Coronal Loops Excited at
Flaring Footpoints
Authors: Wang, Tongjiang; Liu, W.; Ofman, L.; Davila, J. M.
Bibcode: 2011SPD....42.2214W
Altcode: 2011BAAS..43S.2214W
A large number of strongly damped oscillations in hot coronal loops
have been observed by SOHO/SUMER in the past decade in Doppler shifts
of flaring (>6 MK) lines (Fe XIX and Fe XXI). These oscillations
with periods on the order of 10-30 min were interpreted as fundamental
standing slow modes. They often manifest features such as recurrence
and association with a flow (100-300 km/s) pulse preceding to the
oscillation, which suggests that they are likely driven by microflares
at the footpoints. With coordinated RHESSI observations, we have found
a dozen such events supporting this conjecture. A typical event is
presetned here. By analyzing RHESSI hard X-ray and GOES/SXI soft
X-ray emissions as well as SUMER Doppler shifts, we identify the
flare that triggers the loop oscillations. From RHESSI spectra, we
measure physical parameters such as temperature, emission measure,
and thermal/non-thermal energy contents as functions of time. We
discuss the wave excitation mechanism based on these observations. Our
results provide important observational constraints that can be used
for improving theoretical models of magnetosonic wave excitation,
and for coronal seismology.
Title: Explanatory Supplement to the WISE Preliminary Data Release
Products
Authors: Cutri, R. M.; Wright, E. L.; Conrow, T.; Bauer, J.; Benford,
D.; Brandenburg, H.; Dailey, J.; Eisenhardt, P. R. M.; Evans, T.;
Fajardo-Acosta, S.; Fowler, J.; Gelino, C.; Grillmair, C.; Harbut,
M.; Hoffman, D.; Jarrett, T.; Kirkpatrick, J. D.; Liu, W.; Mainzer,
A.; Marsh, K.; Masci, F.; McCallon, H.; Padgett, D.; Ressler, M. E.;
Royer, D.; Skrutskie, M. F.; Stanford, S. A.; Wyatt, P. L.; Tholen,
D.; Tsai, C. W.; Wachter, S.; Wheelock, S. L.; Yan, L.; Alles, R.;
Beck, R.; Grav, T.; Masiero, J.; McCollum, B.; McGehee, P.; Wittman, M.
Bibcode: 2011wise.rept....1C
Altcode:
The Wide-field Infrared Survey Explorer (WISE; Wright et al. 2010)
surveyed the entire sky at 3.4, 4.6, 12 and 22 microns in 2010,
achieving 5-sigma point source sensitivities per band better than
0.08, 0.11, 1 and 6 mJy in unconfused regions on the ecliptic. The WISE
Preliminary Data Release, conducted on April 14, 2011, incorporates data
covering the first ~57% of the sky surveyed that were processed with
initial calibrations and reduction algorithms. Release data products
include: (1) an Atlas of 10,464 sets of calibrated, coadded images,
depth-of-coverage and uncertainty maps in the four WISE bands, (2)
a Source Catalog containing positions and four-band photometry for 257
million objects, and (3) an Explanatory Supplement. Ancillary products
include an archive of 754,000 sets of calibrated WISE single-exposure
images, uncertainty and bit-mask maps, and a database of 2.2 billion
source extractions made from the single-exposure images, and moving
object tracklets identified by the NEOWISE program (Mainzer et
al. 2011). The Explanatory Supplement to the WISE Preliminary Data
Release Products is a general guide for users of the WISE data. The
Supplement contains an overview of the WISE mission, facilities,
and operations, a description of the contents and formats of the WISE
image and tabular data products, and cautionary notes that describe
known limitations of the Preliminary Release products. Instructions
for accessing the WISE data products via the services of the NASA/IPAC
Infrared Science Archive are provided. Detailed descriptions of the
data processing system and algorithms used to ingest and convert
raw WISE data to the calibrated data products are presented,
along with assessments of the achieved sky coverage, photometric
and astrometric characteristics and completeness and reliability
of the Preliminary Release data products. The WISE Preliminary
Release Explanatory Supplement is an on-line document that is updated
frequently to provide the most current information for users of the
WISE data products. The Explanatory Supplement is maintained at: http://wise2.ipac.caltech.edu/docs/release/prelim/expsup/wise_prelrel_toc.html
WISE is a joint project of the University of California,
Los Angeles and the Jet Propulsion Laboratory/California
Institute of Technology, funded by the National Aeronautics and
Space Administration. NEOWISE is a project of the Jet Propulsion
Laboratory/California Institute of Technology, funded by the Planetary
Science Division of the National Aeronautics and Space Administration.
Title: Multispacecraft observations of a foreshock-induced
magnetopause disturbance exhibiting distinct plasma flows and an
intense density compression
Authors: Turner, D. L.; Eriksson, S.; Phan, T. D.; Angelopoulos, V.;
Tu, W.; Liu, W.; Li, X.; Teh, W. -L.; McFadden, J. P.; Glassmeier,
K. -H.
Bibcode: 2011JGRA..116.4230T
Altcode:
Large-scale magnetopause disturbances can result from several different
types of events, including those resulting from phenomena in the
foreshock region. In this observational report, we present multipoint
THEMIS observations of a magnetopause disturbance along the dawnside,
equatorial flank that exhibits distinct flows in the magnetospheric
plasma and an abnormally strong compression of the plasma density
within it, which peaks at >7X the density of the near-Earth solar
wind. We find that the fastest ion and electron flows are related
to two different processes, the ion flows resulting from plasma
being displaced around the disturbance and field-aligned electron
flows, possibly related to magnetic reconnection. Interestingly, the
magnetospheric plasma flows around the disturbance are very similar
to those previously reported around flux transfer events, but we
conclude that the disturbance is most likely the result of regions of
compressed and rarified plasma density in the sheath resulting from
a foreshock cavity. We present simple schematics of this foreshock
cavity and its leading-edge compression region that explain many
of the observed features and discuss possibilities for the intense
density enhancement. Using the simultaneous THEMIS observations from
the magnetosphere, magnetosheath, and solar wind, we propose that
the abnormal density enhancement was the result of a combination
of compression effects due to the magnetosheath and the cavity's
leading-edge compression region coupled with some complex interaction
near the magnetopause along the event's distinct boundary layer.
Title: Discovery of Panguite, a New Ultra-Refractory Titania Mineral
in Allende
Authors: Ma, C.; Tschauner, O.; Beckett, J. R.; Kiefer, B.; Rossman,
G. R.; Liu, W.
Bibcode: 2011LPI....42.1276M
Altcode:
We report here the discovery of panguite (Ti4+,Al,Sc,Mg,Zr,Ca)1.8O3,
a new titania mineral in Allende, and discuss implications of this
phase for processes very early in the history of our solar system.
Title: The Analysis of the Southwestern Landwater Storage Based on
GRACE Data
Authors: Liu, W.; Miao, Y. X.
Bibcode: 2011AcASn..52..145L
Altcode:
Based on the 64-month data of GRACE (Gravity Recovery and Climate
Experiment) from January 2005 to April 2010, the inversion of the
landwater storage in the southwest China is carried out in this
paper. GRACE is a near polar orbiting satellite, so the subsatellite
points become dense with increasing latitude, and thus the region
with a higher latitude has a higher spatial resolution. By repeated
calculations and comparison, it is found that with appropriate
Gaussian radius (R=600 km) in the southwest China and taking the
monthly average gravitational field as the background gravitational
field, the landwater storage estimated from GRACE data well reflects
the climate change and the drought in early 2010.
Title: Formation and disruption of current filaments in a flow-driven
turbulent magnetosphere
Authors: Liu, W. W.; Morales, L. F.; Uritsky, V. M.; Charbonneau, P.
Bibcode: 2011JGRA..116.3213L
Altcode: 2010arXiv1008.2938L
Recent observations have established that the magnetosphere is a system
of natural complexity. The coexistence of multiscale structures such as
auroral arcs, turbulent convective flows, and scale-free distributions
of energy perturbations has lacked a unified explanation, although there
is strong reason to believe that they all stem from a common base of
physics. In this paper we show that a slow but turbulent convection
leads to the formation of multiscale current filaments reminiscent of
auroral arcs. The process involves an interplay between random shuffling
of field lines and dissipation of magnetic energy on sub-MHD scales. As
the filament system reaches a critical level of complexity, local
current disruption can trigger avalanches of energy release of varying
sizes, leading to scale-free distributions over energy perturbation,
power, and event duration. A long-term memory effect is observed whereby
the filament system replicates itself after each avalanche. The results
support the view that that the classical and inverse cascades operate
simultaneously in the magnetosphere. In the former, the high Reynolds
number plasma flow disintegrates into turbulence through successive
breakdowns; in the latter, the interactions of small-scale flow eddies
with the magnetic field can self-organize into elongated current
filaments and large-scale energy avalanches mimicking the substorm.
Title: Chromospheric Jet and Growing "Loop" Observed by Hinode: New
Evidence of Fan-spine Magnetic Topology Resulting from Flux Emergence
Authors: Liu, Wei; Berger, Thomas E.; Title, Alan M.; Tarbell,
Theodore D.; Low, B. C.
Bibcode: 2011ApJ...728..103L
Altcode: 2010arXiv1012.1897L
We present observations of a chromospheric jet and growing "loop" system
that show new evidence of a fan-spine topology resulting from magnetic
flux emergence. This event, occurring in an equatorial coronal hole on
2007 February 9, was observed by the Hinode Solar Optical Telescope in
the Ca II H line in unprecedented detail. The predecessor of the jet is
a bundle of fine material threads that extend above the chromosphere and
appear to rotate about the bundle axis at ~50 km s-1 (period
lsim200 s). These rotations or transverse oscillations propagate upward
at velocities up to 786 km s-1. The bundle first slowly and
then rapidly swings up, with the transition occurring at the onset of an
A4.9 flare. A loop expands simultaneously in these two phases (velocity:
16-135 km s-1). Near the peak of the flare, the loop appears
to rupture; simultaneous upward ejecta and mass downflows faster than
free-fall appear in one of the loop legs. The material bundle then
swings back in a whip-like manner and develops into a collimated jet,
which is orientated along the inferred open-field lines with transverse
oscillations continuing at slower rates. Some material falls back along
smooth streamlines, showing no more oscillations. At low altitudes, the
streamlines bifurcate at presumably a magnetic null point and bypass
an inferred dome, depicting an inverted-Y geometry. These streamlines
closely match in space the late Ca II H loop and X-ray flare loop. These
observations are consistent with the model that flux emergence in an
open-field region leads to magnetic reconnection, forming a jet and
fan-spine topology. We propose that the material bundle and collimated
jet represent the outer spine in quasi-static and eruptive stages,
respectively, and the growing loop is a two-dimensional projection of
the three-dimensional fan surface.
Title: Warm Debris Disk Candidates from the Wide-field Infrared
Survey Explorer (WISE)
Authors: Padgett, Deborah; Liu, W.; Stapelfeldt, K.; Fajardo-Acosta,
S.; Leisawitz, D.
Bibcode: 2011AAS...21733305P
Altcode: 2011BAAS...4333305P
The Wide Field Infrared Survey Explorer (WISE) has just completed
a sensitive all-sky survey in photometric bands at 3.4, 4.6, 12,
and 22 microns. We report on a preliminary investigation of main
sequence Hipparcos catalog stars with 22 micron emission in excess
of photospheric levels. This warm excess emission traces material in
the circumstellar region likely to host terrestrial planets and is
preferentially found in young systems with ages < 1 Gyr. Nearly a
hundred new warm debris disk candidates are detected among FGK stars
within 100 pc and M stars as close as 12 pc, as well as numerous new
A star disks. We are in the process of obtaining spectra to determine
spectral types and activity level of these stars and have proposed
observations to characterize the dust, multiplicity, and substellar
companions of these systems. In this contribution, we will discuss
source selection methods and individual examples from among the WISE
debris disk candidates.
Title: Advances in Coordinated Sun-Earth System Science Through
Interdisciplinary Initiatives and International Programs
Authors: Fichtner, Horst; Liu, W. William
Bibcode: 2011sswh.book..341F
Altcode:
No abstract at ADS
Title: Quantum tunnelling of higher-dimensional Kerr-anti-de Sitter
black holes beyond semi-classical approximation
Authors: Liu, Wei-Wei; Luo, Zhi-Quan; Yang, Juan; Bian, Gang
Bibcode: 2011ChPhC..35...22L
Altcode:
Based on the theory of Klein-Gordon scalar field particles, the Hawking
radiation of a higher-dimensional Kerr-anti-de Sitter black hole with
one rotational parameter is investigated using the beyond semi-classical
approximation method. The corrections of quantum tunnelling probability,
Hawking temperature and Bekenstein-Hawking entropy are also included.
Title: Remote-Sensing Radial Plasma Flows in the Magnetotail Using
Multiscale Vector Field Techniques
Authors: Uritsky, V. M.; Spanswick, E. L.; Donovan, E. F.; Liang,
J.; Birn, J.; Knudsen, D. J.; Liu, W.
Bibcode: 2010AGUFMSM41A1833U
Altcode:
Fast radial plasma flows and the associated traveling magnetic
structures are commonly observed in the magnetotail plasma sheet,
for example, outside the reconnection diffusion region. In this talk,
we present a new methodology for analyzing anisotropic multiscale
signatures of velocity shears, turbulence, and transient vortex
structures generated by such bursty bulk flows. We generalize the
higher-order structure function analysis to transient anisotropic
spatially localized topological features often seen in velocity
and magnetic fields around the flows. The technique is illustrated
using the results from a 3-dimensional MHD simulation (J. Birn et
al, 2009) as well as in situ observations. The time evolution of the
longitudinal and transverse scaling indices computed using our algorithm
shows a distinct reproducible pattern of temporary isotropization
(partly-developed intermittent turbulence) during the passage times
of the flows, followed by a strongly anisotropic transient behavior
dominated by large-scale velocity shears. This pattern can be observed
at a significant azimuthal distance from the flow channel (e.g., several
times the width scale of the fast flow). We also present multi-spectral
auroral observations from time periods associated with magnetotail
equatorial flow channels. We analyze (with similar techniques) the
auroral response in the regions spanning the ionospheric projection of
the structured velocity fields. These result are compared to “quiet
times” where no flow channels are detectable in the magnetotail. The
results show that the proposed methodology can be used to quantify
multiscale plasma sheet response to various types of fast convective
plasma transport in conjunction with ground-based measurements,
and to clarify the physical origin of eddy plasma dynamics driven by
these events.
Title: Solar wind influence on Pc4 and Pc5 ULF wave activity in the
inner magnetosphere
Authors: Liu, W.; Sarris, T. E.; Li, X.; Ergun, R.; Angelopoulos,
V.; Bonnell, J.; Glassmeier, K. H.
Bibcode: 2010JGRA..11512201L
Altcode:
Abundant evidence has shown that ULF wave activity measured at
geosynchronous orbit is well correlated with solar wind parameters,
such as the solar wind velocity and dynamic pressure. However, many
of the past studies were based on magnetic field measurements near the
equatorial plane and thus could not unambiguously describe ULF waves,
as magnetic field oscillations in the fundamental toroidal mode have a
node at the magnetic equator. In this study, we use, for the first time,
simultaneous electric and magnetic field measurements by Time History
of Events and Macroscale Interactions during Substorms satellites
throughout the inner magnetosphere to statistically examine the
correlation between ULF wave activity in the inner magnetosphere and
the solar wind parameters: velocity, dynamic pressure, and variation
in dynamic pressure. On the basis of electric field observations from
August 2007 to May 2009, we found that, among the three parameters,
the solar wind velocity has the strongest correlation with the daily
averaged Pc4 and 5 wave magnitude in 4 ∼ 9 RE. For example,
the correlation coefficient of δEr (the square root of
the integrated power spectral density of the radial component of the
electric field) in the Pc5 frequency range with the solar wind dynamic
pressure is 0.35; with the dynamic pressure variation, it is 0.42;
and with the solar wind velocity, it is 0.55. However, using only
magnetic field observations, the variation in dynamic pressure is
best correlated, with correlation coefficients of δBr
(the square root of the integrated power spectral density of the
radial component of the magnetic field) with the dynamic pressure
being 0.59, with the dynamic pressure variation being 0.63 and with
the solar wind velocity being 0.53. We suggest that this difference
arises because toroidal and poloidal mode pulsations are not detected
with the same effectiveness in the electric field and the magnetic
field near the magnetic equator and/or because of the presence of
broadband ULF noise. We further suggest that either directly measured
or flow-derived electric field measurements are better suited in the
study of the relationship between wave power of fundamental field line
resonance (i.e., in Pc5 frequency range) and solar wind conditions.
Title: Multipoint Observation of Fast Mode Waves Trapped in the
Dayside Plasmasphere
Authors: Takahashi, K.; Bonnell, J. W.; Glassmeier, K.; Angelopoulos,
V.; Singer, H. J.; Chi, P. J.; Denton, R. E.; Nishimura, Y.; Lee,
D.; Nose, M.; Liu, W.
Bibcode: 2010AGUFMSM22A..05T
Altcode:
Multipoint observations of a dayside Pc4 pulsation event provide
evidence of fast mode waves trapped in the plasmasphere (plasmaspheric
cavity mode or virtual resonance). Time History of Events and Macroscale
Interactions during Substorms (THEMIS)-A, the primary source of data
for the present study, was moving outward near noon and detected
poloidal oscillations, characterized by the azimuthal electric field
component Ey and the radial and compressional magnetic field components
Bx and Bz. The structure of the plasmasphere was constructed from the
mass density radial profile estimated from the frequency of toroidal
standing Alfvén waves observed at this spacecraft. The outer edge of
the plasmapause (the maximum of the equatorial Alfvén velocity VAeq)
was located at L ~ 7, and the minimum of VAeq was located at L ~ 4,
forming a potential-well structure required for mode trapping. Relative
to the ground magnetic pulsations observed in the H component at a
low-latitude station (L = 1.5), the Ey component exhibited a broad
amplitude maximum around L ~ 3.5 and maintained a nearly constant
phase from L = 2 to L = 5. In contrast, the Bz component exhibited an
amplitude minimum and switched its phase by 180° at L = 3.8. This
radial mode structure is consistent with theoretical models of mode
trapping. Also, the Ey and Bz components oscillated ±90° out of phase,
as is expected for radially standing waves.
Title: First SDO/AIA Observations of Global Coronal EUV "Waves":
Multiple Components and "Ripples"
Authors: Liu, W.; Nitta, N. V.; Schrijver, C. J.; Title, A. M.;
Tarbell, T. D.
Bibcode: 2010AGUFMSH13A..07L
Altcode:
Global coronal EUV disturbances (so-called "EIT waves") are useful
diagnostics for physical conditions on the Sun. Major drawbacks that
hindered our understanding of this phenomenon were previous instruments'
single view point, low cadence (e.g., 12 minutes of EIT), and limited
wavelength coverage. The Atmospheric Imaging Assembly (AIA) on board
the Solar Dynamics Observatory (SDO) observes the full-sun corona
at 10 EUV and UV wavelengths, covering a wide range of temperatures,
with high resolution (1.4") and cadence (up to 12 s). It thus offers a
great chance to end the decade long debate on the nature of global EUV
"waves". We present here the first AIA observations of such phenomenon
on 2010 April 8 revealed in unprecedented detail and discuss their
physical implications. The disturbance exhibits two components: one
weak, diffuse pulse superimposed by multiple strong, sharp fronts,
which again have slow and fast components. The disturbance originates
in front of erupting coronal loops and the slow sharp front undergoes
acceleration, both implying the disturbance being driven by the
coronal mass ejection (CME). Even at a 20 s cadence, the diffuse pulse
propagates at a surprisingly constant velocity of ~200 km/s, weakly
dependent on direction. The fast sharp front overtakes the slow front,
producing multiple "ripples" and steepening of the local pulse, and both
fronts propagate independently afterwards. These resemble the nature
of real waves. Unexpectedly, the amplitude and FWHM of the diffuse
pulse decreases linearly with distance. The diffuse pulse appears as
emission enhancement at hotter 193 Å but reduction at cooler 171 Å,
suggestive of heating, while the sharp fronts appear as enhancement at
both wavelengths, indicating density increase. As evidence for both
wave and non-wave models of "EIT waves" has been found, we suggest
that a hybrid model combining both mechanisms (e.g., Cohen et al. 2010)
may best explaine the data. In addition to the global EUV disturbance,
we found fast (600-1100 km/s) features repeated at 100 s intervals
as tentative evidence of fast mode MHD waves. Discoveries of the fast
features, multiple ripples, and two-component fronts were made possible
for the first time thanks to AIA's high cadences and sensitivities.
Title: THEMIS measurements of the spatial structure and temporal
evolution of a dayside poloidal ULF wave event
Authors: Liu, W.; Sarris, T. E.; Li, X.; Ergun, R. E.; Angelopoulos,
V.; Glassmeier, K.
Bibcode: 2010AGUFMSM11B1739L
Altcode:
In this work, we investigate a strong poloidal ULF wave event in the
noon sector observed by THEMIS during its coast phase on May 29th,
2007. In this event, five THEMIS probes were lined up in the same
outbound path, and consecutively observed narrow-band ULF pulsations
in the Pc4 and Pc5 frequency range from 0700UT to 1200UT. This
configuration allows us to investigate the spatial and temporal
characteristics of the ULF wave activity. The oscillation is strongest
in the radial component of the magnetic field and extended in the
region from 5 to 9.5 Re at discrete L shells around 1200 LT. The
peak frequency of the pulsation decreases with increasing L shell
from 10mHz to 4mHz. In the region outside the plasmapause, the wave
power decreases and then increases, showing a temporal evolution that
appears to be related to the evolution of the plasmasphere. We will
also discuss the possible excitation mechanism of this poloidal ULF
wave with simultaneous observations of WIND satellite in the solar
wind and of Cluster satellites in the magnetosheath. The solar wind
velocity is relatively steady and there is no sudden impulse of the
solar wind dynamic pressure during this time period. Cluster observe
narrow band fluctuations in the number density of the sheath plasma. The
frequencies of these fluctuations are similar to the frequencies of
some of the narrow-band poloidal pulsations as observed by THEMIS. This
correlation seems to support the idea that density fluctuations in
the upstream might be responsible for the generation of the poloidal
ULF wave at certain location where the local field line resonance
frequency matches some of the driving frequencies.
Title: Dual scaling for self-organized critical models of the
magnetosphere
Authors: VallièRes-Nollet, M. -A.; Charbonneau, P.; Uritsky, V.;
Donovan, E.; Liu, W.
Bibcode: 2010JGRA..11512217V
Altcode:
The central plasma sheet is a complex magnetized plasma structure
located in the equatorial plane of the magnetotail from where
substorms are believed to originate. Dynamically, it may behave
like a self-organized critical (SOC) system, driven by the slow
energy input of the solar wind. The power law distributions for the
sizes, energies, and durations of substorms that are reflected in
observations can be reproduced using such SOC models. However, the
expected scale invariance does not seem to hold for all scale ranges
and observables. Recent observations of all-sky auroras have suggested
a dual regime, where small and large events scale as different power
laws, the smaller events having a steeper slope. On the other hand,
scale-dependent substorm behavior can materialize as a consequence of
an energy loading-unloading cycle. Accordingly, we designed a 2-D SOC
model subject to global deterministic driving and a nonconservative
redistribution law. This model can reproduce the coexistence of two
scaling regimes, with the second regime appearing as a consequence
of the enhanced spatial development of avalanches caused by a higher
spatial intermittency in the energy gradients. Thresholded interevent
waiting time statistics showed a well-defined peak with an exponential
tail, consistent with observations and the expected dynamics of a
loading-unloading cycle. Finally, we show that the coherency index
extracted from the simulations decreases prior to large avalanches, as
is in fact observed in auroral arcs. This suggests that the coherency
index may be a useful substorm predictor.
Title: An Alternative View of the "Masuda" Flare
Authors: Nitta, Nariaki V.; Freeland, Samuel L.; Liu, Wei
Bibcode: 2010ApJ...725L..28N
Altcode:
The limb flare on 1992 January 13, the so-called Masuda flare,
has stimulated scientists to refine theory of solar flares based on
two-dimensional magnetic reconnection. This is primarily because of
the hard X-ray (HXR) source seen above the clearly defined flare loop,
and the outward motions in soft X-rays (SXRs) interpreted as "plasmoid"
ejections. We have revisited Yohkoh HXR and SXR data for this and other
limb flares and found that the Masuda flare is still unique in terms of
the location and spectral properties of the coronal HXR source. However,
the outward motions in SXR outside the flare loop may not be as simply
characterized as plasmoid ejections as in other flares, nor are they
particularly fast. The motions appear complex partly because we also see
trans-equatorial loops in motion, one of whose legs anchors close to the
main flare loop. It is possible that these large-scale loops represent
post-flare loops, and that the flare may also be explained in terms of
three-dimensional quadrupolar reconnection, similar to those flares
where a pair of two loops exchange their footpoints through magnetic
reconnection. It appears that expansion and brightening of large-scale
loops offset from the main flare loop are not common, possibly providing
a reason for the unusual coronal HXR source in the Masuda flare.
Title: Multiscale Anisotropy and Instabilities in a Thin Electron
Current Sheet: Simulation Results and Measurement Recommendations
Authors: Khazanov, I. G.; Uritsky, V. M.; Singh, N.; Donovan, E. F.;
Liu, W.
Bibcode: 2010AGUFMSM51C1833K
Altcode:
Magnetic reconnection is a fundamental plasma process involving
nonlinear interactions of vastly separated spatial scales, ranging from
the large-scale magnetic field geometry enabling the formation of the
global X-line, to the microscopic plasma properties at ion and electron
gyroscales controlling fast energy conversion of the reconnecting
flux and providing physical conditions for particle acceleration
and heating. In this talk, we investigate simulation outputs from a
3-dimensional electromagnetic particle-in-cell code (Singh et al., 2006)
with the objective to understand magnetic signatures of the transient
multiscale dynamics in the electron diffusion region. The simulation
reproduces the formation of a thin embedded electron current layer
in a reversed magnetic field configuration, followed the development
of electron tearing mode and an explosive electrostatic instability
leading to reconnection. We use higher-order anisotropic structure
function (SF) analysis as a tool to quantify topological changes
of the magnetic field inside and outside of the simulated thin
electron current layer. The results show temporal evolution of the
longitudinal and transverse intermittency indices (net deviation of
the SF exponents form the fully developed turbulent state) suggesting a
formation of anisotropic magnetic field structures during the tearing
mode growth. This anisotropy decreases once the instability becomes
explosive. The estimated growth time of 60-70 electron plasma periods
of the transverse SF index is in an agreement with the theoretical
prediction for the electron tearing mode instability. The results
obtained shed new light on the forces and interactions governing
time evolution of the multiscale magnetic field topology accompanying
tearing mode growth at different stages of the initial instability,
and provide important clues for monitoring reconnection onset events
using multiscale in situ measurements conducted at various distances
from the neutral sheet.
Title: Multi-point measurements of the spatial extent and azimuthal
mode number of ULF waves
Authors: Sarris, T. E.; Li, X.; Liu, W.
Bibcode: 2010AGUFMSM11B1745S
Altcode:
Magnetospheric ULF (Ultra-Low Frequency) waves have frequencies in
the mHz range, comparable with the drift frequency of high-energy
particles, with which they are believed to resonantly interact. A
critical parameter in this interaction is the azimuthal mode number of
the waves, which determines the resonant condition for drift-resonant
acceleration, and also the spatial extent of the waves. In this study
we investigate the spatial extent using multi-point measurements
in the magnetosphere and on the ground and we compare different
measurement techniques for estimating the azimuthal mode number, such
as by using azimuthally displaced satellites in the magnetosphere,
by using longitudinally aligned magnetometers on the ground and by
studying signatures of energetic particle flux modulations. Case
studies are presented and compared.
Title: First SDO AIA Observations of a Global Coronal EUV "Wave":
Multiple Components and "Ripples"
Authors: Liu, Wei; Nitta, Nariaki V.; Schrijver, Carolus J.; Title,
Alan M.; Tarbell, Theodore D.
Bibcode: 2010ApJ...723L..53L
Altcode: 2012arXiv1201.0815L
We present the first Solar Dynamics Observatory Atmospheric Imaging
Assembly (AIA) observations of a global coronal EUV disturbance
(so-called "EIT wave") revealed in unprecedented detail. The disturbance
observed on 2010 April 8 exhibits two components: one diffuse pulse
superimposed, on which are multiple sharp fronts that have slow and
fast components. The disturbance originates in front of erupting coronal
loops and some sharp fronts undergo accelerations, both effects implying
that the disturbance is driven by a coronal mass ejection. The diffuse
pulse, propagating at a uniform velocity of 204-238 km s-1
with very little angular dependence within its extent in the south,
maintains its coherence and stable profile for ~30 minutes. Its arrival
at increasing distances coincides with the onsets of loop expansions and
the slow sharp front. The fast sharp front overtakes the slow front,
producing multiple "ripples" and steepening the local pulse, and both
fronts propagate independently afterward. This behavior resembles
the nature of real waves. Unexpectedly, the amplitude and FWHM of
the diffuse pulse decrease linearly with distance. A hybrid model,
combining both wave and non-wave components, can explain many, but
not all, of the observations. Discoveries of the two-component fronts
and multiple ripples were made possible for the first time thanks to
AIA's high cadences (<=20 s) and high signal-to-noise ratio.
Title: Helium-star evolutionary channel to super-Chandrasekhar mass
type Ia supernovae
Authors: Liu, W. -M.; Chen, W. -C.; Wang, B.; Han, Z. W.
Bibcode: 2010A&A...523A...3L
Altcode: 2010arXiv1007.4751L
The recent discovery of several overluminous type Ia supernovae
(SNe Ia) indicates that the explosive masses of white dwarfs may
significantly exceed the canonical Chandrasekhar-mass limit. Rapid
differential rotation may support these massive white dwarfs
(WDs). Based on the single-degenerate scenario and assuming that the
WDs would differentially rotate when the accretion rate dot{M} >
3 × 10-7 M⊙ yr-1, we performed
the numerical calculations for 1000 binary systems consisting of a He
star and a CO WD with Eggleton's stellar evolution code. We present the
initial parameters in the orbital period - helium star-mass plane (for
WD masses of 1.0 M⊙ and 1.2 M⊙, respectively),
which lead to super-Chandrasekhar mass SNe Ia. Our results indicate that
for an initially massive WD of 1.2 M⊙, a large number of
SNe Ia may result from super-Chandrasekhar mass WDs. The highest mass
of the WD at the moment of the SNe Ia explosion is 1.81 M_⊙, but
very massive (>1.85 M⊙) WDs cannot be formed. However,
when the initial mass of WDs is 1.0 M⊙, the explosive
masses of SNe Ia are nearly uniform, which is consistent with the
rareness of super-Chandrasekhar mass SNe Ia in observations.
Title: The littlest Higgs model with T-parity and some lepton flavor
violation decay processes
Authors: Yue, Chongxing; Ma, Wei; Zhang, Tingting; Liu, Wei; Liu,
Jinyan
Bibcode: 2010SCPMA..53.1968Y
Altcode: 2010ScChG..53.1968Y
The new particles predicted by the littlest Higgs model with T-parity
(called LHT model) can induce the lepton flavor violation (LFV)
couplings at the one-loop level, which can add contributions to some
LFV processes. Taking into account the constraints of the experimental
data on the relevant free parameters, we calculate the branching
ratios of the LFV decay processes Z → lbar l' and τ -
→ µ- P 1 P 2 with P 1
P 2 = π + π -, K + K
-, and K 0 bar K^0 in the context of this new
physics model. We find that the LHT model can indeed make significant
contributions to some of these LFV decay processes. The Z factory
option for the future high energy e + e -
collider experiments will give severe constraints on the LHT model.
Title: A transient narrow poleward extrusion from the diffuse aurora
and the concurrent magnetotail activity
Authors: Lui, A. T. Y.; Spanswick, E.; Donovan, E. F.; Liang, J.;
Liu, W. W.; Le Contel, O.; Zong, Q. -G.
Bibcode: 2010JGRA..11510210L
Altcode:
We report observation of a transient narrow auroral feature extruding
from the poleward boundary of the diffuse aurora on March 19, 2009. It
moved westward and poleward initially to form part of a vortex pattern,
followed by its equatorward-dawnward retreat later. During this
auroral activity, THEMIS satellites, projected near the same magnetic
local time of the auroral feature, detected appreciable plasma flows,
increase in the ratio of the ion energy over the electron energy,
and some enhancements of electrostatic waves. The plasma flows were
initially duskward-earthward and changed to duskward-tailward later. The
overall development of the observed plasma flow pattern was detected
during the equatorward-dawnward retreat of the auroral feature when
the Alfvén transit time between the magnetotail and the ionosphere
is taken into account. This suggests that THEMIS satellites remotely
sensed a counter-clockwise flow vortex (viewed from above the equatorial
plane) in the magnetotail with decreasing strength. We suggest that the
process generating the auroral feature is related to the flow vortex
in association with the depletion of the electron energy relative
to the ion energy and wave-particle interaction. An estimate of the
possible associated current density is made. We provide reasoning for
this auroral feature to be an auroral streamer and not a “failed”
transpolar arc.
Title: Record warming in the South Pacific and western Antarctica
associated with the strong central-Pacific El Niño in 2009-10
Authors: Lee, Tong; Hobbs, William R.; Willis, Joshua K.; Halkides,
Daria; Fukumori, Ichiro; Armstrong, Edward M.; Hayashi, Akiko K.;
Liu, W. Timothy; Patzert, William; Wang, Ou
Bibcode: 2010GeoRL..3719704L
Altcode:
Satellite data for the past three decades reveal a record-high
sea surface temperature (SST) anomaly within a large mid-latitude
region of the south-central Pacific (SCP) during the mature phase
of the 2009-10 El Niño, with a peak magnitude that is 5 times
the standard deviation of local SST anomaly and is warmer than the
concurrent tropical-Pacific SST anomaly. The SCP oceanic warming was
confined to the upper 50 meters and is associated with an extreme and
persistent anticyclone. Wind changes associated with the anticyclone
caused the oceanic warming with surface heat flux and ocean processes
playing equally important roles. The anticyclone diverted circumpolar
westerlies and warm air towards Antarctica. Austral-summer SST in
the Bellingshausen Sea also reached a three-decade high. The extreme
atmospheric and oceanic anomalies in the South Pacific may have been
fueled by the 2009-10 El Niño because of its record-high SST anomaly
in the central-equatorial Pacific.
Title: 返回舱动态稳定性分析及被动控制方法研究
Authors: 赵, 海洋; 杨, 小亮; 刘, 伟
Bibcode: 2010SSPMA..40.1156.
Altcode:
No abstract at ADS
Title: Influence of super-strong magnetic field on the electron
chemical potential and β decay in the stellar surroundings
Authors: Liu, Wei-Wei; Luo, Zhi-Quan; Zhang, Jie; Gao, Jie; Bian, Gang
Bibcode: 2010ChPhC..34.1090L
Altcode:
In this paper, considering the quantum effect of electrons in a
super-strong magnetic field, the influence of a super-strong magnetic
field on the chemical potential of a non-zero temperature electron is
analyzed, the rates of β decay under the super-strong magnetic field
are studied, and then we compare them with the case without a magnetic
field. Here, the nucleus 63Co is investigated in detail as
an example. The results show that a magnetic field that is less than
1010 T has little effect on the electron chemical potential
and β decay rates, but the super-strong magnetic field that is greater
than 1010 T depresses the electron chemical potential and
improves the β decay rates clearly.
Title: An in situ XAS study of copper(I) transport as hydrosulfide
complexes in hydrothermal solutions (25-592 °C, 180-600 bar):
Speciation and solubility in vapor and liquid phases
Authors: Etschmann, B. E.; Liu, W.; Testemale, D.; Müller, H.; Rae,
N. A.; Proux, O.; Hazemann, J. L.; Brugger, J.
Bibcode: 2010GeCoA..74.4723E
Altcode:
Chloride and hydrosulfide are the principal ligands assumed to govern
transport of copper in hydrothermal fluids. Existing solubility
experiments suggest that Cu(I)-hydrosulfide complexes are dominant
compared to chloride complexes at low salinities in alkaline solutions
(H 2S (aq)/HS - pH buffer), and
may be important in transporting Cu in low density magmatic vapors,
potentially controlling the liquid-vapor partitioning of Cu. This
study provides the first in situ evidence of the solubility of copper
sulfides and the nature and structure of the predominant Cu species in
sulfur-containing fluids at temperatures up to 592 °C and pressures of
180-600 bar. XANES and EXAFS data show that at elevated T (⩾200 °C),
Cu solubility occurs via a linear Cu complex. At 428 °C in alkaline
solutions, Cu is coordinated by two sulfur atoms in a distorted linear
coordination (angle ∼150-160°). This geometry is consistent with the
species Cu(HS)2- predicted by earlier solubility studies. In addition,
in situ measurements of the solubility of chalcocite in 2 m NaHS
solutions performed in this study are in remarkably good agreement
with the solubilities calculated using available thermodynamic data
for Cu(I)-hydrosulfide complexes, also supporting the interpretation
of speciation in these studies and validating the extrapolation of
low- T thermodynamic properties for Cu(HS)2- to high P- T. Data on
phase separation for the 2 m NaHS solution show that while significant
amounts of copper can be partitioned into the vapor phase, there is no
indication for preferential partitioning of Cu into the vapor. This
is consistent with recent partitioning experiments conducted in
autoclaves by Pokrovski et al. (2008a) and Simon et al. (2006). XANES
data suggest that the species present in the low density phase is very
similar to that present in the high density liquid, i.e., Cu(HS)2-,
although Cu(HS)(H 2S) 0 cannot be excluded on
the basis of XAS data.
Title: THEMIS observations of the spatial extent and pressure-pulse
excitation of field line resonances
Authors: Sarris, T. E.; Liu, W.; Li, X.; Kabin, K.; Talaat, E. R.;
Rankin, R.; Angelopoulos, V.; Bonnell, J.; Glassmeier, K. -H.
Bibcode: 2010GeoRL..3715104S
Altcode:
We present a case study of Field Line Resonances (FLRs) in the dayside
magnetosphere, observed in both electric and magnetic field components
at multiple L-shells near the equator. The event measured by the five
THEMIS probes and the nearby GOES and Geotail satellites provides
a unique opportunity to differentiate between temporal and spatial
characteristics of FLRs. Narrow-band FLRs were excited globally
at different frequencies matching the local field line resonant
frequency. In conjunction with a sharp increase in the upstream solar
wind density, prompt intensification of the FLR power was observed
at different L-shells, simultaneously at different frequencies and
amplitudes.
Title: The Fomalhaut debris disk seen from every angle with
interferometry
Authors: Absil, O.; Mennesson, B.; Le Bouquin, J. -B.; Augereau,
J. -C.; Millan-Gabet, R.; Colavita, M.; Hinz, P.; Liu, W.; Serabyn, G.
Bibcode: 2010SPIE.7734E..17A
Altcode: 2010SPIE.7734E..34A
In this paper, we present the results of three different studies of the
Fomalhaut debris disk with infrared interferometry. First, VLTI/AMBER
measurements are used to determine the position angle of the slightly
oblate rapidly rotating photosphere by means of differential phase
measurements across the Br-gamma photospheric line. This measurement
allows us to confirm that the debris disk is located in the equatorial
plane of its host star. Second, we use VLTI/VINCI to search for
resolved near-infrared emission around the stellar photosphere, which
would correspond to the presence of large amounts of hot dust grains
located between the sublimation radius and the habitable zone. Our
observations reveal a small excess of 0.88%+/-0.12% in K band relative
to the photospheric flux. Finally, we use the Keck Interferometer Nuller
in order to derive additional constraints on the nature of the resolved
infrared emission. Our observations suggest a marginal detection of a
circumstellar excess at 10 μm, which we use together with the VINCI
detection to model the circumstellar emission. Preliminary results
from this modeling effort are discussed.
Title: Neutron Spectroscopic Factors of 7Li and
Astrophysical 6Li(n,γ)7Li Reaction Rates
Authors: Su, Jun; Li, Zhi-Hong; Guo, Bing; Bai, Xi-Xiang; Li,
Zhi-Chang; Liu, Jian-Cheng; Wang, You-Bao; Lian, Gang; Zeng, Sheng;
Wang, Bao-Xiang; Yan, Sheng-Quan; Li, Yun-Ju; Li, Er-Tao; Fan, Qi-Wen;
Liu, Wei-Ping
Bibcode: 2010ChPhL..27e2101S
Altcode: 2010arXiv1001.4329S
Angular distributions of the 7Li(6Li,
6Li)7Li elastic scattering
and the 7Li(6Li,
7Lig.s.)6Li,
7Li(6Li,
7Li0.48)6Li transfer reactions
at Ec.m. = 23.7 MeV are measured with the Q3D magnetic
spectrograph. The optical potential of 6Li + 7Li
is obtained by fitting the elastic scattering differential cross
sections. Based on the distorted wave Born approximation (DWBA)
analysis, spectroscopic factors of 7Li = 6Li
otimes n are determined to be 0.73 ± 0.05 and 0.90 ± 0.09 for the
ground and first exited states in 7Li, respectively. Using
the spectroscopic factors, the cross sections of the 6Li(n,
γ0, 1)7Li direct neutron capture reactions and
the astrophysical 6Li(n, γ)7Li reaction rates
are derived.
Title: New Insights to Global Coronal EUV Waves: First Double
Quadrature Observations by SDO/AIA and STEREO/EUVI
Authors: Liu, Wei; Nitta, N. V.; Schrijver, C. J.; Title, A. M.
Bibcode: 2010AAS...21640230L
Altcode:
Global coronal EUV waves are useful diagnostic tools for physical
conditions on the Sun. Major drawbacks that hindered our understanding
of EUV waves were previous instruments' low cadence (e.g., 12
minutes for SoHO/EIT) and limited spatial resolution and wavelength
coverage. The Atmospheric Imaging Assembly (AIA) on board the recently
launched Solar Dynamics Observatory (SDO), joined by the STEREO EUV
Imager (EUVI), offers a great chance to end the decade long debate
on the nature of global EUV waves. AIA observes the corona at 10 EUV
and UV wavelengths, covering a wide range of temperatures. It has high
resolution (0.6") and cadence (20 s, 7 times faster than EUVI). These
capabilities allow us to study the thermal structure and kinematics
of EUV waves in unprecedented detail. We present here the first AIA
observations of an EUV wave occurring on 2010 April 8. AIA observed
this event on the solar disk, while the STEREO Ahead (A) and Behind
(B) spacecraft, which were 67 degree ahead and 72 degree behind the
Earth, respectively, provided side views of both the EUV wave and the
halo coronal mass ejection (seen by SoHO/LASCO) near the limb. This
formed a double quadrature configuration with great advantages to
infer the 3D structure. Initial analysis indicates that this wave
exhibited strong anisotropy, propagating primarily toward the south,
on the same side of the erupting loop system. We will examine its
spatial and temporal relationship with the erupting loop and CME and
discuss physical implications.
Title: Direct Imaging of an Emerging Flux Rope and a Resulting
Chromospheric Jet Observed by Hinode
Authors: Liu, Wei; Berger, T.; Title, A. M.; Tarbell, T. D.; DeRosa, M.
Bibcode: 2010AAS...21640307L
Altcode: 2010BAAS...41R.878L
Magnetic flux emergence has been traditionally observed on the disk by
identifying changes in magnetograms. Observations near the limb offer
an alternative perspective and allow direct imaging of emerging flux
ropes. We present Hinode/SOT Ca II H observations of such an event in
an equatorial coronal hole on 2007 February 9. The precursor of the
event was a bundle of fine material threads that extended at an oblique
angle above the chromosphere and appeared to rotate about a common
axis. This bundle first slowly and then rapidly swung up, accompanied
by a loop that appeared at the base of the bundle and expanded at
comparable rates. During the first (slow rise) stage, the apex of the
loop ascended at 16 km/s, a velocity similar to that of H-alpha arch
filaments (e.g., Chou & Zirin) and of emerging flux ropes expanding
into the corona as found in MHD simulations (e.g., Fan & Gibson;
Martinez-Sykora). The second stage started at the onset of a GOES A5
flare and the loop expansion accelerated, reaching a velocity of 130
km/s when the loop appeared to rupture near the peak of the flare. The
material bundle then swung back in a whiplike manner and developed into
a collimated jet, exhibiting oscillatory transverse motions across its
axis, as expected from unwinding twists. Some jet material fell back
along smooth streamlines, which bypass an unseen dome and presumably
a null point in the low corona, depicting an inverted-Y shape. Some
of these observations resemble the model (e.g., Uchida & Shibata)
of the emergence of a twisted flux rope into an open field region that
leads to reconnection and formation of a jet. Some observations are,
however, not predicted in previous models and we will discuss their
implications.
Title: Energetics in Two-ribbon Flares
Authors: Qiu, Jiong; Liu, W.; Hill, N.; Kazachenko, M.
Bibcode: 2010AAS...21632101Q
Altcode: 2010BAAS...41..911Q
We conduct a semi-quantitative analysis of two-ribbon flares to relate
the pattern of magnetic reconnection and energetics during the flare. We
establish a correlation between UV emission and >30 keV hard X-ray
emission, so that evolution of the flare morphology illustrated in
high resolution UV images is used to infer non-thermal particle
precipitation. In the few two-ribbon flares under investigation,
the flare UV ribbons exhibit apparent motion both parallel with
and perpendicular to the magnetic polarity inversion line of the
active region. We note that the perpendicular spread of the UV ribbon
dominates the peak phase of hard X-rays, when the parallel motion is
nearly halted. With a local 2.5D assumption, we decompose the magnetic
reconnection rate into two parts ψ|| and ψperp,
ψ|| being related to the parallel expansion of the UV
ribbon, and ψperp being related to the perpendicular
expansion of the UV ribbon. It is found that non-thermal energy
release is strongly correlated with ψperp. We explore
an empirical scaling law between non-thermal energy release and the
pattern of magnetic reconnection. This work is supported by the NSF
grant ATM-0748428, NASA grant NNX08AE44G, and NSF REU grant ATM-0552958.
Title: Indirect measurement of nuclear reactions of astrophysical
interest
Authors: Liu, W. P.; Li, Z. H.; Bai, X. X.; Wang, Y. B.; Guo, B.;
Lian, G.; Su, J.; Zeng, S.; Wang, B. X.; Yan, S. Q.; Li, Y. J.; Li,
E. T.; Jin, S. J.
Bibcode: 2010AIPC.1235..322L
Altcode:
Systematic indirect measurements of nuclear astrophysical
reactions using the unstable ion beam facility GIRAFFE in CIAE
were performed. We have measured the angular distributions of
transfer reactions, such as 8Li(d,p)9Li,
8Li(d,n)9Be and 8Li(p,d)7Li
in inverse kinematics, and derived the astrophysical S-factors
or reaction rates for 8Li(n,γ)9Li and
8Li(p,γ)9Be by using asymptotic normalization
coefficient (ANC) or spectroscopic factor methods.
Title: Salinity Variations in Water Column due to Outflows Estimated
by Multi-Sensor Remote Sensing
Authors: Yan, Xiao-Hai; Jo, Young-Heon; Liu, W. Timothy; Dai, Minhan
Bibcode: 2010aogs...18..109Y
Altcode:
The following sections are included: * Introduction *
Theoretical Background, Methodology, Data and Error Analysis *
Results * River discharge * Amazon river discharge * Yangtze
river discharge * Mediterranean eddy and outflow * Conclusions
* Acknowledgments * References
Title: Electrostatic field and ion temperature drop in thin current
sheets: A theory
Authors: Liu, W. W.; Liang, J.; Donovan, E. F.
Bibcode: 2010JGRA..115.3211L
Altcode: 2010JGRA..11503211L
The observational evidence presented by Liang et al. (2009) showed
that a neutral sheet-pointing electrostatic field frequently arises in
the late growth-phase current sheet in the magnetotail. In this paper,
we elaborate on the suggestion that this electric field is associated
with the thinning of the current sheet to the ion scale at which
the electron and ion current sheets begin to separate. The attendant
effect of a decreasing ion temperature, also interpreted in terms of
a thinning current sheet, suggests that a cold plasma population is
involved. We review existing theories of “charged” Harris sheet
that can produce electrostatic fields and show that they cannot explain
the observations for various reasons. A particular problem is the over
shielding of the electrostatic field by the cold population embedding
the current sheet. We argue that this problem stems from not treating
the cold plasma as a separate population from the hot plasma forming
the thin current sheet (TCS). We show that if the cold population is
treated as external to the TCS and behaving in a largely MHD manner,
the resultant solution yields an electrostatic field and ion temperature
drop consistent with the observations.
Title: Lithium induced nuclear reactions of astrophysical interest
Authors: Liu, W. P.; Li, Z. H.; Bai, X. X.; Wang, Y. B.; Lian, G.; Guo,
B.; Su, J.; Zeng, S.; Wang, B. X.; Yan, S. Q.; Li, Y. J.; Li, E. T.
Bibcode: 2010NuPhA.834..651L
Altcode:
Systematic studies of nuclear astrophysical reactions induced by lithium
isotopes using the unstable ion beam facility GIRAFFE in CIAE were
performed. We have measured the angular distributions of some single
nucleon transfer reactions, such as 8Li(d,p)9Li,
8Li(d,n)9Be and 8Li(p,d)7Li
in inverse kinematics, and derived the astrophysical S-factors
or reaction rates for 8Li(n,γ)9Li and
8Li(p,γ)9Be by using asymptotic normalization
coefficient (ANC) or spectroscopic factor.
Title: 2H(6He,7Li)n,
12C(7Li, 6He)13N reactions
and 12C(p,γ)13N astrophysical S(E) factors
Authors: Li, Z. H.; Su, J.; Guo, B.; Li, E. T.; Li, Z. C.; Bai, X. X.;
Li, Y. J.; Liu, J. C.; Yan, S. Q.; Wang, B. X.; Wang, Y. B.; Lian,
G.; Zeng, S.; Fang, X.; Liu, W. P.; Chen, Y. S.; Shu, N. C.; Fan, Q. W.
Bibcode: 2010NuPhA.834..661L
Altcode:
Angular distributions of 2H(6He,7Li)n
and 12C(7Li,6He)13N
reactions were measured at the HI-13 tandem accelerator,
Beijing. Asymptotic normalization coefficient (ANC) of 13N
→ 12C + p was derived to be 1.64±0.11 fm-1
through distorted wave Born approximation (DWBA) analysis, which was
then used to deduce the astrophysical S(E) factors for direct capture
in 12C(p,γ)13N at energies of astrophysical
relevance.
Title: The 33S(p,γ)34Cl reaction in classical nova explosions
Authors: Parikh, A.; Faestermann, T.; Krücken, R.; Bildstein, V.;
Bishop, S.; Eppinger, K.; Herlitzius, C.; Lepyoshkina, O.; Maierbeck,
P.; Seiler, D.; Wimmer, K.; Hertenberger, R.; Wirth, H. F.; Fallis,
J.; Hager, U.; Hutcheon, D. A.; Ruiz, C.; Buchmann, L.; Ottewell,
D.; Freeman, B.; Wrede, C.; Garcia, A.; Delbridge, B.; Knecht, A.;
Sallaska, A.; Chen, A.; Clark, J. A.; Deibel, C.; Fulton, B. R.;
Laird, A.; Greife, U.; Guo, B.; Li, E.; Li, Z.; Lian, G.; Wang, Y.;
Liu, W.; Parker, P.; Setoodehnia, K.
Bibcode: 2010nuco.confE..52P
Altcode: 2010PoS...100E..52P
No abstract at ADS
Title: System-level musings about system-level science (Invited)
Authors: Liu, W.
Bibcode: 2009AGUFMSM11D..01L
Altcode:
In teleology, a system has a purpose. In physics, a system has a
tendency. For example, a mechanical system has a tendency to lower
its potential energy. A thermodynamic system has a tendency to
increase its entropy. Therefore, if geospace is seen as a system,
what is its tendency? Surprisingly or not, there is no simple answer
to this question. Or, to flip the statement, the answer is complex,
or complexity. We can understand generally why complexity arises,
as the geospace boundary is open to influences from the solar wind
and Earth’s atmosphere and components of the system couple to
each other in a myriad of ways to make the systemic behavior highly
nonlinear. But this still begs the question: What is the system-level
approach to geospace science? A reductionist view might assert that
as our understanding of a component or subsystem progresses to a
certain point, we can couple some together to understand the system
on a higher level. However, in practice, a subsystem can almost never
been observed in isolation with others. Even if such is possible,
there is no guarantee that the subsystem behavior will not change
when coupled to others. Hence, there is no guarantee that a subsystem,
such as the ring current, has an innate and intrinsic behavior like a
hydrogen atom. An absolutist conclusion from this logic can be sobering,
as one would have to trace a flash of aurora to the nucleosynthesis
in the solar core. The practical answer, however, is more promising;
it is a mix of the common sense we call reductionism and awareness
that, especially when strongly coupled, subsystems can experience
behavioral changes, breakdowns, and catastrophes. If the stock answer
to the systemic tendency of geospace is complexity, the objective of
the system-level approach to geospace science is to define, measure,
and understand this complexity. I will use the example of magnetotail
dynamics to illuminate some key points in this talk.
Title: Motion of Auroral Features and Plasmasheet Flow
Authors: Spanswick, E. L.; Donovan, E. F.; Lui, A.; Kepko, E. L.;
Liang, J.; Liu, W.
Bibcode: 2009AGUFMSM53D..06S
Altcode:
The aurora is often interpreted as a projection of large scale dynamics
occurring in the central plasma sheet. This is only one mechanism
for driving changes in auroral structure and luminosity and we do not
know when (and to what extent) magnetotail processes determine auroral
morphology. What specific auroral features are directly driven by and/or
related to individual magnetospheric processes? Using data from the
THEMIS white light and NORSTAR multi-spectral imagers we investigate
the relationship between plasma sheet flow and the motion of auroral
features. We use data from a twenty day period, starting in late March
2009, when the NORSTAR imagers operated in a high resolution mode
capturing the red-line aurora at a six second cadence (synchronized
with the THEMIS ASI array). Concurrent THEMIS spacecraft observations
are used as a measure of local plasma sheet flow. We present results
from the survey of optical and spacecraft data and discuss the possible
connection between auroral and magnetospheric motion.
Title: An Intriguing Chromospheric Jet Observed by Hinode: Fine
Structure Kinematics and Evidence of Unwinding Twists
Authors: Liu, Wei; Berger, Thomas E.; Title, Alan M.; Tarbell,
Theodore D.
Bibcode: 2009ApJ...707L..37L
Altcode: 2009arXiv0910.5186L
We report a chromospheric jet lasting for more than 1 hr observed by
the Hinode Solar Optical Telescope in unprecedented detail. The ejection
occurred in three episodes separated by 12-14 minutes, with the amount
and velocity of material decreasing with time. The upward velocities
range from 438 to 33 km\nolimits s\nolimits ^{-1}, while the downward
velocities of the material falling back have smaller values (mean:
-56 km\nolimits s\nolimits ^{-1}) and a narrower distribution (standard
deviation: 14 km\nolimits s\nolimits ^{-1}). The average acceleration
inferred from parabolic spacetime tracks is 141 m\nolimits s^{-2}, a
fraction of the solar gravitational acceleration. The jet consists of
fine threads (0farcs5-2'' wide), which exhibit coherent, oscillatory
transverse motions perpendicular to the jet axis and about a common
equilibrium position. These motions propagate upward along the jet,
with the maximum phase speed of 744 ± 11 km\nolimits s\nolimits ^{-1}
at the leading front of the jet. The transverse oscillation velocities
range from 151 to 26 km\nolimits s\nolimits ^{-1}, amplitudes from
6.0 to 1.9 Mm\nolimits, and periods from 250 to 536 s\nolimits. The
oscillations slow down with time and cease when the material starts to
fall back. The falling material travels along almost straight lines in
the original direction of ascent, showing no transverse motions. These
observations are consistent with the scenario that the jet involves
untwisting helical threads, which rotate about the axis of a single
large cylinder and shed magnetic helicity into the upper atmosphere.
Title: Electric and magnetic field observations of Pc4 and Pc5
pulsations in the inner magnetosphere: A statistical study
Authors: Liu, W.; Sarris, T. E.; Li, X.; Elkington, S. R.; Ergun,
R.; Angelopoulos, V.; Bonnell, J.; Glassmeier, K. H.
Bibcode: 2009JGRA..11412206L
Altcode:
Ultralow frequency (ULF) waves in the Pc4 and Pc5 bands are ubiquitous
in the inner magnetosphere and have significant influence on energetic
particle transport. Investigating the source and characteristics of
ULF waves also helps us better understand the interaction processes
between the solar wind and the magnetosphere. However, owing to the
limitation in instrumentation and spatial coverage, the distribution
of ULF waves in local time and L shell in the inner magnetosphere has
not been completely studied. The recent Time History of Events and
Macroscale Interactions During Substorms (THEMIS) mission provides
unique opportunities to investigate the spatial distribution of ULF
pulsations across different L shells with full local time coverage in
the inner magnetosphere during solar minimum, with both electric and
magnetic field measurements. Pc4 and Pc5 pulsations in the electric
field observations are identified throughout 13 months of measurements,
covering 24 h in local time. The pulsations are characterized as either
toroidal or poloidal (including compressional) mode, depending on
the polarization of the electric field. Subsequently, the pulsations'
occurrence rate and wave power distributions in radial distance and
local time are recorded. While the distributions of both Pc4 and Pc5
events vary greatly with radial distance and local time, Pc4 events are
more frequently observed in the inner region around 5-6 RE
and Pc5 events are more frequently observed in the outer region around
7-9 RE, which suggests that the field line resonance is
an important source of the ULF waves. In the flank regions, the wave
power is dominated by the toroidal mode, likely associated with the
Kelvin-Helmholtz (KH) instability. In the noon sector, the Pc5 ULF
wave power is dominated by the poloidal mode, likely associated with
the solar wind dynamic pressure disturbance. The KH instability plays
an important role, suggested by our observations, during the solar
minimum when the solar wind dynamic pressure is relatively weak. We
also find that the contributions to the Pc5 ULF wave power from the
external sources are larger than the contributions from the internal
sources. These statistical results are important in characterizing
Pc4 and Pc5 waves and also important for any efforts to model the
transport of energetic particles in the magnetosphere.
Title: PFSIR observations of equatorward-expanding ionospheric
F-region patch and its association with the flow and auroral
activities
Authors: Liang, J.; Spanswick, E. L.; Nicolls, M. J.; Donovan, E. F.;
Lummerzheim, D.; Liu, W.
Bibcode: 2009AGUFMSM53D..08L
Altcode:
We present an event study with conjunctive THEMIS and PFISR observations
on March 3, 2009, 10-12 UT. During this event interval mid-tail probe
THEMIS-C detected a series of fast earthward flows. Correspondingly,
ground-based optical observations revealed strong red-line (630nm)
emission intensifications and equatorward-moving auroral structures,
but they were not accompanied by a substorm expansion. Using the
Poker Flat incoherent radar (PFISR) observations we are able to
fully explore the 4-D (time, latitude, longitude, and altitude)
properties of the ionospheric electron density profile for this
event. We found that localized density enhancements (patches) appeared
with the start of the flow and auroral activities, and then expanded
progressively equatorward. The patches were limited within roughly
the same latitudinal/latitudinal range of a moving auroral arc,
and existed dominantly in F-region (~150-300 km), suggesting that
the precipitating particles generating the patches were relatively
soft in energy (<1keV), similar to that responsible for the
red-line auroral emissions. More interestingly, when the patches
extended further equatorward they were substantially elevated in
altitudes. Synthesizing all observations we discuss the possible
particle sources and mechanisms, both magnetospheric and ionospheric,
that lead to the of the observed F-region patch dynamics.
Title: Solar wind influence on Pc4 and Pc5 ULF wave activity in the
inner magnetosphere
Authors: Liu, W.; Sarris, T. E.; Li, X.; Ergun, R. E.; Angelopoulos,
V.; Bonnell, J. W.; Glassmeier, K.
Bibcode: 2009AGUFMSM11A1569L
Altcode:
Abundant evidences have previously been shown that the ULF wave
activities measured at geosynchronous orbit are well correlated with
solar wind parameters, such as solar wind dynamic pressure. However,
these studies, based only magnetic field measurements near the
equatorial plane, cannot determine the actual ULF wave power
because magnetic field oscillation in torodial mode has a node
at the equator. In this study, we use both electric and magnetic
field measurements by THEMIS satellites in the inner magnetosphere
to statistically examine the correlation between the overall
ULF wave activities in the inner magnetosphere and the solar wind
parameters. Based on the electric field observations from July 2007 to
May 2009, a strong correlation has been found between the daily averaged
integral Pc4&5 wave power in 4~9 Re and the solar wind velocity;
the correlation with solar wind dynamic pressure is not as obvious. The
THEMIS magnetic field measurements show that the correlation coefficient
decreases with solar velocity but increases with dynamic pressure, in
contrast to the results based on the electric field measurements. We
suggest that the difference is due to the detection of different
ULF mode pulsations (toridal and poloidal) and that electric field
measurements near the equator are critical to investigate Pc4 and Pc5
ULF wave activities.
Title: Low-frequency waves in auroral arcs: optical echo of
magnetotail dynamics (Invited)
Authors: Uritsky, V. M.; Liang, J.; Donovan, E. F.; Spanswick, E. L.;
Knudsen, D. J.; Liu, W.
Bibcode: 2009AGUFMSM52B..03U
Altcode:
We report new results of our analysis of longitudinally propagating
low-frequency (period 0.5 - 2.0 min) wave oscillations in optical
auroral arcs, with the emphasis on the underlying physics. Several
alternative wave mechanisms are considered, including a variety of
wave modes in the ionosphere and the auroral acceleration region,
field line resonances, and plasma waves in the magnetotail. A
representative set of well-documented episodes of wave activity
recorded by ground-based and in situ THEMIS instruments is studied
in this context. Our analysis rules out three of the four wave
locations listed above. The ionospheric origin of the arc wave is
unlikely considering the measured phase velocities which require
unrealistically strong convection electric fields. The acceleration
region is able to produce fast-traveling localized auroral features
such as folds and rays, but not for the observed range of wavelengths
(up to ~400 km in the ionospheric frame), and not for the observed
propagation direction (predominantly westward at both southern
and northern edges of pre-midnight arcs). It is noteworthy that the
majority of wave events are not accompanied by field line resonances,
indicating that this effect is not the primary cause of the arc wave,
contrary to some recent claims. The only interpretation consistent
with our quantitative analysis of the relevant data tests is that the
arc waves are a manifestation of an azimuthally propagating wave in
the magnetotail. We present several examples of a nearly one-to-one
correspondence between low-frequency tail waves (e.g. flapping motion)
and the auroral arc waves, the parameters of the optical wave being
consistent with theoretical predictions for drift wave oscillations in
a thin current sheet. Although the detailed physical picture of the
underlying magnetosphere -ionosphere interaction is still lacking,
our results strongly suggest that further investigation of optical
arc waves will provide a valuable piece of information on spatial
propagation of plasma instabilities associated with substorm growth and
expansion phases as well as other magnetospheric conditions. Detrended
ewogram representation (MLON vs UT, color-coded optical intensity)
of a longitudinally propagating arc wave prior to 8:04 03/03/08
substorm onset observed by the Fort Simpson ASI. Parameters of several
representative pre-onset arc wave events. Letters N and S correspond to
northern and southern arcs in double-arc systems. Numbers in brackets
are expected magnetotail values from T89 mapping.
Title: Fine Structures and Kinematics of an Intriguing Chromospheric
Jet Observed by Hinode Solar Optical Telescope
Authors: Liu, W.; Berger, T. E.; Title, A. M.; Tarbell, T. D.
Bibcode: 2009AGUFMSH51A1266L
Altcode:
Transient, small-scale ejections of plasma from the lower atmosphere
are common manifestations of solar activity. Hinode, with its superior
resolutions, has spurred renewed interest in solar jets since its
launch. Here we report a chromospheric jet lasting for more than 1
hr on 2007 February 9 observed by the Hinode Solar Optical Telescope
(SOT) in unprecedented detail. SOT Ca II H passband observations
at high resolution of 0.2 arcsecond and cadence of 8 s allowed us to
investigate the fine structures and kinematics of the jet. The ejection
occurred in three episodes, rather than continuously, with the amount
and velocity of material decreasing with time. The upward velocities
along the jet range from ~440 to ~30 km/s, while the downward velocities
of the material falling back have much smaller values (mean: -60 km/s)
and a narrower distribution. Some tracks in the space-time plot clearly
show parabolic shapes and the inferred acceleration is a fraction of
the solar gravitational acceleration. The jet consists of fine threads
(0.5-2 arcsecond wide), which exhibit coherent, oscillatory transverse
motions perpendicular to the jet axis and about a common equilibrium
position. These motions propagate upward, with the maximum phase speed
of ~740 km/s found at the leading front of the jet. The transverse
oscillation velocities range from 150 to 30 km/s, amplitudes from 6 to 2
Mm, and periods from 250 to 550 s. The oscillations slow down with time
and cease when the material starts to fall back. The falling material
travels along almost straight lines in the original direction of ascent,
showing no transverse motions. These observations are consistent with
the models suggested by Shibata & Uchida (1985) and Canfield et
al. (1996). In this scenario, the jet involves untwisting helical
threads, which rotate about the axis of a single large cylinder and
shed magnetic helicity into the upper atmosphere. Implications of this
event in the context of multiwavelength data in H-alpha, EUV, and X-rays
will be discussed. A chromospheric jet observed by Hinode SOT in the
Ca II H passband (T=1-2×10 4 K). Note the helical-like fine threads.
Title: When the rubber hits the road: turbulence and intermittencies
in Earth’s magnetosphere (Invited)
Authors: Liu, W.; Uritsky, V. M.; Charbonneau, P.; Valliere-Nollet,
M.; Morales, L. F.
Bibcode: 2009AGUFMSM41C..02L
Altcode:
The theory of MHD turbulence has a long history of development, but its
application to actual physical systems has not been as widespread as
the omnipresence of turbulent phenomena in these systems. The reasons
can be many. For example, the geometry, constitution, coupling, and
boundary conditions in an actual system may place it well beyond the
limit of the current theory. Or our measurement capability has not
progressed to the point that the salient theoretical predictions
can be reliably tested. In our view, however, the most pertinent
reason is the specialist’s unfamiliarity with and reluctance to
use the ‘generalist’ approach of complexity and turbulence, and
the generalist’s lack of attention to the particulars of specific
systems. Clearly, a closer dialogue between the two communities holds
significant promise for further advances. In this talk, complexity
and turbulence observed in Earth’s magnetosphere are reviewed. A
distinguishing characteristic of magnetospheric processes is strong
intermittency in global episodes and ever-present turbulence on
local scales. We explore the suggestion that avalanches of localized
turbulence are responsible for global dynamics. Some new theoretical
advances in elaborating this concept are discussed.
Title: Go With the Flow: The Reductionist View of Geospace at the
System Level (Invited)
Authors: Liemohn, M. W.; Brandt, P. C.; Denton, M. H.; Donovan, E. F.;
Frey, H. U.; Lester, M.; Liu, W.; Milan, S. E.; Ostgaard, N.; Palmroth,
M. M.; Ridley, A. J.; Uritsky, V. M.; Zhang, X.
Bibcode: 2009AGUFMSM11D..02L
Altcode:
A typical approach to understanding geospace is to solve the
first-principles equations for the motion of particles and for the
electric and magnetic fields within the region of interest. This is the
reductionist approach to space physics and has been the primary (and
highly successful) methodology of our field for many decades. When only
a small part of geospace of being investigated, then the researcher
must assume boundary conditions for those plasma and field regions
not being solved by the equation set. For many problems, this is
entirely acceptable and such an approach has delivered excellent
scientific results that have significantly advanced understanding of
geospace. For some problems, though, this boundary condition approach is
insufficient. That is, the population or region of interest can modify
the boundary conditions through some system-level feedback mechanism
of geospace. These feedbacks invariably relate to the flow of mass and
energy through the system. The simplified regional model is no longer
adequate for this problem and a larger-scale system-level approach
is warranted. This presentation discusses a number of system-level
problems that require full tracking of these mass and energy flows
through the geospace system. This reductionist view of system-level
science is then compared with analysis of emergent phenomena and the
study of the geospace system’s natural complexity. The presentation
concludes with ideas of how these two views of system-level science
could, and in many ways should, be used together.
Title: Combined Fokker-Planck Modeling of Particle
Acceleration/Transport and Hydrodynamic Simulation of Atmospheric
Response in Solar Flares
Authors: Petrosian, V.; Liu, W.; Mariska, J. T.
Bibcode: 2009AGUFMSH21C..04P
Altcode:
Acceleration and transport of high-energy particles and fluid dynamics
of atmospheric plasma are interrelated aspects of solar flares, but for
simplicity they were artificially separated in the past. We present
here self-consistently combined Fokker-Planck modeling of particles
and hydrodynamic simulation of flare plasma. Energetic electrons are
modeled with the Stanford unified code of acceleration, transport,
and radiation, while plasma is modeled with the NRL flux tube code
(Mariska et al. 1989). We calculated the collisional heating rate
directly from the particle transport code, which is more accurate
than those in previous studies based on approximate analytical
solutions. We used a more realistic spectrum of injected electrons
provided by the stochastic acceleration model of Petrosian & Liu
(2004), which has a smooth transition from a quasi-thermal background
at low energies to a nonthermal tail at high energies. The inclusion of
low-energy electrons results in relatively more heating in the corona
(vs. chromosphere) and thus a larger downward heat conduction flux. The
interplay of electron heating, conduction, and radiative loss leads to
stronger chromospheric evaporation than obtained in previous studies,
which had a deficit in low-energy electrons due to an arbitrarily
assumed low-energy cutoff. The energy and spatial distributions of
energetic electrons and bremsstrahlung photons bear signatures of the
changing density distribution caused by chromospheric evaporation. In
particular, the density jump at the evaporation front gives rise to
enhanced X-ray emission, which could be responsible for the X-ray
sources moving along flare loops observed by RHESSI (Sui et al. 2006,
ApJL 645; Liu et al. 2006, ApJ 649). Various energy contents from the
simulations can be used to test the empirical Neupert effect. This
technique can also be applied to investigate a variety of high-energy
processes in solar, space, and astrophysical plasmas, such as planetary
auroras. Geometry of the model flare loop assumed in this study.
Title: An Active Auroral Streamer And The Concurrent Magnetotail
Activity
Authors: Lui, A.; Spanswick, E. L.; Donovan, E. F.; Liang, J.; Liu,
W.; Uritsky, V. M.; McFadden, J. P.; Larson, D. E.
Bibcode: 2009AGUFMSM53D..02L
Altcode:
We report the observations of an active auroral streamer and the
concurrent activity in the magnetotail monitored by the five THEMIS
satellites. The auroral streamer was a low intensity feature obtained
by the Rankin Inlet EMCCD ASI. It emerged from the diffuse aurora,
advancing poleward and then retreating equatorward. This occurred during
a major THEMIS tail conjunction period and the ground projections of
THEMIS satellites were near the MLT of the auroral streamer. During
this interval, tailward plasma flows were observed by the five THEMIS
satellites, followed by earthward plasma flows by four of them. These
plasma flows were mostly field-aligned and had low speeds of 40-100
km/s. The possible connection between the ground auroral activity and
the magnetotail activity will be discussed
Title: THEMIS Observations of Field Line Resonance Excitation in
Responce to a Solar Wind Pressure Pulse
Authors: Sarris, T. E.; Liu, W.; Li, X.; Kabin, K.; Angelopoulos,
V.; Bonnell, J. W.; Glassmeier, K.
Bibcode: 2009AGUFMSM31B1534S
Altcode:
The THEMIS multi-probe mission performs electric and magnetic field
measurements with identical instrumentation at different locations,
providing unique opportunities to differentiate between temporal and
spatial characteristics of Field Line Resonances (FLRs) and to identify
their extent in the Earth magnetosphere. In the case study presented,
narrow-band FLRs are observed to be excited globally at different
frequencies that match the local field line resonant frequency; for
one instance where the intensification of the FLR power coincides
with a solar wind pressure pulse, we are able to conclusively and
definitively identify the excitation mechanism, and we thus consider
this instance to be a proof that FLRs can be excited globally at the
local FLR frequency by a solar wind pressure pulse.
Title: Using Optical and Riometer Observations to Study the
Relationship Between the Spatio-temporal Evolution of Magnetic Field
Topology and Dispersionless Electron Injection
Authors: Donovan, E.; Spanswick, E.; Liang, J.; Jackel, B. J.; Liu,
W.; Kabin, K.; Rankin, R.
Bibcode: 2009AGUFMSM41A1680D
Altcode:
In an electron injection, inner central plasma sheet fluxes of energetic
electrons increase dramatically around the time of a substorm expansion
phase onset. If the injection is dispersionless, then the increase is
simultaneous across a broad range of energies. It is widely accepted
that the Dispersionless Injection (DI) is observed in the region of
space and at the time of the dipolarization. Recent observational
studies of various signatures of DI and other onset related phenomena
have led to a number of conclusions about the spatio-temporal evolution
of DI. These include the fact that DI begins on field lines threading
the transition region between dipolar and stretched magnetic field
topologies and subsequently expands both tailward and earthward, and
that DI begins in a radially narrow and azimuthally extended region. In
this paper, we present observations of proton and electron aurora,
riometer absorption, and in situ high-energy electron fluxes, all from
the minutes around substorm expansion phase onset. We describe how
these observations corroborate the idea that DI begins in the region
of transition between dipolar and tail-like topologies, and further
how they support the hypothesis that in the last few minutes of the
growth phase the transition region is radially narrow, that after
onset the narrow transition retreats tailward, and that this retreat
is the tailward expansion of the DI. We assert that these results set
the quantitative stage for numerical simulations that can be used to
explore the physical mechanism responsible for DI.
Title: How well can satellite data characterize the water cycle of
the Madden-Julian Oscillation?
Authors: Waliser, Duane E.; Tian, Baijun; Xie, Xiaosu; Liu, W. Timothy;
Schwartz, Michael J.; Fetzer, Eric J.
Bibcode: 2009GeoRL..3621803W
Altcode:
Most characterizations of the Madden-Julian Oscillation (MJO) have
focused on its convection and circulation features, ocean interactions,
and weather and climate impacts. The water cycle of the MJO has
yet to be examined or quantified despite it offering an additional
constraint on model representations of the MJO, which are still woefully
poor. Recent satellite products now make it possible to characterize the
MJO water cycle from observations. These include water vapor profiles,
column water vapor, cloud ice profiles, total cloud liquid, rainfall,
surface evaporation and column moisture convergence. From these,
we quantify the water budget for disturbed and suppressed phases of
the MJO. The column-integrated results indicate that precipitation is
nearly balanced with moisture convergence, with variations in surface
evaporation being an order of magnitude smaller. However, residuals
in the column-integrated budget are relatively large, indicating the
need for improved satellite retrievals and/or the necessity of using
model-based assimilation products.
Title: Longitudinally propagating arc wave in the pre-onset optical
aurora
Authors: Uritsky, V. M.; Liang, J.; Donovan, E.; Spanswick, E.;
Knudsen, D.; Liu, W.; Bonnell, J.; Glassmeier, K. H.
Bibcode: 2009GeoRL..3621103U
Altcode:
We present the first systematic observational evidence for a traveling
periodic structure in the pre-onset optical aurora - the longitudinally
propagating arc wave (LPAW) - associated with flapping oscillations
in the magnetotail. The LPAW is characterized by azimuthally
moving intensity enhancements inside auroral arcs as seen by THEMIS
ground-based all-sky imagers. It travels westward in the pre-midnight
auroral sector during the 10-20 minutes preceding auroral breakup with
a velocity of 2-10 km/s, time period 40-110 s, and wavelength 250-420
km. Magnetically conjugate measurements by THEMIS satellites show low
frequency plasma oscillations consistent with the parameters of the arc
wave in the course of current sheet thinning. When mapped into tail,
wavelength (4800-9400 km) and velocity (70-190 km/s) of the LPAW are
compatible with observations and theoretical predictions for current
sheet flapping motions. Our results strongly suggest that LPAW is an
auroral footprint of the drift wave mode (kink, sausage, ballooning,
etc.) in a stretched magnetotail.
Title: 3D Magnetic Reconnection of Relativistic Pair Plasmas
Authors: Liu, Wei; Yin, Lin; Albright, Brian; Bowers, Kevin; Li, Hui;
Liang, Edison
Bibcode: 2009APS..DPPNM9008L
Altcode:
Relativistic plasma physics plays an essential role in a number of
famous and longstanding astrophysical problems. Using the ultrafast
code VPIC, we present one of the largest scale 3D particle-in-cell
(PIC) simulations to date to examine relativistic magnetic reconnection
in pair plasmas. These simulations are large enough to accommodate a
sufficient number of kink modes. It is demonstrated that multiple,
patchy reconnection sites form during the initial stage and then
self-organize to form an elongated diffusion region with increased
system size. The secondary kinking folds the current sheet in the
orthogonal direction. The interaction between kink and tearing
instabilities results in plasmoids, which affect the particle
acceleration and reconnection rate. The reconnection rate remains fast
and time varying. The relativistic effects increase the linear kink mode
wavelengths and results in almost identical growth rates for initial
linear kink and tearing modes. Relativistic drift kink instability,
reconnection, folding of the diffusion region due to the secondary
kink and plasmoids all contribute to the particle energization.
Title: Long Term Evolution of Magnetized Bubbles in Galaxy Clusters
Authors: Liu, Wei; Li, Hui; Hsu, Scott; Li, Shengtai
Bibcode: 2009APS..DPPXP8023L
Altcode:
We have performed nonlinear ideal MHD simulations of the long term
evolution of a magnetized low-density ``bubble'' plasma formed by
a radio galaxy in a stratified cluster medium. It is found that
about 3.5% of the initial magnetic energy remains in the bubble
after 8 billion years, and the initial magnetic bubble expansion is
adiabatic. The bubble can survive for at least 8 billion years due to
the stabilizing effect of the bubble magnetic field on Rayleigh-Taylor
and Kelvin-Holmholtz instabilities, possibly accounting for ``ghost
cavities'' as observed in Perseus-A. A filament structure spanning
about 500 kpc is formed along the path of bubble motion. The mean value
of the magnetic field inside this structure is 0.88 micro Gauss at 8
billion years. Finally, the initial bubble momentum and rotation have
limited influence on the long term evolution of the bubble.
Title: Ion temperature drop and quasi-electrostatic electric field
at the current sheet boundary minutes prior to the local current
disruption
Authors: Liang, Jun; Liu, W. W.; Donovan, E. F.
Bibcode: 2009JGRA..11410215L
Altcode:
From a survey of the cross-tail current disruption (CD) events in the
near-Earth plasma sheet collected from the Time History of Events and
Macroscale Interactions during Substorms (THEMIS) mission, we identify a
highly repeatable class of event occurring at the current sheet boundary
in a few minutes before the local CD onset. Salient features of this
class of event include (1) a precipitous drop of the ion temperature,
(2) concurrent growth of a neutral sheet-pointing electric field,
and (3) ULF wave activations at Pi1/Pi2 bands. We interpret the
ion temperature drop as a manifestation of the extremely thinning
of the local current sheet prior to its disruption. This thinning
process is inferred as nonadiabatic by nature. Particularly, when
the current sheet thickness is down to ion kinetic scales, the ions
are demagnetized, and a quasi-electrostatic neutral sheet-pointing
electric field emerges owing to the charge separation. The ULF
fluctuations of electric/magnetic field have a two-band structure. The
lower-frequency band with a period of 50 to 80 s is interpreted as an
Alfvenic mode coupled from other preonset wave modes excited at the
equatorial plasma sheet such as the ballooning. The higher-frequency
wave at 10- to 20-s periods is attributed to some instability mode,
directly leading to the disruption of the thin current sheet (TCS). We
suggest that an extremely thinned non-Harris TCS and the emergence of
quasi-electrostatic field constitute the conducive conditions for a
local CD to occur. A companion paper by Liu et al. (2009) covers some
theoretical aspects of this study.
Title: Ideal magnetohydrodynamic simulations of low beta compact
toroid injection into a hot strongly magnetized plasma
Authors: Liu, Wei; Hsu, Scott C.; Li, Hui
Bibcode: 2009NucFu..49i5008L
Altcode: 2009arXiv0902.2485L
We present results from three-dimensional ideal magnetohydrodynamic
simulations of low β compact toroid (CT) injection into a hot strongly
magnetized plasma, with the aim of providing insight into CT fuelling of
a tokamak with parameters relevant for the International Thermonuclear
Experimental Reactor (ITER). A regime is identified in terms of CT
injection speed and CT-to-background magnetic field ratio that appears
promising for precise core fuelling. Shock-dominated regimes, which are
probably unfavourable for tokamak fuelling, are also identified. The
CT penetration depth is proportional to the CT injection speed and
density. The entire CT evolution can be divided into three stages: (1)
initial penetration, (2) compression in the direction of propagation
and reconnection with the background magnetic field, and (3) coming to
rest and spreading in the direction perpendicular to injection. Tilting
of the CT is not observed due to the fast transit time of the CT across
the background plasma.
Title: Combined Modeling of Acceleration, Transport, and Hydrodynamic
Response in Solar Flares. I. The Numerical Model
Authors: Liu, Wei; Petrosian, Vahé; Mariska, John T.
Bibcode: 2009ApJ...702.1553L
Altcode: 2009arXiv0906.2449L
Acceleration and transport of high-energy particles and fluid dynamics
of atmospheric plasma are interrelated aspects of solar flares, but
for convenience and simplicity they were artificially separated in the
past. We present here self-consistently combined Fokker-Planck modeling
of particles and hydrodynamic simulation of flare plasma. Energetic
electrons are modeled with the Stanford unified code of acceleration,
transport, and radiation, while plasma is modeled with the Naval
Research Laboratory flux tube code. We calculated the collisional
heating rate directly from the particle transport code, which is
more accurate than those in previous studies based on approximate
analytical solutions. We repeated the simulation of Mariska et
al. with an injection of power law, downward-beamed electrons using
the new heating rate. For this case, a ~10% difference was found from
their old result. We also used a more realistic spectrum of injected
electrons provided by the stochastic acceleration model, which has a
smooth transition from a quasi-thermal background at low energies to a
nonthermal tail at high energies. The inclusion of low-energy electrons
results in relatively more heating in the corona (versus chromosphere)
and thus a larger downward heat conduction flux. The interplay of
electron heating, conduction, and radiative loss leads to stronger
chromospheric evaporation than obtained in previous studies, which had a
deficit in low-energy electrons due to an arbitrarily assumed low-energy
cutoff. The energy and spatial distributions of energetic electrons
and bremsstrahlung photons bear signatures of the changing density
distribution caused by chromospheric evaporation. In particular, the
density jump at the evaporation front gives rise to enhanced emission,
which, in principle, can be imaged by X-ray telescopes. This model can
be applied to investigate a variety of high-energy processes in solar,
space, and astrophysical plasmas.
Title: Copper speciation and partitioning between vapor and liquid
phases in sulphuric solution: An XAS study
Authors: Etschmann, B.; Liu, W.; Brugger, J.; Testemale, D.; Hazemann,
J. L.; Müller, H.; Proux, O.
Bibcode: 2009GeCAS..73R.341E
Altcode:
No abstract at ADS
Title: Episodic X-Ray Emission Accompanying the Activation of an
Eruptive Prominence: Evidence of Episodic Magnetic Reconnection
Authors: Liu, Wei; Wang, Tong-Jiang; Dennis, Brian R.; Holman,
Gordon D.
Bibcode: 2009ApJ...698..632L
Altcode: 2009arXiv0902.1805L
We present an X-ray imaging and spectroscopic study of a partially
occulted (N16W93) C7.7 flare on 2003 April 24 observed by Reuven Ramaty
High Energy Solar Spectroscopy Imager that accompanied a prominence
eruption observed by Transition Region and Coronal Explorer. (1) The
activation and rise of the prominence occurs during the preheating phase
of the flare. The initial X-ray emission appears as a single coronal
source at one leg of the prominence and it then splits into a double
source. Such a source splitting happens three times, each coinciding
with an increased X-ray flux and plasma temperature, suggestive of fast
reconnection in a localized current sheet and an enhanced energy-release
rate. In the late stage of this phase, the prominence displays a helical
structure. These observations are consistent with the tether-cutting
and/or kink-instability model for triggering solar eruptions. (2)
The eruption of the prominence takes place during the flare impulsive
phase. Since then, there appear signatures predicted by the classical
model of two-ribbon flares occurring in a vertical current sheet
trailing an eruption. These signatures include an extreme-ultraviolet
(EUV) cusp and current-sheet-like feature (or ridge) above it. There is
also X-ray emission along the EUV ridge both below and above the cusp,
which in both regions appears closer to the cusp at higher energies
in the thermal regime (lsim20 keV). This trend is reversed in the
nonthermal regime. (3) Spectral analysis indicates thermal X-rays
from all sources throughout the flare, while during the impulsive
phase there is additional nonthermal emission which primarily comes
from the coronal source below the cusp. This source also has a lower
temperature (T = 20 ± 1 vs. 25 ± 1 MK), a higher emission measure (EM
= (3.3 ± 0.4) vs. (1.2 ± 0.4) × 1047 cm-3),
and a harder nonthermal spectrum (electron power-law index δ = 5.4
± 0.4 vs. 8 ± 1) than the upper sources.
Title: Monitoring Traveling Magnetospheric Waves In Optical Aurora
Authors: Uritsky, V.; Liang, J.; Donovan, E.; Spanswick, E.; Mende,
S.; Liu, W.
Bibcode: 2009AGUSMSM22A..01U
Altcode:
The network of THEMIS all-sky imagers provides an unprecedented
opportunity of studying time evolution of multiscale auroral
disturbances associated with the magnetospheric substorm onset. In
this talk, we report our recent results suggesting a possibility of
direct optical monitoring of propagating low-frequency magnetotail
disturbances associated with pre- and post-onset conditions. The results
show a significant enhancement of spatial and temporal coherence of
the growth phase aurora accompanied by increased ambipolar electric
field fluctuations in the tail signaling a formation of a thin current
sheet about ∼5 minutes prior to the main auroral breakup. During
this time, growth phase arcs reveal various forms of azimuthal plasma
motion including multiscale turbulence and westward propagating waves
with traveling speeds of 2.0 -- 5.0 km/s. The post-breakup auroral
dynamics exhibits wave-like forms which typically travel duskward at
the velocity 8.0 -- 12.0 km/s, recurrence time 20 -- 30 s. These waves
first appear within a local pre-midnight sector (∼1 hour MLT wide)
shortly before to the global expansion onset, and they can be reliably
detected during the first 10+ minutes following the breakup. The
analysis of simultaneous in situ THEMIS measurements suggests that
the observed pre-onset wave patterns can be an auroral footprint of
flapping oscillations and/or other drift wave modes in the magnetotail
which can arguably be related to the development of the initial plasma
instability triggering the substorm onset.
Title: Ideal Magnetohydrodynamic Simulations of Magnetic Bubble
Expansion as a Model for Extragalactic Radio Lobes
Authors: Liu, Wei; Hsu, Scott; Li, Hui; Li, Shengtai; Lynn, Alan
Bibcode: 2009APS..APR.K1013L
Altcode:
Recent astronomical observations indicate that radio lobes are gigantic
relaxed magnetized plasmas with kilo-to-megaparsec scale jets providing
a source of magnetic energy from the galaxy to the lobes. Therefore
we are conducting a laboratory plasma experiment, the Plasma Bubble
Expansion Experiment (PBEX) in which a higher pressure magnetized plasma
bubble (i.e., the lobe) is injected into a lower pressure background
plasma (i.e., the intergalactic medium) to study key nonlinear plasma
physics issues. Here we present detailed ideal magnetohydrodynamic
(MHD) three-dimensional simulations of PBEX. First, the direction of
bubble expansion depends on the ratio of the bubble toroidal to poloidal
magnetic field, with a higher ratio leading to expansion predominantly
in the direction of propagation and a lower ratio leading to expansion
predominantly normal to the direction of propagation. Second, a
leading MHD shock and a trailing slow-mode compressible MHD wave front
are formed ahead of the bubble as it propagates into the background
plasma. Third, the bubble expansion and propagation develop asymmetries
about its propagation axis due to reconnection arising from numerical
resistivity and to inhomogeneous angular momentum transport due to the
background magnetic field. These results will help guide the initial
experiments and diagnostic measurements on PBEX.
Title: Elasticity of (Mg 0.87Fe 0.13)
2SiO 4 wadsleyite to 12 GPa and 1073 K
Authors: Liu, Wei; Kung, Jennifer; Li, Baosheng; Nishiyama, Nori;
Wang, Yanbin
Bibcode: 2009PEPI..174...98L
Altcode:
Elasticity of (Mg 0.87Fe 0.13) 2SiO
4 wadsleyite has been measured at simultaneous high
pressure and high temperature to 12 GPa and 1073 K using ultrasonic
interferometry in conjunction with synchrotron X-radiation. The elastic
moduli and their pressure and temperature derivatives are precisely
determined using pressure-standard-free third-order and fourth-order
finite strain equations. Combined with previous thermoelastic data
on olivine, the density, velocity and acoustic impedance contrasts
between α- and β-(Mg 0.9Fe 0.1) 2SiO
4 at 410-km depth are calculated along a 1673 K adiabatic
geotherm. Both the third- and fourth-order finite strain equation
fitting results give estimation of ∼33-58% olivine content in the
upper mantle to account for a seismic discontinuity of ∼5% velocity
jumps, and 8.5% ( P wave) and 11.1% ( S wave) impedance jumps at 410
km depth.
Title: Helicity Transfer and Energy Release in the Bastille Day Flare
Authors: Hill, Nicholas; Kazachenko, M.; Liu, W.; Qiu, J.
Bibcode: 2009SPD....40.2011H
Altcode:
Spatial and temporal analysis of the 2000 Bastille Day event
observed with SOHO and TRACE instrumentation is viewed in light of a
three-dimensional topological reconnection model. The model measures
the injection of helicity into the active region in a 36-hour build-up
to the flare as well as the evolution of connected segmented areas of
the active region to calculate flux available for the reconnection
process. Utilizing the spatial evolution of the flare, the model
predicts a reconnection flux of 9.45 x 1021 Mx and a
helicity transfer of -9.3 x 1042 Mx2 into a
twisted flux rope subsequently ejected as a coronal mass ejection
(CME). The results compare well with the flux swept out by the two
flare ribbons (1.44 x 1022 Mx) as viewed in TRACE 1600Å
images and the helicity in magnetic cloud measurements (-15.0 x
1042 Mx2). Further analyses also reveal spatial
and temporal correlation between reconnection rate and X-ray emissions,
yielding evidence that reconnection governs energy release in flares. This work was accomplished during the Solar REU program at Montana
State University, which is in part supported by the National Science
Foundation through contract ATM-0552958.
Title: Unshearing Motions, Asymmetries, and Correlations of Conjugate
Hard X-ray Footpoints in the 2003 October 29 X10 Flare: an Imaging
Spectroscopic Study
Authors: Liu, Wei; Petrosian, V.; Dennis, B. R.; Holman, G. D.
Bibcode: 2009SPD....40.1916L
Altcode:
We present a detailed imaging spectroscopic study of the conjugate hard
X-ray (HXR) footpoints (FPs) observed with RHESSI in the 2003 October
29 X10 flare. (1) The double FPs first move toward and then away from
each other, mainly parallel and perpendicular to the magnetic neutral
line, respectively. The transition of these two phases of FP unshearing
motions coincides with the direction reversal of the motion of the
loop-top (LT) source, and with the minima of the estimated loop length
and LT height. (2) Asymmetries are observed between the FPs: on average,
the eastern FP is 2.2 times brighter in HXR flux and 1.8 times weaker
in magnetic field strength, and moves 2.8 times faster away from the
neutral line than the western FP; the estimated coronal column density
to the eastern FP from the LT source is 1.7 times smaller. The two FPs
have marginally different spectral indexes. The eastern-to-western FP
HXR flux ratio and magnetic field ratio are anti-correlated only before
the second HXR peak's maximum. Neither magnetic mirroring nor column
density alone can explain these observations when taken together,
but their combination, along with other transport effects (e.g.,
non-uniform target ionization, relativistic beaming, photospheric
albedo, and return currents), might provide a full explanation. (3) The
FPs show temporal correlations between the HXR flux, spectral index,
and magnetic field strength. The HXR flux exponentially correlates
with the magnetic field strength which also anti-correlates with
the spectral index before the second HXR peak's maximum, suggesting
that particle acceleration sensitively depends on the magnetic field
strength and/or reconnection rate. (4) We have also developed novel
techniques to remove particle contamination from HXR counts and to
estimate effects of pulse pileup in imaging spectroscopy, which can
be applied to other RHESSI flares in similar circumstances.
Title: Long-Term Evolution of Magnetized Bubbles in Galaxy Clusters
Authors: Liu, Wei; Li, Hui; Li, Shengtai; Hsu, Scott
Bibcode: 2009APS..APR.K1012L
Altcode:
An unsolved problem in active galactic nuclei (AGN) feedback on
clusters is how to account for the the morphology and stability of
buoyant bubbles and their interactions with the ambient intracluster
medium (ICM). Appreciable magnetic energy has been observed in both
cluster and radio lobe plasmas. We have performed nonlinear ideal
magnetohydrodynamic simulations of the long term evolution of a
magnetized low-density ``bubble'' plasma formed by a radio galaxy
in a stratified cluster medium. It is found that about 3.5% of the
initial magnetic energy remains in the bubble after ∼8 x10^9 years,
and the initial magnetic bubble expansion is adiabatic. The bubble
can survive for at least 8x10^9 years due to the stabilizing effect
of the bubble magnetic field on Rayleigh-Taylor and Kelvin-Holmholtz
instabilities, possibly accounting for ``ghost cavities" as observed
in Perseus-A. A filament structure spanning about 500 kpc is formed
along the path of bubble motion. The mean value of the magnetic field
inside this structure is ∼0.88 μG at ∼8x10^9 years. Finally,
the initial bubble momentum and rotation have limited influence on
the long term evolution of the bubble.
Title: Episodic X-ray Emission Accompanying the Activation of an
Eruptive Prominence: Evidence of Episodic Magnetic Reconnection
Authors: Liu, Wei; Wang, T.; Dennis, B. R.; Holman, G. D.
Bibcode: 2009SPD....40.1911L
Altcode:
We present an X-ray imaging and spectroscopic study of a partially
occulted (N16W93) C7.7 flare on 2003 April 24 observed by RHESSI that
accompanied a prominence eruption observed by TRACE. (1) The activation
and rise of the prominence occurs during the preheating phase of
the flare. The initial X-ray emission appears as a single coronal
source at one leg of the prominence and it then splits into a double
source. Such a source splitting happens three times, each coinciding
with an increased X-ray flux and plasma temperature, suggestive
of fast reconnection in a localized current sheet and an enhanced
energy release rate. In the late stage of this phase, the prominence
displays a helical structure. These observations are consistent with
the tether-cutting and/or kink instability model for triggering solar
eruptions. (2) The eruption of the prominence takes place during the
flare impulsive phase. Since then, there appear signatures predicted by
the classical CSHKP model of two-ribbon flares occurring in a vertical
current sheet trailing an eruption. These signatures include an EUV
cusp and current-sheet-like feature (or ridge) above it. There is also
X-ray emission along the EUV ridge both below and above the cusp, which
in both regions appears closer to the cusp at higher energies in the
thermal regime (<20 keV). This trend is reversed in the nonthermal
regime (>20 keV). (3) Spectral analysis indicates thermal X-rays
from all sources throughout the flare, while during the impulsive phase
there is additional nonthermal emission which primarily comes from the
coronal source below the cusp. This source also has a lower temperature
(T=20±1 vs. 25±1 MK), a higher emission measure (EM=[3.3±0.4]
vs. [1.2±0.4] x1047 cm-3), and a much harder
nonthermal spectrum (electron power-law index \delta=5.4±0.4 vs. 8±1)
than the upper sources.
Title: Coexistence of distinct power-law regimes in Self Organized
Model for the Magnetosphere
Authors: Vallieres-Nollet, M.; Charbonneau, P.; Uritsky, V.; Liu, W.
Bibcode: 2009AGUSMSM22A..06V
Altcode:
It is now argued that the Central Pasma Sheet (CPS) may behave like a
Self-Organized Critical (SOC) system, driven by the the solar wind. The
power law distributions for the sizes, energy and durations of substorms
that are reflected in observations can be reproduced using such SOC
models. However, recent observations made with the POLAR-UVI instrument
showed that there is in fact two distinct regimes in substorms energies
: small and big events scales as different power laws, the smaller
events having a steeper slope. We used a 2D-SOC model subject to a
deterministic driving, with conservative redistributions laws. We where
able, with a slow driving together with a small dissipation in energy
redistribution, to reproduce the coexistence of these two scaling
regimes. The computation of the waiting-times, under the imposition
of a threshold, showed truncated exponentials distributions, which
is consistent with observations. Finally, we computed statistics
of substorms depending on their onset position, and found that the
southward mapping events tends to exhibit the dual power-law scaling,
while a single slope statistic was found for northward mapping
substorms, which is again consistent with recent observations.
Title: GEOPHYSICS, ASTRONOMY, AND ASTROPHYSICS: Reply to the
“Comment on 'Ported from Self-Similar Analytic Solutions of
Ginzburg-Landau Equation with Varying Coefficients'"
Authors: Feng, Jie; Xu, Wen-Cheng; Li, Shu-Xian; Liu, Wei-Ci; Liu,
Song-Hao
Bibcode: 2009ChPhL..26e9902F
Altcode:
No abstract at ADS
Title: Magnetic Bubble Expansion as an Experimental Model for
Extra-Galactic Radio Lobes
Authors: Lynn, Alan; Zhang, Yue; Hsu, Scott; Li, Hui; Liu, Wei;
Gilmore, Mark; Watts, Christopher
Bibcode: 2009APS..APR.K1014L
Altcode:
The Plasma Bubble Expansion Experiment (PBEX) has begun laboratory
experiments and coordinated nonlinear MHD simulations to address
outstanding nonlinear plasma physics issues related to how magnetic
energy and helicity carried by extra-galactic jets interacts with the
intergalactic medium to form radio lobe structures. Experiments are
being conducted in the 4 meter long, 50 cm diameter HELCAT linear plasma
device at UNM. A pulsed magnetized coaxial gun (∼10 kV, ∼100 kA,
∼2 mWb) forms and injects magnetized plasma bubbles perpendicularly
into a lower pressure weakly magnetized background plasma formed by a
helicon and/or hot cathode source in HELCAT. Experimental parameters
can be adjusted so that important dimensionless parameters are relevant
to the astrophysical context. Ideal MHD simulations show that an MHD
shock develops ahead of the bubble as it propagates, and that the
bubble develops asymmetries due to the background field [1]. First
experimental data from plasma bubble injection into a background
plasma, including magnetic probe measurements and high-speed camera
imaging, will be presented. [1] W. Liu et al., Phys. Plasmas 15, 072905
(2008). Supported by NSF-AST/DOE grant AST-0613577 and LANL LDRD.
Title: Conjugate Hard X-Ray Footpoints in the 2003 October 29 X10
Flare: Unshearing Motions, Correlations, and Asymmetries
Authors: Liu, Wei; Petrosian, Vahé; Dennis, Brian R.; Holman,
Gordon D.
Bibcode: 2009ApJ...693..847L
Altcode: 2008arXiv0805.1055L
We present a detailed imaging and spectroscopic study of the conjugate
hard X-ray (HXR) footpoints (FPs) observed with the Ramaty High
Energy Solar Spectroscopic Imager (RHESSI) in the 2003 October 29
X10 flare. The double FPs first move toward and then away from each
other, mainly parallel and perpendicular to the magnetic neutral line,
respectively. The transition of these two phases of FP unshearing
motions coincides with the direction reversal of the motion of the
loop-top (LT) source, and with the minima of the estimated loop length
and LT height. We find temporal correlations between the HXR flux,
spectral index, and magnetic field strength of each FP. The HXR flux
exponentially correlates with the magnetic field strength, which also
anticorrelates with the spectral index before the second HXR peak's
maximum, suggesting that particle acceleration sensitively depends
on the magnetic field strength and/or reconnection rate. Asymmetries
are observed between the FPs: on average, the eastern FP is 2.2
times brighter in HXR flux and 1.8 times weaker in magnetic field
strength, and moves 2.8 times faster away from the neutral line
than the western FP; the estimated coronal column density to the
eastern FP from the LT source is 1.7 times smaller. The two FPs have
marginally different spectral indices. The eastern-to-western FP HXR
flux ratio and magnetic field strength ratio are anticorrelated only
before the second HXR peak's maximum. Neither magnetic mirroring nor
column density alone can explain the totality of these observations,
but their combination, together with other transport effects, might
provide a full explanation. We have also developed novel techniques to
remove particle contamination from HXR counts and to estimate effects
of pulse pileup in imaging spectroscopy, which can be applied to other
RHESSI flares in similar circumstances.
Title: Calculation of astrophysical reaction rate of
82Ge(n,γ)83Ge
Authors: Wang, Mian; Chen, Yong-Shou; Li, Zhi-Hong; Liu, Wei-Ping;
Shu, Neng-Chuan
Bibcode: 2009ChPhC..33...79W
Altcode:
The neutron capture reaction on a neutron-rich near closed-shell nucleus
82Ge may play an important role in the r-process following
the fallout from nuclear statistical equilibrium in core-collapse
supernovae. By carrying out a DWBA analysis for the experimental
angular distribution of 82Ge(d, p)83Ge reaction
we obtain the single particle spectroscopic factors, S2,5/2
and S0,1/2 for the ground and first excited states
of 83Ge = 82Geotimesn, respectively. And
then these spectroscopic factors are used to calculate the direct
capture cross sections for the 82Ge(n, γ)83Ge
reaction at energies of astrophysical interest. The optical potential
for neutron scattering on unstable nucleus 82Ge is not
known experimentally. We employed a real folding potential which was
calculated by using the proper 82Ge density distribution
and an effective nucleon-nucleon force DDM3Y. The neutron capture
reactions on neutron-rich closed-shell nuclei are expected to be
dominated by the direct capture to bound states. We will show that the
direct capture rates on these nuclei are sensitive to the structure
of the low-lying states.
Title: Characterization of ULF pulsations by THEMIS
Authors: Sarris, T. E.; Liu, W.; Kabin, K.; Li, X.; Elkington, S. R.;
Ergun, R.; Rankin, R.; Angelopoulos, V.; Bonnell, J.; Glassmeier,
K. H.; Auster, U.
Bibcode: 2009GeoRL..36.4104S
Altcode: 2009GeoRL..3604104S
The THEMIS five-probe constellation was launched in 17 February 2007
to study substorms; however its instrumentation and the alignment
at distances <1RE among some of the THEMIS probes,
particularly in the first period of its mission, provides unique
opportunities to study ULF pulsations in the magnetosphere. In the
case study presented, electric and magnetic field fluctuations are
identified as field line resonances and their modes of oscillation are
discussed. Phase-difference calculations between probes allow estimates
of the mode number of the fluctuations. These observations give an
excellent source for the verification of model estimates of frequency
and polarization of the various modes of field line resonances.
Title: Observation and modeling of the injection observed by THEMIS
and LANL satellites during the 23 March 2007 substorm event
Authors: Liu, W. L.; Li, X.; Sarris, T.; Cully, C.; Ergun, R.;
Angelopoulos, V.; Larson, D.; Keiling, A.; Glassmeier, K. H.; Auster,
H. U.
Bibcode: 2009JGRA..114.0C18L
Altcode: 2009JGRA..11400C18L
During the encounter of a substorm on 23 March 2007, the THEMIS
constellation observed energetic particle injections and dipolarizations
in the premidnight sector. Clear injection and dipolarization signatures
were observed during the main intensification by three probes (A,
B, and D) in the region around 11 R E and 2100 local
time (LT). THEMIS C, which was leading in the constellation at 8.3
R E , also observed a clear injection signature, but
the dipolarization was not so clear. From the timing based on these
observations, a fast westward expanding ion injection and dipolarization
front was identified. In combination with the energetic particle
observations from Los Alamos National Laboratory (LANL) geosynchronous
satellites, the particle injection seemed to initiate between 2100 and
0100 LT. This event provides an excellent opportunity to examine the
dipolarization and particle injection processes beyond geosynchronous
orbit and over a wide LT range. We model this injection event by means
of test particle simulation, setting up an initial particle distribution
and sending an earthward dipolarization-like pulse from the tail that
also expands azimuthally, then recording the ions and electrons at the
various satellite locations. Most features of the injected particles
are reproduced by the test particle simulation. These include not only
the earthward injections but also the fast westward expansion of the
injection, as well as the timing of the injections as observed among
different satellites that made the observations. On the basis of the
observations and the simulation results, we suggest that this substorm
injection was initiated around 2300 LT, farther down the tail, and
propagated radially inward and expanded azimuthally.
Title: Noise-sustained Convective Instability in a Magnetized
Taylor-Couette Flow
Authors: Liu, Wei
Bibcode: 2009ApJ...692..998L
Altcode: 2008arXiv0808.2513L
The helical magnetorotational instability of the magnetized
Taylor-Couette flow is studied numerically in a finite cylinder. A
distant upstream insulating boundary is shown to stabilize the
convective instability entirely while reducing the growth rate of
the absolute instability. The reduction is less severe with greater
height. After we model the boundary conditions properly, the wave
patterns observed in the experiment turn out to be a noise-sustained
convective instability. After the source of the noise resulting
from unstable Ekman and Stewartson layers is switched off, a slowly
decaying inertial oscillation is observed in the simulation. We reach
the conclusion that the experiments completed to date have not yet
reached the regime of absolute instability.
Title: Warm ocean anomaly, air sea fluxes, and the rapid
intensification of tropical cyclone Nargis (2008)
Authors: Lin, I. -I.; Chen, Chi-Hong; Pun, Iam-Fei; Liu, W. Timothy;
Wu, Chun-Chieh
Bibcode: 2009GeoRL..36.3817L
Altcode: 2009GeoRL..3603817L
On 2 May 2008, category-4 tropical cyclone Nargis devastated Myanmar. It
was observed that just prior to its landfall, Nargis rapidly intensified
from a weak category-1 storm to an intense category-4 storm within only
24 h. Using in situ ocean depth-temperature measurements and satellite
altimetry, it is found that Nargis' rapid intensification took place
on a pre-existing warm ocean anomaly in the Bay of Bengal. In the
anomaly, the subsurface ocean is evidently warmer than climatology,
as characterized by the depth of the 26°C isotherm of 73-101 m and
the tropical cyclone heat potential of 77-105 kj cm-2. This
pre-existing deep, warm subsurface layer leads to reduction in the
cyclone-induced ocean cooling, as shown from the ocean mixed layer
numerical experiments. As a result, there was a near 300% increase in
the air-sea enthalpy flux to support Nargis' rapid intensification.
Title: Energy Spectrum of the Electrons Accelerated by a Reconnection
Electric Field: Exponential or Power Law?
Authors: Liu, W. J.; Chen, P. F.; Ding, M. D.; Fang, C.
Bibcode: 2009ApJ...690.1633L
Altcode: 2008arXiv0809.1212L
The direct current (DC) electric field near the reconnection region
has been proposed as an effective mechanism to accelerate protons and
electrons in solar flares. A power-law energy spectrum was generally
claimed in the simulations of electron acceleration by the reconnection
electric field. However in most of the literature, the electric and
magnetic fields were chosen independently. In this paper, we perform
test-particle simulations of electron acceleration in a reconnecting
magnetic field, where both the electric and magnetic fields are adopted
from numerical simulations of the MHD equations. It is found that the
accelerated electrons present a truncated power-law energy spectrum
with an exponential tail at high energies, which is analogous to the
case of diffusive shock acceleration. The influences of reconnection
parameters on the spectral feature are also investigated, such as the
longitudinal and transverse components of the magnetic field and the
size of the current sheet. It is suggested that the DC electric field
alone might not be able to reproduce the observed single or double
power-law distributions.
Title: Statefinder Diagnostic for Quintessence with or Without
Thermal Interaction
Authors: Liu, Wei-Zhong; Liu, Dao-Jun
Bibcode: 2009IJMPD..18...43L
Altcode: 2008arXiv0803.4039L
The cosmological dynamics of a minimally coupled scalar field
that couples to the background matter with thermal interactions is
investigated using statefinder diagnostics. The time evolution of the
statefinder pairs {r, s} and {r, q} are obtained under the circumstance
that different values of model parameters are chosen. We show that the
thermal coupling term does not affect the location of the late-time
attractor, but exerts an influence on the evolution of the statefinder
parameters. The most notable feature of the r-s plane for the thermal
coupling model, which is distinguished from the other dark energy
models, is that some part of the curve with thermal coupling can form
a closed loop in the second quadrant (r > 1, s < 0).
Title: Records from Lake Qinghai: Holocene climate history of
Northeastern Tibetan Plateau linking to global change
Authors: An, Z.; Colman, S.; Zhou, W.; Brown, E.; Li, X.; Jull, T.;
Wang, S.; Liu, W.; Sun, Y.; Lu, X.; Song, Y.; Chang, H.; Cai, Y.; Xu,
H.; Wang, X.; Liu, X.; Wu, F.; Han, Y.; Cheng, P.; Ai, L.; Wang, Z.;
Qiang, X.; Shen, J.; Zhu, Y.; Wu, Z.; Liu, X.
Bibcode: 2008AGUFMPP24A..04A
Altcode:
Lake Qinghai (99°36'-100°16'E, 36°32'-37°15'N ) of the north eastern
margin of Tibet Plateau is the largest inland lake of China. It sits
on the transitional zone of Asian monsoon- arid areas, receives
influences of Asian monsoons and Westerlies, thus sensitive to
global climate changes. Although previous studies had investigated
Holocene climate change of Lake Qinghai area, it is rare to see
precise Holocene climatic sequences of Lake Qinghai, nor in-depth
discussions on controlling factors of Lake Qinghai climate changes. In
Year 2005, with support from ICDP, Chinese Academy of Sciences (CAS),
Chinese Ministry of Science and Technology (MOST) and National Science
Foundation of China (NSFC), Drilling, Observation and Sampling of the
Earths Continental Crust Corporation (DOSECC) and Institute of Earth
Environment, Chinese Academy of Sciences (IEECAS) took a series of
shallows cores from the southern basin of Lake Qinghai. West sub-basin
sediments display Holocene lacustrine feature for the upper 5m, while
the 5-18m are interbeded sediments of shallow lake, eolian-lacustrine
and eolian loess. Chinese and US scientists with support from NSFC,
MOST, CAS and NSF analysed 1F core from west sub-basin depocenter
of the south basin with multiple physical, chemical, biological
approaches. By comparing with modern process observation records, we
obtained proxies that respectfully reflect precipitation, temperature
and lake salinity changes, etc., reconstructed high resolution time
sequences of magnetic susceptibility, colour scale, grain size, Corg,
C/N, δ13Corg, carbonate, δ13C and δ18O of carbonate and ostracodes,
elements, char-soot,Uk'37 and %C37:4 as well as pollen of the last
13Ka. They indicate the climatic change history of Lake Qinghai since
past 13Ka, and agreeable evidences are found from adjacent tree ring
and stalagmite records. Comparison of Lake Qinghai Holocene climate
change sequence with those from high altitude ice core, stalagmites
and ocean records for East Asian monsoon and Indian monsoon show that,
in accordance with Asian monsoon climate changes, at 11-5ka cal. 14C BP
Lake Qinghai revealed the warm and humid Optimal climate, while since
5ka cal.14C BP the Lake showed relatively cold and dry climate of New
Glaciation, this orbital climate trend resembled northern hemisphere
summer solar insolation changes. Lake Qinghai millennial-centennial
climate events in Holocene are linked with Westerlies changes, and
with East Asian summer monsoon front shift as well as winter monsoon,
on centennial-decadal scale Lake Qinghai climate changes are controlled
more by solar activities.
Title: First Results from the THEMIS Mission
Authors: Angelopoulos, V.; Sibeck, D.; Carlson, C. W.; McFadden,
J. P.; Larson, D.; Lin, R. P.; Bonnell, J. W.; Mozer, F. S.; Ergun,
R.; Cully, C.; Glassmeier, K. H.; Auster, U.; Roux, A.; Le Contel,
O.; Frey, S.; Phan, T.; Mende, S.; Frey, H.; Donovan, E.; Russell,
C. T.; Strangeway, R.; Liu, J.; Mann, I.; Rae, J.; Raeder, J.; Li,
X.; Liu, W.; Singer, H. J.; Sergeev, V. A.; Apatenkov, S.; Parks,
G.; Fillingim, M.; Sigwarth, J.
Bibcode: 2008SSRv..141..453A
Altcode: 2008SSRv..tmp...90A
THEMIS was launched on February 17, 2007 to determine the trigger and
large-scale evolution of substorms. During the first seven months of
the mission the five satellites coasted near their injection orbit
to avoid differential precession in anticipation of orbit placement,
which started in September 2007 and led to a commencement of the
baseline mission in December 2007. During the coast phase the probes
were put into a string-of-pearls configuration at 100 s of km to 2
RE along-track separations, which provided a unique view of
the magnetosphere and enabled an unprecedented dataset in anticipation
of the first tail season. In this paper we describe the first THEMIS
substorm observations, captured during instrument commissioning on
March 23, 2007. THEMIS measured the rapid expansion of the plasma sheet
at a speed that is commensurate with the simultaneous expansion of the
auroras on the ground. These are the first unequivocal observations of
the rapid westward expansion process in space and on the ground. Aided
by the remote sensing technique at energetic particle boundaries and
combined with ancillary measurements and MHD simulations, they allow
determination and mapping of space currents. These measurements show
the power of the THEMIS instrumentation in the tail and the radiation
belts. We also present THEMIS Flux Transfer Events (FTE) observations
at the magnetopause, which demonstrate the importance of multi-point
observations there and the quality of the THEMIS instrumentation in
that region of space.
Title: A Pleistocene Indian Monsoon record from Heqing Basin, SW China
Authors: Qiang, X.; An, Z.; Shen, J.; Jin, Z.; Sun, Y.; Tong, G.;
Chang, H.; Liu, X.; Liu, W.; Wang, S.; Zhou, W.; Song, Y.; Xiao, X.;
Xiao, H.
Bibcode: 2008AGUFMPP24A..01Q
Altcode:
Heqing Basin (100°06'-100°16'E, 26°28'-26°46'N) is situated in
southeastern margin of Tibetan Plateau, a geological conjunction
zone of three tectonic units separated by Jinshajiang, Honghe and
Xiaojinhe-Lijiang fault belts. Modern climate in this region is mainly
influenced by Indian monsoon circulation. In Year 2002, a 665.83 m
long core was retrieved from the Heqing basin under the support of
Chinese Environmental Scientific Drilling program, which permits a
high-resolution reconstruction of the Indian monsoon evolution from
a continental perspective. The core mainly consists of gray clay,
silty clay and silt. Magnetostratographic result generated by both
thermal and alternating-field demagnetization methods indicates that
the bottom age of the Heqing core is about 2.78 Myr. Multiple proxies
(magnetic susceptibility, grain size, CaCO3 content, loss of ignite,
pollen concentrations, and major/trace elements) were generated
to reconstruct regional climate change and its dynamical links to
Indian summer monsoon and solar insolation forcing. The results
suggest that during glacial periods, this region is characterized
by reduced vegetation cover (e.g., low total pollen concentration)
and enhanced physical weathering (e.g., high Rb/Sr ratio), whereas
during interglacial times, vegetation cover was extensive and chemical
weathering is relatively strong around Heqing basin. Good correlation
between variations in proxy indicators from Heqing core and stacked
Indian summer monsoon record from Arabian Sea (Clemens and Prell, 2003)
indicates that over the last 0.35 Myr, Heqing basin is predominantly
influenced by Indian summer monsoon. Unlike Indian monsoon records from
the Arabian Sea and Indian Ocean which resolution is relatively low,
our high-resolution proxy variations permit a robust understanding of
the Indian summer monsoon variations over the last 2.6 Myr. Comparisons
of monsoon proxies from land and ocean indicate that solar insolation
is the dominant factor controlling the Indian summer monsoon variation,
particularly low-latitude radiation difference between northern and
southern Hemisphere. However, an evident 100-kyr cycle occurred around
1.2 Myr and became remarkable after 0.5 Myr, implying that global ice
volume might have a significant influence on the monsoon records in
Heqing basin since at least mid- Pleistocene.
Title: Statistical study on the characterization of ULF Pulsations
in the Inner Magnetosphere by THEMIS
Authors: Liu, W.; Sarris, T.; Liu, X.; Elkington, S. R.; Ergun, R.;
Kabin, K.; Rankin, R.; Angelopoulos, V.; Bonnell, J.; Glassmeier,
K.; Auster, U.
Bibcode: 2008AGUFMSM33A1753L
Altcode:
ULF pulsations (2~25 mHz) have significant influence on the transport
of energetic particles trapped in the outer radiation belt, which have
drift frequencies comparable to this range. However recent studies
indicate that not all classes of ULF waves are equally important
for radiation belt electron acceleration. For example, simulations
suggest that electrons could be adiabatically accelerated through a
drift-resonance interaction with either azimuthal (toroidal) mode or
radial (poloidal) mode ULF waves. THEMIS electric field observations
provide a good opportunity to study and fully characterize the features
of the ULF pulsations in the inner magnetosphere. The ULF polarization
study by Sarris et al [2008] focuses on the observations made by one
THEMIS probe during its out-bound pass on September 4th, 2007. Here
we will present the statistical studies of the polarizations of ULF
pulsations, based on the spin-fit electric and magnetic field data
from July 2007 to June 2008, with full local time coverage. Through
this global coverage, ULF polarizations are characterized at different
regions, in terms of radial distance and local times. Preliminary
analysis indicates that the polarizations of electric field pulsation
are more radial in dawn/dusk sectors and more azimuthal in noon/midnight
sectors.
Title: Ion temperature drop and quasi-electrostatic electric field
on edge of the current sheet minutes prior to the local current
disruption
Authors: Liang, J.; Liu, W. W.; McFadden, J. P.
Bibcode: 2008AGUFMSM43A1725L
Altcode:
Cross-tail current disruption (CD) in the near-Earth plasma sheet has
been well recognized as the key process at the substorm expansion
phase onset. However, some outstanding questions such as: what
is the principal local magnetospheric parameters that control the
stableness/unstableness of a thin current sheet (TCS), what is the
dominating plasma instability mode leading to the CD, remain to be
answered. Recent theoretical studies indicated that the stableness of
the TCS is particularly sensitive to the distribution of ion drift
velocity across the thickness of the current sheet, and that the
quasi-electrostatic electric field developed in an ion-kinetic-scale
TCS may play a key role in driving the TCS to instability. This
motivates an investigation of the variations of plasma parameters
at the edge of the TCS during the final minutes prior to the local
CD. On a statistical survey of the near-Earth CD events during substorm
intervals collected form the first tail season of the THEMIS mission,
we identify a consistent behavior of precipitous drops of the thermal
ion temperature at the edge of the current sheet in a couple of minutes
before the local CD. Such ion temperature drop is interpreted as
associated with the extreme thinning of an embedded TCS structure that
leads to its ultimate disruption. The observed ion cooling is always
accompanied with significant electric and magnetic field perturbations
containing both systematic shift and wave oscillations. In particular
we also reveal the concurrent growth of a neutral sheet-pointing
quasi-electrostatic electric field minutes prior to the local CD. We
discuss and simulate the role of such quasi-electrostatic field in
leading to the ion temperature drop and the subsequent CD process. The
wave components of the observed electric/magnetic perturbations are
interpreted as Alfvenic effects of the kinetic ballooning mode.
Title: Electrostatic field prior to local current sheet disruption
Authors: Liu, W.; Liang, J.; Donovan, E.
Bibcode: 2008AGUFMSM43A1726L
Altcode:
We present observation of plasma waves in the current sheet across
multiple THEMIS satellites in a substorm event on March 5, 2008. It is
shown that the arrival of a kinetic ballooning perturbation interacts
with the local current sheet to generate a quasi-electrostatic wave
a few minutes before local onset, consistent with the prediction
that the current sheet thins after the passage of a rarefaction
wave. It is proposed that the presence of the quasi-electrostatic
field may change the local stability condition and induce local current
disruption. Preliminary theoretical calculation is given to substantiate
this idea.
Title: Characterization of ULF Pulsations by THEMIS
Authors: Sarris, T. E.; Liu, W.; Kabin, K.; Li, X.; Elkington, S.;
Ergun, R.; Rankin, R.; Angelopoulos, V.; Bonnel, J.; Glassmeier, K.;
Auster, U.
Bibcode: 2008AGUFMSM33A1754S
Altcode:
This paper reports the first use of THEMIS to determine the polarization
properties of ULF waves in a non- dipolar magnetic topology: The
instrumentation and the alignment at close distances (less than
1 RE) among some of the THEMIS probes (particularly in the first
period of its mission) provides unique opportunities to characterize
ULF pulsations in the magnetosphere and enables us to validate and
parameterize existing models. In the case study presented, electric and
magnetic field fluctuations are identified as field line resonances
and their modes of oscillation are compared to model estimates. Out
of the various modes predicted by the model, the second fundamental
mode, or toroidal mode, appears to have most similarities to the
measured polarizations. Furthermore, phase-difference calculations
using the probes' small separations allow estimates of mode number
and propagation characteristics. It is shown that these observations
give an excellent source for the verification of model estimates of
frequency and polarization of the various modes of field line resonances
in the magnetosphere.
Title: Multiple intensifications inside the auroral bulge and their
association with plasma sheet activities
Authors: Keiling, A.; Angelopoulos, V.; Larson, D.; McFadden, J.;
Carlson, C.; Fillingim, M.; Parks, G.; Frey, S.; Glassmeier, K. -H.;
Auster, H. U.; Magnes, W.; Liu, W.; Li, X.
Bibcode: 2008JGRA..11312216K
Altcode:
In this coordinated ground and space study, we report multiprobe
measurements from Time History of Events and Macroscale Interactions
during Substorms (THEMIS), LANL-97A, Polar, and ground observatories
for a substorm that occurred on 23 March 2007. The THEMIS fleet and
LANL-97A were located in the premidnight, near-Earth plasma sheet in
the radial range from 6.6 to 13 RE, placing the spacecraft
into different plasma environments which were subject to different
activities. Simultaneous global Polar Ultraviolet Imager images of
the aurora revealed a fine structure in the auroral bulge in the
form of several time-delayed regions of brightening. We demonstrate a
correspondence between this fine structure and the spatially separated
plasma sheet activities (substorm injections with energies >100
keV) by showing that both executed periodic (100-150 s) one-to-one
correlated modulations. Additionally, the different auroral brightening
regions were modulated approximately out of phase to one another,
as were the separated plasma sheet activities. The periodic plasma
sheet and optical modulations were also one-to-one correlated with
large-amplitude (δH ∼ 150 nT) ground Pi2 pulsations. In contrast
to the most energetic ions (>100 keV), the lower-energetic plasma
sheet ions executed separate oscillations during the development of
the substorm, including the preintensification phase, and showed the
following properties. (1) The oscillation periods were different at
different spacecraft locations and had a tendency to increase during
the evolution of the substorm. During the preintensification phase,
multiple (possibly harmonic) spectral components existed. (2) The
oscillations were coupled to westward moving perturbations of an
energized plasma boundary. The boundary perturbations were likely
conjugate to azimuthally spaced auroral forms ("beads") observed by
Polar-UVI during the preintensification phase and could play a role
in the onset of the substorm intensification. (3) The oscillations
of the lower-energetic ions were also one-to-one correlated with
smaller-amplitude ground Pi2 pulsations (<15 nT). In conclusion, the
combination of these observations allowed us to construct a 3-D picture
of low-frequency, near-Earth plasma sheet phenomena associated with a
substorm and their connection to aurora and the ground. It appeared that
not only one substorm current wedge, but additional current structures
existed which started at different times, pulsated out of phase,
and mapped from different active regions into the ionosphere. The
active space regions appeared to be coupled and transferring energy
from one region to the other while pulsating. We propose that the
wave-like structures in the plasma sheet, observed before and during
the substorm/intensification phase, and their demonstrated properties
support a wave phenomenon (such as a ballooning-type mode) for the
onset and development of the substorm/intensification, rather than
directly driven periodic bursty bulk flow activations.
Title: The magnetotail implications of optical observations of the
brightening substorm aurora
Authors: Donovan, E.; Spanswick, E.; Moores, K.; Liu, W.; Liang, J.;
Strangeway, R.; McFadden, J.; Carlson, C.
Bibcode: 2008AGUFMSM23B1709D
Altcode:
Ground-based optical and topside in situ observations have shown
conclusively that many substorm auroral onsets occur immediately
poleward of the proton aurora brightness peak. This has long been
interpreted as placing a rather stringent constraint on the location
of whatever magnetospheric process corresponds to the brightening
auroral arc, namely that the relevant field lines thread the
region of transition between dipole- and tail-like magnetic field
topologies. However, this constraint, by itself, presents us with a
number of critical questions. For example, we do not know how abrupt
the transition between dipole- and tail-like topologies is, nor do we
know the location of that transition in the magnetosphere on either an
event by event or even a general basis. Not knowing the radial extent of
the transition region limits our ability to explore the nature of the
onset instability. Not knowing the actual location of the transition
limits our ability to optimally utilize the ionospheric observations
in conjunction with contemporaneous satellite observations. In this
paper we take a step back from event studies and explore broader
implications of the location of the onset arc relative to the peak
in proton auroral brightness. More specifically, we use pitch-angle
resolved FAST ESA ion observations from more than 20000 transits of
the auroral zone to explore the latitudinal separation between the peak
precipitating ion energy flux (which corresponds to the peak in proton
auroral brightness) and the inner edge of the electron and ion plasma
sheets. We use these results, in conjunction with magnetic mapping and
published observations of the equatorial location of the inner edge of
the ion and electron plasma sheets, to explore the range of locations
in the magnetotail to which the onset arc is most likely to map, as
well as how the relative distance between the transition region and
the inner edge of the plasma sheet varies through the substorm cycle.
Title: Global observations of injection region evolution during a
reconnection initiated substorm
Authors: Spanswick, E.; Donovan, E.; Blake, J. B.; Cully, C.; Reeves,
G.; Friedel, R.; Weatherwax, A.; Liu, W.
Bibcode: 2008AGUFMSM43A1714S
Altcode:
Recent studies have shown that dispersionless injections can be
identified in riometer data [Spanswick et al., 2007]. This raises
the possibility of using a network of riometers to identify the time
when and location (at least as projected in the ionosphere) where
an injection began, and of following its subsequent spatio- temporal
evolution. In this paper, we present a detailed picture of the evolution
of a large substorm injection. The event occurred on August 27, 2001,
and has been discussed in numerous publications. The expansion phase
in question followed several smaller activations that would reasonably
be described as pseudobreakups. Baker et al. [2002] used Cluster in
situ and IMAGE FUV observations to argue that near- Earth reconnection
preceded the auroral onset. Blake et al. [2005] used Cluster, Polar, and
Chandra data to investigate the large-scale expansion of the injection
region, subject to the caveat that the injection was well underway when
it expanded over the satellites. In this paper, we present riometer
and in situ observations of an injection seen at more than 20 separate
locations (including 6 satellites: Cluster, Polar, Chandra, and 3 LANL
spacecraft). The injection is observed to be dispersionless at 12 of
these locations (three of them are observations previously reported
by Blake). We are able to identify the time and location at which
the injection begins. Combining these observations with information
from the GOES-8 geosynchronous satellite we argue that the injection
initiated near-geosynchronous orbit and expanded poleward (tailward)
and equatorward (earthward) from its beginning. Further, the injection
began several minutes after the reconnection identified in the Cluster
data, providing concrete evidence that near-Earth reconnection, in at
least some events, has little if any ionospheric signature.
Title: Long Term Evolution of Magnetized Bubbles in Galaxy Clusters
Authors: Liu, Wei; Li, Hui; Li, Shengtai; Hsu, Scott
Bibcode: 2008APS..DPPUP6020L
Altcode:
We have performed nonlinear ideal magnetohydrodynamic simulations of
the long term evolution of a magnetized low-density ``bubble" plasma
formed by a radio galaxy in a stratified cluster medium. It is found
that about 3.5% of the initial magnetic energy remains in the bubble
after ∼8 x10^9 years, and the initial magnetic bubble expansion is
adiabatic. The bubble can survive for at least 8 x10^9 years due to
the stabilizing effect of the bubble magnetic field on Rayleigh-Taylor
and Kelvin-Holmholtz instabilities, possibly accounting for ``ghost
cavities" as observed in Perseus-A@. A filament structure spanning
about 500 kpc is formed along the path of bubble motion. The mean
value of the magnetic field inside this structure is ∼0.57 μG at
∼8x10^9 years. Finally, the initial bubble momentum and rotation
have limited influence on the long term evolution of the bubble.
Title: Magnetic Bubble Expansion as an Experimental Model for
Extra-Galactic Radio Lobes
Authors: Lynn, Alan G.; Zhang, Yue; Hsu, Scott; Li, Hui; Liu, Wei;
Gilmore, Mark; Watts, Christopher
Bibcode: 2008APS..DPPUP6046L
Altcode:
The Plasma Bubble Expansion Experiment (PBEX) has begun laboratory
experiments and coordinated nonlinear MHD simulations to address
outstanding nonlinear plasma physics issues related to how magnetic
energy and helicity carried by extra-galactic jets interacts with the
intergalactic medium to form radio lobe structures. Experiments are
being conducted in the 4 meter long, 50 cm diameter HELCAT linear plasma
device at UNM. A pulsed magnetized coaxial gun (∼10 kV, ∼100 kA,
∼2 mWb) forms and injects magnetized plasma bubbles perpendicularly
into a lower pressure weakly magnetized background plasma formed by a
helicon and/or hot cathode source in HELCAT. Experimental parameters
can be adjusted so that important dimensionless parameters are
relevant to the astrophysical context. Ideal MHD simulations show
that an MHD shock develops ahead of the bubble as it propagates,
and that the bubble develops asymmetries due to the background field
[1]. First experimental data, including magnetic probe measurements
and high-speed camera imaging, will be presented. [1] W. Liu et al.,
Phys. Plasmas 15, 072905 (2008).
Title: Ideal MHD simulations of laboratory and astrophysical magnetic
bubble expansion as a model for extragalactic radio lobes.
Authors: Liu, Wei; Hsu, Scott; Li, Hui; Li, Shengtai; Lynn, Alan
Bibcode: 2008APS..DPPYP6053L
Altcode:
Nonlinear ideal magnetohydrodynamic (MHD) simulations of the propagation
and expansion of a magnetic ``bubble'' plasma into a lower density,
weakly-magnetized background plasma are presented. These simulations
mimic the geometry and parameters of the Plasma Bubble Expansion
Experiment (PBEX), which is studying magnetic bubble expansion as a
model for extra-galactic radio lobes. The simulations predict several
key features of the bubble evolution. First, the direction of bubble
expansion depends on the ratio of the bubble toroidal to poloidal
magnetic field, with a higher ratio leading to expansion predominantly
in the direction of propagation and a lower ratio leading to expansion
predominantly normal to the direction of propagation. Second, an MHD
shock and a trailing slow-mode compressible MHD wavefront are formed
ahead of the bubble as it propagates into the background plasma. Third,
the bubble expansion and propagation develop asymmetries about
its propagation axis due to reconnection facilitated by numerical
resistivity and to inhomogeneous angular momentum transport mainly
due to the background magnetic field. These results will help guide
the initial experiments and diagnostic measurements on PBEX.
Title: Magnetic Fields and Turbulence in the Intra-cluster Medium
of Galaxy Clusters
Authors: Li, Hui; Xu, Hao; Liu, Wei
Bibcode: 2008APS..DPPUP6021L
Altcode:
Recent observations have revealed that the intra-cluster medium (ICM) of
galaxy clusters could be significantly magnetized. Observations further
revealed that magnetic fields in the ICM have large amount of fluxes,
yet appearing to have a power-law spectrum. It is often suggested that
such magentic fields could be generated via a turbulent dynamo. Here,
we study a different scenario where significant magnetic fields are
produced by supermassive black holes (SMBHs) in the centers of massive
galaxies, then these magnetic fields are transported to the wider
ICM via jets/lobes during the lifetime of active galaxies (∼ 100
Myr). Subsequent cluster mergers during the cluster evolution (up to
10 Gyr) will stir, shear, and shock the ICM as well as the magnetic
fields provided by SMBHs. We present numerical simulations of the
evolution of clusters with magnetic fields using the newly developed
cosmological MHD code with adaptive mesh refinement. The evolution
of magnetic field energy and flux, along with the ICM dynamics,
will be discussed in detail. By comparing our simulations with the
observations, we will explore the implications for MHD turbulence and
dynamo mechanisms in the ICM.
Title: Overview of the Princeton MagnetoRotational Instability
Experiment
Authors: Schartman, E.; Nornberg, M.; Roach, A.; Ji, H. T.; Coster,
D.; Liu, W.; Goodman, J.; Burin, M. J.
Bibcode: 2008APS..DPPUP6037S
Altcode:
A turbulent viscosity is required to explain the
observationally-inferred rates of angular momentum transport in
accretion disks. Investigation of thin disks has focused on two
sources of instability to drive the turbulence: the MagnetoRotational
Instability (MRI) and Subcritical Hydrodynamic Instability (SHI). In
MRI a weak ambient magnetic field causes the radially-decreasing angular
velocity to become a source of free energy. In SHI, stable perturbations
allow access to unstable modes. This experiment investigates both of
these instabilities in a Couette-Taylor flow. Using water or liquid
Gallium alloy we generate rotating shear flows with linear stability
properties analagous to astrophysical disks. Differentially rotatable
end-rings reduce boundary effects. We found no evidence of SHI, up
to Reynolds number of order one million. During the MHD experiments a
solenoidal magnetic field of up to 5 kG is applied. Radially-aligned
induction coils detect magnetic perturbations generated by the liquid
metal. Initial magnetized experiments focussed on magneto-Coriolis waves
which at large magnetic Reynolds number are expected to transition into
MRI modes. Results of the current search for the MRI will be presented.
Title: Actuality and futurity of San Juan 7406 SLR Station
Authors: Liu, W.; Han, Y.; Actis, E.; Alonso, E.; Podesta, R.;
Gonzalez, A. A.; Pacheco, A. M.; Zhao, L.; Liu, C.; Yin, Z.
Bibcode: 2008lara.workE..96L
Altcode:
No abstract at ADS
Title: Interaction between kinetic ballooning perturbation and thin
current sheet: Quasi-electrostatic field, local onset, and global
characteristics
Authors: Liu, W. W.; Liang, J.; Donovan, E. F.
Bibcode: 2008GeoRL..3520107L
Altcode:
We present observation of plasma waves in the current sheet across
multiple THEMIS satellites in a substorm event on March 5, 2008. It is
shown that the arrival of a kinetic ballooning perturbation interacts
with the local current sheet to generate a quasi-electrostatic wave
a few minutes before local onset, consistent with the prediction that
the current sheet thins after the passage of a rarefaction wave. The
propagation speed of current disruption front is found to be ~100
km/s, about a tenth of the fast mode speed. The observed pattern of
interaction was constant across radial distances between 10 and 20
R E in the event reported. It is further proposed that
the presence of the quasi-electrostatic field may change the local
stability condition and induce local current disruption.
Title: Numerical Study of the Magnetorotational Instability in
Princeton MRI Experiment
Authors: Liu, Wei
Bibcode: 2008ApJ...684..515L
Altcode: 2008arXiv0804.0044L
In preparation for an experimental study of magnetorotational
instability (MRI) in liquid metal, we present nonideal axisymmetric
magnetohydrodynamic simulations of the nonlinear evolution of MRI in the
experimental geometry. The simulations adopt fully insulating boundary
conditions. No-slip conditions are imposed at all boundaries. A clear
linear phase is observed with reduced linear growth rate. MRI results in
an inflowing "jet" near the midplane and enhances the angular momentum
transport at saturation.
Title: Long-Term Evolution of Magnetized Bubbles in Galaxy Clusters
Authors: Liu, Wei; Li, Hui; Li, Shengtai; Hsu, Scott C.
Bibcode: 2008ApJ...684L..57L
Altcode: 2008arXiv0806.3717L
We have performed nonlinear ideal magnetohydrodynamic simulations
of the long-term evolution of a magnetized low-density "bubble"
plasma formed by a radio galaxy in a stratified cluster medium. It
is found that about 3.5% of the initial magnetic energy remains in
the bubble after ~8 × 109 yr, and the initial magnetic
bubble expansion is adiabatic. The bubble can survive for at least
8 × 109 yr due to the stabilizing effect of the bubble
magnetic field on Rayleigh-Taylor and Kelvin-Helmholtz instabilities,
possibly accounting for "ghost cavities" as observed in Perseus A. A
filament structure spanning about 500 kpc is formed along the path
of bubble motion. The mean value of the magnetic field inside this
structure is ~0.88 μG at ~8 × 109 yr. Finally, the initial
bubble momentum and rotation have limited influence on the long-term
evolution of the bubble.
Title: Simultaneous THEMIS in situ and auroral observations of a
small substorm
Authors: Donovan, E.; Liu, W.; Liang, J.; Spanswick, E.; Voronkov,
I.; Connors, M.; Syrjäsuo, M.; Baker, G.; Jackel, B.; Trondsen, T.;
Greffen, M.; Angelopoulos, V.; Russell, C. T.; Mende, S. B.; Frey,
H. U.; Keiling, A.; Carlson, C. W.; McFadden, J. P.; Glassmeier,
K. -H.; Auster, U.; Hayashi, K.; Sakaguchi, K.; Shiokawa, K.; Wild,
J. A.; Rae, I. J.
Bibcode: 2008GeoRL..3517S18D
Altcode:
We present ground-based and in situ observations from March 13,
2007. The THEMIS satellites were in the evening sector conjugate to
THEMIS ground-based imagers. At ~0507 UT there was an optical onset on
inner CPS field lines. This involved near-simultaneous brightening of 1
MLT hour longitudinal segment of the onset arc. The part of the arc that
brightened was that closest to the equatorward boundary of the diffuse
(proton) aurora. Within one minute, a dipolarization front moved across
four THEMIS satellites. Based on their locations, the order in which
they detected the dipolarization front, and the auroral evolution, we
assert that the expansion phase began earthward of the four satellites
and evolved radially outwards. We conclude that this onset occurred
in an azimuthally localized region of highly stretched field lines.
Title: Wind power distribution over the ocean
Authors: Liu, W. Timothy; Tang, Wenqing; Xie, Xiaosu
Bibcode: 2008GeoRL..3513808L
Altcode:
Probability distribution and power density of wind speed over global
oceans are computed from eight years of QuikSCAT measurements. They
describe the variation and higher moments of wind speed that are
critical in relating the non-linear effects of wind on electric
power generation capability, shipping hazard, and air-sea exchanges
in heat, water, and greenhouse gases. The power density distribution
confirms our general knowledge of atmospheric circulation related to
mid-latitude storm tracks, trade winds, and monsoons. It also reveals
regions of high wind power associated with flow distortion by land,
wind channeled by land topography, and buoyancy effect on turbulent
stress driven by ocean fronts.
Title: Ideal magnetohydrodynamic simulation of magnetic bubble
expansion as a model for extragalactic radio lobes
Authors: Liu, Wei; Hsu, Scott C.; Li, Hui; Li, Shengtai; Lynn, Alan G.
Bibcode: 2008PhPl...15g2905L
Altcode: 2008arXiv0804.3379L
Nonlinear ideal magnetohydrodynamic (MHD) simulations of the propagation
and expansion of a magnetic ``bubble'' plasma into a lower density,
weakly magnetized background plasma, are presented. These simulations
mimic the geometry and parameters of the Plasma Bubble Expansion
Experiment (PBEX) [A. G. Lynn, Y. Zhang, S. C. Hsu, H. Li, W. Liu,
M. Gilmore, and C. Watts, Bull. Am. Phys. Soc. 52, 53 (2007)], which
is studying magnetic bubble expansion as a model for extragalactic
radio lobes. The simulations predict several key features of the
bubble evolution. First, the direction of bubble expansion depends
on the ratio of the bubble toroidal to poloidal magnetic field, with
a higher ratio leading to expansion predominantly in the direction
of propagation and a lower ratio leading to expansion predominantly
normal to the direction of propagation. Second, a MHD shock and a
trailing slow-mode compressible MHD wavefront are formed ahead of the
bubble as it propagates into the background plasma. Third, the bubble
expansion and propagation develop asymmetries about its propagation
axis due to reconnection facilitated by numerical resistivity and to
inhomogeneous angular momentum transport mainly due to the background
magnetic field. These results will help guide the initial experiments
and diagnostic measurements on PBEX.
Title: Solar Flares as Natural Particle Accelerators: A High-energy
View from X-ray Observations and Theoretical Models
Authors: Liu, Wei
Bibcode: 2008sfpa.book.....L
Altcode:
Solar flares, which have significant space weather consequences,
are natural particle accelerators and one of the most spectacular
phenomena of solar activity. RHESSI is the most advanced solar X-ray
and gamma-ray mission ever flown and has opened a new era in solar
flare research following its launch in 2002. This book offers a
glimpse of this active research area from a high-energy perspective
and contains a comprehensive guideline for RHESSI data analysis. Its
main theme is the investigation of particle acceleration and transport
in solar flares. The strength of this book lies in its well-balanced
account of the latest X-ray observations and theoretical models. The
observational focus is on the morphology and spectra of imaged X-ray
sources produced by nonthermal electrons or hot plasma. The modeling
takes the novel approach of combining the Fokker-Planck treatment of
the accelerated particles with the hydrodynamic treatment of the heated
atmosphere. Applications of this modeling technique reach beyond the
Sun to other exotic environments in the universe, such as extrasolar
planetary auroras, stellar flares, and flares on accretion disks around
neutron stars and black holes.
Title: Correlation of substorm injections, auroral modulations,
and ground Pi2
Authors: Keiling, A.; Angelopoulos, V.; Larson, D.; Lin, R.; McFadden,
J.; Carlson, C.; Bonnell, J. W.; Mozer, F. S.; Glassmeier, K. -H.;
Auster, H. U.; Magnes, W.; Mende, S.; Frey, H.; Roux, A.; Le Contel,
O.; Frey, S.; Phan, T.; Donovan, E.; Russell, C. T.; Mann, I.; Liu,
W.; Li, X.; Fillingim, M.; Parks, G.; Shiokawa, K.; Raeder, J.
Bibcode: 2008GeoRL..3517S22K
Altcode:
In this case study we report a substorm, 23 March 2007, which exhibited
oscillations with a period of ~135 s in three substorm phenomena all
of which were one-to-one correlated. The in-situ observations are
from one THEMIS spacecraft (8.3 R E geocentric distance)
and the geosynchronous LANL-97A spacecraft. The focus here is on the
intensification phase during which THEMIS was conjugate to the region
of auroral brightening and its foot point was near the high-latitude
ground station Kiana. The following results will be demonstrated: (1)
THEMIS and LANL-97A (time-delayed) recorded periodic ion injections
(>100 keV). (2) Near-conjugate high-latitude ground magnetometer
data show very large Pi2 (δH~150 nT) with a 6-s time delay compared
to the THEMIS ion injections. (3) Low-latitude ground magnetometer
data also show Pi2 with the same waveform as the high-latitude Pi2
but with longer time delays (20-31 s). (4) Auroral luminosity was
periodically modulated during the intensification phase. (5) All three
signatures (ion injections, ground Pi2, optical modulation) had the same
periodicity of ~135 s but with various time delays with respect to the
THEMIS ion injections. These observations demonstrate that the three
substorm phenomena had a common source which controlled the periodicity.
Title: Intensification of preexisting auroral arc at substorm
expansion phase onset: Wave-like disruption during the first tens
of seconds
Authors: Liang, Jun; Donovan, E. F.; Liu, W. W.; Jackel, B.; Syrjäsuo,
M.; Mende, S. B.; Frey, H. U.; Angelopoulos, V.; Connors, M.
Bibcode: 2008GeoRL..3517S19L
Altcode:
With the deployment of the all-sky imager array of the THEMIS mission,
we were able to construct a preliminary database of auroral substorm
expansion phase onsets, from which we have established a number
of common features characterizing the first tens of seconds of the
substorm auroral intensification. We find that the intensification
occurs within ~10 sec over an arc segment extending approximately 1 h
MLT and featuring wave-like formations distributed in longitude. The
longitudinal wave number ranges between 100 and 300 such that the
wavelength is comparable to the ion gyroradius in the central plasma
sheet. The scale the intensification is about 10-30 sec. This study
casts important observational constraints on substorm onset theories.
Title: Ideal Magnetohydrodynamical Simulations of Magnetic Bubble
Expansion as a Model for Extragalactic Radio Lobes
Authors: Liu, Wei; Hsu, S.; Li, S.; Li, H.
Bibcode: 2008AAS...212.0339L
Altcode: 2008BAAS...40..191L
Recent observations indicate that radio lobes are gigantic "relaxed"
magnetized plasmas with kilo-to-megaparsec scale jets providing a source
of magnetic energy from the galaxy to the lobes. We therefore have
proposed a laboratory plasma experiment, in which a higher pressure
magnetized plasma bubble (i.e., the lobe) is injected into a
lower pressure background plasma (i.e., the intergalactic medium) to
study key nonlinear plasma physics issues. Here we present detailed
ideal magnetohydrodynamical (MHD) three-dimensional simulations of
this experiment. The properties of the evolution of the bubble
is dependent on the value of α. Larger α results in a axially
expanding bubble like a growing ``mushroom" while smaller α produces
something like a "crab", expanding horizontally. The expansion of the
bubble generates one perpendicular shock and one reversal slow-mode
compressible MHD wave front, where 3-D reconnection is happening. The
structure of shock/wavefront is almost independent of the injection
velocity if it is reasonably low. The initially uniformly rotating
bubble quickly evolves into a quasi-force-free state and transits to
two oppositely-rotating bubbles. The axial angular momentum has been
transported from the side where the bubble field is along the background
field to the side where the bubble field is opposite to the background
field. The discovery of MHD shocks shows that our experimental
facility provides a good opportunity to study the MHD shocks, which
are hardly to be observed in a laboratory experiment. Comparison of
models and measurements will be used to validate the theoretical tools,
which we will apply to nonlinear relaxation of magnetized plasma in
astrophysical systems.
Title: Laboratory Study of Angular Momentum Transport in Sheared
Rotating Flows
Authors: Ji, Hantao; Nornberg, M.; Schartman, E.; Goodman, J.; Liu,
W.; Roach, A.
Bibcode: 2008AAS...212.0344J
Altcode: 2008BAAS...40..192J
Rapid angular momentum transport in accretion disks is a longstanding
astrophysical puzzle. Transport by molecular viscosity is inadequate
to explain observationally inferred accretion rates. Since Keplerian
flows are linearly stable in hydrodynamics, there exist only two
main viable mechanisms for the required turbulence: nonlinear
hydrodynamic instability or linear magnetorotational instability
(MRI). The latter is regarded as a dominant mechanism for rapid
angular momentum transport in hot accretion disks ranging from quasars
and X-ray binaries to cataclysmic variables. The former is proposed
mainly for cooler protoplanetary disks, whose Reynolds numbers are
typically large. Despite their popularity, however, there is limited
experimental evidence for either mechanism. In this talk, I will
describe a laboratory experiment at Princeton (http://mri.pppl.gov)
in a short Taylor-Couette flow geometry intended to study these
mechanisms. Based on the results from prototype experiments and
simulations, the apparatus contains novel features for better controls
of the boundary-driven secondary flows. The experiments in water have
shown1 that nonmagnetic quasi-Keplerian flows at Reynolds
numbers as large as 2× 106 are essentially laminar, through
means of direct measurements of Reynolds stress via a synchronized, dual
Laser Doppler Velocimetry. Scaled to accretion disks, rates of angular
momentum transport lie far below astrophysical requirements. By ruling
out hydrodynamic turbulence, our results indirectly support MRI as the
likely cause of turbulence even in cool disks. The experiments in liquid
gallium eutectic alloy have recently begun, and initial results on MRI
as well as other related phenomena including numerical predictions will
be also discussed if available. 1. H. Ji, M. Burin, E. Schartman,
& J. Goodman, Nature 444, 343-346 (2006).
Title: Magnetized Ekman layer and Stewartson layer in a magnetized
Taylor-Couette flow
Authors: Liu, Wei
Bibcode: 2008PhRvE..77e6314L
Altcode: 2007arXiv0712.2543L
In this paper we present axisymmetric nonlinear simulations of
magnetized Ekman and Stewartson layers in a magnetized Taylor-Couette
flow with a centrifugally stable angular-momentum profile and with a
magnetic Reynolds number below the threshold of magnetorotational
instability. The magnetic field is found to inhibit the Ekman
suction. The width of the Ekman layer is reduced with increased magnetic
field normal to the end plate. A uniformly rotating region forms
near the outer cylinder. A strong magnetic field leads to a steady
Stewartson layer emanating from the junction between differentially
rotating rings at the endcaps. The Stewartson layer becomes thinner
with larger Reynolds number and penetrates deeper into the bulk flow
with stronger magnetic field and larger Reynolds number. However, at
Reynolds number larger than a critical value ∼600 , axisymmetric,
and perhaps also nonaxisymmetric, instabilities occur and result in a
less prominent Stewartson layer that extends less far from the boundary.
Title: Ideal Magnetohydrodynamical Simulations of Magnetic Bubble
Expansion as a model for extragalactic radio lobes
Authors: Liu, Wei; Hsu, Scott; Li, Hui; Li, Shengtai; Lynn, Allan
Bibcode: 2008APS..APR.K1025L
Altcode:
Recent astronomical observations indicate that radio lobes are gigantic
relaxed magnetized plasmas with kilo-to-megaparsec scale jets providing
a source of magnetic energy from the galaxy to the lobes. Therefore
we are conducting a laboratory plasma experiment, the Plasma Bubble
Expansion Experiment (PBEX) in which a higher pressure magnetized plasma
bubble (i.e., the lobe) is injected into a lower pressure background
plasma (i.e., the intergalactic medium) to study key nonlinear plasma
physics issues. Here we present detailed ideal magnetohydrodynamic (MHD)
three-dimensional simulations of PBEX. Given reasonably low injection
speeds of the magnetic bubble, its expansion due to the Lorentz force
leads to one perpendicular MHD shock and one compressible reversal
MHD wavefront, where three-dimensional reconnection results due to
numerical resistivity. With the expansion, some angular momentum is
transported from the rotating magnetic bubble to the background plasma
mainly due to advection. The discovery of MHD shocks in the simulations
shows that PBEX provides a rare opportunity to study MHD shocks in
a laboratory experiment. Comparison of models and measurements will
be used to validate the theoretical tools, which we will apply to
nonlinear relaxation of magnetized plasmas in astrophysical systems.
Title: Experimental study of plasma bubble expansion as a model for
extragalactic radio lobes
Authors: Hsu, Scott; Lynn, Alan G.; Zhang, Yue; Liu, Wei; Li, Hui;
Watts, Christopher; Gilmore, Mark
Bibcode: 2008APS..APR.K1024H
Altcode:
Recent work in plasma astrophysics has suggested that magnetic
energy features prominently in the large-scale evolution of active
galaxies. The Plasma Bubble Expansion Experiment (PBEX) at UNM will
conduct laboratory experiments to address outstanding nonlinear plasma
physics issues related to how magnetic energy and helicity carried by
extra-galactic jets interacts with the intergalactic medium to form
extra-galactic radio lobe structures. A newly-built pulsed coaxial
gun will form and inject magnetized plasma bubbles into a lower
pressure weakly-magnetized background plasma formed by the helicon
and/or hot cathode source in HELCAT, a 4 m long and 50 cm diameter
linear plasma device. Plasma properties can be adjusted such that
important dimensionless parameters are relevant to the astrophysical
context. Ideal MHD simulations of the experiment have indicated the
strong possibility of MHD shocks appearing. This poster will provide
an overview of the physics goals, experimental design/status, and
coordinated theory/modeling of PBEX.
Title: Double Coronal Hard and Soft X-Ray Source Observed by RHESSI:
Evidence for Magnetic Reconnection and Particle Acceleration in
Solar Flares
Authors: Liu, Wei; Petrosian, Vahé; Dennis, Brian R.; Jiang, Yan Wei
Bibcode: 2008ApJ...676..704L
Altcode: 2007arXiv0709.1963L
We present data analysis and interpretation of an M1.4 class flare
observed with the Reuven Ramaty High Energy Solar Spectroscopic Imager
(RHESSI) on 2002 April 30. This event, with its footpoints occulted by
the solar limb, exhibits a rarely observed, but theoretically expected,
double-source structure in the corona. The two coronal sources,
observed over the 6-30 keV range, appear at different altitudes and show
energy-dependent structures with the higher energy emission being closer
together. Spectral analysis implies that the emission at higher energies
in the inner region between the two sources is mainly nonthermal,
while the emission at lower energies in the outer region is primarily
thermal. The two sources are both visible for about 12 minutes and have
similar light curves and power-law spectra above about 20 keV. These
observations suggest that the magnetic reconnection site lies between
the two sources. Bidirectional outflows of the released energy in the
form of turbulence and/or particles from the reconnection site could be
the source of the observed radiation. The spatially resolved thermal
emission below about 15 keV, on the other hand, indicates that the
lower source has a larger emission measure but a lower temperature
than the upper source. This is likely the result of the differences
in the magnetic field and plasma density of the two sources.
Title: Impact of the Three Gorges Dam water storage on the Yangtze
River outflow into the East China Sea
Authors: Yan, Xiao-Hai; Jo, Young-Heon; Jiang, Lide; Wan, Zhenwen;
Liu, W. Timothy; Li, Yan; Zhan, Jiemin; Du, Tao
Bibcode: 2008GeoRL..35.5610Y
Altcode:
The role of the Three Gorges Dam Water Storage (TGDWS) in changing
salinity in the East China Sea (ECS) near the Yangtze River Estuary
(YRE) was investigated using a multi-sensor remote sensing technique,
namely the salt steric height anomaly, calculated from Sea Surface
Height Anomaly (SSHA) and Sea Surface Temperature (SST) data. The
patterns of the salt steric height anomaly near the YRE agreed
well with the in situ Sea Surface Salinity (SSS) measurements. In
order to examine the changes in stability in the mixed layer near
the YRE due to TGDWS, the time series of the steric height anomaly
ratio (Rs') between heat and salt at three locations were
estimated. The Rs' was strongly associated with a coastal
upwelling in the ECS, because the reduced freshwater outflow gives rise
to changes of both mixed layer depth and surface current patterns off
the YRE.
Title: Auroral Processes and Atmospheric Response of Jupiters Around
Red Giants: a Combined Fokker-Planck and Hydrodynamic Approach
Authors: Liu, Wei; Airapetian, V.
Bibcode: 2008AAS...21115901L
Altcode:
A number of Jupiters have recently been detected around giant stars
including one of the brightest stars in the sky and a well-studied
K0 giant, β Gem. Giants stars have cool and massive winds that
may affect the magnetospheres of Jupiters and cause a number of
observational effects. We show that rescaling of intensities of auroral
events observed on Jupiter and Saturn can provide an estimate for UV
emission line intensities that can be observed by largest ground-based
telescopes and/or space missions. In this study, we model the auroral
processes and an evaporation scenario caused by injection of energetic
electrons into the outer atmospheres of massive Jupiters located at
1 AU from β Gem. We apply a state-of-the-art combined Fokker-Planck
(Leach & Petrosian 1981) and 1-D hydrodynamic (Mariska et al. 1989)
code to study, for the first time, the transient effects of injection of
energetic electrons with energies > 10 keV heating the atmospheres
due to Coulomb collisions. The energetic particles are produced
as a result of the interaction between the magnetic fields of the
stellar wind and the exoplanetary magnetosphere at the magnetopause
or reconnection in the magnetotail. The combined Fokker-Plank and
hydrodynamic code is capable of treating particle transport and the
hydrodynamic atmospheric response in a self-consistent manner, and
has been successfully used to study chromospheric evaporation during
solar flares (Liu 2006). We discuss expected fluxes in UV continuum
and emission lines and new observations that can be used to search
for evaporating Jupiters around stars with high mass-loss rates.
Title: Observation of isolated high-speed auroral streamers and their
interpretation as optical signatures of Alfvén waves generated by
bursty bulk flows
Authors: Liu, W. W.; Liang, J.; Donovan, E. F.; Trondsen, T.; Baker,
G.; Sofko, G.; Jackel, B.; Wang, C. -P.; Mende, S.; Frey, H. U.;
Angelopoulos, V.
Bibcode: 2008GeoRL..35.4104L
Altcode:
The THEMIS All-Sky Imager at Fort Smith, Canada observed a sudden
appearance and subsequent evolution of auroral streamers on April 15,
2006. The event took place in an oval that was optically dark, and
evolved into a 20-minute period of intense equatorward streaming of
red aurora. We characterize the incipient event as isolated streamers,
a phenomenon previously linked with bursty bulk flows in the plasma
sheet. Thanks to the high time and spatial resolution of THEMIS
ASI, the observed streamer reveals some detailed features hitherto
not reported. Aside from their exceptionally high speed and fine
transient structures, the streamers are found to exhibit an unusual
convergent motion (equatorward from high latitudes and poleward from
low latitudes) to form a complete flow channel. Our analysis shows that
this observation is best explained with a new theory on the origin of
auroral streamers.
Title: Testing the Neupert Effect With Combined Fokker-Planck and
Hydrodynamic Simulations
Authors: Liu, Wei; Petrosian, Vahe; Holman, Gordon D.; Dennis, Brian
Bibcode: 2008cosp...37.1804L
Altcode: 2008cosp.meet.1804L
The Neupert effect in solar flares is an empirical temporal correlation
between the microwave or hard X-ray (HXR) flux and the time derivative
of the soft X-ray (SXR) flux. Such a correlation is expected from a
simple energy argument and is considered as evidence of chromospheric
evaporation. However, a quantitative statistical correlation and
physical connection between these emissions have not been established,
and in some flares the Neupert effect is not observed. In this study we
apply a state-of-the-art combined Fokker-Planck (Petrosian et al. 2001)
and hydrodynamic (Mariska et al. 1989) code to model the atmospheric
response to collisional heating by accelerated electrons. This code
treats acceleration and transport of particles and hydrodynamics of
plasma in a self-consistent manner (Liu 2006). It also evaluates various
energy contents and thermal SXR and nonthermal HXR bremsstrahlung
emissions. We confirm the existence of a temporal and statistical
correlation between the SXR derivative and the HXR flux. In addition,
we find a statistically more significant and physically more natural
correlation between the SXR derivative and the thermal energy variation
rate. The simulation results will be presented and implications for
the energy release and particle acceleration processes in solar flares
will be discussed.
Title: Measurements of stellar and explosive nuclear astrophysics
reactions
Authors: Liu, W. P.; Li, Z. H.; Bai, X. X.; Wang, Y. B.; Lian, G.; Guo,
B.; Su, J.; Zeng, S.; Wang, B. P.; Li, Z. H.; Bai, X. X.; Wang, Y. B.;
Lian, G.; Guo, B.; Su, J.; Zeng, S.; Wang, B. X.; Yan, S. Q.; Li, Y. J.
Bibcode: 2008nuco.confE..11L
Altcode: 2008PoS....53E..11L
No abstract at ADS
Title: Statefinder diagnostic for cosmology with the abnormally
weighting energy hypothesis
Authors: Liu, Dao-Jun; Liu, Wei-Zhong
Bibcode: 2008PhRvD..77b7301L
Altcode: 2007arXiv0711.4854L
In this paper, we apply the statefinder diagnostic to the cosmology
with the abnormally weighting energy hypothesis (AWE cosmology),
in which dark energy in the observational (ordinary matter) frame
results from the violation of the weak equivalence principle by
pressureless matter. It is found that there exist closed loops in
the statefinder plane, which is an interesting characteristic of the
evolution trajectories of statefinder parameters and can be used to
distinguish AWE cosmology from other cosmological models.
Title: Determination of the substorm initiation region from a major
conjunction interval of THEMIS satellites
Authors: Lui, A. T. Y.; Angelopoulos, V.; Le Contel, O.; Frey, H.;
Donovan, E.; Sibeck, D. G.; Liu, W.; Auster, H. U.; Larson, D.; Li,
X.; Nosé, M.; Fillingim, M. O.
Bibcode: 2008JGRA..113.0C04L
Altcode:
We investigate in detail the time history of substorm disturbances
in the magnetotail observed during a major tail conjunction of Time
History of Events and Macroscale Interactions during Substorms (THEMIS)
satellites on 29 January 2008, 0700-0900 UT. During this interval,
all THEMIS satellites were closely aligned along the tail axis near
midnight and were bracketed in local time by GOES 11 and 12. The radial
distance covered ranges from the geosynchronous altitude to ∼30
RE in the tail. This interval consists of three activations
detected by the THEMIS satellites with good ground all-sky-camera
observations of auroral activity. The first activation is a small
substorm with spatially limited disturbance in the tail. The onset
arc was equatorward of an undisturbed arc. The second activation is
a moderate size substorm with the onset arc also being equatorward of
an undisturbed arc. The third activation is an intensification of the
substorm with its onset indicated by the second activation. The active
auroral arc for this intensification was near the poleward boundary
of the auroral oval. Analysis of these observations indicates that the
first activation is a small substorm initiated in the near-Earth plasma
sheet and does not involve magnetic reconnection of open magnetic field
lines. Magnetic reconnection on closed field lines can be ruled out
for this substorm because it cannot generate the observed high-speed
plasma flow. The second and third activations are part of a moderate
size substorm initiated also in the near-Earth plasma sheet, with
a subsequent substorm intensification involving activity initiated
tailward of ∼30 RE. Overall, the time history of substorm
activity for these two substorms is consistent with the near-Earth
initiation model.
Title: Azimuthal evolution of the aurora in tens of seconds around
the expansive phase onset
Authors: Liang, J.; Donovan, E.; Liu, W.; Jackel, B.; Spanswick, E.;
Syrjaesuo, M.; Partamies, N.; Voronkov, I.; Connors, M.; Mende, S.;
Angelopoulos, V.; Frey, H.; Ge, Y.; Russell, C.; Rae, J.; Mann, I.
Bibcode: 2007AGUFMSM21B..03L
Altcode:
Using data from the implementation phase (2004-2007) of the THEMIS
All-Sky Imager (ASI) array, we carry out a study of the temporal
evolution and fine structure of the substorm onset arc in the tens
of seconds around expansive phase (EP) onset. The continent-wide
array provides an unprecedented combination of mesoscale imaging
with relatively high time resolution (3 second cadence), subject to
the limitations imposed by viewing conditions. We have identified
eight events in which we have excellent viewing of the onset
aurora. Our results show the following salient features: 1. The
initial brightening occurs along an azimuthally extended region of
the arc. This brightening typically spans ~1 hour of MLT. In cases
that the camera provides ideal coverage of the arc, the length of
the brightening does not noticeably change during the first tens of
seconds of EP. 2. Periodic structures along the arc emerge from ~10 s
before the EP onset, and significantly brightens within ~10 s after the
onset, constituting the most unambiguous and prominent feature from the
optical auroral aspects of the substorm EP onset. Those periodic "wave"
structure, on its initial formation and brightening, are usually well
aligned (<15 deg) with the L-shell. The wavelength is about 40-130
km. These structures either remain stationary or propagate east or west
during the initial brightening. 3. About 20-30 s after the onset, the
brightening arc is no longer aligned with the L-shell. Titled structure,
typically appears as a "bifurcation" of the initial onset arc, starts to
develop and leads the poleward progression of the substorm auroras. We
interpret these results as follows. First, the auroral breakup is on
field lines connected to a region in the CPS that is unstable over an
extended azimuthal range, but in a limited radial range (the latter
a conclusion based on contemporaneous riometer observations). Second,
the instability grows very rapidly across this initially unstable region
but the region itself does not grow in size for tens of seconds after
the initial onset. Third, the alignment between the onset-associated
periodic structures and the magnetic L-shell gives strongly hints
that they are controlled by near-Earth magnetotail dynamics. If that
is true, then waves associated with the breakup in the CPS appear to
have no preferred propagation direction. We finish by discussing the
implications of these results for substorm onset mechanism theories.
Title: Investigation of space and ground low-frequency particle and
field oscillations during the 23 March 2007 substorm
Authors: Keiling, A.; Angelopoulos, V.; Larson, D.; McFadden, J.;
Carlson, C.; Bonnell, J. W.; Mozer, F.; Glassmeier, K.; Auster, U.;
Roux, A.; Le Contel, O.; Mende, S.; Frey, H.; Donovan, E.; Mann, I.;
Shiokawa, K.; Yumoto, K.; Liu, W.; Li, X.; Parks, G.; Fillingim, M.;
Lui, A.
Bibcode: 2007AGUFMSM22A..03K
Altcode:
We will report in-situ THEMIS and ground observations and analyses
of various quantities at and after the onset of the 23 March 2007
substorm. The spacecraft were located in the Southern Hemisphere
magnetotail between 8 and 12 RE (radial distance) while their local time
meridians approximately mapped onto the 210MM magnetometer network. The
following key results will be presented: (1) Alfven waves (circularly
polarized) coincided with substorm-related energetic ion injections. (2)
Strong ion outflow occurred on the same field lines as those carrying
the Alfven waves and the ion injections. (3) Simultaneously, ground
magnetometer recorded very large, long-period Pi2 (~135 sec) covering
low- to high latitudes. (4) Periodic (~135 sec) energetic ion fluxes at
THEMIS were temporally one-to-one correlated with the ground Pi2, both
of which showing similar characteristics. Results of all five THEMIS
spacecraft, THEMIS ground stations, and the 210MM ground stations will
be included.
Title: THEMIS overview, first results and near future
Authors: Angelopoulos, V.; Sibeck, D.; McFadden, J. P.; Carlson, C. W.;
Larson, D.; Bonnell, J. W.; Mozer, F. S.; Phan, K. H.; Glassmeier,
K. H.; Auster, U.; Roux, A.; Le Contel, O.; Parks, G.; Fillingim, M.;
Sigwarth, J.; Mende, S.; Frey, H.; Donovan, E. T.; Russell, C. T.;
Strangeway, R.; Mann, I.; Rae, J.; Raeder, J.; Ergun, R. E.; Li, X.;
Liu, W.; Singer, H. J.
Bibcode: 2007AGUFMSM13D..01A
Altcode:
Since its launch, on February 17 2007, the five-satellite (or -probe)
THEMIS mission has been operating nominally in a 14.6Re apogee
(low-perigee), near-equatorial orbit. Most instruments have been on
since March 15. Electric field (EFI) instruments on three probes were
turned on and operating nominally since mid-June. EFI instruments on
the other two probes will be deployed in early winter. THEMIS nominal
science operations commenced on July 1. In its early orbits through
the dusk magnetotail, the THEMIS probes captured several substorms
and a small storm at roughly radial alignments along the 20-23MLT
meridian. The THEMIS first-light (a single orbit in nominal science
mode during early operations) on March-23, was nature's welcome:
Two substorm sequences were captured in fast survey mode: particle
injections and dipolarization signatures were seen propagating from
one probe to another. An Earthward flow pulse ahead of a predominantly
duskward flow accompanied a strong field-aligned current pair signature
at the THEMIS altitude. POLAR VIS,UVI imaged the global evolution of
the aurora. The THEMIS GBO array captured the salient features of the
largest intensification of the first substorm, concurrent with the
most intense particle injection on THEMIS probes. FAST, whose orbit
passed through the vicinity of the THEMIS footprints 3 min after the
major intensification, made detailed observations of the field aligned
currents, arc and outflowing ions. In July and August, the THEMIS probes
repeatedly encountered the magnetopause and bow shock, observing FTEs,
LLBL and boundary layers with the three inner, deployed-EFI-bearing
probes (C,D,E) at 100-500km separations, and the two outer probes
(B, A) at 5,000-10,000 km separations. Dissecting FTEs, providing
evidence for simultaneous reconnection at both cusps for northward IMF
orientation, and directly relating magnetopause and boundary layer
motion to corresponding ULF waves in the magnetosphere, are some of
the exciting findings from this dayside interlude. In September 2007
the probes commenced the series maneuvers that will place them into
their final orbits with approximately 30Re, 20Re, 12Re (2) and 10Re
apogees and orbital periods of 4, 2, and 1 days. In these orbits,
they will be aligned along the Sun-Earth line in Earth's magnetotail
in January - March 2008. Results obtained demonstrate the high data
quality and the potential for scientific discovery, particularly when
combined with existing ancillary data or campaigns.
Title: Magnetic Reconnection Site Suggested by a Double Coronal
X-ray Source Observed by RHESSI
Authors: Liu, W.; Petrosian, V.; Dennis, B. R.; Jiang, Y.
Bibcode: 2007AGUFMSH44A1732L
Altcode:
In the classical reconnection model, magnetic field annihilation in a
current sheet generates turbulence and outflows of high speed plasmas
in opposite directions. The turbulence accelerates particles and heats
the background plasma. Observational signatures, such as radio emission
and hard and soft X-rays produced by these high-energy particles and
hot plasmas, are thus expected to show the two oppositely directed
outflows. However, such observations have rarely been reported in
the past. In this talk, we present data analysis and interpretation
of an M1.4-class flare observed with the Reuven Ramaty High Energy
Solar Spectroscopic Imager (RHESSI) on April 30, 2002. This event,
with its footpoints occulted by the solar limb, exhibits such a rarely
observed double-source morphology in the corona over the 6--30~keV
range. The two coronal sources, appearing at different altitudes, show
energy-dependent structures with the higher-energy emission being closer
together. Spectral analysis implies that the emission at higher energies
in the inner region between the two sources is mainly nonthermal,
while the emission at lower energies in the outer region is primarily
thermal. The two sources are both visible for about 12 minutes and
have similar light curves and power-law spectra (assumed nonthermal)
above about 20~keV. These observations suggest that the magnetic
reconnection site lies between the two sources. Bi-directional outflows
of the released energy in the form of turbulence and/or particle beams
away from the reconnection site can be the source of the observed
radiation. The spatially resolved thermal emission below about 15~keV,
on the other hand, indicates that the lower coronal source has a larger
emission measure but a lower temperature than the upper source. This
is likely the result of the different magnetic topologies of the two
sources. Implications of these results for particle acceleration and
plasma heating in theoretical flare models will be discussed.
Title: Observation and modeling of the injection observed by THEMIS
and LANL satellites during March 23rd, 2007 substorm event
Authors: Liu, W.; Li, X.; Sarris, T.; Cully, C.; Ergun, R.;
Angelopoulos, V.; Larson, D.; Keiling, A.; Glassmeier, K.; Auster, U.
Bibcode: 2007AGUFMSM23A1179L
Altcode:
During the first encounter of a substorm on March 23rd, 2007, THEMIS
constellation observed energetic particle injections and dipolarizations
in the pre-midnight sector during the onset. Clear injection and
dipolarization signatures were observed by three probes (A, B and D)
in the region around 11 Re and 21:00 local time. THEMIS C, which was
leading in the constellation at 8.3 Re, also observed a good injection
signature, but the dipolarization is not so clear. From the timing
based on these observations, a westward expanding ion injection and
dipolarization front is identified. In combination with the energetic
particle observations from LANL geosynchronous satellites, the particle
injection seemed to initiate between LANL-97A (21 LT) and 1989-046 (1
LT). Ion injection can only be observed west of the center, whereas
electron injections can only be seen east of the center. This event
provides us an excellent opportunity to examine the dipolarization and
particle injection processes beyond geosynchronous orbit. We model this
injection event by sending an earthward dipolarization-like pulse at 23
local time and record the injected ions and electrons associated this
pulse at the various satellite locations. Most of the basic features
of the injected particles during the main injection are reproduced
and the timing among satellites is consistent with observations. It
is suggested from the model that the center of this substorm injection
was initiated around 23 local time and located beyond 19 Re.
Title: Multiscale magnetospheric physics from a simple model of
self-organized dynamics
Authors: Liu, W.; Charbonneau, P.
Bibcode: 2007AGUFMSM54A..05L
Altcode:
Distributions of geomagnetic indices and aurora have been used to show
the nonlinear characteristics of magnetospheric dynamics. However,
the physics underlying these distributions is often not clear. Self
organization of micro-scale perturbations has been suggested as a
possibility whereby robust power-law distributions of magnetospheric
dynamics indices can be produced. Earlier we proposed that some aspects
of observed substorm distributions can be explained qualitatively by
a model featuring interactive discrete flux tubes which are used to
simulate the central plasma sheet dynamics driven by a constant energy
input. A one- dimensional simulation of the model yielded scale-free
distributions of auroral activity and quasiperiodic injection. This
result raised the question what dynamical category the substorm belongs
to, scale-free or with definite scales. In this talk, we present the
latest two-dimensional simulation and auroral observational results,
in an attempt to elucidate the dynamical nature of the substorm.
Title: Comparison of Auroral and Inner CPS in situ Measurements
During an Expansive Phase Onset
Authors: Donovan, E.; Spanswick, E.; Jackel, B.; Trondsen, T.;
Syrjaesuo, M.; Liang, J.; Liu, W.; Connors, M.; Voronkov, I.; Wild,
J.; Daum, P.; Mende, S.; Frey, H.; Angelopoulos, V.; Russell, C.;
McFadden, J.; Glassmeier, K.; Auster, U.; Singer, H.; Sakaguchi, K.;
Shiokawa, K.; Rostoker, G.; Rae, J.; Mann, I.; Dunlop, M.; Reme, H.;
Fazakerly, A.
Bibcode: 2007AGUFMSM14A..03D
Altcode:
On March 13, 2007, there was a sequence of auroral and contemporaneous
magnetotail activity that occurred during a period when the THEMIS
constellation was in the evening sector inner CPS. The satellites were
magnetically conjugate to the auroral zone in western Canada. The
viewing conditions over numerous All-Sky Imagers (ASIs) in Canada
were excellent. Although the THEMIS satellites were still in
commissioning phase, the fluxgate magnetometers (FGM) were operating
on all five satellites during this event, as was the electrostatic
analyzer instrument on THEMIS A. As well, three GOES satellites were
collecting geosynchronous magnetic field data over Canada throughout
the event. Preliminary analysis shows the following. There was an
onset at roughly 0508 UT either at or earthward of the position of
THEMIS D (just beyond geosynchronous distance), and then propagated
outwards over THEMIS B, A, and E in turn. This appears as an outwardly
propagating decrease in cross-tail current as inferred from FGM;
however, the current sheet in the vicinity of THEMIS E was increasing
in strength and/or thinning while the onset was already in progress
closer to the Earth. ASI, meridian scanning photometer, and riometer
data show that the onset occurs in the same meridian as the THEMIS
spacecraft, and allow us to identify the ionospheric signatures
of the dispersionless injection and the earthward edge of the ion
plasma sheet. Our conclusions based on this preliminary study are as
follows: 1) the 0508 UT onset occurred near geosynchronous orbit and
was not preceded by a fast earthward flow; 2) growth phase continued
further from the Earth on probes to the East of the onset meridian;
3) the optical onset, dispersionless injection (from riometers), and
local decrease in cross tail current all happened at the same time; 4)
inter-comparison of ground- based and in situ observations highlight
the importance of the coordinated use of ground and satellite data
for overcoming azimuthal and radial magnetic projection uncertainties.
Title: An XAS study of the structure and thermodynamics of Cu(I)
chloride complexes in brines up to high temperature (400 °C, 600 bar)
Authors: Brugger, J.; Etschmann, B.; Liu, W.; Testemale, D.; Hazemann,
J. L.; Emerich, H.; van Beek, W.; Proux, O.
Bibcode: 2007GeCoA..71.4920B
Altcode:
The transport and deposition of copper in saline hydrothermal
fluids are controlled by the stability of copper(I) complexes with
ligands such as chloride. Despite their role in the formation of
most hydrothermal copper deposits, the nature and stability of Cu(I)
chloride complexes in highly saline brines remains controversial. We
present new X-ray absorption data ( P = 600 bar, T = 25-400 °C,
salinity up to 17.2 m Cl), which indicate that the linear CuClx1-x ( x
= 1, 2) complexes are stable up to supercritical conditions. Distorted
trigonal planar CuCl32- complexes predominate at room temperature and
at high salinity (>3 m LiCl): subtle changes in the XANES spectrum
with increasing salinity may reflect geometric distortions of this
CuCl32- complex. Similar changes were observed in UV-Vis data [Liu,
W., Brugger, J., McPhail, D.C., Spiccia, L., 2002. A spectrophotometric
study of aqueous copper(I) chloride complexes in LiCl solutions between
100 °C and 250 °C. Geochim. Cosmochim. Acta66, 3615-3633], and were
erroneously interpreted as a new species, CuCl42-. Our XAS data and
ab-initio XANES calculations show that this tetrahedral species is
not present to any significant degree in our solutions. The stability
of the CuCl32- complexe decreases with increasing temperature; under
supercritical conditions and in brines under magmatic-hydrothermal
conditions (e.g., 15.58 m Cl, 400 °C, 600 bar), only the linear Cu(I)
chloride complexes were observed. This result and the instability of the
CuCl42- complex are also consistent with the recent ab-initio molecular
dynamic calculations of Sherman [Sherman D. M.(2007) Complexation
of Cu + in hydrothermal NaCl brines: ab-initio molecular
dynamics and energetics. Geochim. Cosmochim. Acta71, 714-722]. This
study illustrates the power of the quantitative nature of XANES and
EXAFS measurements for deciphering the speciation of weak transition
metal complexes up to magmatic-hydrothermal conditions. The systematic
XANES data are used to retrieve the formation constant for CuCl32- at
150 °C, which is in good agreement with the reinterpretation of the
UV-Vis data of Liu et al. (Liu et al., 2002). At high temperatures
(≫400 °C), the solubility of chalcopyrite in equilibrium with
hematite-magnetite-pyrite and K-feldspar-muscovite-quartz calculated
with the new properties is lower than that calculated using the previous
model, and the calculated solubilities are at the lower end of the range
of values measured in brine inclusions from porphyry copper systems.
Title: On the equatorward motion and fading of proton aurora during
substorm growth phase
Authors: Liu, W. W.; Donovan, E. F.; Liang, Jun; Voronkov, Igor;
Spanswick, Emma; Jayachandran, P. T.; Jackel, Brian; Meurant, Mathieu
Bibcode: 2007JGRA..11210217L
Altcode:
Using 50 high-quality events from the Canadian Auroral Network for
the OPEN Program Unified Study (CANOPUS) Gillam Meridian Scanning
Photometer over 10 a (1989-1998), we show that proton aurora in the
substorm growth phase exhibits a systematic tendency to fade. The
average pattern of fading consists of a period of relatively stable
proton aurora brightness and then a period of 15-20 min before onset
during which the brightness decreases by an average of 15%. We interpret
the observed proton aurora brightness variation in terms of the magnetic
field stretching in the near-Earth magnetosphere; in particular, the
fading is interpreted as a result of the central plasma sheet magnetic
field lines having stretched to such a degree that the loss cone closing
effect dominates precipitation due to nonadiabatic proton motions.
Title: A MHD mechanism for the generation of the meridional current
system during substorm expansion phase
Authors: Liang, Jun; Liu, W. W.
Bibcode: 2007JGRA..112.9208L
Altcode: 2007JGRA..11209208L
In this study we propose a MHD mechanism for the generation of the
meridional current system (MCS) during the substorm expansion phase
(EP). The upward field-aligned current (FAC) intensifies as the
dawn-dusk plasma pressure gradient enhances in the Harang region during
the substorm EP. As a consequence of this intensification, the plasma
convection pattern changes, with eastward flow accelerations observed
in both the ionosphere and midmagnetotail during early substorm EP. The
increasing eastward flow is associated with an inertial current in
the midtail whose divergence give rise to a downward FAC poleward of
the upward FAC region, constituting a MCS configuration. Theoretical
calculations based upon the mechanism shows consistency with many
observed features of the MCS. We further discuss how the present work
relates to the large-scale FAC system and the interactions among its
various components, with a particular emphasis on the MCS contribution
to the overall substorm current closure.
Title: Azimuthal structures of substorm electron injection and their
signatures in riometer observations
Authors: Liang, Jun; Liu, W. W.; Spanswick, E.; Donovan, E. F.
Bibcode: 2007JGRA..112.9209L
Altcode: 2007JGRA..11209209L
We propose a theoretical model to investigate the effects of the
curvature/gradient (c/g) drift and the finite azimuthal extent of the
dipolarization region on the electron injection process associated
with the substorm dipolarization. We study the azimuthal structure
of high-energy (>30 keV) electron precipitation flux and compare
the result with riometer observations. We are able to reproduce
three basic archetypes of riometer responses to substorms, namely,
the spike, dispersionless injection, and dispersed injection events
catalogued in previous observations. The electron injection near
the duskward edge of the dipolarization region is most subject to
azimuthal c/g drift loss, appearing in riometer observations as the
``spike'' feature. The ``dispersionless injection'' response is
seen inside the dipolarization region but some distance away from
its western border: or, alternatively, when the substorm has a rapid
westward expansion, so that the gain and loss of electrons from the
duskside and dawnside of a dipolarizing flux tube roughly balance. The
``dispersed injection'' feature is seen east of the dipolarization
region. Our theory successfully explains the statistical differences
in terms of magnetic local time location and peak intensity between
spikes and injection events. Through the substorm event on 23 May 1998
we demonstrate that our theoretical predictions of riometer responses
are very consistent with the observations. We highlight the potential
of riometers in resolving the azimuthal extent and evolution of the
dipolarization region, which provides a new ground-based technique of
remote sensing the substorm process.
Title: Axisymmetric numerical and analytical studies of the
magnetorotational instability in a magnetized Taylor-Couette flow
Authors: Liu, Wei
Bibcode: 2007PhDT........19L
Altcode:
The magnetorotational instability (MRI) is probably the main cause
of turbulence and accretion in sufficiently ionized astrophysical
disks. However, despite much theoretical and computational work,
the nonlinear saturation of MRI is imperfectly understood. In Chap. 2
and Chap. 3 of this thesis we present non-ideal magnetohydrodynamic
simulations of the Princeton MRI experiment. In vertically infinite or
periodic cylinders, MRI saturates in a resistive current-sheet with a
significant reduction of the mean shear, and with poloidal circulation
scaling as the square root of resistivity. Angular momentum transport
scales as the reciprocal square root of viscosity but only weakly
depends on resistivity. For finite cylinders with insulating end caps,
a method for implementing the fully insulating boundary condition is
introduced. MRI grows with a clear linear phase from small amplitudes
at rates in good agreement with linear analysis. In the final state
one inflowing "jet" opposite to the usual Ekman "jet" is found near
the inner cylinder. The MRI enhances the angular momentum transport
at saturation. Under proper conditions, our experimental facility
is a good platform to show that MRI could be suppressed by a strong
magnetic field. Recently, Hollerbach and Rüdiger have reported
that MRI modes may grow at much reduced magnetic Reynolds number (
Re m ) and Lundquist number S in the presence of a helical background
field, a current-free combination of axial and toroidal field. We
have investigated these helical MRI modes in Chap. 4 and Chap. 5. In
vertically infinite or periodic cylinders, resistive HMRI is a weakly
destabilized hydrodynamic inertial oscillation propagating axially
along the background Poynting flux. Growth rates are small, however,
and require large axial currents. Furthermore, finite cylinders
with insulating endcaps were shown to reduce the growth rate and to
stabilize highly resistive, inviscid flows entirely, and the new mode
is stable in Keplerian flow profiles regardless of end conditions. We
also numerically investigate a traveling wave pattern observed in
experimental magnetized Taylor-Couette flow at low magnetic Reynolds
number. By accurately modeling viscous and magnetic boundaries in all
directions, we reproduce the experimentally measured wave patterns
and their amplitudes. Contrary to previous claims, the waves are
shown to be transiently amplified disturbances launched by viscous
boundary layers rather than globally unstable magnetorotational
modes. The experiment is complicated by the extremely large
Reynolds number and by Ekman circulation and Stewartson layers,
even though the experimental apparatus has been designed to minimize
the circulation ( e.g. by the use of independently controlled split
endcaps). Understanding the role of the boundary layers is critical to
this research. In Chap. 6 the magnetic field is found to inhibit the
Ekman suction. While we quantitatively confirmed the conclusions of
Gilman et al , the finite differential rotation cannot be neglected
and modifies the linear Ekman layer. The width of the Ekman layer
is reduced with increased magnetic field normal to the end plate. A
uniformly-rotating region forms near the outer cylinder. The Stewartson
layer penetrates deeper into the fluid with larger Reynolds number and
stronger magnetic field. Furthermore a strong magnetic field leads to
a steady Stewartson layer, at least in axisymmetric configuration.
Title: Traveling waves in a magnetized Taylor-Couette flow
Authors: Liu, Wei; Goodman, Jeremy; Ji, Hantao
Bibcode: 2007PhRvE..76a6310L
Altcode: 2007astro.ph..3525L
We investigate numerically a traveling wave pattern observed in
experimental magnetized Taylor-Couette flow at low magnetic Reynolds
number. By accurately modeling viscous and magnetic boundaries in all
directions, we reproduce the experimentally measured wave patterns
and their amplitudes. Contrary to previous claims, the waves are shown
to be transiently amplified disturbances launched by viscous boundary
layers, rather than globally unstable magnetorotational modes.
Title: Polar cap potential saturation: An energy conservation
perspective
Authors: Liu, W. William
Bibcode: 2007JGRA..112.7210L
Altcode: 2007JGRA..11207210L
In the long run, energy entering the magnetosphere from the solar
wind must be balanced by energy dissipation in or escape from the
system. It then follows that the Joule heating rate in the ionosphere
statistically should be bounded from the upside by the solar wind
energy input function (e.g., the Perrault-Akasofu parameter). We
show that this energy constraint, coupled with some observationally
motivated assumptions about the behavior of the auroral oval under
escalating solar wind conditions, leads to the prediction of polar
cap potential saturation.
Title: In search of the near-Earth neutral line: How much a role
can ground-based observations play?
Authors: Liu, W.; Liang, J.; Voronkov, I.; Spanswick, E.; Jackel,
B.; Jayachandran, P.
Bibcode: 2007AGUSMSM22A..03L
Altcode:
The launch of THEMIS has raised the expectation that new progress
will be made on the assessment and evaluation of competing substorm
models. While the THEMIS spacecraft will offer much improved capability
to delimit and localize substorm triggers, they will measure primarily
"perpendicular" signatures of a near-Earth neutral line (e.g.,
BBFs). For "parallel" signatures of NENL, ground-based observations
should prove more advantageous. However, there has been relatively
little attention to what effects can be uniquely attributed to a
would-be NENL, as a given auroral signature can receive more than one
theoretical explanations. There is therefore a need to systematize
and quantify our approach to the use of ground-based observations to
detect, constrain, and characterize NENL. In this talk, we will review
the ground-based observations that will be made in conjunction with
THEMIS during its tail operation, identify some candidate signatures
that might be related to the NENL, and outline steps to evolve this
line of research through focused theory and modeling efforts.
Title: Characteristics of Solar Flare Hard X-ray Emissions:
Observations and Models
Authors: Liu, Wei
Bibcode: 2007AAS...210.6801L
Altcode: 2007BAAS...39..175L
The main theme of this dissertation is the investigation of the
physics of acceleration and transport of particles in solar flares
and their radiative signatures. The observational studies, using
hard X-rays (HXRs) observed by RHESSI, concentrate on four flares,
which support the classical magnetic reconnection model of flares in
various ways. In the 11/03/2003 X3.9 flare, there is an upward motion
of the loop-top source, accompanied by a systematic increase in the
separation of the foot-point sources at a comparable speed. This is
consistent with the reconnection model with an inverted-Y geometry. The
04/30/2002 M1.3 event exhibits rarely observed two coronal sources,
with very similar spectra and their higher-energy emission being
close together. This suggests that reconnection occurs between the two
sources. In the 10/29/2003 X10 flare, the logarithmic total HXR flux
of the two foot-points correlates with their mean magnetic field. The
foot-points show asymmetric HXR fluxes, qualitatively consistent
with the magnetic mirroring effect. The 11/13/2003 M1.7 flare reveals
evidence of chromospheric evaporation directly imaged by RHESSI for the
first time. The emission centroids move toward the loop-top, indicating
a density increase in the loop. The theoretical modeling of this
work combines the Stanford stochastic acceleration model with the NRL
hydrodynamic model to study the interplay of the particle acceleration,
transport, and radiation effects and the atmospheric response to the
energy deposition by electrons. I find that low-energy electrons in
the quasi-thermal portion of the spectrum affects the hydrodynamics
by producing more heating in the corona than the previous models
that used a power-law spectrum with a low-energy cutoff. The Neupert
effect is found to be present and effects of suppression of thermal
conduction are tested in the presence of hydrodynamic flows. I
gratefully thank my adviser, Prof. Vahe' Petrosian, my collaborators,
and funding support from NSF and NASA.
Title: Remote-sensing magnetospheric dynamics with riometers:
Observation and theory
Authors: Liu, W. W.; Liang, J.; Spanswick, E.; Donovan, E. F.
Bibcode: 2007JGRA..112.5214L
Altcode: 2007JGRA..11205214L
The importance of monitoring particle injection into the inner
magnetosphere from the plasma sheet is exceeded perhaps only by its
difficulty. The recent progress in using ground-based riometer data
[e.g., Spanswick et al., 2007] to detect by proxy particle injection
has raised much hope that this important aspect of substorms can be
more consistently monitored. In this paper we develop a theoretical
model for explaining the observed dispersionless injection events
reported by Spanswick et al. The substorm event on 3 October 1998 is
analyzed to give the empirical context for riometer responses during a
typical substorm. Our simulation shows that riometer electrons produce
a clean and strong signal that can be uniquely and easily related to
magnetic field dipolarization that normally gives rise to injection.
Title: Global auroral imaging in the ILWS era
Authors: Donovan, E.; Trondsen, T.; Spann, J.; Liu, W.; Spanswick, E.;
Lester, M.; Tu, C. -Y.; Ridley, A.; Henderson, M.; Immel, T.; Mende,
S.; Bonnell, J.; Syrjäsuo, M.; Sofko, G.; Cogger, L.; Murphree, J.;
Jayachandran, P. T.; Pulkkinen, T.; Rankin, R.; Sigwarth, J.
Bibcode: 2007AdSpR..40..409D
Altcode:
The overarching objective of the ILWS Geospace program is to facilitate
system level science. This demands synoptic observations such as global
auroral imaging. At present, there is no funded mission during ILWS
that incorporates a global auroral imager. The imaging community
needs to move now to address this important gap. While doing so,
it is interesting to take stock of global auroral observations that
have not been achieved, or that have been achieved only to a limited
extent. These include simultaneous imaging across all relevant
scales, spectral resolution of sufficient quality to allow for
global maps of characteristic energy and energy flux of precipitating
electrons, continuous global auroral imaging for time periods spanning
long-duration geomagnetic events, systematic interhemispheric conjugate
observations, auroral observations magnetically conjugate to in situ
measurements, and automatic classification of auroral images. These
observations can be achieved within the next decade. If they are,
then they will facilitate exciting new science.
Title: Evolution of electron energy spectrum during solar flares
Authors: Liu, W. J.; Chen, P. F.; Fang, C.; Ding, M. D.
Bibcode: 2007AdSpR..39.1394L
Altcode:
Particle acceleration by direct current electric field in the current
sheet has been extensively studied, in which an electric and a magnetic
field are generally prescribed, and a power law distribution of the
electron energy is obtained. Based on MHD numerical simulations of
flares, this paper aims at investigating the time evolution of the
electron energy spectrum during solar flares. It turns out that the
model reproduces the soft-hard-hard spectral feature which was observed
in some flares.
Title: Determination of astrophysical 11C(p,
γ)12N reaction rate from the asymptotic normalization
coefficients of 12B →11B + n
Authors: Guo, B.; Li, Z. H.; Liu, W. P.; Bai, X. X.
Bibcode: 2007JPhG...34..103G
Altcode:
The squares of the neutron asymptotic normalization coefficient (ANC)
for the virtual decay 12B →11B + n are extracted
to be 1.20 ± 0.26, 0.354 ± 0.107 and 1.98 ± 0.35 fm-1 from
the angular distributions of the 11B(d, p)12B
reaction leading to the ground, first and second excited states of
12B respectively, using the Johnson Soper approach. According
to charge symmetry of strong interaction, the square of proton ANC
of virtual decay 12N →11C + p is determined
to be 1.63 ± 0.35 fm-1 and then utilized to calculate the
astrophysical S-factor and the rate of the direct capture contribution
in the 11C(p, γ)12N reaction. The astrophysical
S-factor at zero energy for the direct capture, S(0), is derived to be
0.088 ± 0.019 keV b. An evaluated S(0) of 0.092 ± 0.009 keV b is then
given by using the present and pre-existing experimental results. In
addition, the proton widths of the first and second excited states of
12N are derived to be 0.91 ± 0.29 and 99 ± 20 keV from
the neutron ANCs of 12B and used to compute the contribution
from the first two resonances of 12N, respectively. We have
also calculated the contribution from the interference effect between
the direct capture and the second resonance.
Title: Magnetic reconnection configurations and particle acceleration
in solar flares
Authors: Chen, P. F.; Liu, W. J.; Fang, C.
Bibcode: 2007AdSpR..39.1421C
Altcode:
Numerical simulations of two types of flares indicate that magnetic
reconnection can provide environments favorable for various particle
acceleration mechanisms to work. This paper reviews recent test particle
simulations of DC electric field mechanism, and discusses how the flare
particles can escape into the interplanetary space under different
magnetic configurations.
Title: Laboratory Spectroscopy of Planetary Molecules
Authors: Brown, L.; Drouin, B.; Miller, C.; Pearson, J.; Orton,
G.; Toth, R.; Benner, C.; Devi, M.; Blake, T.; Masiello, T.; Sams,
R.; Butler, R.; Champion, J.; Chelin, P.; Dehayem, A.; Kleiner, I.;
Orphal, J.; Sagui, L.; Gamache, R.; Humphrey, C.; Liu, W.; Predoi
Bibcode: 2007plat.work...19B
Altcode:
An international team of laboratory spectroscopists are working
in concert to support remote sensing of planetary atmospheres and
Titan. An overview of high resolution laboratory investigations will
be presented for spectral bands from the rotational wavelengths into
the near infrared. The studies include measurements and theoretical
analyses of the line positions, intensities and/or broadening
coefficients needed to improve the spectroscopic databases required
for planetary applications. The molecular studies include water (H2O)
broadened by carbon dioxide in the far- and mid-infrared; positions,
intensities, broadening and line mixing of carbon dioxide (CO2) in the
near-IR; broadening and line mixing of methane in the mid- and near-IR;
frequencies of methyl cyanide (CH3CN) in the rotational region and line
positions, intensities and nitrogen broadening of methyl cyanide in
the low fundamental bands; global theoretical modeling of the phosphine
(PH3) parameters; and frequencies of acetaldehyde (CH3CHO), methylamine
(CH3NH2) and deuterated acetylene (HCCD, DCCD) in the rotational region.
Title: Characteristics of Solar Flare Hard X-ray Emissions:
Observations and Models
Authors: Liu, Wei
Bibcode: 2006PhDT........35L
Altcode:
The main theme of this thesis is the investigation of the physics of
acceleration and transport of particles in solar flares, and their
thermal and nonthermal radiative signatures. The observational
studies, using hard X-rays (HXRs) observed by the RHESSI mission,
concentrate on four flares, which support the classical magnetic
reconnection model of solar flares in various ways. In the X3.9 flare
occurring on 11/03/2003, there is a monotonic upward motion of the loop
top (LT) source accompanied by a systematic increase in the separation
of the footpoint (FP) sources at a comparable speed. This is consistent
with the reconnection model with an inverted-Y geometry. The 04/30/2002
event exhibits rarely observed two coronal sources. The two sources
(with almost identical spectra) show energy-dependent structures,
with higher-energy emission being close together. This suggests that
reconnection takes place within the region between the sources. In
the 10/29/2003 X10 flare, the logarithmic total HXR flux of the FPs
correlates with the mean magnetic field. The two FPs show asymmetric HXR
fluxes, which is qualitatively consistent with the magnetic mirroring
effect. The M1.7 flare on 11/13/2003 reveals evidence of evaporation
directly imaged by RHESSI for the first time, in which emission from the
legs of the loop appears at intermediate energies. The emission centroid
moves toward the LT as time proceeds, indicating an increase of density
in the loop. The theoretical modeling of this work combines the
stochastic acceleration model with the NRL hydrodynamic model to study
the interplay of the particle acceleration, transport, and radiation
effects and the atmospheric response to the energy deposition by
nonthermal electrons. We find that low-energy electrons in the
quasi-thermal portion of the spectrum affects the hydrodynamics by
producing more heating in the corona than the previous models that
used a power-law spectrum with a low-energy cutoff. The Neupert
effect is found to be present and effects of suppression of conduction
are tested in the presence of hydrodynamic flows.
Title: Magnetorotational instability and angular momentum transport
in magnetized Taylor- Couette flows
Authors: Liu, W.; Goodman, J.; Ji, H.
Bibcode: 2006AGUFMGP43A1029L
Altcode:
The magnetorotational instability (MRI) is probably the main cause
of turbulence and accretion in sufficiently ionized astrophysical
disks. Despite much theoretical and computational work, however,
nonlinear MRI is imperfectly understood. We present non-ideal
magnetohydrodynamic simulations of MRI in the geometry of the Princeton
MRI experiment. MRI saturates in a resistive current-sheet with
significant reduction of the mean shear, and with poloidal circulation
scaling as the square root of resistivity. Angular momentum transport
scales as the reciprocal square root of viscosity but hardly depends on
resistivity [1]. Separately, we have studied MRI in the presence of a a
current-free combination of toroidal and axial magnetic field. The new
mode (HMRI) persists to smaller magnetic Reynolds number and Lundquist
number than standard MRI, which relies on axial field alone. This
would seem to make HMRI attractive for experiments and perhaps for
application to resistive astrophysical disks. In vertically infinite or
periodic cylinders, resistive HMRI is a weakly destabilized hydrodynamic
inertial oscillation propagating axially along the background Poynting
flux [2]. Growth rates are small, however, and require large axial
currents. Furthermore, highly resistive HMRI is stabilized in finite
cylinders with insulating endcaps, and also in keplerian flow profiles
regardless of end conditions. In both of these studies, comparison of
models and measurements is used to validate our theoretical tools,
which we will apply to nonlinear saturation of resistive MRI in
astrophysical systems. Theoretical modeling has already played a major
role in the design of the MRI experiment, and the physics of these
modes may be of interest for fluid dynamics and geophysics as well
as astrophysics. {[1]} Wei Liu, Jeremy Goodman and Hantao Ji, ApJ,
643, 306. {[2]} Wei Liu, Jeremy Goodman, Hantao Ji and Isom Herron,
submitted to PRE. Supported by DoE, NASA and NSF.
Title: High-energy electron injection associated with substorm
dipolarization: Models and comparison with riometer observations
Authors: Liang, J.; Liu, W.; Donovan, E. F.; Spanswick, E.
Bibcode: 2006AGUFMSM51B1404L
Altcode:
Energetic particle injection has long been recognized as a common
signature of magnetospheric substorms. In this study the injection
process is modeled via the Fokker-Planck equation wherein the convective
transport terms are associated with adiabatic changes imposed on the
distribution of high-energy electrons by a rapid- varying magnetic
fields simulating the substorm dipolarization. The model results are
compared with the riometer observations of ionospheric absorption of
cosmic radio noises, which is known to respond to the precipitation
of magnetospheric electrons with energy >30 keV. In particular, our
model is capable of reproducing the riometer dispersionless injection
event defined by Spanswick [2006]. The interrelationship between the
riometer injections and observations from other instruments prescribed
by our theoretic framework is discussed. We suggest the possibility
that the riometer data become one of the most accurate methods to
pinpoint and quantify the magnetospheric dynamics underlying a substorm.
Title: Helical magnetorotational instability in magnetized
Taylor-Couette flow
Authors: Liu, Wei; Goodman, Jeremy; Herron, Isom; Ji, Hantao
Bibcode: 2006PhRvE..74e6302L
Altcode: 2006astro.ph..6125L
Hollerbach and Rüdiger have reported a new type of magnetorotational
instability (MRI) in magnetized Taylor-Couette flow in the presence of
combined axial and azimuthal magnetic fields. The salient advantage of
this “helical” MRI (HMRI) is that marginal instability occurs at
arbitrarily low magnetic Reynolds and Lundquist numbers, suggesting
that HMRI might be easier to realize than standard MRI (axial field
only), and that it might be relevant to cooler astrophysical disks,
especially those around protostars, which may be quite resistive. We
confirm previous results for marginal stability and calculate HMRI
growth rates. We show that in the resistive limit, HMRI is a weakly
destabilized inertial oscillation propagating in a unique direction
along the axis. But we report other features of HMRI that make it less
attractive for experiments and for resistive astrophysical disks. Large
axial currents are required. More fundamentally, instability of highly
resistive flow is peculiar to infinitely long or periodic cylinders:
finite cylinders with insulating endcaps are shown to be stable
in this limit, at least if viscosity is neglected. Also, Keplerian
rotation profiles are stable in the resistive limit regardless of
axial boundary conditions. Nevertheless, the addition of a toroidal
field lowers thresholds for instability even in finite cylinders.
Title: Indirect measurements of nuclear astrophysics reactions at CIAE
Authors: Liu, Wei-Ping; Li, Zhi-Hong; Bai, Xi-Xiang; Wang, You-Bao;
Lian, Gang; Guo, Bing; Zeng, Sheng; Yan, Sheng-Quan; Wang, Bao-Xiang;
Su, Jun; Shu, Neng-Chuan; Chen, Yong-Shou
Bibcode: 2006AIPC..865..358L
Altcode:
This paper described the nuclear astrophysical studies using the
unstable ion beam facility GIRAFFE, by indirect measurements. We
measured the angular distributions for some single proton or
neutron transfer reactions, such as 7Be(d,n)8B,
11C(d,n)12N, 8Li(d,n)9Be,
8Li(d,p)9Li and 13N(d,n)14O
in inverse kinematics, and derived the astrophysical S-factors
or reaction rates of 7Be(p,γ)8B,
11C(p,γ)12N, 8Li(n,γ)9Li,
13N(p,γ)14O by asymptotic normalization
coefficient, spectroscopic factor, and R-matrix approach at
astrophysically relevant energies.
Title: RHESSI Observation of Chromospheric Evaporation
Authors: Liu, Wei; Liu, Siming; Jiang, Yan Wei; Petrosian, Vahé
Bibcode: 2006ApJ...649.1124L
Altcode: 2006astro.ph..3510L
We present analyses of the spatial and spectral evolution of hard
X-ray emission observed by RHESSI during the impulsive phase of an
M1.7 flare on 2003 November 13. In general, as expected, the loop top
(LT) source dominates at low energies, while the footpoint (FP) sources
dominate the high-energy emission. At intermediate energies, both the
LT and FPs may be seen, but during certain intervals emission from the
legs of the loop dominates, in contrast to the commonly observed LT
and FP emission. The hard X-ray emission tends to rise above the FPs
and eventually merge into a single LT source. This evolution starts
at low energies and proceeds to higher energies. The spectrum of
the resultant LT source becomes more and more dominated by a thermal
component with an increasing emission measure as the flare proceeds. The
soft and hard X-rays show a Neupert-type behavior. With a nonthermal
bremsstrahlung model, the brightness profile along the loop is used to
determine the density profile and its evolution, which reveals a gradual
increase of the gas density in the loop. These results are evidence
for chromospheric evaporation and are consistent with the qualitative
features of hydrodynamic simulations of this phenomenon. However, some
observed source morphologies and their evolution cannot be accounted
for by previous simulations. Therefore, simulations with more realistic
physical conditions are required to explain the results and the particle
acceleration and plasma heating processes.
Title: Heat flux in magnetospheric convection: A calculation based
on adiabatic drift theory
Authors: Liu, W. William
Bibcode: 2006GeoRL..3319104L
Altcode:
Empiric evidence and theoretical argument indicate that magnetospheric
convection is globally sub-adiabatic. Reconciliation of the
sub-adiabaticity with the underlying adiabatic particle drifts is a
problem that has not been conclusively demonstrated. In this paper,
through an ensemble average, we show that the Rice Convection Model
contains a heat flux due to thermal inequilibrium between two adjacent
flux tubes of equal volume. The averaged theory is based on field
variables obeying a set of partial differential equations (Eulerian
formulation), instead of conservative variables advecting with fluid
elements (Langrangian formulation). We apply the theory to investigate
a one-dimensional case of subadiabatic variation of thermodynamic
properties in the plasma sheet.
Title: Energy avalanches in the central plasma sheet
Authors: Liu, W. W.; Charbonneau, P.; Thibault, K.; Morales, L.
Bibcode: 2006GeoRL..3319106L
Altcode:
The central plasma sheet (CPS) is simulated as a 1D cellular
automaton. The system is driven deterministically and globally by
a spatially non-uniform energy loading (convection). Each node (a
flux tube) evolves until one of two local instability criteria is
exceeded. The unstable node releases a small amount of energy to the
ionosphere and another small amount is distributed to its neighboring
nodes. The partition between the two modes of energy distribution
is the only random factor in the model. The energy redistribution
relaxes the node deterministically to a stable state. The simulation
suggests that a central plasma sheet driven in the above manner is
in a self-organized critical state, with energy avalanches obeying
a scale-free distribution. The avalanches, however, co-exist with
quasi-periodic intermittencies manifested in ring-current injection,
which is correlated with strong CPS avalanches, and tailward energy
ejection, which shows no apparent correlation in this aspect.
Title: Magnetorotational instability in magnetized Taylor-Couette
flows
Authors: Liu, Wei; Goodman, Jeremy; Ji, Hantao
Bibcode: 2006APS..DPPBP1100L
Altcode:
We present non-ideal magnetohydrodynamic simulations of MRI in the
geometry of the Princeton MRI experiment. MRI saturates in a resistive
current-sheet with significant reduction of the mean shear, and with
poloidal circulation scaling as the square root of resistivity. Angular
momentum transport scales as the reciprocal square root of viscosity but
hardly depends on resistivity. Separately, we have studied MRI in the
presence of a current-free combination of toroidal and axial magnetic
field. The new mode (HMRI) persists to smaller magnetic Reynolds number
and Lundquist number than standard MRI, which relies on axial field
alone. In vertically infinite or periodic cylinders, resistive HMRI is
a weakly destabilized hydrodynamic inertial oscillation propagating
axially along the background Poynting flux. Growth rates are small,
however, and require large axial currents. Furthermore, highly resistive
HMRI is stabilized in finite cylinders with insulating endcaps, and also
in keplerian flow profiles regardless of end conditions. Comparison of
models and measurements is used to validate our theoretical tools, which
we will apply to nonlinear saturation of resistive MRI in astrophysical
systems. Theoretical modeling has already played a major role in the
design of the MRI experiment, and the physics of these modes may be
of interest for fluid dynamics and geophysics as well as astrophysics
Title: An efficient control of ultrashort laser filament location
in air for the purpose of remote sensing
Authors: Liu, W.; Théberge, F.; Daigle, J. -F.; Simard, P. T.;
Sarifi, S. M.; Kamali, Y.; Xu, H. L.; Chin, S. L.
Bibcode: 2006ApPhB..85...55L
Altcode:
The unavoidable hot spots in a practical terawatt level laser pulse
will self-focus in air at a short distance. The short distance
cannot be changed significantly by only controlling the chirp
or divergence. We overcome such early self-focusing by using a
telescope, which enlarges the diameter of the beam, thus that of the
hot spots. The telescope’s effective focal length is much shorter
than the self-focusing distance of both the enlarged beam and the hot
spots. Then, the resulting filaments merge into the geometrical focus
whose position is controllable by the telescope. This technique also
minimizes the generation of white light.
Title: N13(d,n)O14 reaction and the astrophysical N13(p,γ)O14
reaction rate
Authors: Li, Z. H.; Guo, B.; Yan, S. Q.; Lian, G.; Bai, X. X.; Wang,
Y. B.; Zeng, S.; Su, J.; Wang, B. X.; Liu, W. P.; Shu, N. C.; Chen,
Y. S.; Chang, H. W.; Jiang, L. Y.
Bibcode: 2006PhRvC..74c5801L
Altcode: 2009arXiv0903.3094L
N13(p,γ)O14 is one of the key reactions in the hot CNO cycle which
occurs at stellar temperatures around T9⩾0.1. Up to now,
some uncertainties still exist for the direct capture component in
this reaction, thus an independent measurement is of importance. In
present work, the angular distribution of the N13(d,n)O14 reaction at
Ec.m.=8.9 MeV has been measured in inverse kinematics, for
the first time. Based on the distorted-wave Born approximation (DWBA)
analysis, the nuclear asymptotic normalization coefficient (ANC),
C1,1/214O, for the ground state of
O14 →N13 + p is derived to be 5.42±0.48 fm-1/2. The
N13(p,γ)O14 reaction is analyzed with the R-matrix approach, its
astrophysical S factors and reaction rates at energies of astrophysical
relevance are then determined with the ANC. The implications of the
present reaction rates on the evolution of novae are then discussed
with the reaction network calculations.
Title: Thermal equation of state of (Mg 0.9Fe
0.1) 2SiO 4 olivine
Authors: Liu, Wei; Li, Baosheng
Bibcode: 2006PEPI..157..188L
Altcode:
In situ synchrotron X-ray diffraction measurements have been carried
out on San Carlos olivine (Mg 0.9Fe 0.1)
2SiO 4 up to 8 GPa and 1073 K. Data analysis
using the high-temperature Birch-Murnaghan (HTBM) equation of
state (EoS) yields the temperature derivative of the bulk modulus
(∂ KT/∂ T) P = -0.019 ± 0.002 GPa K
-1. The thermal pressure (TH) approach gives αKT
= 4.08 ± 0.10 × 10 -3 GPa K -1, from which (∂
KT/∂ T) P = -0.019 ± 0.001 GPa K -1
is derived. Fitting the present data to the Mie-Grüneisen-Debye (MGD)
formalism, the Grüneisen parameter at ambient conditions γ0
is constrained to be 1.14 ± 0.02 with fixed volume dependence q =
1. Combining the present data with previous results on iron-bearing
olivine and fitting to MGD EoS, we obtain γ0 = 1.11 ±
0.01 and q = 0.54 ± 0.36. In this study the thermoelastic parameters
obtained from various approaches are in good agreement with one another
and previous results.
Title: SHRIMP zircon geochronological constraints on a Pan-African
orogeny in the Yadong Area, Southern Tibet
Authors: Liu, W. C.; Zhou, Z. G.; Zhang, X. X.; Zhao, X. G.
Bibcode: 2006GeCAS..70Q.365L
Altcode:
No abstract at ADS
Title: Copper(I) in brines up to supercritical conditions
Authors: Brugger, J.; Liu, W.; Hazemann, J. -L.; Etschmann, B.;
Testemale, D.
Bibcode: 2006GeCAS..70R..70B
Altcode:
No abstract at ADS
Title: Speciation of FeII in hydrothermal saline brines
by X-ray absorption techniques
Authors: Testemale, D.; Brugger, J.; Liu, W.; Etschmann, B.; Hazemann,
J. -L.
Bibcode: 2006GeCAS..70R.646T
Altcode:
No abstract at ADS
Title: A XANES study of Zn and Fe(II) chloride complexes in
hypersaline brines
Authors: Liu, W.; Etschmann, B.; Foran, G.; Shelley, M.; Brugger, J.
Bibcode: 2006GeCAS..70R.364L
Altcode:
No abstract at ADS
Title: Rossby Wave and Eddies in the North Pacific Subtropical
Countercurrent
Authors: Liu, Q.; Li, L.; Liu, W.
Bibcode: 2006ESASP.614E..28L
Altcode:
In the North Pacific, Subtropical Countercurrent (STCC) has two
branches: one located in the Northwestern Pacific and the other is to
the west of Hawaii Islands. In both STCC regions, the SSHA exhibits
remarkable oscillations with period of 80-210 days, corresponding to
westward propagation of free Rossby waves. The larger amplitude of
those Rossby waves in the west end of the Northwest STCC seemingly
due to stronger baroclinic instability. In addition, there is also a
vortex pair with the orbital period of 10-11days and the radius of
58-68km to the west of Hawaii Islands. The average T/P SSHA shows
general distribution of the vortices in a region broader than that
covered by the trajectories. The T/P SSHA clearly demonstrates two
symmetrical arrays of cyclonic and anticyclonic vortices that are
similar to the pattern of the vortex Street.
Title: X-ray Emission from Flaring Loops: Comparison Between RHESSI
Observations and Hydrodynamic Simulations
Authors: Liu, Wei; Jiang, Y. W.; Petrosian, V.; Liu, S.; Mariska, J. T.
Bibcode: 2006SPD....37.2705L
Altcode: 2006BAAS...38..254L
RHESSI with its high temporal, spatial, and spectral resolution
has revealed many interesting results on the X-ray emission from
solar flares, some of which can shed light on the processes of
energy release, particle acceleration, heating, and evaporation of
chromospheric plasmas. During the impulsive phase of a limb flare,
Liu et al. (2006) reported hard X-ray (HXR) emission dominated by the
legs of the loop, as opposed to the commonly observed loop top (LT)
and footpoint (FP) emissions. The HXR emission tends to rise above
the FPs and eventually merge into a single LT source, suggestive of a
gradual density increase in the loop possibly caused by chromospheric
evaporation. During the decay phase of six limb flares, Jiang et
al. (2006) found that the thermal LT source is confined in a small
region near the top of the loop rather than spreading throughout the
whole loop. The total energy of the source decays much slower than
expected from the classical Spitzer conductive cooling alone. A
quasi-steady loop model that includes significant suppression of
thermal conductivity and/or continuous heating of the LT plasma,
presumably by plasma wave turbulence, was proposed to account for
this observation. A more thorough understanding of these phenomena
requires a solution of the time-dependent hydrodynamics of the flaring
plasma. We have embarked on combining our particle acceleration and
transport code with a one-dimensional hydrodynamics code (Mariska et
al. 1989) to simulate the response of the atmosphere to the energy
input during the impulsive and decay phases, and investigate the
effects of such response on the energy transport, X-ray radiation,
and even particle acceleration and plasma heating processes. Current
results from this work in progress will be presented. We will also
compare the results with RHESSI observations and thus put important
constraints on theoretical models.
Title: Princeton MagnetoRotational Instability (MRI) Experiment:
Overview and Recent Progress in the Search for the MRI
Authors: Schartman, E.; Ji, H.; Burin, M. J.; Cutler, R.;
Heitzenroeder, P.; Liu, W.; Raftopoulos, S.; Waksman, J.; Goodman,
J.; Stone, J.; Kageyama, A.
Bibcode: 2006AAS...20721107S
Altcode:
The MagnetoRotational Instability (MRI) is likely to be the dominant
mechanism for angular momentum transport in electrically conducting
accretion disks, such as those found in Quasars, X-ray binaries,
cataclysmic variables and possibly protoplanetary disks. To date,
the MRI has not been convincingly demonstrated in the laboratory. The
Princeton MagnetoRotational Instability Experiment investigates the
MRI in a magnetized liquid Gallium flow between concentric spinning
cylinders. The low aspect ratio of our apparatus is vulnerable to
large boundary effects, which are mitigated by splitting the ends
of the chamber into pairs of differentially rotating rings. Initial
experiments in water demonstrate reduction of the boundary effects
and a scaling of the velocity profile with Reynolds Number. Also
investigated are non-linear hydrodynamic effects which have also been
proposed to drive angular momentum transport in accretion disks. The
role of purely hydrodynamic processes is uncertain, with experiments
and simulations giving apparently different results. The apparatus
will next be filled with Gallium to search for signatures of the MRI:
namely, an amplification of the non-axial components of the magnetic
field, and an enhanced effective viscosity coupling the inner and
outer cylinders. Initial diagnostics measure torque and external
radial magnetic fields. In the near future internal magnetic field
and flow diagnostics will be implemented. Our main objectives are
(1) to clearly demonstrate MRI; (2) to study its nonlinear behavior
and angular momentum transport; (3) to compare with state-of-the-art
simulations similar to those used for astrophysical disks. This work
is supported by the US DOE, NSF, and NASA.
Title: Simulations of Magnetorotational Instability in a Magnetized
Couette Flow
Authors: Liu, Wei; Goodman, Jeremy; Ji, Hantao
Bibcode: 2006ApJ...643..306L
Altcode: 2005astro.ph..8665L
In preparation for an experimental study of magnetorotational
instability (MRI) in liquid metal, we present nonideal two-dimensional
magnetohydrodynamic simulations of the nonlinear evolution of MRI in
the experimental geometry. The simulations adopt initially uniform
vertical magnetic fields, conducting radial boundaries, and periodic
vertical boundary conditions. No-slip conditions are imposed at
the cylinders. Our linear growth rates compare well with existing
local and global linear analyses. The MRI saturates nonlinearly
with horizontal magnetic fields comparable to the initial axial
field. The rate of angular momentum transport increases modestly but
significantly over the initial state. For modest fluid and magnetic
Reynolds numbers Re,Rem~102-103,
the final state is laminar reduced mean shear except near the radial
boundaries, and with poloidal circulation scaling as the square root
of resistivity, in partial agreement with the analysis of Knobloch
and Julien. A sequence of simulations at Rem=20 and
102<~Re<~104.4 enables extrapolation
to the experimental regime (Rem~20, Re~107),
albeit with unrealistic boundary conditions. MRI should increase the
experimentally measured torque substantially over its initial purely
hydrodynamic value.
Title: A New Color-Magnitude Diagram for Palomar 11
Authors: Lewis, Matthew S.; Liu, W. M.; Paust, N. E. Q.; Chaboyer,
Brian
Bibcode: 2006AJ....131.2538L
Altcode: 2006astro.ph..1294L
We present new photometry for the Galactic thick-disk globular cluster
Palomar 11 extending well past the main-sequence turnoff in the V
and I bands. This photometry shows noticeable, but depleted, red
giant and subgiant branches. The difference in magnitude between the
red horizontal branch (red clump) and the subgiant branch is used to
determine that Palomar 11 has an age of 10.4+/-0.5 Gyr. The red clump
is used to derive a distance dsolar=14.3+/-0.4 kpc and a mean
cluster reddening of E(V-I)=0.40+/-0.03. There is differential reddening
across the cluster, of order δE(V-I)~0.07. The color-magnitude diagram
of Palomar 11 is virtually identical to that of the thick-disk globular
cluster NGC 5927, implying that these two clusters have a similar age
and metallicity. Palomar 11 has a slightly redder red giant branch
than 47 Tuc, implying that Palomar 11 is 0.15 dex more metal-rich, or
1 Gyr older, than 47 Tuc. Ca II triplet observations, such as those
of Rutledge and coworkers, favor the hypothesis that Palomar 11 is
the same age as 47 Tuc, but slightly more metal-rich.
Title: Spacebased observations of oceanic influence on the annual
variation of South American water balance
Authors: Liu, W. Timothy; Xie, Xiaosu; Tang, Wenqing; Zlotnicki, Victor
Bibcode: 2006GeoRL..33.8710L
Altcode:
The mass change of South America (SA) continent measured by the
Gravity Recovery and Climate Experiment (GRACE) imposes a constraint
on the uncertainties in estimating the annual variation of rainfall
measured by Tropical Rain Measuring Mission (TRMM) and ocean moisture
influx derived from QuikSCAT data. The approximate balance of the
mass change rate with the moisture influx less climatological river
discharge, in agreement with the conservation principle, bolsters
not only the credibility of the spacebased measurements, but supports
the characterization of ocean's influence on the annual variation of
continental water balance. The annual variation of rainfall is found to
be in phase with the mass change rate in the Amazon and the La Plata
basins, and the moisture advection across relevant segments of the
Pacific and Atlantic coasts agrees with the annual cycle of rainfall
in the two basins and the Andes mountains.
Title: Determination of the astrophysical Si26(p,γ)P27 reaction rate
from the asymptotic normalization coefficients of Mg27 → Mg26 + n
Authors: Guo, B.; Li, Z. H.; Bai, X. X.; Liu, W. P.; Shu, N. C.;
Chen, Y. S.
Bibcode: 2006PhRvC..73d8801G
Altcode:
The squares of neutron asymptotic normalization coefficient (ANC)
for Mg27 → Mg26 + n are extracted to be 44.0 ± 5.3, 3.40 ± 0.32
and 0.90 ± 0.08 fm-1 from the angular distributions of
the Mg26(d,p)Mg27 reaction leading to the ground, first, and second
excited states of Mg27, respectively, based on distorted wave Born
approximation (DWBA) analysis. According to charge symmetry of mirror
nuclei, the square of proton ANC for P27 → Si26 + p is determined
to be 1840 ± 240 fm-1 and then utilized to calculate the
astrophysical S-factor and rate for the direct capture into the P27
ground state. In addition, the proton widths for the first and second
excited states in P27 are derived to be 1.30 ± 0.12 × 10-8
and 1.79 ± 0.15 × 10-5 MeV from the neutron ANCs and used
to compute the contribution of the resonant captures. Furthermore, we
have also presented the total astrophysical Si26(p,γ)P27 reaction rate.
Title: Study of Magnetorotational Instability and Hydrodynamic
Stability at Large Reynolds Numbers in a Short Couette Flow
Authors: Ji, Hantao; Burin, Michael; Schartman, Ethan; Goodman,
Jeremy; Liu, Wei
Bibcode: 2006APS..APR.D1042J
Altcode:
Rapid angular momentum transport in accretion disks has been a
longstanding astrophysical puzzle. Molecular viscosity is inadequate
to explain observationally inferred accretion rates. Since Keplerian
flow profiles are linearly stable in hydrodynamics, there exist
only two viable mechanisms for the required turbulence: nonlinear
hydrodynamic instability or magnetorotational instability (MRI). The
latter is regarded as a dominant mechanism for rapid angular momentum
transport in hot accretion disks ranging from quasars and X-ray
binaries to cataclysmic variables. The former has been proposed mainly
for colder protoplanetary disks, whose Reynolds numbers are typically
large. Despite their popularity, however, both candidate mechanisms have
been rarely demonstrated and studied in the laboratory. In this paper,
I will describe a laboratory experiment in a short Taylor-Couette flow
geometry intended for such purposes. Based on the results from prototype
experiments and simulations, the apparatus containing novel features
for better controls of the boundary-driven secondary flows has been
constructed. Initial results on hydrodynamic stability have shown,
somewhat surprisingly, robust quiescence of the Keplerian-like flows
with million Reynolds numbers, casting questions on viability of the
nonlinear hydrodynamic instability.
Title: Impact of atmospheric submonthly oscillations on sea surface
temperature of the tropical Indian Ocean
Authors: Han, Weiqing; Liu, W. Timothy; Lin, Jialin
Bibcode: 2006GeoRL..33.3609H
Altcode: 2006GeoRL..3303609H
Impacts of atmospheric intraseasonal oscillations (ISOs) at submonthly
periods (10-30 days) on Indian Ocean sea surface temperature (SST)
are studied using satellite observed outgoing long wave radiation,
QuikSCAT winds, SST and an ocean general circulation model for the
period of 1999-2004. The results suggest that submonthly ISOs can cause
significant 10-30 day SST changes throughout the equatorial basin and
northern Bay of Bengal, with an amplitude of as large as 0.5°C and
standard deviation of exceeding 0.2°C for a 4-year record. Impact
of the submonthly ISO associated with the Indian summer monsoon is
separately examined. It is associated with basin-scale SST evolution
with distinct spatial structures. The SST variation results mainly from
submonthly wind forcing, which causes changes in oceanic processes and
surface turbulent heat fluxes. Radiative fluxes can also have large
influences in some regions for some ISO events.
Title: Evolution of the Loop-Top Source of Solar Flares: Heating
and Cooling Processes
Authors: Jiang, Yan Wei; Liu, Siming; Liu, Wei; Petrosian, Vahé
Bibcode: 2006ApJ...638.1140J
Altcode: 2005astro.ph..8532J
We present a study of the spatial and spectral evolution of the loop-top
(LT) sources in a sample of six flares near the solar limb observed by
RHESSI. A distinct coronal source, which we identify as the LT source,
was seen in each of these flares from the early ``preheating'' phase
through the late decay phase. Spectral analyses reveal an evident
steep power-law component in the preheating and impulsive phases,
suggesting that the particle acceleration starts upon the onset of the
flares. In the late decay phase the LT source has a thermal spectrum
and appears to be confined within a small region near the top of the
flare loop and does not spread throughout the loop, as is observed
at lower energies. The total energy of this source decreases usually
faster than expected from the radiative cooling but much slower than
that due to the classical Spitzer conductive cooling along the flare
loop. These results indicate the presence of a distinct LT region,
where the thermal conductivity is suppressed significantly and/or there
is a continuous energy input. We suggest that plasma wave turbulence
could play important roles in both heating the plasma and suppressing
the conduction during the decay phase of solar flares. With a simple
quasi-steady loop model we show that the energy input in the gradual
phase can be comparable to that in the impulsive phase and demonstrate
how the observed cooling and confinement of the LT source can be used
to constrain the wave-particle interaction.
Title: Methane-rich fluid inclusions from ophiolitic dunite and
post-collisional mafic ultramafic intrusion: The mantle dynamics
underneath the Palaeo-Asian Ocean through to the post-collisional
period
Authors: Liu, Wei; Fei, Pan Xiao
Bibcode: 2006E&PSL.242..286L
Altcode:
The protracted development history of the Palaeo-Asian Ocean starting
from ∼1000 Ma to ∼320 Ma, and continuation of mantle-derived
magmatism right through the post-collisional period as manifested by the
widespread mafic-ultramafic intrusion and alkaline-peralkaline granite
suggest a vigorous, long-running mantle dynamo. Using the micro-laser
Raman spectrometer, we analyzed olivine- and plagioclase-hosted fluid
inclusions from ophiolitic dunite, Kudi of the western Kunlun Range,
and post-collisional mafic-ultramafic intrusions of the Xiangshan and
the Huangshandong, eastern Chinese Tienshan Mountains. Our results
show that fluids brought from the mantle by these rocks are rich
in H 2O and CH 4 with variable amounts of N
2. Estimation of the redox state, pressure and depth of
formation for the melt-CH 4-H 2O + N 2
fluid systems from the 3 rock suites of the Xinjiang, and comparison
of these parameters with those of the peridotite-fluid parageneses for
the sub-cratonic upper mantle give meaningful results. These fluids
were formed in the asthenosphere, were originally CH 4-N
2-rich, primordial mantle fluid, but have been progressively
diluted with H 2O and become oxidized by repeated
subduction of oceanic slab. We propose that repeated redox melting
in the mantle due to dilution of CH 4 with H 2O
and oxidation caused formation of the long-lived Palaeo-Asian Ocean,
brought about extensive intrusion of mafic-ultramafic complexes and
alkaline-peralkaline granites right through the post-collisional period,
and, consequently, resulted in significant Phanerozoic continental
growth in the Central Asian Orogenic Belt. Rise of atmospheric O
2 and the Earth's major oxidation occurred at about 2.4 to
2.2 Ga. Oxidation of the Earth's mantle promoted the mantle melting
and magma input to the crust, resulting in major continental growth
after 2.5 Ga. However, much-postponed oxidation of the primordial
mantle underneath the Central Asian Orogenic Belt led to significant
continental growth in the Phanerozoic times.
Title: Indirect Measurements of Nuclear Astrophysics Reactions Using
Unstable Nuclear Beams
Authors: Liu, Wei-Ping; Li, Zhi-Hong; Bai, Xi-Xiang; Wang, You-Bao;
Lian, Gang; Guo, Bing; Zeng, Sheng; Yan, Sheng-Quan; Wang, Bao-Xiang;
Su, Jun; Shu, Neng-Chuan; Chen, Yong-Shou
Bibcode: 2006IJMPE..15.1899L
Altcode:
This paper described the nuclear astrophysical studies using the
unstable ion beam facility GIRAFFE, by indirect measurements. We
measured the angular distributions for some single proton or
neutron transfer reactions, such as 7Be(d,n)8B,
11C(d,n)12N, 8Li(d,n)9Be,
8Li(d,p)9Li and 13N(d,n)14O
in inverse kinematics, and derived the astrophysical S-factors
or reaction rates of 7Be(p,γ)8B,
11C(p,γ)12N, 8Li(n,γ)9Li,
13N(p,γ)14O by asymptotic normalization
coefficient, spectroscopic factor, and R-matrix approach at
astrophysically relevant energies.
Title: Laboratory Study of Magnetorotational Instability and
Hydrodynamic Stability at Large Reynolds Numbers
Authors: Ji, H.; Burin, M.; Schartman, E.; Goodman, J.; Liu, W.
Bibcode: 2006nla..conf..106J
Altcode:
Two plausible mechanisms have been proposed to explain rapid angular
momentum transport during accretion processes in astrophysical disks:
nonlinear hydrodynamic instabilities and magnetorotational instability
(MRI). A laboratory experiment in a short Taylor-Couette flow geometry
has been constructed in Princeton to study both mechanisms, with novel
features for better controls of the boundary-driven secondary flows
(Ekman circulation). Initial results on hydrodynamic stability have
shown negligible angular momentum transport in Keplerian-like flows
with Reynolds numbers approaching one million, casting strong doubt
on the viability of nonlinear hydrodynamic instability as a source
for accretion disk turbulence.
Title: A machine learning based approach to remote sensing image
classification
Authors: Zhang, J.; Liu, W.; Gruenwald, L.
Bibcode: 2006cosp...36..235Z
Altcode: 2006cosp.meet..235Z
Decision Tree DT has been widely used for training and classification
of remotely sensed image data due to its capability to generate human
interpretable decision rules and its relatively fast speed in training
and classification This paper proposes a Successive Decision Tree SDT
approach where the samples in the ill-classified branches of a previous
resulting decision tree are used to construct a successive decision tree
The decision trees are chained together through pointers and used for
classification The proposed approach is applied to two real remotely
sensed image data sets for evaluations in terms of classification
accuracy and interpretability of the resulting decision rules
Title: Deramp Range Migration Processing for Satellite-borne Spotlight
Synthetic Aperture Radar
Authors: Ding, Z.; Zeng, T.; Long, T.; Liu, W.
Bibcode: 2006cosp...36.3786D
Altcode: 2006cosp.meet.3786D
Based on the two-step algorithm and range migration algorithm the deramp
range migration algorithm for the high-resolution satellite-borne
spotlight synthetic aperture radar SAR is presented The algorithm
combines the advantages of SPECAN algorithm and range migration
algorithm The first step of the proposed algorithm implements a
linear and space-invariant azimuth filtering that is carried out via
a deramp-based technique representing a simplified version of SPECAN
approach This operation allows us to perform a bulk azimuth raw data
compression and to achieve a pixel spacing no larger than the expected
azimuth resolution of the fully focused image Thus the azimuth spectral
folding phenomenon which is typical for satellite-borne spotlight SAR
is overcome And the space-variant characteristics of the strip-map
system transfer function are preserved Secondly the residual and
precise focusing of the SAR data is achieved by applying the range
migration algorithm The range migration algorithm can be applied to
carry out by simply accounting for a new system transfer function and
by considering the new azimuth sampling frequency In this algorithm
the squinted equivalent range model that is fitter for satellite-borne
SAR is introduced The equivalent velocity and equivalent squint angle
are two important parameters in the algorithm and should accurately
be acquired When the equivalent velocity and equivalent squint angle
acquired form the spacecraft ancillary data are imprecise the estimation
of the two parameters is circumvent through estimating the Doppler
Title: Time-frequency Analysis for Acoustic Emission Signals of
Hypervelocity Impact
Authors: Liu, W. G.; Pang, B. J.; Zhang, W.; Sun, F.; Guan, G. S.
Bibcode: 2006cosp...36.2724L
Altcode: 2006cosp.meet.2724L
The risk of collision of man-made orbital debris with spacecraft in
near Earth orbits continues to increase A major of the space debris
between 1mm and 10mm can t be well tracked in Earth orbits Damage from
these un-tracked debris impacts is a serious hazard to aircraft and
spacecraft These on-orbit collisions occur at velocities exceeding
10km s and at these velocities even very small particles can create
significant damage The development of in-situ impact detecting system is
indispensable for protecting the spacecraft from tragedy malfunction
by the debris Acoustic Emission AE detecting technique has been
recognized as an important technology for non-destructive detecting
due to the AE signals offering a potentially useful additional means
of non-invasively gathering concerning the state of spacecrafts Also
Acoustic emission health monitoring is able to detect locate and assess
impact damage when the spacecrafts is impacted by hypervelocity space
debris and micrometeoroids This information can help operators and
designers at the ground station take effective measures to maintain
the function of spacecraft In this article Acoustic emission AE is
used for characterization and location for hypervelocity Impacts Two
different Acoustic Emission AE sensors were used to detect the arrival
time and signals of the hits Hypervelocity Impacts were generated with
a two-stage light-gas gun firing small Aluminum ball projectiles 4mm
6 4mm In the impact studies the signals were recorded with Disp AEwin
PAC instruments by the conventional crossing
Title: System-level science in the ILWS era
Authors: Liu, W.
Bibcode: 2006cosp...36..988L
Altcode: 2006cosp.meet..988L
Solar system plasma physics is moving steadily toward the era of true
system-level science While multiscale computational modeling has seen
rapid progress over the past decade our experimental methodology has
also moved toward the orientation of observing the multiscale coupling
in solar system plasmas A more comprehensive and at the same time less
ambiguous observational description of the system is fundamental to
further understanding and is a goal that the International Living With
a Star promotes Some noteworthy trends in our science are broader
international participation greater awareness of mission synergy
carefully coordinated satellite constellations and last but not least
a much closer integration of ground-based observations as part of the
frontline scientific programs A much improved observational description
will provide more sharply defined constraints to which computational
models must meet not only in principle but also in detail While the
task is obviously daunting I will give a synthesis of where we are
in multiscale system-level science with an emphasis on mission and
experimental elements associated with the ILWS program
Title: Astrophysical Reaction Rates of the
8Li(p,γ)9Beg.s. Direct Capture
Reaction
Authors: Su, Jun; Li, Zhi-Hong; Guo, Bing; Liu, Wei-Ping; Bai,
Xi-Xiang; Zeng, Sheng; Lian, Gang; Yan, Sheng-Quan; Wang, Bao-Xiang;
Wang, You-Bao
Bibcode: 2006ChPhL..23...55S
Altcode:
Based on the angular distribution of the
8Li(d,n)9Beg.s. reaction at
Ec.m. = 8.0 MeV and distorted wave Born approximation
analysis, the single particle spectroscopic factor S1,3/2 for
the ground state of 9Be = 8Liotimesp is derived
to be 0.64 ± 0.21. In addition, we deduce the astrophysical S-factors
and rates of the 8Li(p,γ)9Beg.s.
direct capture reaction at energies of astrophysical interests.
Title: Magnetic reconnection configurations and particle accelerations
on the Sun
Authors: Chen, P. F.; Liu, W. J.; Fang, C.
Bibcode: 2006cosp...36.3345C
Altcode: 2006cosp.meet.3345C
The electric field near the small-scale reconnection site has been
suggested to be a plausible mechanism for the nonthermal particles
that produce type III radio bursts and hard X-ray emissions in the
corona and chromosphere It has been demonstrated that the magnetic
configuration near the reconnection site plays an important role in
determining the final energy spectrum of the particles In this paper we
first review different reconnection configurations in the Sun which are
associated with various eruptive phenomena such as two-ribbon flares
emerging flux coronal loop-loop interactions and so on We then perform
test particle simulations with these magnetic configurations in order
to investigate their effect on the energy spectrum of the accelerated
particles Their application to observations is discussed
Title: Investigation of Electron Energy Spectrum During Solar Flares
Authors: Liu, W. J.; Chen, P. F.; Fang, C.; Ding, M. D.
Bibcode: 2006cosp...36.2650L
Altcode: 2006cosp.meet.2650L
Observations indicated that the energy spectrum of non-thermal
particles during the evolution of solar flares changes rapidly with
the power index alternating from soft to hard and soft again Based on
MHD numerical simulation of a flare with the typical prephase impulsive
and decay phases we perform the test-particle simulations in order to
investigate the time evolution of the electron spectrum The results
are compared with observations in detail
Title: The 21Na(p, γ) 22Mg Reaction from
Ecm = 200 to 850 KeV in Explosive Stellar Events
Authors: Bishop, S.; D'Auria, J. M.; Chen, A.; Hunter, D.; Lamey, M.;
Liu, W.; Wrede, C.; Azuma, R. E.; King, J. D.; Buchmann, L.; Hutcheon,
D.; Laird, A. M.; Olin, A.; Ottewell, D.; Rogers, J.; Chatterjee,
M. L.; Engel, S.; Gigliotti, D.; Hussein, A.; Greife, U.; Jewett,
C. C.; José, J.; Kubono, S.; Michimasa, S.; Lewis, R.; Parker, P.
Bibcode: 2005omeg.conf..375B
Altcode:
The long-lived radioactive nuclide 22Na (t1/2 =
2.6 y) is, in principle, an astronomical observable for understanding
the physics processes of oxygen-neon novae. Production and abundance
yields of 22Na in these events are dependent to the hitherto
unknown rate of the 21Na(p,γ)22Mg reaction. Using
a high intensity radioactive 21Na beam at the TRIUMF-ISAC
facility, direct measurements of the strengths of six potentially
astrophysically important resonances have been made at center of
mass energies in the range: Ecm = 200 to 850 keV. Reported
herein are preliminary results obtained for these strengths and their
respective contributions to the 21Na(p,γ)22Mg
stellar reaction rate.
Title: A New Color-Magnitude Diagram for Palomar 11
Authors: Chaboyer, B.; Lewis, M. S.; Liu, W. M.; Paust, N. E. Q.
Bibcode: 2005AAS...20712805C
Altcode: 2005BAAS...37R1372C
We present new photometry for the Galactic thick disk globular cluster
Palomar 11 extending well past the main sequence turn-off in the
V and I bands. This photometry shows noticeable, but depleted red
giant and subgiant branches. The difference in magnitude between the
red horizontal branch (red clump) and the subgiant branch is used to
determine that Palomar 11 has an age of 10.4± 0.5 Gyr. The red clump
is used to derive a distance d⊙=14.3± 0.4 kpc, and a
cluster reddening of E(V-I)=0.40± 0.03. The colour magnitude diagram
of Palomar 11 is virtually identically to the thick disk globular
cluster NGC 5927, implying that these two clusters have a similar age
and metallicity. Palomar 11 has a slightly bluer red giant branch than
47 Tuc, implying that Palomar 11 is 0.15 dex more metal-rich, or 1 Gyr
older than 47 Tuc. Ca II triplet observations (Rutledge et al. 1997,
PASP, 109, 907) favour the hypothesis that Palomar 11 is the same age
as 47 Tuc, but slightly more metal-rich. Research supported in
part by a NSF CAREER grant 0094231 to BC. BC is a Cottrell Scholar of
the Research Corporation.
Title: Hard X-ray Emissions From The Legs of Flaring Loops
Authors: Liu, W.; Liu, S.; Jiang, Y.; Petrosian, V.
Bibcode: 2005AGUFMSH13A0287L
Altcode:
or the first time in the RHESSI era, Liu et al. (2005) reported hard
X-ray emissions coming from the legs of a flaring loop at intermediate
energies, as opposed to the commonly observed looptop (LT) and footpoint
(FP) emissions. In an M-1.7 flare observed by RHESSI on November 13,
2003, we found that the FPs in the 9-20 keV energy range rose up to
the legs and eventually merged at the LT, suggestive of a gradual
density enhancement in the loop possibly caused by chromospheric
evaporation. We identified several flares with similar behavior and
analyzed their images, spectra, and imaging spectroscopy, in an effort
to better understand the nature of the leg emissions. We will present
the results of our data analysis of all such flares and discuss their
implications for the particle acceleration and other theoretical aspects
of flares such as chromospheric evaporation. The work is supported
by NASA grants NAG5-12111, NAG5 11918-1, and NSF grant ATM-0312344 at
Stanford University.
Title: Magnetic topologies and two-class coronal mass ejections:
a numerical magnetohydrodynamic study
Authors: Liu, W.; Zhao, X. P.; Wu, S. T.; Scherrer, P. H.
Bibcode: 2005astro.ph.11023L
Altcode:
White-light observations of the solar corona show that there are two
characteristic types of Coronal Mass Ejections (CMEs) in terms of
speed-height profiles: so-called fast CMEs that attain high speeds
low in the corona and slow CMEs that gradually accelerate from low
initial speeds. Low and Zhang (2002) have recently proposed that fast
and slow CMEs result from initial states with magnetic configurations
characterized by normal prominences (NPs) and inverse prominences (IPs),
respectively. To test their theory, we employed a two-dimensional,
time-dependent, resistive magnetohydrodynamic code to simulate the
expulsion of CMEs in these two different prominence environments. Our
numerical simulations demonstrate that (i) a CME-like expulsion is more
readily produced in an NP than in an IP environment, and, (ii) a CME
originating from an NP environment tends to have a higher speed early
in the event than one originating from an IP environment. Magnetic
reconnection plays distinct roles in the two different field
topologies of these two environments to produce their characteristic
CME speed-height profiles. Our numerical simulations support the
proposal of Low and Zhang (2002) although the reconnection development
for the NP associated CME is different from the one sketched in their
theory. Observational implications of our simulations are discussed.
Title: The 8Li(d,p)9Li reaction and
astrophysical 8B(p,γ)9C reaction rate
Authors: Guo, B.; Li, Z. H.; Liu, W. P.; Bai, X. X.; Lian, G.; Yan,
S. Q.; Wang, B. X.; Zeng, S.; Su, J.; Lu, Y.
Bibcode: 2005NuPhA.761..162G
Altcode:
Angular distribution of the Li8(d,p)Lig.s.9 reaction at
E=7.8MeV was measured in inverse kinematics. The square of
asymptotic normalization coefficient (ANC) for the virtual decay
Li9→Li8+n was derived to be 1.33±0.33fm through
distorted wave Born approximation (DWBA) analysis, for the first
time. According to charge symmetry, (ANC)2 for C9→B8+p
was then extracted to be 1.14±0.29fm. We have deduced
the astrophysical S-factors and reaction rates for direct capture in
B8(p,γ)C9 at energies of astrophysical relevance using the ANC for
C9→B8+p extracted from the mirror system.
Title: Exact soliton solutions and nonlinear modulation instability
in spinor Bose-Einstein condensates
Authors: Li, Lu; Li, Zaidong; Malomed, Boris A.; Mihalache, Dumitru;
Liu, W. M.
Bibcode: 2005PhRvA..72c3611L
Altcode:
We find one-, two-, and three-component solitons of the polar and
ferromagnetic (FM) types in the general (nonintegrable) model of a
spinor (three-component) model of the Bose-Einstein condensate, based on
a system of three nonlinearly coupled Gross-Pitaevskii equations. The
stability of the solitons is studied by means of direct simulations
and, in a part, analytically, using linearized equations for small
perturbations. Global stability of the solitons is considered by means
of an energy comparison. As a result, ground-state and metastable
soliton states of the FM and polar types are identified. For the
special integrable version of the model, we develop the Darboux
transformation (DT). As an application of the DT, analytical solutions
are obtained that display full nonlinear evolution of the modulational
instability of a continuous-wave state seeded by a small spatially
periodic perturbation. Additionally, by dint of direct simulations,
we demonstrate that solitons of both the polar and FM types, found in
the integrable system, are structurally stable; i.e., they are robust
under random changes of the relevant nonlinear coefficient in time.
Title: Acoustic Emission Detection and Location for Hypervelocity
Impacts
Authors: Liu, W. G.; Sun, F.; Pang, B. J.; Zhang, W.
Bibcode: 2005ESASP.587..661L
Altcode: 2005spde.conf..661L
No abstract at ADS
Title: Variations of N+/O+ in the ring current
during magnetic storms
Authors: Liu, W. L.; Fu, S. Y.; Zong, Q. -G.; Pu, Z. Y.; Yang, J.;
Ruan, P.
Bibcode: 2005GeoRL..3215102L
Altcode:
Based on the energetic particle measurements obtained by CRRES/MICS,
variations of the third most important ion species, N+,
in the ring current region have been investigated in detail. The
ratio of N+/O+ during geomagnetic quiet times
is found to be about 0.314 +/- 0.043 and decreases with enhanced
solar radiation, as indicated by the F10.7 index. Through a statistic
study, the ratio of N+/O+ has been demonstrated
to decrease with enhanced geomagnetic activity for strong storms,
whereas for small storms, there is no obvious correlation found for
this ratio. It is worthy to note that not all the values during active
times are higher than those at quiet times. The quite different ratios
of N+/O+ (up to 50%) in the ring current region
found between quiet and storm times in this paper, together with the
different combination rates of atomic oxygen and nitrogen, suggest
that the ionospheric nitrogen ions may play a crucial role during
some magnetic storms and should have a strong impact on the magnetic
storm simulation works on the build-up and/or decay processes of the
ring current.
Title: Elasticity of San Carlos olivine to 8 GPa and 1073 K
Authors: Liu, Wei; Kung, Jennifer; Li, Baosheng
Bibcode: 2005GeoRL..3216301L
Altcode:
Elasticity of San Carlos olivine, (Mg0.9,
Fe0.1)2SiO4, has been measured at
simultaneous high pressure and high temperature to 8.2 GPa and 1073
K using ultrasonic interferometry in conjunction with synchrotron
X-radiation. The elastic moduli and their pressure and temperature
derivatives are precisely determined using a pressure standard
free fit using third-order finite strain equations to the velocity
and unit cell volume data in the entire pressure and temperature
range, yielding KS0 = 130.3(4) GPa, G0
= 77.4(2) GPa, K'S0 = 4.61(11), G'0 =
1.61(4), ∂KS/∂T = -0.0164(5) GPa/K, and ∂G/∂T
= -0.0130(3) GPa/K. Combined with previous thermoelastic data
on wadsleyite, the velocity contrasts between α- and β-(Mg,
Fe)2SiO4 at 410-km depth are calculated along a
1673 K adiabatic geotherm with plausible iron partition between the
two phases. The fraction of olivine consistent with a ~5% seismic
discontinuity in an anhydrous mantle is constrained to be less than
~50% with the possibility that a hydrous or a cooler mantle increases
the olivine content towards pyrolitic composition.
Title: The 11C(p,γ)12N reaction rate and the
conversion of 3He into CNO
Authors: Shu, N. -C.; Chen, Y. -S.; Wu, K. -S.; Bai, X. -X.; Li,
Z. -H.; Liu, W. -P.
Bibcode: 2005NuPhA.758..419S
Altcode:
The reaction sequence of
3He(α,γ)7Be(α,γ)11C(p,γ)12N
to CNO could be an alterative way of 3α →12C to
convert 3He into CNO. It may become important in some
specific environments, such as in a very massive star with low
metallicity. Whether it is significant depends on the reactions
involved, one of the important reactions is the 11C
p-capture competing with its β+ decay. The S factor for
the 11C(p,γ)12N direct capture was obtained in
our previous work. This work is to update the reaction rate by adding
uncertainty and fitting with the Thielemann format. With the new rate,
nucleosynthesis simulations are performed to study the bridge of the
p-p chains to CNO through the above sequence.
Title: Impulsive Phase Hard X-Ray Source Motions Observed by RHESSI
Authors: Liu, W.; Liu, S.; Jiang, Y.; Petrosian, V.
Bibcode: 2005AGUSMSP41C..06L
Altcode:
High temporal, spatial, and spectral resolution observations by RHESSI
have provided some interesting and surprising results. In this paper
we present results of our analyses of the spatial evolution during
the impulsive phase, in particular the motions of the looptop (LT)
and footpoint (FP) sources of flares with a simple loop structure. For
the first time, on November 13, 2003 RHESSI observed HXR emissions
from the legs of a flaring loop, in contrast to the commonly observed
LT and FP emissions. In the 9-30 keV energy range, emissions from
the FPs initially appear to extend toward the legs, then rise up,
and eventually merge at the LT. This motion happens first at lower
energies and proceeds to higher energies, indicating a gradual density
increase in the flaring loop, induced possibly by chromospheric
evaporation. Spectral analyses are carried out to determine the nature
of these sources. We discuss the implications of these results on the
particle acceleration, plasma heating, and chromospheric evaporation
processes. The work is supported by NASA grants NAG5-12111, NAG5
11918-1, and NSF grant ATM-0312344 at Stanford University.
Title: The 8Li(d,p)9Li reaction and the
astrophysical 8Li(n,γ)9Li reaction rate
Authors: Li, Z. H.; Liu, W. P.; Bai, X. X.; Guo, B.; Lian, G.; Yan,
S. Q.; Wang, B. X.; Zeng, S.; Lu, Y.; Su, J.; Chen, Y. S.; Wu, K. S.;
Shu, N. C.; Kajino, T.
Bibcode: 2005PhRvC..71e2801L
Altcode: 2009arXiv0903.3092L
The 8Li(n,γ)9Li reaction plays an
important role in both the r-process nucleosynthesis and the
inhomogeneous big bang models. Its direct capture rates can be
extracted from the 8Li(d,p)9Li reaction,
indirectly. We have measured the angular distribution of the
8Li(d,p)9Lig.s. reaction at
Ec.m. = 7.8 in inverse kinematics using coincidence
detection of 9Li and the recoil proton, for the first
time. Based on distorted wave Born approximation (DWBA) analysis,
the 8Li(d,p)9Lig.s. cross
section was determined to be 7.9 ± 2.0 mb. The single particle
spectroscopic factor S1,3/2 for the ground state of
9Li=8Li⊗n was derived to be 0.68±0.14,
and then used to calculate the direct capture cross sections for
the 8Li(n,γ)9Lig.s. reaction
at energies of astrophysical interest. The astrophysical
8Li(n,γ)9Lig.s.
reaction rate for the direct capture was found to be
3970±950cm3mole-1s-1 at
T9=1. This presents the first experimental constraint for
the 8Li(n,γ)9Li reaction rates of astrophysical
relevance.
Title: On the cooling processes of solar flare loops in the gradual
decaying phase---Suppression of conduction and heating by plasma
wave turbulence
Authors: Jiang, Y.; Liu, S.; Liu, W.; Petrosian, V.
Bibcode: 2005AGUSMSP23B..05J
Altcode:
High spectral and spatial resolution observations of RHESSI show
that emission in the gradual phase of many solar flares is dominated
by a thermal looptop source, which cools down faster than expected
from the radiative cooling but much slower than that due to the
cooling by classical Spitzer conductivity. This could be due to a
continuous energy input at a rate equal to the conduction rate. One
would then expect a nearly isothermal loop with an almost uniform
emission along the loop and significant energy injections at the foot
points. However, the looptop image is resolved along the loop and
appears to be confined to the top portion of the loop. This requires a
suppression of conduction within the source region. Combining imaging
spectroscopic observations of RHESSI with the GOES light curves,
we model the evolution of the loops in the gradual phase of several
flares. We find that the suppression of conduction alone can not
account for the RHESSI observations in a quasi-steady equilibrium
loop model. A sustained (although declining) energy input is also
needed. Thermal damping of turbulence produced continuously (albeit
at a declining rate) during the decay phase can be responsible for
the heating process. Presence of turbulence could also suppress the
conduction rate. This work is supported by NASA grants NAG5-12111,
NAG5 11918-1, and NSF grant ATM-0312344.
Title: The 21Na(p,γ)22Mg reaction in novae
and x-ray bursts
Authors: Chen, A. A.; Azuma, R. E.; Bishop, S.; Buchmann, L.;
Chatterjee, M. L.; D'Auria, J. M.; Engel, S.; Gigliotti, D.; Greife,
U.; Hunter, D.; Hussein, A.; Hutcheon, D.; Jewett, C. C.; José, J.;
King, J. D.; Laird, A. M.; Lamey, M.; Lewis, R.; Liu, W.; Olin, A.;
Ottewell, D.; Parker, P.; Rogers, J.; Ruiz, C.; Trinczek, M.; Wrede, C.
Bibcode: 2005NuPhA.752..510C
Altcode:
The 21Na(p,γ)22Mg reaction is an important link
in the synthesis of 22Na in oxygenneon novae, and serves
as one of the first steps of the rp-process in x-ray bursts. This
reaction has recently been studied at the TRIUMF-ISAC radioactive beam
facility with the new DRAGON recoil separator. Resonant contributions
have been measured for seven 22Mg states, from near the
proton threshold to about 6 MeV in excitation energy. We report the
results and their impact on the 21Na(p,γ)22Mg
reaction rate in novae and x-ray bursts.
Title: Substorm Associated Spikes in High Energy Particle
Precipitation
Authors: Spanswick, E.; Donovan, E.; Liu, W.; Wallis, D.; Aasnes,
A.; Hiebert, T.; Jackel, B.; Henderson, M.; Frey, H.
Bibcode: 2005GMS...155..227S
Altcode:
Using data from the 13 instrument CANOPUS riometer array in
north-central Canada, we have examined a large number of substorm
events. Here, we focus on a substorm associated transient "spike"
of significant absorption. We present a statistical analysis
of temporal structure, propagation characteristics, and relative
occurrence of absorption spikes seen with the CANOPUS array. We also
present examples of both isolated transient spike events and a single
propagating event. Seen from any one station, the spike lasts several
minutes. More globally, it typically takes tens of minutes to propagate
across the CANOPUS array. The propagation is in general a combination
of azimuthal (ie., East or West) and poleward motion. Spikes are
associated with the vast majority of substorms and at least some
pseudobreakups. Simultaneous X-ray images confirm that the spike is
a spatially localized region of high-energy precipitation and not,
for example, a boundary. We discuss possible magnetospheric sources
of this precipitation.
Title: Ion composition variations in the plasma sheet observed
by Cluster/RAPID
Authors: Ruan, P.; Fu, S. Y.; Zong, Q. -G.; Pu, Z. Y.; Cao, X.; Liu,
W. L.; Zhou, X. Z.; Daly, P. W.
Bibcode: 2005GeoRL..32.1105R
Altcode: 2005GeoRL..3201105R
Based on the energetic particle measurements obtained by Cluster/RAPID
(Research with Adaptive Particle Imaging Detectors), ion composition
variations in the plasma sheet have been investigated. By comparing
observations during quiet and storm intervals, it is found that,
in addition to the enhanced energy density for all ion species, the
ratio of energetic O+ ions to protons shows an increase
during geomagnetic active periods in the near-Earth plasma sheet
(-15 RE < X < -12 RE). However, the ratio
shows a decrease in the middle plasma sheet (-19 RE <
X < -15 RE). These observation results have been further
confirmed by a statistical study of all the plasma sheet crossing
events from 2001 to 2003. Observations also show that energetic
particles embedded in the earthward high-speed streams observed in
the plasma sheet have an obvious low abundance of heavy ions compared
with surrounding plasmas. It is implied that energetic O+
ions could be distributed in a limited region in the plasma sheet and
much less ionosphere origin particles could reach the region beyond
X = -15 RE. Bursty Bulk Flows (BBFs) could not supply more
energetic O+ ions to the near-Earth plasma sheet, whereas
the ionospheric supplement, together with local acceleration processes,
leads to an enhanced oxygen abundance during active times.
Title: Canadian space environment program and international living
with a star
Authors: Liu, W. William
Bibcode: 2005AdSpR..35...51L
Altcode:
Canada has a vibrant and balanced research program in the space
environment discipline. Two major thrusts are manifested in the
current program direction, the integration of ground instruments for
the remote-sensing of the magnetosphere-ionosphere system (geospace
monitoring), and the development and flight of a small satellite for
the study of particle acceleration and radio tomography in the auroral
ionosphere (enhanced polar outflow probe). A general description of
the mission science objectives is given. These and other potential
Canadian contributions are discussed in the context of international
living with a star.
Title: A study of the freshwater discharge from the Amazon River
into the tropical Atlantic using multi-sensor data
Authors: Jo, Young-Heon; Yan, Xiao-Hai; Dzwonkowski, Brian; Liu,
W. Timothy
Bibcode: 2005GeoRL..32.2605J
Altcode: 2005GeoRL..3202605J
We study freshwater discharge from the Amazon River into the tropical
Atlantic using monthly mean multi-sensor data from September 1997
to July 2003. In order to demonstrate freshwater discharge, we used
chlorophyll concentration (Chl_a) and diffuse attenuation coefficient
(DAC) measured by the Sea-viewing Wide Field-of-view Sensor (SeaWiFS),
and salt steric height anomaly (Δη'S) derived from
Integrated Multi-Sensor Data Analysis (IMSDA). IMSDA was obtained from
estimating the long term-time series of Δη'S by removing
the thermal steric height anomaly (η'T) from altimetry
data. Comparisons of long-term time series of Δη'S, Chl_a,
and DAC were made with mooring data at 8°N, 38°W, which were highly
correlated. There are three- to five-month lags between the Amazon
River discharge and 4°N latitude estimated from latitude-time diagram
derived from SeaWiFS measurements.
Title: Energization of the Inner Magnetosphere by Solar Wind
Pressure Pulses
Authors: Liu, W. William
Bibcode: 2005GMS...155..113L
Altcode:
Geomagnetic storms involve the entry of a prodigious amount of energy
into the inner magnetosphere. Despite decades of research, there remain
serious, if often overlooked, gaps in our understanding of how energy
transport is effected in the storm process. A minimal theory of storm
energization must explain the following observations: 1) The timescale
of energization is shorter than that of radial diffusion and perhaps
also convection; 2) the energization favors the ring current region
(L≤5) and 3) the transferred energy is of a significant magnitude, on
the order of 1015 J or more. Resonant magnetospheric coupling
with solar wind pressure pulses has been considered in the past as a
candidate mechanism for the energy transfer; however, this view has not
been elaborated quantitatively to show that the mechanism is powerful
enough to meet the energy requirement of a storm. In this paper, we
construct a theoretical model to show that pressure pulse coupling can
attain the requisite magnitude to provide for storm-time energization.
Title: Multiscale Geospace Physics in Canada
Authors: Liu, W.; Burchill, J.; Cogger, L.; Donovan, E.; James, G.;
Kendall, D.; Knudsen, D.; Lu, J.; Mann, I.; Michaud, R.; Murphree, S.;
Rankin, R.; Samson, J.; Spanswick, E.; Sofko, G.; Trondsen, T.; Yau, A.
Bibcode: 2005mcsp.conf..487L
Altcode:
No abstract at ADS
Title: Four Years of Nulling Interferometry: A Summary of Results
Since PPIV
Authors: Liu, W. M.; Hinz, P. M.; Hoffmann, W. F.; Meyer, M. R.;
Mamajek, E. E.; Mmt Adaptive Optics Group
Bibcode: 2005prpl.conf.8564L
Altcode: 2005LPICo1286.8564L
No abstract at ADS
Title: Spatial distribution of energetic ion compositions in the
plasma sheet observed by Cluster/RAPID
Authors: Yang, J.; Fu, S.; Liu, W.; Ruan, P.; Pu, Z.; Daly, P.;
Wang, Y.
Bibcode: 2005ChJGC..48.1226Y
Altcode:
No abstract at ADS
Title: The Near-Infrared Synchrotron Spectral Index of Cassiopeia A
Authors: Eriksen, K. A.; McCarthy, D. W.; Liu, W. M.
Bibcode: 2004AAS...205.7001E
Altcode: 2004BAAS...36.1462E
We report on our observations of diffuse near-infrared emission in the
young supernova remnant Cassiopeia A with the PISCES infrared camera on
the University of Arizona Bok 2.3 meter telescope. While previous K-band
imaging (Gerardy and Fesen 2001) and polarimetry (Jones et al. 2003)
confirms its synchrotron origin, our J and H detections allow us to
measure the first near-infrared spectral index for this emission. We
compare our results with radio, microwave, and X-ray observations,
and discuss the implications for models of diffusive shock acceleration
of cosmic rays.
Title: The Princeton Magnetorotational Instability Experiment:
Overview and Initial Results
Authors: Burin, M. J.; Goodman, J.; Ji, H.; Schartman, E.; Liu, W.
Bibcode: 2004AAS...205.0702B
Altcode: 2004AAS...205..702B; 2004BAAS...36.1346B
Accretion disk turbulence is thought to be governed by the
magnetorotational instability (MRI). To date however there has been no
clear experimental demonstration of this instability, though it appears
plausible to do so via a suitably designed laboratory apparatus. To
this end a modified Taylor-Couette apparatus, to be filled with a liquid
gallium alloy and placed within a magnetic field, has been designed and
built. Here we discuss various engineering challenges of the design,
and detail the controls, diagnostics, and data acquisition methods
of the experiment. We also review some supportive numerical modeling
work. In preparation for MRI studies with gallium we have tested
the device with water. The data resulting from these initial studies
bears upon recent work involving nonlinear hydrodynamic instabilities,
which may be a competing mechanism in cool accretion disks. This work
is supported by DoE, NSF, and NASA.
Title: Adaptive Optics Nulling Interferometric Observations of AB
Aur and V892 Tau: Resolved Disks in the Mid-IR
Authors: Liu, W. M.; Hinz, P. M.; Hoffmann, W. F.; Brusa, G.; Miller,
D.; Kenworthy, M. A.
Bibcode: 2004AAS...205.1716L
Altcode: 2004BAAS...36.1367L
We present the results of adaptive optics nulling interferometric
observations of two Herbig Ae stars, AB Aur and V892 Tau, at 10.3
microns. Our observations show resolved circumstellar emission from both
sources. The emission from AB Aur suggests that there is an inclined
disk surrounding the star. The diameter of the disk is derived to
be 24 to 30 AU with an inclination of 45 to 65 degrees from face-on,
and a major-axis PA of 30 +/- 15 degrees (E of N). Differences in the
physical characteristics between the mid-IR emission and emission at
other wavelengths found in previous studies suggest a complex structure
for AB Aur's circumstellar environment, which may not be explained by
a disk alone. The similarity in the observed size of AB Aur's resolved
emission and that of another Herbig Ae star, HD 100546, is likely
coincidental, as their respective evolutionary states and spectral
energy distributions suggest significantly different circumstellar
environments. The PI was supported under a Michelson Graduate
Fellowship
Title: Geomagnetic Activity Dependence of the Ratio N+/O+ in the
Ring Current
Authors: Fu, S.; Liu, W.; Zong, Q.; Pu, Z.; Ruan, P.
Bibcode: 2004AGUFMSM13A1182F
Altcode:
Based on the energetic particle measurement obtained by
CRRES/MICS, ion composition variations in the ring current have been
investigated. Observation shows that in addition to O+ and H+, N+ ions
are also an important composition in the ring current region. The ratio
of N+/O+ during geomagnetic quiet times is about 0.26, while a smaller
valued could be found for strong active times. The variation of the
ratio follows the same trace as the Dst index. Through a statistic
study, it is demonstrated that the ratio of N+/O+ decreases with an
enhanced geomagnetic activity for strong storms, whereas for small
storms, there is no obvious correlations of the ratio to the activity
level. Based on the IRI model, we show that different ion species reach
their peak values at different altitude. The maximum of oxygen ions
sit in a lower altitude than that of nitrogen ions. It is thus implied
that the altitude of the ion up-flowing in the ionosphere is closely
related to the geomagnetic activity. The stronger storms, the lower
ionosphere could be involved in the magnetosphere-ionosphere coupling.
Title: Magnetorotational Instability in a Short Couette Flow of
Liquid Gallium
Authors: Ji, Hantao; Goodman, Jeremy; Kageyama, Akira; Burin, Michael;
Schartman, Ethan; Liu, Wei
Bibcode: 2004AIPC..733...21J
Altcode:
A concise review is given of an experimental project to study
magnetorotational instability (MRI) in a short Couette geometry
using liquid gallium. Motivated by the astrophysical importance and
lack of direct observation of MRI in nature and in the laboratory, a
theoretical stability analysis was performed to predict the required
experimental parameters. Despite the long-wavelength nature of MRI,
local analysis agrees excellently with global eigenmode calculations
when periodic boundary conditions are used in the axial direction. To
explore the effects of rigidly rotating vertical boundaries (endcaps),
a prototype water experiment was conducted using dimensions and
rotation rates favored by the above analysis. Significant deviations
from the expected Couette flow profiles were found. The cause of the
discrepancy was investigated by nonlinear hydrodynamic simulations using
realistic boundary conditions. It was found that Ekman circulation
driven by the endcaps transports angular momentum and qualitatively
modifies the azimuthal flow. Based on this new understanding, a new
design was made to incorporate two independently driven rings at each
endcap. Simulations were used to optimize the design by minimizing
Ekman circulation while remaining within engineering capabilities. The
new apparatus, which has been constructed and assembled, is currently
being tested with water and will be ready for the MRI experiment
with gallium soon. This development process illustrates the value of
interplay between experiment, simulation, and analytic insight.
Title: Princeton Magnetorotational Instability Experiment ---
Background and Overview
Authors: Ji, H.; Burin, M.; Schartman, E.; Raftopoulos, S.; Cutler,
R.; Heitzenroeder, P.; Liu, W.; Goodman, J.; Stone, J.; Kageyama, A.
Bibcode: 2004APS..DPPEP1004J
Altcode:
The magnetorotational instability (MRI) has been proposed as
a dominant mechanism for rapid angular momentum transport in
electrically-conducting accretion disks ranging from quasars
and X-ray binaries to cataclysmic variables and perhaps even
protoplanetary disks. Despite its popularity, however, the MRI has
never been clearly demonstrated and studied in the laboratory. Based
on theoretical analysis(H. Ji, J. Goodman, and A. Kageyama,
Mon. Not. Roy. Astron. Soc. 325), L1(2001); J. Goodman and H. Ji,
J. Fluid Mech. 462, 365(2002). and the results from prototype water
experiments and hydrodynamic simulations(A. Kageyama, et al.), to
be published in J. Phys. Soc. Jpn. (2004)., we have constructed
a short Couette flow apparatus with two differentially rotating
rings at each end of the flow to minimize the Ekman effect. Liquid
gallium alloy is used after initial water tests. A computer-based
control and data acquisition system is implemented to achieve reliable
operations. Signatures of the MRI are monitored by diagnostics measuring
torque coupling between rotating components, as well as magnetic and
pressure perturbations, and internal velocity. Our main objectives are
(1) to clearly demonstrate MRI; (2) to study its nonlinear behavior
and angular momentum transport; (3) to compare with state-of-the-art
simulations similar to those used in astrophysical disks. This work
is supported by DoE, NSF, and NASA.
Title: RHESSI Observations of a Simple Large X-Ray Flare on 2003
November 3
Authors: Liu, Wei; Jiang, Yan Wei; Liu, Siming; Petrosian, Vahé
Bibcode: 2004ApJ...611L..53L
Altcode: 2004astro.ph..1381L
We present data analysis and interpretation of a simple X-class flare
observed with RHESSI on 2003 November 3. In contrast to other X-class
flares observed previously, this flare shows a very simple morphology
with well-defined looptop (LT) and footpoint (FP) sources. The almost
monotonic upward motion of the LT source and increase in separation of
the two FP sources are consistent with magnetic reconnection models
proposed for solar flares. In addition, we find that the source
motions are relatively slower during the more active phases of hard
X-ray emission; the emission centroid of the LT source shifts toward
higher altitudes with the increase of energy; and the separation
between the LT emission centroids at two different photon energies
is anticorrelated with the FP flux. Nonuniformity of the reconnecting
magnetic fields could be a possible explanation of these features.
Title: The 21 Na (p,γ) 22
Mg reaction from Ec.m. =200 to 1103 keV in
novae and x-ray bursts
Authors: D'Auria, J. M.; Azuma, R. E.; Bishop, S.; Buchmann, L.;
Chatterjee, M. L.; Chen, A. A.; Engel, S.; Gigliotti, D.; Greife,
U.; Hunter, D.; Hussein, A.; Hutcheon, D.; Jewett, C. C.; José, J.;
King, J. D.; Laird, A. M.; Lamey, M.; Lewis, R.; Liu, W.; Olin, A.;
Ottewell, D.; Parker, P.; Rogers, J.; Ruiz, C.; Trinczek, M.; Wrede, C.
Bibcode: 2004PhRvC..69f5803D
Altcode:
The long-lived radioactive nuclide 22 Na (
t1/2 =2.6 yr) is an astronomical observable for understanding
the physical processes of oxygen-neon novae. Yields of 22Na
in these events are sensitive to the unknown total rate of the 21
Na (p,γ) 22 Mg reaction. Using
a high intensity 21 Na beam at the TRIUMF-ISAC
facility, the strengths of seven resonances in 22
Mg , of potential astrophysical importance, have been directly
measured at center of mass energies from Ec.m. =200 to
1103 keV . We report the results obtained for these resonances and
their respective contributions to the 21 Na
(p,γ) 22 Mg rate in novae and x-ray bursts,
and their impact on 22 Na production in novae.
Title: Evolution of the Loop Top Source of Solar Flares --- Heating
and Cooling Processes
Authors: Jiang, Y. W.; Liu, S. M.; Liu, W.; Petrosian, V.
Bibcode: 2004AAS...204.9805J
Altcode: 2004BAAS...36..985J
We present a study of the spectral evolution of the loop top (LT)
sources of a sample of solar flares observed by RHESSI. Distinct LT
sources are seen in many flares from the pre-heating to the decay
phase. In most cases, their spectrum can be fitted with either a
thermal or a power law model. The spectra of preheating phase are
somewhat complex. While the impulsive phase spectra seem fit a power
law better. The LT source in decay phase can be well described as a
thermal source. The temperature obtained from the thermal fit decays
10 times faster than that expected from radiative cooling but 10 times
slower than that due to conduction cooling along the loops. This can
come about as a combined result of continuous heating and suppression
of conductivity along the loop. Both these effects can be produced
by turbulence. Implication of this process as the so-called Neupert
effects will also be discussed.
Title: Source Motions and Foot-point Asymmetries in the 2003
October-November X-class Flares Observed by RHESSI
Authors: Liu, W.; Jiang, Y. W.; Liu, S.; Petrosian, V.
Bibcode: 2004AAS...204.4714L
Altcode: 2004BAAS...36..739L
Motions and flux asymmetries of foot-point (FP) sources and related
motions of loop-top (LT) sources play essential roles in understanding
the energy release, particle acceleration, and transport processes
in solar flares. During the October-November 2003 storms, 12 X-class
flares, occurring at different locations across the solar disk,
were observed by the high resolution spectroscopic imager, RHESSI,
with generally good coverage. This provides an excellent opportunity
for a comprehensive investigation of these flare characteristics. For
a selected sample of these flares, we study the motions of the LT and
FP sources. We use the component maps of images obtained by the CLEAN
algorithm to determine the brightness-weighted centroids of the HXR
sources and compare them with the corresponding peak positions. The
sources are well defined in these maps, where there is no residual
which is usually added back to the resulting CLEAN images and makes
it difficult to infer accurate source centroids. The FP motions are
combined with the SOHO/MDI magnetograms to estimate the electric field
along the reconnecting current sheet. We also study the flux asymmetries
between the conjugate FPs, using the more computationally intensive
PIXON algorithm. A comparison between the results obtained with CLEAN
and PIXON will be presented, and implications for particle acceleration
processes and other theoretical aspects of solar flares will be
discussed as well. The work is supported by NASA grants NAG5-12111,
NAG5 11918-1, and NSF grant ATM-0312344 at Stanford University.
Title: Systematic error of microwave scatterometer wind related to
the basin-scale plankton bloom
Authors: Hashizume, Hiroshi; Liu, W. Timothy
Bibcode: 2004GeoRL..31.6307H
Altcode: 2004GeoRL..3106307H
Chlorophyll-a concentration derived from satellite ocean color
sensor are compared with coincident wind speed difference between
microwave scatterometer QuikSCAT product and reanalysis product
from the National Center for Environmental Prediction over global
oceans. The objective is to explore if a natural surface film, which
originates in biological productivity, causes the underestimation
of surface wind in scatterometer measurement by damping the small
capillary wave through the surface tension. The wind speed difference
(Reanalysis wind - QuikSCAT wind) is found to correlate positively
with chlorophyll-a over the biologically highly productive areas,
especially from intra-seasonal to seasonal time scales, indicating
the surface film effect. The wind speed difference increases from ~-1
m s-1 to ~0.5 m s-1 as chlorophyll-a increases
from ~0.1 mg m-3 to ~3 mg m-3, which is comparable
with the results of previous laboratory experiments with artificial oil.
Title: The Canadian Enhanced Polar Outflow Probe (e-POP) Mission
in ILWS
Authors: Yau, A. W.; James, H. G.; Liu, W.
Bibcode: 2004cosp...35.1871Y
Altcode: 2004cosp.meet.1871Y
The Enhanced Polar Outflow Probe (e-POP) small satellite mission will be
Canada's first mission contribution to the International Living with a
Star (ILWS) initiative. The e-POP project comprises three important and
interconnected components: a small-satellite component to investigate
atmospheric and plasma flows and related wave-particle interaction
processes in the topside ionosphere, coordinated ground-based
measurements and a theoretical simulation component. Its scientific
objectives are to quantify the micro-scale characteristics of plasma
outflow and related micro- and meso-scale plasma processes in the polar
ionosphere, explore the occurrence morphology of neutral escape in the
upper atmosphere, and study the effects of auroral currents on plasma
outflow and those of plasma microstructures on radio propagation. The
escape of plasma from the polar ionosphere - and its subsequent
acceleration and transport towards the magnetosphere - is one of the
most important processes in the Ionosphere-Thermosphere-Magnetosphere
system. The e-POP science instrument payload will carry a suite of 8
scientific instruments, including imaging plasma and neutral particle
sensors, magnetometers, dual-frequency GPS receivers, CCD cameras,
a radio wave receiver and a beacon transmitter. The imaging plasma
sensors will measure particle distributions and the magnetometers
field-aligned currents on a time scale of 10 ms and a spatial scale
of (100 m. The CCD cameras will perform auroral imaging on a time
scale of 100 ms. The radio wave and GPS receivers will perform near
real-time imaging of the ionosphere in conjunction with ground-based
radars, and the beacon transmitter in conjunction with ground receiving
stations. The e-POP payload is scheduled for launch in early 2007 as
part of the Canadian CASSIOPE multi-purpose small satellite, and will
be placed in a low-altitude, elliptical polar orbit (80( inclination,
300 km perigee, and 1500 km apogee). e-POP will utilize the companion
communications technology demonstration payload onboard the satellite
bus, and use both S-band and Ka-band telemetry downlink at a maximum
rate of 30 Mbit/s, to support the large volume (up to 20 GBytes/day)
of high-resolution science data that it generates.
Title: Comparison of photometer and global MHD determination of the
open-closed field line boundary
Authors: Rae, I. J.; Kabin, K.; Rankin, R.; Fenrich, F. R.; Liu, W.;
Wanliss, J. A.; Ridley, A. J.; Gombosi, T. I.; de Zeeuw, D. L.
Bibcode: 2004JGRA..109.1204R
Altcode:
We compare open-closed field line boundary positions from the
BATS-R-US Global MHD model and CANOPUS photometer measurements of
red-line emissions. We choose intervals of steady interplanetary
and ionospheric conditions in order to adhere to the "steady-state"
picture that we are trying to address. Nine intervals are chosen that
correspond to stable IMF and auroral conditions that can be simulated
with the MHD model. We find that on average, the steady-state BATS-R-US
MHD model provides an excellent estimate of the open-closed field line
boundary proxy as determined by the red-line auroral emissions. Typical
errors between the model calculations of the open-closed field line
boundary and the observations are within the inherent error in using
the red-line emissions.
Title: International Living With a Star: The road ahead
Authors: Liu, W.
Bibcode: 2004cosp...35.2296L
Altcode: 2004cosp.meet.2296L
Entering into its second year, International Living With a Star has been
a remarkable success, with approximately 30 member organizations now
part of the program. As solar-terrestrial science enters into a period
of uncertainty, the raison d'etre of ILWS has become more compelling,
and its strategic importance more obvious. In the coming months, ILWS
will begin work on 1) formulating and advancing the political argument
for continued support of solar terrestrial science and 2) developing
a compelling scientific vision which will excite and challenge the
scientific community on an international scale. To succeed in either,
ILWS requires active participation and support from the scientists. In
this talk, I present the major findings and results of the Second ILWS
Working Group meeting held in Banff, Canada on May 25 and 26, 2004. I
further invite all scientists to inject their thoughts and suggestions,
as we move forward on this crucial international collaboration.
Title: Excitation of Non-Atmospheric Polar Motion by the Migration
of the Pacific Warm Pool
Authors: Yan, X.; Zhou, Y.; Zheng, D.; Liao, X.; Ding, X.; Pan, J.;
Fang, M.; He, M.; Liu, W.
Bibcode: 2003AGUFM.G22C0317Y
Altcode:
Changes in the annual variation of the Earth's polar motion are found to
be largely caused by the variation of the atmospheric angular momentum
(AAM). Recent simulation results of oceanic general circulation models
further suggested global oceanic effects on the annual polar motion
other than the atmosphere. In parallel to previous model studies
of global oceanic effect, this research particularly singles out
an active large-scale ocean anomaly and investigates its effect on
the annual polar motion, determined from satellite observations of
the movement of the Western Pacific Warm Pool (WPWP). Although the
scale of the warm pool is much smaller than that of the solid Earth,
analysis of the non-atmospheric polar motion excitation has shown that
the WPWP does contribute non-negligible effects to the annual polar
motion. The analysis consisted of over thirty years of the WPWP data
(1970-2000) and shows the polar motion excitation is (2.5mas, -78o)
for the x-component and (0.1mas, -14o) for the y-component. Comparing
this result with the total geodetic non-atmospheric polar motion
excitation of (10.3mas, 59o) for the x-component and (10.6mas, 62o)
for the y-component, shows the significance of the WPWP. The difference
between the WPWP's excitation on (x, y) components of the polar motion
may originate from the WPWP's location and general pattern. Changes
in the Earth's polar motion has attracted significant attention, not
only because it is an important geodetic issue, but also because it
has significant value as a global measure of variations within the
hydrosphere, atmosphere, cryosphere, and solid Earth; hence global
changes. Key Words. Polar motion - Western Pacific Warm Pool
Title: A Resolved Circumstellar Disk around the Herbig Ae Star HD
100546 in the Thermal Infrared
Authors: Liu, W. M.; Hinz, P. M.; Meyer, M. R.; Mamajek, E. E.;
Hoffmann, W. F.; Hora, J. L.
Bibcode: 2003AAS...203.1304L
Altcode: 2003BAAS...35.1226L
We present mid-infrared nulling interferometric and direct imaging
observations of the Herbig Ae star HD 100546 obtained with the Magellan
I (Baade) 6.5 m telescope. The observations show resolved circumstellar
emission at 10.3, 11.7, 12.5, 18.0, and 24.5 microns. Through the
nulling observations (10.3, 11.7 and 12.5 microns), we detect a
circumstellar disk, with an inclination of 45 ± 15 degrees with respect
to a face-on disk, a semimajor axis position angle of 150 ± 10 degrees
(E of N), and a spatial extent of about 25 AU. The direct images (18.0
and 24.5 microns) show evidence for cooler dust with a spatial extent
of 30-40 AU from the star. The direct images also show evidence for an
inclined disk with a similar position angle as the disk detected by
nulling. This morphology is consistent with models in which a flared
circumstellar disk dominates the emission. However, the similarity
in relative disk size we derive for different wavelengths suggests
that the disk may have a large inner gap, possibly cleared out by the
formation of a giant protoplanet. The existence of a protoplanet in the
system also provides a natural explanation for the observed difference
between HD 100546 and other Herbig Ae stars.
Title: Temporal and Spatial Structure of Substorm Associated High
Energy Particle Precipitation
Authors: Spanswick, E.; Donovan, E.; Liu, W.; Hiebert, T.; Henderson,
M.; Wallis, D.; Honary, F.
Bibcode: 2003AGUFMSM51B0528S
Altcode:
The evolution of the high-energy electron population through the
substorm cycle has been studied directly with in situ observations
such as those provided by the LANL-SOPA instruments, and indirectly
through precipitation seen via riometers, X-ray imagers, and other
instruments. Ground-based and other remote sensing techniques provide
the advantage of being able to track such disturbances in both space
and time, with caveats including the fact that information about
the energy of the precipitating particles is limited. Using data
from the 13 instrument NORSTAR (formerly CANOPUS) riometer array in
north-central Canada, we are examining a large number of substorm
events. We are focussing on a transient ``spike'' of significant
absorption that occurs during most substorm expansive phases. Seen
from any one station, the spike lasts several minutes. More globally,
it typically takes tens of minutes to propagate across the NORSTAR
array. The propagation is in general a combination of azimuthal (ie.,
East or West) and poleward. In this paper, we present a statistical
comparision between the propagation characteristics of the spike and
other substorm features such as dipolarization, auroral bulge, Pi2s,
and injections. As well, we present a detailed analysis of several
events. Our objective is to determine the magnetospheric source of
this transient high energy precipitation.
Title: Increasing Tracking Bandwidth for Deep-Space Optical
Communications Using Linear Accelerometers
Authors: Lee, S.; Ortiz, G. G.; Liu, W.; Garkanian, V.
Bibcode: 2003IPNPR.155H...1L
Altcode:
In deep-space optical communications, acquisition, tracking, and
pointing are all challenging because of the stringent -- on the
order of submicroradian -- pointing requirement. To achieve this
level of pointing accuracy, one must maintain high-bandwidth tracking
control. Feasible tracking sources (beacons) include uplink laser beams
and celestial objects such as the Earth, Moon, and stars. However,
these tracking sources do not all provide the kilohertz tracking
rate needed for pointing in deep space. One approach to enable a high
tracking rate is to augment the tracking loop with inertial sensors
to estimate high-frequency beacon movements. In this article, we
discuss the use of linear accelerometers, mounted in a configuration
to measure angular displacement, to achieve high-bandwidth tracking
with dim beacon sources. The advantages of linear accelerometers (or
angular accelerometers) are their low cost, high bandwidth, and small
size compared with other inertial sensors such as gyros. Simulation
and experimental results show good agreement. A tracking bandwidth
increase of 11 times is demonstrated.
Title: Effects of magnetic topology on CME kinematic properties
Authors: Liu, Wei; Zhao, Xue Pu; Wu, S. T.; Scherrer, Philip
Bibcode: 2003ESASP.535..459L
Altcode: 2003iscs.symp..459L
Coronal Mass Ejections (CMEs) exhibit two types of kinematic property:
fast CMEs with high initial speeds and slow CMEs with low initial speeds
but gradual accelerations. To account for this dual character. Low and
Zhang (LZ 2002) proposed that fast and slow CMEs result from initial
states with magnetic configurations characterized by normal and inverse
quiescent prominences, respectively. To test their theory and further
explore the effects of topology on the kinematic properties of CMEs we
employed a self-consistent magnetohydrodynamic (MHD) model [Guo, Wu, et
al.] to simulate the evolution of CMEs respectively in the normal and
inverse prominence environments. The numerical results show that CMEs
originating from a normal prominence environment do have higher initial
speeds than those from an inverse one. In addition, our simulations
demonstrate the distinct roles played by magnetic reconnection in
these two topologically different magnetic environments to produce
the two different CME height-time profiles as suggested by LZ 2002.
Title: Exact soliton solution and inelastic two-soliton collision
in a spin chain driven by a time-dependent magnetic field
Authors: Li, Zai-Dong; Li, Lu; Liu, W. M.; Liang, Jiu-Qing; Ziman, T.
Bibcode: 2003PhRvE..68c6102L
Altcode: 2005cond.mat..6102L
We investigate dynamics of exact N-soliton trains in a spin chain driven
by a time-dependent magnetic field by means of an inverse scattering
transformation. The one-soliton solution indicates obviously the spin
precession around the magnetic field and periodic shape variation
induced by the time-varying field as well. In terms of the general
soliton solutions, N-soliton interaction and particularly various
two-soliton collisions are analyzed. The inelastic collision by which
we mean the soliton shape change before and after collision appears
is generally due to the time-varying field. We, moreover, show that
complete inelastic collisions can be achieved by adjusting spectrum
and field parameters. This may lead to a potential technique of shape
control of soliton.
Title: Air-sea interaction at an oceanic front: Implications for
frontogenesis and primary production
Authors: Chen, Dake; Liu, W. Timothy; Tang, Wenqing; Wang, Zhiren
Bibcode: 2003GeoRL..30.1745C
Altcode: 2003GeoRL..30nOCE3C
Based on recent satellite observations, we hypothesize that there exists
a significant air-sea interaction at the shelf-break front in the East
China Sea. An idealized ocean-atmosphere coupled model was designed
to test this hypothesis and to study the physical processes involved
in such an interaction, with emphasis on the oceanic part. A positive
feedback between ocean and atmosphere was identified in the model and
its consequences were evaluated. We found that air-sea interaction,
when combined with sloping topography, could provide a mechanism for
the genesis of the shelf-break front. The resulting frontal circulation
and vertical mixing could bring nutrient-rich subsurface water into
the surface euphotic zone, thus making the frontal region a conspicuous
place for primary production.
Title: First evidence for the detection of natural surface films by
the QuikSCAT scatterometer
Authors: Lin, I. -I.; Alpers, Werner; Liu, W. Timothy
Bibcode: 2003GeoRL..30.1713L
Altcode: 2003GeoRL..30m..46L
For the first time it is demonstrated that with the QuikSCAT
scatterometer it is possible to detect natural surface films
resulting from enhanced biological activity in the ocean. It is
shown for two regions in the Norwegian and Baltic Sea that areas
of strongly reduced Normalized Radar Cross Section (NRCS) are
associated with areas of enhanced chlorophyll-a concentration as
evidenced by quasi-simultaneously acquired SeaWiFS data. This result
has two implications. Firstly, it opens up the possibility to map
globally natural surface film coverage using QuikSCAT data. Secondly,
it demonstrates that in ocean areas with high biological activity
the presence of natural surface films can give rise to significant
errors in wind vector retrieval when using the current QuikSCAT wind
retrieval algorithm.
Title: Breached Pairing Superfluidity: Possible Realization in QCD
Authors: Gubankova, Elena; Liu, W. Vincent; Wilczek, Frank
Bibcode: 2003PhRvL..91c2001G
Altcode: 2003hep.ph....4016G
We propose a wide universality class of gapless superfluids,
and analyze a limit that might be realized in quark matter at
intermediate densities. In the breached pairing color superconducting
phase heavy s quarks, with a small Fermi surface, pair with light
u or d quarks. The ground state has a superfluid and a normal Fermi
component simultaneously. We expect a second-order phase transition,
as a function of increasing density, from the breached pairing phase
to the conventional color-flavor locked phase.
Title: New evidence for enhanced ocean primary production triggered
by tropical cyclone
Authors: Lin, I.; Liu, W. Timothy; Wu, Chun-Chieh; Wong, George T. F.;
Hu, Chuanmin; Chen, Zhiqiang; Liang, Wen-Der; Yang, Yih; Liu, Kon-Kee
Bibcode: 2003GeoRL..30.1718L
Altcode: 2003GeoRL..30m..51L
New evidence based on recent satellite data is presented to provide
a rare opportunity in quantifying the long-speculated contribution of
tropical cyclones to enhance ocean primary production. In July 2000,
moderate cyclone Kai-Tak passed over the South China Sea (SCS). During
its short 3-day stay, Kai-Tak triggered an average 30-fold increase
in surface chlorophyll-a concentration. The estimated carbon fixation
resulting from this event alone is 0.8 Mt, or 2-4% of SCS's annual
new production. Given an average of 14 cyclones passing over the
SCS annually, we suggest the long-neglected contribution of tropical
cyclones to SCS's annual new production may be as much as 20-30%.
Title: A linear relationship between ENSO intensity and tropical
instability wave activity in the eastern Pacific Ocean
Authors: Yu, Jin-Yi; Liu, W. Timothy
Bibcode: 2003GeoRL..30.1735Y
Altcode: 2003GeoRL..30nCLM5Y
The interannual variations of tropical instability waves (TIWs) in
the eastern Pacific Ocean and their relationships with ENSO intensity
are studied using a 28-year long coupled atmosphere-ocean general
circulation model (CGCM) simulation. The activity of TIWs is measured by
the root-mean-square value of the 50-day high-pass filtered sea surface
temperature (SST) perturbations produced in the simulation. The CGCM
realistically produces two branches of large TIW activity near the
equator: one at 2°N and the other at 2°S. It is found that along
both branches there are linear relationships between the year-to-year
variations of TIW activity and those of ENSO intensity. TIW activity
is enhanced or reduced in proportion to the NINO3 SST anomalies, with
larger activity in La Niña years and smaller activity in El Niño
years. It is found that ENSO modulates TIW activity in both branches
primarily by changing the latitudinal SST gradient associated with the
SST front immediately north of the equator. Weaker correlations are
found between the year-to-year variations of TIW activity and those of
the ocean current shears between the south equatorial current and the
equatorial undercurrent or the north equatorial countercurrent. This
CGCM study suggests that the baroclinic instability associated with
the northern SST front is a major generation mechanism for both the
northern and southern TIW branches in the eastern Pacific Ocean.
Title: Erratum: 21Na(p,γ)22Mg Reaction and
Oxygen-Neon Novae [Phys. Rev. Lett. 90, 162501 (2003)]
Authors: Bishop, S.; Azuma, R. E.; Buchmann, L.; Chen, A. A.;
Chatterjee, M. L.; D'Auria, J. M.; Engel, S.; Gigliotti, D.; Greife,
U.; Hernanz, M.; Hunter, D.; Hussein, A.; Hutcheon, D.; Jewett, C.;
José, J.; King, J.; Kubono, S.; Laird, A. M.; Lamey, M.; Lewis,
R.; Liu, W.; Michimasa, S.; Olin, A.; Ottewell, D.; Parker, P. D.;
Rogers, J. G.; Strieder, F.; Wrede, C.
Bibcode: 2003PhRvL..90v9902B
Altcode:
No abstract at ADS
Title: A Statistical Study of Limb Flares Observed by RHESSI:
Relative Spectra of loop top and footpoint sources
Authors: Jiang, Y. W.; Liu, W.; Petrosian, V.; McTiernan, J.
Bibcode: 2003SPD....34.1803J
Altcode: 2003BAAS...35..840J
Hard X-ray observations of YOHKOH/HXT and preliminary data form RHESSI
have shown that the spectra and intensities from loop top sources
are different from those at footpoints. These differences provide
a great insight into the mechanism of the electron acceleration
process and physical conditions of the flare loop. We have begun the
investigation of a sample of limb flares observed by RHESSI. Using the
imaging analysis described in the accompanying paper, we select flares
with well-defined loop top and footpoint sources and calculate their
relative intensities and spectra. The results from these and previous
observations will be compared with the predictions of the stochastic
acceleration model with the aim of constraining acceleration and its
model parameters. The work at Stanford is supported by NASA grants
NAG5-12111, NAG5 11918-1, and SUB2001-402-01 through the University
of Alabama in Huntsville (PI: J. Miller). J. McTiernan would like to
acknowledge support from grant NAS5-98033-05/03.
Title: The DRAGON facility for nuclear astrophysics at TRIUMF-ISAC
Authors: Hutcheon, D. A.; Bishop, S.; Buchmann, L.; Chatterjee, M. L.;
Chen, A. A.; D'Auria, J. M.; Engel, S.; Gigliotti, D.; Greifef, U.;
Hunter, D.; Hussein, A.; Jewett, C.; Khan, N.; Lamey, A.; Liu, W.;
Olin, A.; Ottewell, D.; Rogers, J. G.; Roy, G.; Sprenger, H.; Wrede, C.
Bibcode: 2003NuPhA.718..515H
Altcode:
No abstract at ADS
Title: A Statistical Study of Limb Flares Observed by RHESSI: Imaging
Authors: Liu, W.; Jiang, Y. W.; Petrosian, V.; Metcalf, T. R.
Bibcode: 2003SPD....34.1802L
Altcode: 2003BAAS...35..839L
Hard X-ray observations by the Reuven Ramaty High Energy Solar
Spectroscopic Imager (RHESSI) provide unprecedented opportunities
to understand the underlying physics driving solar flares. We have
embarked on an investigation of a sample of \it limb flares observed by
RHESSI. RHESSI flare images, combined with TRACE EUV observations and
SoHO/MDI magnetograms, are used to infer flaring loop structures and
to distinguish between footpoint, loop top and other possible types of
sources. We will present an analysis of the lightcurves and images for
these features and will show statistics on the occurrence of loop top
and footpoint sources. These will be compared with previous studies
utilizing YOHKOH/HXT observations, and the implications for particle
acceleration processes and other theoretical aspects of flares will
be discussed. The work at Stanford is supported by NASA grants
NAG5-12111, NAG5 11918-1, and SUB2001-402-01 through the University
of Alabama in Huntsville (PI: J. Miller). T. Metcalf would like to
acknowledge support from grant NAS-98033-05/03.
Title: Measurements with DRAGON on resonances in the
21Na(p, γ)22Mg reaction with a radioactive
ion beam
Authors: Engel, S.; Bishop, S.; Buchmann, L.; Chatterjee, M. L.; Chen,
A.; D'Auria, J. M.; Gigliotti, D.; Greife, U.; Hunter, D.; Hussein,
A.; Lewis, R.; Liu, W.; Olin, A.; Ottewell, D.; Parker, P.; Rogers,
J.; Strieder, F.; Wrede, C.
Bibcode: 2003NuPhA.719..107E
Altcode:
In the modelling of nucleosynthesis in nova explosions,
temperature and density are important parameters to describe the
hydrodynamics. Those parameters are not easy to observe, but specific
gamma-ray emitters produced in the explosion provide constrains on
the models, such as 22Na, produced via 21Na(p,
γ)22Mg(β+)22Na. The new DRAGON
recoil separator facility, designed and built to measure directly
the rates of radiative proton and alpha capture reactions, important
for nuclear astrophysics, is now operational. Experiments have been
conducted on the 21Na(p, γ)22Mg reaction using
a radioactive 21Na beam incident onto a windowless hydrogen
gas target. Yield measurements have been performed detecting the prompt
gamma and the reaction recoils at Ecm ~ 821 keV and 204 keV.
Title: Nuclear astrophysics studiesat dragon: The
21Na(p,γ)22Mg reaction and oxygen-neon novae
Authors: Bishop, S.; Azuma, R.; Buchmann, L.; Chen, A. A.; Chatterjee,
M. L.; D'Auria, J. M.; Engel, S.; Gigliotti, D.; Greife, U.; Hunter,
D.; Hussein, A.; Hutcheon, D.; Jewett, C.; King, J.; Kubono, S.;
Lamey, M.; Lewis, R.; Liu, W.; Michimasa, S.; Olin, A.; Ottewell,
D.; Parker, P. D.; Rogers, J.; Wrede, C.
Bibcode: 2003NuPhA.718..263B
Altcode:
The rate of the 21Na(p,γ)22Mg reaction is
expected to play a major role in the nucleosynthesis of 22Na
in Oxygen-Neon novae, leading to the emission of a characteristic 1.28
MeV gamma-line. This paper reports on preliminary results of the first
direct measurements of this reaction and its astrophysical implications.
Title: Results of 21Na+p experiments at ISAC
Authors: Azuma, R. E.; Bishop, S.; Buchmann, L.; Chatterjee, M. L.;
Chen, A. A.; D'Auria, J. M.; Davinson, T.; Engel, S.; Fulton, B. R.;
Gigliotti, D.; Greife, U.; Groombridge, D.; Hunter, D.; Hussein, A.;
Hutcheon, D.; Jewett, C.; King, J. D.; Khan, N.; Kubono, S.; Laird,
A. M.; Lamey, M.; Lewis, R.; Ling, L.; Liu, W.; Michimasa, S.; Murphy,
A. S.; Olin, A.; Ottewell, D.; Parker, P.; Pearson, J.; Roberts, I.;
Robinson, A.; Rogers, J. G.; Roy, G.; Ruiz, C.; Sarazin, F.; Shotter,
A. C.; Sprenger, H.; Strieder, F.; Walden, P.; Woods, P. J.; Wrede, C.
Bibcode: 2003NuPhA.718..119A
Altcode:
Several resonances in 22Mg have been observed with a
radioactive beam of 21Na impinging on a hydrogen target at
ISAC. Both elastic scattering as well as radiative capture have been
investigated. Some results together with the experimental methods used
will be reported.
Title: 21Na(p,γ)22Mg Reaction and Oxygen-Neon
Novae
Authors: Bishop, S.; Azuma, R. E.; Buchmann, L.; Chen, A. A.;
Chatterjee, M. L.; D'Auria, J. M.; Engel, S.; Gigliotti, D.; Greife,
U.; Hernanz, M.; Hunter, D.; Hussein, A.; Hutcheon, D.; Jewett, C.;
José, J.; King, J.; Kubono, S.; Laird, A. M.; Lamey, M.; Lewis,
R.; Liu, W.; Michimasa, S.; Olin, A.; Ottewell, D.; Parker, P. D.;
Rogers, J. G.; Strieder, F.; Wrede, C.
Bibcode: 2003PhRvL..90p2501B
Altcode: 2003astro.ph..3285B
The 21
Na(p,γ)22
Mg
reaction is expected to play an important role in the nucleosynthesis
of 22
Na in oxygen-neon novae. The decay of
22
Na leads to the emission of a characteristic
1.275MeV gamma-ray line. This report provides the first direct
measurement of the rate of this reaction using a radioactive
21
Na beam, and discusses its astrophysical
implications. The energy of the important state was measured
to be Ec.m.=205.7±0.5 keV with a resonance strength
ωγ=1.03±0.16stat±0.14sys meV.
Title: International Living With a Star (ILWS), a new collaborative
space program in Solar, Heliospheric and Solar-Terrestrial Physics
Authors: Opgenoorth, H. J.; Guhathakurta, M.; Liu, W.; Kosugi, T.;
Zelenyi, L.
Bibcode: 2003EAEJA.....5360O
Altcode:
International cooperation has long been a vital element in the
scientific investigation of solar variability and its impact on Earth
and its space environment. Recently a new international cooeperative
program in solar terrestrial physics has been established by the
major space agencies of the world, called the International Living
With a Star (ILWS) program. ILWS is a follow on to the highly
successful International Solar Terrestrial Physics (ISTP) program
which involved international parterners. ISTP, with its steady flow
of discoveries and new knowledge in solar Terrestrial physics, has
laid the foundation for the coordinated study of the Sun-Earth sytem
as a connected stellar-planetary system, system which is humanity's
home. The first step in establishing ILWS was taken in the fall of
2000 when funding was approved for the NASA's Living With a Star
(LWS) program whose goal is to develop the scientific understanding
necessary to effectively address those aspects of the connected
Sun-Earth system that directly affect life and society. The scientific
goals of ILWS are defined in a broader sense, aiming to include future
solar, heliospheric and solar terrestrial missions of both applied
and fundamental scientific focus. The ultimate goal of ILWS wil be
to increase our understanding of how solar variability affects the
terrestrial and other planetary environments both in the short and
long term, and in particular how man and society may be affected by
solar variability and its consequences. The mission charter of ILWS is
'to stimulate, strengthen and coordinate space research in order to
understand the governing processes of the connected Sun-Earth System as
an integrated entity'. More detailed ILWS Objectives are to stimulate
and facilitate: - The study of the Sun Earth connected system and the
effects which influence life and society - Collaboration among all
potential partners in solar-terrestrial space missions - Synergistic
coordination of international research in solar-terrestrial studies,
including all relevant data sources as well as theory and modeling. The
future ILWS program will be supervised by an international steering
committee, involving representatives from the 4 main space agencies
NASA, ESA, ISAS, RSA, and, emphasising the importance of ground-based
instrumentation in the systematic approach of the ILWS programme,
also from the Canadian Space Agency (CSA). More specific work will be
carried out through an IWLS Working Group, membership to which is open
to space organizations committed to contribute to ILWS over the next
decade. Adequate contributions to ILWS can include any of the following:
- Space Flight Missions - Mission payloads or subsystems - Mission
launch or tracking services - Additional data sources supporting S/C
(sounding rockets, balloon, or ground-based) - Data dissemination,
storage, distribution and value adding systems In addition topical
ILWS Task Groups will be established as necessary to support specific
ILWS-WG projects/studies. This poster will biefly summarize the origins,
objectives, and provisional organizational structure for ILWS and
how this program can benifit from and contribute to international
collaborative efforts towards International Heliospheric Year (IHY).
Title: The DRAGON facility for nuclear astrophysics at TRIUMF-ISAC:
design, construction and operation
Authors: Hutcheon, D. A.; Bishop, S.; Buchmann, L.; Chatterjee, M. L.;
Chen, A. A.; D'Auria, J. M.; Engel, S.; Gigliotti, D.; Greife, U.;
Hunter, D.; Hussein, A.; Jewett, C. C.; Khan, N.; Lamey, M.; Laird,
A. M.; Liu, W.; Olin, A.; Ottewell, D.; Rogers, J. G.; Roy, G.;
Sprenger, H.; Wrede, C.
Bibcode: 2003NIMPA.498..190H
Altcode:
A facility for measuring cross-sections (resonance strengths)
for reactions of astrophysical importance involving short-lived,
radioactive reactants has been designed, built and installed at the
new TRIUMF-ISAC Radioactive Beams Laboratory in Canada. Named DRAGON
(Detector of Recoils And Gamma-rays of Nuclear reactions), it has been
successfully commissioned with stable and radioactive heavy ion beams
from ISAC. This report presents the main components of the facility,
namely, the windowless gas target, the surrounding /γ detector
array, the subsequent electromagnetic recoil mass separator, the
focal plane detectors for recoils, the detection system for elastics,
and the modular electronics and computer software used for the data
acquisition. Examples of the operation of the facility for both
stable beam reactions and the first radioactive beam reaction study,
21Na(p,γ)22Mg are also presented, along with
future plans for the program.
Title: Satellite observations of modulation of surface winds by
typhoon-induced upper ocean cooling
Authors: Lin, I. -I.; Liu, W. Timothy; Wu, Chun-Chieh; Chiang,
J. C. H.; Sui, Chung-Hsiung
Bibcode: 2003GeoRL..30.1131L
Altcode: 2003GeoRL..30c..31L
Two remote sensing data sets, the Tropical Rainfall Measurement Mission
Sea Surface Temperature (SST) and the NASA QuikSCAT ocean surface wind
vectors, are analysed to study ocean-atmosphere interactions in cold
SST regions formed in the trail of two typhoon events. Anomalously
cold SST patches up to 6°C below the surrounding warm tropical ocean
SST are found along the trail of typhoon tracks as cold, deep waters
are entrained up to the mixed layer due to typhoon forcing. In both
typhoon events, significant and systematic weakening of surface wind
speed is found over cold SST patches relative to surface wind speed in
surrounding regions. The wind speed anomalies disappear as the patches
recover to the level of the surrounding SST. The results are consistent
with the mechanism proposed by Wallace et al. that surface winds are
modulated by SST via stability. As wind within the well-mixed boundary
layer moves over the cold patch, boundary layer stability increases,
vertical mixing is suppressed, and the vertical wind shear increases;
reduction in surface wind speed is caused. In particular, our result
shows that this mechanism can act on relatively small spatial (~100 km)
and short (~1 day) time scales.
Title: Correction to ``CO2 exchange coefficients from
remotely sensed wind speed measurements: SSM/I versus QuikSCAT in
2000'' by Mary-Elena Carr, Wenqing Tang, and W. Timothy Liu
Authors: Carr, M. -E.; Tang, W.; Liu, W. T.
Bibcode: 2003GeoRL..30.1038C
Altcode: 2003GeoRL..30b..10C
No abstract at ADS
Title: Some projects related to Stanford Solar Physics Group
Authors: Liu, Wei; Liu, Yang; Zhao, Jun-Wei
Bibcode: 2003PYunO..93...71L
Altcode:
Stanford Solar Physics Group has endeavored to pursue the goal of
understanding the origins of solar variability and its effects on the
terrestrial environment. To accomplish this objective, we are actively
involved in a variety of ongoing and upcoming projects. An overview
of these projects and some of our related activities are presented.
Title: Preliminary Results of Video Observations from Sino-Dutch
2001 Leonids Expedition
Authors: Guan, M.; de Lignie, M.; Zhu, J.; Dijkstra, S.; Gao, J.;
Haas, R.; Ter Kuile, C.; Liu, W.; Meng, H.; Miskotte, K.; Nijland,
J.; Qi, R.; Tukkers, A.; Vandeputte, M.; Xia, D.; Yang, B.
Bibcode: 2003pimo.conf...12G
Altcode:
The preliminary 2001 Leonids results of multi-station video observations
are presented. The observations were obtained at Miyun, Panshan,
Xinglong and Huairou in China during 2001 November 18-20. Thirty
Leonid meteors are reduced. The coordinates of the radiant are
alpha=154.49+-1.80 deg and delta=21.32+-0.74 deg (J2000.0) for mean
solar longitude of 236.486 deg based on these 30 Leonids.
Title: Direct Observations of Atmospheric Boundary Layer Response
to SST Variations Associated with Tropical Instability Waves over
the Eastern Equatorial Pacific(.
Authors: Hashizume, Hiroshi; Xie, Shang-Ping; Fujiwara, Masatomo;
Shiotani, Masato; Watanabe, Tomowo; Tanimoto, Youichi; Liu, W. Timothy;
Takeuchi, Kensuke
Bibcode: 2002JCli...15.3379H
Altcode:
Tropical instability waves (TIWs), with a typical wavelength of 1000
km and period of 30 days, cause the equatorial front to meander and
result in SST variations on the order of 1°-2°C. Vertical soundings
of temperature, humidity, and wind velocity were obtained on board a
Japanese research vessel, which sailed through three fully developed SST
waves from 140° to 110°W along 2°N during 21-28 September 1999. A
strong temperature inversion is observed throughout the cruise along
2°N, capping the planetary boundary layer (PBL) that is 1-1.5 km
deep. Temperature response to TIW-induced SST changes penetrates the
whole depth of the PBL. In response to an SST increase, air temperature
rises in the lowest kilometer and shows a strong cooling at the mean
inversion height. As a result, this temperature dipole is associated
with little TIW signal in the observed sea level pressure (SLP).The
cruise mean vertical profiles show a speed maximum at 400-500 m for
both zonal and meridional velocities. SST-based composite profiles of
zonal wind velocity show weakened (intensified) vertical shear within
the PBL that is consistent with enhanced (reduced) vertical mixing,
causing surface wind to accelerate (decelerate) over warm (cold)
SSTs. Taken together, the temperature and wind soundings indicate the
dominance of the vertical mixing over the SLP-driving mechanism. Based
on the authors' measurements, a physical interpretation of the widely
used PBL model proposed by Lindzen and Nigam is presented.
Title: Direct observations of atmospheric boundary layer response
to SST variations associated with tropical instability waves over
the eastern equatorial Pacific
Authors: Hashizume, H.; Xie, S.; Fujiwara, M.; Shiotani, M.; Watanabe,
T.; Tanimoto, Y.; Liu, W.; Takeuchi, K.
Bibcode: 2002AGUFM.A21D..08H
Altcode:
Tropical instability waves (TIWs), with a typical wavelength of 1000
km and period of 30 days, cause the equatorial front to meander and
result in sea surface temperature (SST) variations on the order of
1-2C. Vertical soundings of temperature, humidity and wind velocity
were obtained on board of a Japanese research vessel, which sailed
through three fully developed SST waves from 140W to 110W along 2N
during September 21-28, 1999. A strong temperature inversion is observed
throughout the cruise along 2N, capping the planetary boundary layer
(PBL) that is 1-1.5 km deep. Temperature response to TIW-induced SST
changes penetrates the whole depth of the PBL. In response to a SST
increase, air temperature rises in the lowest km and shows a strong
cooling at the mean inversion height. As a result, this temperature
dipole is associated with little TIW signal in the observed sea level
pressure (SLP). The cruise-mean vertical profiles show a speed maximum
at 400-500 m for both zonal and meridional velocities. SST-based
composite profiles of zonal wind velocity show weakened (intensified)
vertical shear within the PBL that is consistent with enhanced (reduced)
vertical mixing, causing surface wind to accelerate (decelerate) over
warm (cold) SSTs. Taken together, our temperature and wind soundings
indicate the dominance of the vertical mixing over the SLP-driving
mechanism. Based on our measurements, a physical interpretation
of the widely used PBL model proposed by Lindzen and Nigam (1987,
J. Atmos. Sci.,p.2418-2436) is presented.
Title: HST/NICMOS Observations of NGC 2024: The Emergent Mass
Distribution and Stellar Multiplicity
Authors: Liu, W. M.; Meyer, M. R.; Cotera, A. S.; Young, E. T.
Bibcode: 2002AAS...201.9309L
Altcode: 2002BAAS...34.1260L
We present an analysis of NICMOS observations of the embedded cluster
NGC 2024. An analysis of the cluster color-magnitude diagram (CMD)
using models of D'Antona & Mazzitelli (1998) and Baraffe et
al. (1998) indicates that the ratio of intermediate mass (1.0 to
10.0 Msun) to low mass (0.1 to 1.0 Msun) stars
is consistent with a field star IMF. We also present results on the
multiplicity of stars in the region. Three companions (in a sample of
94 potential primaries) were found, with an angular separations between
0".4 and 1".0, translating to a projected linear separation of 184 AU to
460 AU for an estimated distance of 470 pc. The completeness of binary
detections is assessed using recovery fractions calculated by a series
of tests using artificially generated companions to potential primaries
in the data frames. We find that the binary fraction is similar to
that of Duquennoy & Mayor (1991) for solar-type stars over the
range of separations and companion masses appropriate for our survey.
Title: Bathymetric effect on the winter sea surface temperature and
climate of the Yellow and East China Seas
Authors: Xie, Shang-Ping; Hafner, Jan; Tanimoto, Youichi; Liu,
W. Timothy; Tokinaga, Hiroki; Xu, Haiming
Bibcode: 2002GeoRL..29.2228X
Altcode: 2002GeoRL..29x..81X
Whether and how the atmosphere reacts to changes in extratropical
sea surface temperature (SST) is under intense debate and this lack
of understanding has been a major obstacle in the study of non-El
Nino climate variability. Using new satellite measurements, we detect
clear ocean-to-atmospheric feedback in the Yellow and East China (YEC)
Seas that is triggered by the submerged ocean bottom topography. Under
intense surface cooling in winter, water properties are well mixed
up to 100 m deep. Ocean depth thus has a strong influence on SST of
the continental shelf, leading to a remarkable collocation of warm
tongues and deep channels. High winds and increased cloudiness are
found over these warm tongues; one such band of ocean-atmospheric
co-variation meanders through the basin, following a deep channel for
an amazing distance of 1000 km. In addition to these climatic effects,
the Kuroshio Front-where the warm current meets the much colder shelf
water-strengthens the growth of storms.
Title: Pacific warm pool excitation, earth rotation and El Niño
southern oscillations
Authors: Yan, Xiao-Hai; Zhou, Yonghong; Pan, Jiayi; Zheng, Dawei; Fang,
Mingqiang; Liao, Xinhao; He, Ming-Xia; Liu, W. Timothy; Ding, Xiaoli
Bibcode: 2002GeoRL..29.2031Y
Altcode: 2002GeoRL..29u..27Y
The interannual changes in the Earth's rotation rate, and hence in
the length of day (LOD), are thought to be caused by the variation
of the atmospheric angular momentum (AAM). However, there is
still a considerable portion of the LOD variations that remain
unexplained. Through analyzing the non-atmospheric LOD excitation
contributed by the Western Pacific Warm Pool (WPWP) during the period
of 1970-2000, the positive effects of the WPWP on the interannual
LOD variation are found, although the scale of the warm pool is much
smaller than that of the solid Earth. These effects are specifically
intensified by the El Niño events, since more components of the LOD-AAM
were accounted for by the warm pool excitation in the strong El Niño
years. Changes in the Earth's rotation rate has attracted significant
attention, not only because it is an important geodetic issue but also
because it has significant value as a global measure of variations
within the hydrosphere, atmosphere, cryosphere and solid Earth, and
hence the global changes.
Title: Double intertropical convergence zones-a new look using
scatterometer
Authors: Liu, W. Timothy; Xie, X.
Bibcode: 2002GeoRL..29.2072L
Altcode: 2002GeoRL..29v..29L
The high-resolution wind vectors observed by the space-based
scatterometer QuikSCAT, from 1999 to 2002, show that the double
intertropical convergence zones (ITCZ) exist in the Atlantic and the
eastern Pacific oceans for most of the annual cycle, and are far more
extensive than previously recognized. For most of the time, the southern
ITCZ is weaker than the northern one. The stronger ITCZ occurs when the
northerly trade winds meet the southerly trade winds over warm water,
resulting in deep convection. The weaker ITCZ over cooler water is
caused by the deceleration of the surface winds as they approach the
cold upwelling water near the equator. Decreases in vertical mixing
and increases in vertical wind shear in the atmospheric boundary layer
are suggested to be the causes of the deceleration of the trade winds
as they move from warmer to colder water.
Title: Solar mean magnetic field variability: A wavelet approach
to Wilcox Solar Observatory and SOHO/Michelson Doppler Imager
observations
Authors: Boberg, Fredrik; Lundstedt, Henrik; Hoeksema, J. Todd;
Scherrer, Philip H.; Liu, Wei
Bibcode: 2002JGRA..107.1318B
Altcode:
Solar mean magnetic field (SMMF) measurements from the Wilcox
Solar Observatory and with the SOHO/MDI instrument are described and
analyzed. Even though two completely different methods of observation
are used, the two data sets obtained show a strong similarity. Using
continuous wavelet transforms, SMMF variability is found at a number
of temporal scales. Detected SMMF signals with a 1-2 year period are
considered to be linked to variations in the internal rotation of the
Sun. Intermediate SMMF oscillations with a period of 80-200 days are
probably connected to the evolution of large active regions. We also
find evidence for 90 min variations with coronal mass ejections as a
suggested origin.
Title: Present and future studies with DRAGON at ISAC
Authors: Chen, A. A.; Bishop, S.; Buchmann, L.; Chatterjee, M. L.;
D'Auria, J. M.; Engel, S.; Galovich, C. S.; Gigliotti, D.; Greife,
U.; Hunter, D.; Hussein, A.; Hutcheon, D. A.; Jewett, C.; King, J.;
Kubono, S.; Laird, A.; Lamey, M.; Lewis, R.; Liu, W.; Michimasa,
S.; Olin, A.; Ottewell, D.; Parker, P. D.; Rogers, J.; Strieder, F.;
Wiescher, M.; Wrede, C.
Bibcode: 2002APS..DNP.DE011C
Altcode:
The isotope ^22Na (T_1/2 2.6 years) in nova ejecta may serve as an
important target for gamma-ray astronomy with orbiting telescopes. The
^21Na(p,γ)^22Mg reaction, in turn, is a key link in the production
of ^22Na in nova nucleosynthesis. We present recent results from a
measurement of the ^21Na(p,γ)^22Mg reaction rate, using radioactive
^21Na beams from ISAC and the DRAGON recoil separator. We also discuss
future plans to measure with DRAGON other reactions of importance
to stellar explosions, such as ^13N(p,γ)^14O, ^19Ne(p,γ)^20Na,
and ^25Al(p,γ)^26Si, among others.
Title: QuikSCAT reveals the surface circulation of the Catalina Eddy
Authors: Hu, Hua; Liu, W. Timothy
Bibcode: 2002GeoRL..29.1821H
Altcode: 2002GeoRL..29q...2H
The Catalina Eddy, a small, recurring cyclonic vortex in the ocean off
Los Angeles, is of keen interest to local weather forecasters because of
the moderating oceanic effect it brings to the city. Its small size and
shallow vertical extent have made it difficult to monitor and predict
using conventional data. The microwave scatterometer on the QuikSCAT
spacecraft has generated high-resolution surface wind vectors that
provide the first visualization of the complete cyclonic flow of the
eddy. Moreover, the superior performance of the QuikSCAT scatterometer
demonstrates the relative inaccuracy and inconsistency of predictions
of the eddy based upon numerical weather prediction models.
Title: Observation of western boundary current atmospheric convergence
zones using scatterometer winds
Authors: Pan, Jiayi; Yan, Xiao-Hai; Zheng, Quanan; Liu, W. Timothy
Bibcode: 2002GeoRL..29.1832P
Altcode: 2002GeoRL..29q..13P
A merged scatterometer wind data set from ERS-1/2, NSCAT, and QuikSCAT
missions was used to observe the atmospheric convergence zones
(ACZs) caused by the western boundary currents, the Gulf Stream and
Kuroshio. The long-term means of the atmospheric convergence show
the ACZs' spatial features, which are related to the precipitation
patterns in these regions. Seasonal images of the ACZs were produced
to show annual cycles of the ACZs, indicating that the intensities
of the ACZs over these two regions strengthen in winter and weaken
in summer. Furthermore, we calculated the total convergence over the
Gulf Stream and Kuroshio ACZs, which is defined as the integral of the
convergence over the ACZs. The interannual variability of the total
convergence was extracted by using a multi-stage filter, revealing
that in response to strong El Niño events in 1991-92 and 1997-98,
the total convergence reached maxima.
Title: Determination of geometrical and kinematical properties of
halo coronal mass ejections using the cone model
Authors: Zhao, X. P.; Plunkett, S. P.; Liu, W.
Bibcode: 2002JGRA..107.1223Z
Altcode:
Many broadside coronal mass ejections (CMEs) propagate almost radially
beyond the first couple of solar radii, and their angular widths remain
nearly constant while propagating through the corona. Assuming that
these characteristics hold true for halo CMEs that originate far from
solar limbs, some useful geometric and kinematic properties of halo
CMEs may be reproduced using a simple geometrical model of a CME as
a cone. The cone model uses three free parameters, characterizing the
angular width and the central position of the halo CME. These geometric
properties can be determined by matching the observed halos at a series
of times with the modeled halos for a series of radial distances. The
kinematic properties, the radial velocity and acceleration, of the
halo CME can also be determined on the basis of the series of times
and radial distances. These properties are important for predicting
the geoeffectiveness of a halo CME and cannot be observed directly
with currently available instrumentation. As a test, the geometric and
kinematic properties of the 12 May 1997 halo CME have been inferred
using the cone model. This shows that the cone model does provide a
new way of testing our understanding of halo CMEs, though there are
limitations for some halo CMEs.
Title: CO2 exchange coefficients from remotely sensed
wind speed measurements: SSM/I versus QuikSCAT in 2000
Authors: Carr, Mary-Elena; Tang, Wenqing; Liu, W. Timothy
Bibcode: 2002GeoRL..29.1740C
Altcode: 2002GeoRL..29o..30C
We compare here the air-sea exchange coefficient for CO2
estimated with monthly mean wind speed measured by the Special Sensing
Microwave Imager (SSM/I), KS, and by the scatterometer
QuikSCAT, KQ, for the year 2000. KS and
KQ present the same patterns, although are larger than in
~65% of the world ocean. Zonal mean KS are consistently
larger, except ~50°S and north of 10°S in the Indian Ocean. Global
oceanic uptake, FQ, estimated using KQ and
climatological ΔpCO2 ranges from 0.43 (July) to 2.6 Gt
C y-1 (December). The global sink estimated from SSM/I is
~10% larger than FQ for most of the year. This comparison
supports the use of SSM/I to quantify interannual variability of the
global exchange coefficient of CO2.
Title: Effects of Topology on CME Kinematic Properties
Authors: Liu, W.; Zhao, X. P.; Wu, S. T.; Scherrer, P. H.
Bibcode: 2002AAS...200.3602L
Altcode: 2002BAAS...34Q.693L
Coronal Mass Ejections (CMEs) exhibit two types of kinematic property:
fast CMEs with high initial speeds and slow CMEs with low initial speeds
but gradual accelerations. Efforts have been made for years to probe
the underlying physics responsible for this dual character. Within
these efforts, magnetic topology has gained much attention. Low and
Zhang (ApJ, 564, L53, 2002) proposed that fast or slow CMEs result from
initial states with magnetic configurations characterized by the normal
or inverse quiescent prominences, respectively. To test their theory
and further explore the effects of topology on kinematic properties
of CMEs, we employed a 2-D, axisymmetric, resistive MHD model to
simulate the evolution of CMEs in the normal and inverse prominence
environments, respectively. The numerical results show that the CMEs
originating from a normal prominence environment do have higher initial
speeds than those from an inverse one. In addition, our simulations
demonstrate the distinct roles played by magnetic reconnection in
these two topologically different magnetic environments to produce
the two different CME height-time profiles as suggested by Low and
Zhang. The implication of the results and discussion on future work
are described. SOHO is a project of international cooperation between
ESA and NASA.
Title: Photometric monitoring of 12 BL Lacertae objects
Authors: Xie, G. Z.; Zhou, S. B.; Dai, B. Z.; Liang, E. W.; Li, K. H.;
Bai, J. M.; Xing, S. Y.; Liu, W. W.
Bibcode: 2002MNRAS.329..689X
Altcode:
We present the results of our monitoring the flux variability of 12
BL Lac objects, which have variabilities on time-scales ranging from
hours to months. Individual sources are discussed in detail. Three of
them, OY091, H0548-322 and 0048-097, show significant rapid variation
(hours). Two of them, 3C 66A and Mrk 501, exhibit significant
variability on time-scales of months. We find that 3C 66A has a
variability period of 63+/-5d, supporting the 65-d period obtained
by Lainela et al. The periodicity seems to be weak according to the
Jurkevich Vm2 test. We also find a correlation between B-V colour index
and B magnitude for Mrk 421. We discuss possible physical mechanisms
on the basis of these observational phenomena.
Title: A Cone Model for Coronal Mass Ejections
Authors: Liu, W.; Plunkett, S. P.; Zhao, X. P.
Bibcode: 2002stma.conf..267L
Altcode:
No abstract at ADS
Title: The effect of the host galaxy on the short timescale
variability of γ-ray loud blazars
Authors: Dai, Ben-Zhong; Xie, Guang-Zhong; Jiang, Ze-Jun; Li, Kai-Hua;
Zhou, Shu-Bai; Liu, Wei-Wei
Bibcode: 2002PYunO..90....1D
Altcode:
We present the optical (V and R) photometry for three GeV and/or TeV
γ-ray blazars, which were observed from 2000 through 2001, with the 1-m
telescope at Yunnan Observatory. Through the observational period, the
GeV γ-ray-loud source, PKS 1510-089, was very active and, it showed a
significant variability of 2.0 mag within 41 min in the R band. This is
the most violently rapid variability in our optical monitoring program
for blazars since 1982. For this source, some physical parameters,
namely the emission size, Doppler factor δ, the efficiency (η)
for conversion of accreted matter into energy and luminosity are
calculated. A η = 59.6 was obtained, strongly implying that the
relativistic beaming is responsible for the rapid variability of the
γ-ray loud source. The influence of variable seeing conditions on
the observations was carefully investigated. There is weak correlation
between the observed variability and the local seeing conditions for
the object 1ES 2344+514. The results show that the seeing fluctuations
would influence the spurious variation in microvariability when the
variability parameter C<5.
Title: Intense phytoplankton bloom induced by typhoon in coastal water
Authors: Lin, I.; Liu, W.
Bibcode: 2002cosp...34E1447L
Altcode: 2002cosp.meetE1447L
Typhoon landfall is devastating to the economy and may cause
human lives. Yet typhoon may also enhance other forms of life -
the primary productivity of coastal water. Large human population
lives near the coast and understands the threat of strong wind and
heavy rain of marine storms. Coastal water and marginal seas are the
most productive part of global oceans, but few people realize that
typhoons may pump nutrients to the surface water and benefit fishery
after their passages. . The typhoon forcing and oceanic responses over
coastal water have strong temporal and spatial variability that cannot
be sufficiently resolved by operational numerical weather prediction
models and ground measurements. Two spaceborne microwave sensors,
QuikSCAT and the Tropical Rain Measuring Mission Microwave Imager
(TMI) allow us to measure ocean surface wind vectors and sea surface
temperature (SST) under the cloud cover of typhoons day and night,
and the Sea Viewing Wide-Field-of-View Sensor (SeaWifs) shows us
the ocean color, and the biological activities it denotes, after the
typhoon passage. An interdisciplinary study of physical forcing and
biological response based on synergistic applications of the three space
missions will be presented. Three typhoons were tracked, through the
QuikSCAT surface wind field and Ekman pumping, over the coastal water
and marginal seas of East Asia in the summer of 2000. Super-typhoon
Bilis left a cold wake in the deep water east of Taiwan as observed by
TMI, but with no increase in biological activities near the surface as
observed by SeaWifs. A weaker typhoon Prapirron followed Bilis a week
later producing a cold wake at the north east tip of Taiwan. SeaWifs
observed increase in biological activities in this wake after Prapirron
passage. Climatological in situ measurements show that in the ocean
east of Taiwan, the nutrients lie deep. They do not rise to the surface
even with the passage of super-typhoon. However, in the coastal shallow
water, nutrients are near the surface and they rise to the surface
even with the passage of a weak typhoon. Typhoon Kai-Tak passed slowly
through the northern part of South China Sea, which is a semi-enclosed
marginal sea. TMI and SeaWifs show a 10 C cooling of SST and 100 time
increases (from 0.1 to 10 mg/m3 ) chlorophyll-a (indicating biological
activities), confirming that the biological response to Ekman pumping
by typhoons can be much stronger than generally believed in coastal
water and marginal seas where nutrients reside in shallow water.
Title: The Canadian Space Environment Program and International
Living With a Star
Authors: Liu, W.
Bibcode: 2002cosp...34E3252L
Altcode: 2002cosp.meetE3252L
The Canadian space environment program involves a number of
universities, government departments and agencies. The Canadian
Space Agency acts as the coordinator of many activities in Canada
and represents Canada in the ILWS working group. The Canadian space
environment strategy is based on two elements: 1) ensure a strong,
diverse, and self-sustainable national program capitalizing on Canada's
existing resources and advantages, and 2) using the national program as
the core, create and pursue new international collaborations to maximize
the impact of Canadian scientific activities. In this presentation,
I will outline the core Canadian national space environment program,
consisting of Geospace Monitoring and Near- Earth Space Environment
Study Using Small Satellites. The core Canadian National Program will be
closely coordinated with the overall ILWS program architecture through
scientific, as well inter-agency interactions. I will also describe
the current state of planning and consultation in Canada concerning
an enhanced ILWS initiative, with a preliminary discussion of some
mission scenarios and options.
Title: Rapid Optical Variability of Gamma-Ray-loud Blazars
Authors: Dai, B. Z.; Xie, G. Z.; Li, K. H.; Zhou, S. B.; Liu, W. W.;
Jiang, Z. J.
Bibcode: 2001AJ....122.2901D
Altcode:
We present the optical (B, V, and R) photometry for nine GeV and/or TeV
γ-ray blazars, which were observed from 2000 through 2001 with the 1 m
telescope at Yunnan Astronomical Observatory. The GeV γ-ray-loud source
PKS 1510-089 was very active during our observation period, showing an
apparent variation of 2.0 mag within 41 minutes in the R band. This is
the most violently rapid variability in our optical monitoring program
since 1982. Some physics parameters are calculated for this source,
namely, the emission size, Doppler factor δ, the efficiency (η) for
conversion of accreted matter into energy, and luminosity. An η=62.2
was obtained, strongly implying that relativistic beaming is responsible
for the rapid variability of the γ-ray-loud source. The influence of
variable seeing conditions on the observations was investigated. There
is a weak correlation between the observed variability and the local
seeing conditions for the object 1ES 2344+51.4.
Title: Vector empirical orthogonal function modes of the ocean
surface wind variability derived from satellite scatterometer data
Authors: Pan, Jiayi; Yan, Xiao-Hai; Zheng, Quanan; Liu, W. Timothy
Bibcode: 2001GeoRL..28.3951P
Altcode:
Ocean surface winds derived from NSCAT, QuikSCAT and ERS-1/2
scatterometer observations during a period from January 1992 to April
2000 were analyzed using the vector empirical orthogonal function (VEOF)
method. With the boreal winter and summer oscillation, the first VEOF
is dominated by the Indian and East Asian monsoons and also shows an
annual cycle of the trade winds. The second VEOF represents the boreal
autumn and spring oscillation, and reveals a transition state between
winter and summer. The third VEOF indicates the wind variability
associated with El Niño Southern Oscillation (ENSO) events, because
the temporal mode has a high correlation coefficient of 0.8 with the
Southern Oscillation Index (SOI). Furthermore, the third mode reveals
the teleconnection of the Indian monsoon and wind variability over
high latitude oceans, such as the Aleutian Low system, with ENSO events.
Title: Oceanic and atmospheric anomalies of tropical instability waves
Authors: Polito, Paulo S.; Ryan, John P.; Liu, W. Timothy; Chavez,
Francisco P.
Bibcode: 2001GeoRL..28.2233P
Altcode:
Tropical instability waves (TIWs) are detected in remotely-sensed
sea surface height (SSH), temperature (SST), and wind records of the
eastern equatorial Pacific. Analyses of TIW anomaly relationships
reveal strong dynamical influence of TIWs within approximately 5° of
the equator. The first influence is advective heat flux. The primary
forcing of TIW SST anomalies is advection of the meridional temperature
gradient by TIW currents. The second influence is modification of the
wind stress and Ekman pumping fields by TIW surface ocean currents. By
affecting surface stress and hence roughness, TIW currents in this
low-wind region introduce a significant bias in scatterometer vector
wind measurement. This bias is evident in both NSCAT and QuikSCAT
winds. The difference between wind measurements from TAO moorings and
scatterometers is phase-locked with TIW SST oscillations. These results
have important implications for scatterometry and for understanding
tropical dynamics, thermodynamics and biogeochemistry.
Title: Are the Signals in the Sun's Mean Magnetic Field Associated
With Coronal Mass Ejections?
Authors: Liu, W.; Liu, Y.; Zhao, X.; Scherrer, P.
Bibcode: 2001AGUSM..SH41A06L
Altcode:
A study on time-frequency variability of the solar mean magnetic field
(SMMF) using wavelet analysis is presented. The SMMF data of Michelson
Doppler Imager (MDI) contain an offset most likely introduced by the
random error of the exposure time of MDI. Without the offset correction,
the peaks of wavelet power spectra for the full-disk SMMF time series
coincide with the onset of coronal mass ejections. It has thus been
suggested that the peak of wavelet power spectra is associated with
coronal mass ejections [Boberg and Lundstedt 2000]. To localize the
source of the peak, the full solar disk has been divided into four
quadrants. It turns out unexpectedly that the time series for each
quadrant closely resembles that of the full-disk series. In addition,
all the five series are nearly in phase. On the other hand, the peaks
of wavelet power spectra that coincide with coronal mass ejections
disappear for the full-disk SMMF series obtained after the offset
correction, suggesting that the signal actually occurs in the offset
series. These results give rise to the question -- what is the cause
of the signals detected in the offset series by the wavelet technique?
Title: QuikSCAT's sea winds facilitates early identification of
tropical depressions in 1999 hurricane season
Authors: Katsaros, Kristina B.; Forde, Evan B.; Chang, Paul; Liu,
W. Timothy
Bibcode: 2001GeoRL..28.1043K
Altcode:
Far from land and surface ship observations, most tropical depressions
are identified by examining images from geostationary satellites for
the presence of rotation of the convective cloud masses. During the
1999 hurricane season, surface wind vectors obtained by the SeaWinds
scatterometer on the QuikSCAT satellite for the tropical Atlantic and
Caribbean Sea were examined to test the hypothesis that developing
tropical depressions (TDs) could be observed with this satellite
sensor, before identification by the traditional means. QuikSCAT
was able to detect the presence of closed circulation in the
surface winds before the systems were designated as depressions. The
satellite's unprecedented large swath width of 1800 km allows twice
a day observation of most of the tropical oceans. SeaWinds data can,
therefore, provide valuable guidance that are an important addition
to the tools available to the tropical cyclone forecasting community.
Title: Search for Short Variability Timescale of the GEV
Gamma-Ray-Loud Blazars
Authors: Xie, G. Z.; Li, K. H.; Bai, J. M.; Dai, B. Z.; Liu, W. W.;
Zhang, X.; Xing, S. Y.
Bibcode: 2001ApJ...548..200X
Altcode:
In this paper we report a brief description of 13 γ-ray-loud blazars as
the second batch of the results of our blazar monitoring program. Six
of the monitored objects show significant rapid variations. We found
the typical minimum variability timescale to be about 1 hr. We have
analyzed the relationships between optical variability and γ-ray
variability and found that during 1995-1996 the TeV γ-ray emission
of Mrk 501 correlated to its optical emission, based on our monitoring
data in the optical band. This result will provide a strong constraint
to the emission models.
Title: The structure of protosolar accretion disk
Authors: Liu, W. J.; Huang, K. L.; Zhou, H. N.
Bibcode: 2001AcASn..42....1L
Altcode:
The structure of protosolar accretion disk during viscous diffusion
stage is calculated. The standard αmodel is used to describe the
viscosity in the optically thick protosolar accretion disc. The energy
transport associated with radial motions is neglected and the vertical
structure is constructed by assuming a Keplerian rotation and local
hydrostatic and thermal equilibrium. The disk is heated by viscous
dissipation and energy is transported by convection or radiation. It
is found that the dependence of opacity on temperature is important to
the disk structure. For the cold protosolar accretion disc, convective
instability will gradually end from the outer region to the center and
from the surface to central plane. So the formation of planets should
first take place in the region where convection ends.
Title: Bursty bulk flows without a near-Earth neutral line: Generation
of fast intermittent flow in a highly curved magnetic field
Authors: Liu, W. William
Bibcode: 2001JGR...106..289L
Altcode:
Despite the heightened interest in bursty bulk flows (BBFs) in
the magnetotail, there have been relatively few studies on how
these fast intermittent flows occur in a region where slow and
steady convection is expected. Conventional wisdom attributes
BBFs to the formation of a near-Earth neutral line (NENL) on the
appropriate side of the flow. We demonstrate that this view is
not inevitable or necessary. We develop an alternate mechanism
of BBFs generation based on the magnetohydrodynamics of a plasma
situated in a Harris-type current sheet. We find that without a
NENL or other extraneous assumptions, a highly curved current sheet
(characterized by a field ratio |Bz/Bx|<<1)
can generate high-speed cross-field flows of >100 km/s when
perturbed by modest impulses of ~10 km/s at its boundary. The
flow has an Earthward sense in a thinning current sheet. The
dependence on the field ratio of the maximal speed has the form
c1+c2|Bx/Bz|2,
where c1 and c2 are constants. For
reasonable parameters the BBF threshold of 400 km/s is reached when
Bz/Bx is approximately 0.1. The investigation
also reveals attendant effects and signatures of the BBF-generating
process, and these effects and signatures are listed as our theoretical
predictions, against which better resolved satellite data from upcoming
missions may be compared. We conclude with discussions on the potential
role fast intermittent flows might play in the excitation of the
substorm and other interesting magnetotail phenomena.
Title: Coronal Magnetic Flux Rope Equilibria and Magnetic Helicity
Authors: Hu, You-Qiu; Jiang, Yan-Wei; Liu, Wei
Bibcode: 2001ChJAA...1...77H
Altcode:
Using a 2.5-dimensional (2.5-D) ideal MHD model, this paper analyzes
the equilibrium properties of coronal magnetic flux ropes in a bipolar
ambient magnetic field. It is found that the geometrical features
of the magnetic flux rope, including the height of the rope axis,
the half-width of the rope, and the length of the vertical current
sheet below the rope, are determined by a single magnetic parameter,
the magnetic helicity, which is the sum of the self-helicity of the
rope and the mutual helicity between the rope field and the ambient
magnetic field. All the geometrical parameters increase monotonically
with increasing magnetic helicity. The implication of this result in
solar active phenomena is briefly discussed.
Title: A 2.5-dimensional Ideal Magnetohydrodynamic Model for Coronal
Magnetic Flux Ropes
Authors: Hu, Y. Q.; Liu, W.
Bibcode: 2000ApJ...540.1119H
Altcode:
Coronal magnetic flux ropes are closely related to various solar active
phenomena such as prominences, flares, and coronal mass ejections. Using
a 2.5-dimensional (2.5-D), time-dependent ideal MHD model in Cartesian
coordinates, a numerical study is carried out to find the equilibrium
solution associated with a magnetic flux rope in the corona, which
is assumed to emerge as a whole from the photosphere. The rope in
equilibrium is characterized by its geometrical features such as the
height of the axis, the half-width of the rope, and the length of the
vertical current sheet below the rope, and its magnetic properties such
as the axial and annular magnetic fluxes and the magnetic helicity as
well, which are conserved quantities of the rope in the frame of ideal
MHD. It is shown that, for a given bipolar ambient magnetic field, the
magnetic flux rope is detached from the photosphere, leaving a vertical
current sheet below, when its axial magnetic flux, annular magnetic
flux, or magnetic helicity exceeds a certain critical value. The
magnetic field is nearly force free in the rope but not in the
prominence region, where the Lorentz force takes an important role in
supporting the prominence appearing below the rope axis. The geometrical
features of the rope vary smoothly with its magnetic properties, and
no catastrophe occurs, a similar conclusion to that reached by Forbes
& Isenberg for magnetic flux ropes of large radius. Major Project
19791090 supported by the National Natural Science Foundation of China.
Title: Boron concentration and isotopic composition of halite from
experiments and salt lakes in the Qaidam Basin
Authors: Liu, W. G.; Xiao, Y. K.; Peng, Z. C.; An, Z. S.; He, X. X.
Bibcode: 2000GeCoA..64.2177L
Altcode:
The concentration and isotopic abundance of boron in salt can be used to
trace paleosalinities and depositional environments for marine and non
marine evaporites. However, the mechanism of incorporating boron into
halite during evaporation of salt lake brines is subject to dispute,
and there have been few studies of boron concentrations and isotopic
compositions during this process due to the low boron concentration in
halite. A group of evaporation experiments from artificial solutions
and salt lake brines have been analyzed in this study. The results of
boron concentration and isotopic analyses demonstrate that the boron in
halite comes mainly from fluid inclusions, with a lesser amount from
coprecipitation. The isotopic fractionation factors between the brine
and halite are from 0.9857 to 1.0000 for the evaporation experiments,
and 0.9945 to 1.0009 for natural samples from the salt lake. The δ
11B values of halite from the Qaidam Basin salt lakes vary
from -4.7 to 25.8‰, compared to -4.7 to 31.4‰ in the salt lake
brines. These values are controlled by the boron isotopic composition
of the boron sources, pH values and Na/Ca ratios in the salt lake
brines. The variation of boron isotopes in halite may be used to
trace the hydrochemical evolution and paleoevaporation environment in
salt lakes.
Title: An SST anomaly dipole in the northern subtropical Pacific
and its relationships with ENSO
Authors: Yu, Jin-Yi; Liu, W. Timothy; Mechoso, Carlos R.
Bibcode: 2000GeoRL..27.1931Y
Altcode:
This study examines the links between tropical and subtropical sea
surface temperature (SST) anomalies in the Pacific Ocean during ENSO
(El Niño-Southern Oscillation) events. A long-term simulation by the
UCLA coupled atmosphere-ocean general circulation model is used. It is
found that a zonally-oriented SST anomaly dipole in the subtropical
Pacific develops almost simultaneously with and is closely related
to tropical ENSO events. The dipole is located east of the dateline
between 20°N and 40°N and consists of an anomaly center off the
coast of the North America and another anomaly center with opposite
sign further to the west. It is demonstrated that this dipole feature
is primarily driven by anomalous surface heat fluxes associated with
the altered atmospheric circulation during ENSO events.
Title: Importance of salinity measurements in the heat storage
estimation from TOPEX/POSEIDON
Authors: Sato, Olga T.; Polito, Paulo S.; Liu, W. Timothy
Bibcode: 2000GeoRL..27..549S
Altcode:
Sea surface height anomalies from satellite altimeter data are used
to estimate heat storage. Since variability in sea surface height is
mostly due to expansion and contraction of the water column it can be
correlated with variations in the heat and salt content. Therefore,
estimation of heat storage from altimeter data, when compared to in
situ estimates, requires corrections for the haline effect. Three
sites with a nearly continuous time series of temperature and salinity
profiles simultaneous with TOPEX/POSEIDON data are studied: HOT,
CalCOFI and Hydrostation “S”. Haline corrections based on in
situ and climatological salinity measurements are contrasted. For the
studied regions, the haline corrections based on climatology provide
equivalent or worse results than not applying a correction at all. The
use of in situ salinity estimates decreased the differences between the
heat storage estimates (up to 17 × 107 J m-2)
and significantly improved their correlation (up to 0.18).
Title: Disturbance of prominence caused by magnetic cancellation
Authors: Liu, Wei; Hu, You-qiu; Xia, Li-dong; Yang, Yu-lin
Bibcode: 2000ChA&A..24..365L
Altcode:
Using a two-dimensional, three-component magnetohydrodynamic model, a
numerical study is presented on the disturbance of prominence caused by
photospheric magnetic cancellation. Photospheric magnetic cancellation
below the prominence transports magnetic flux into the prominence,
resulting in an increase of both magnetic flux and helicity in the
prominence. The state of the prominence is related to its accumulated
magnetic flux (or magnetic helicity). As shown in the numerical results,
when δF (the relative increment of magnetic flux in the
prominence) or δH (the corresponding relative increment
of magnetic helicity) is small, the prominence rises and expands only
slightly, and remains in contact with the photosphere. On the other
hand, when δF or δH is large, the prominence
is detached from the photosphere and eventually is suspended in the
lower corona, leading to the formation of a vertical current sheet
below the prominence.
Title: What Will Happen When an Accelerating Black Hole Touches its
Rindler Horizon
Authors: Zhao, Z.; Liu, W. B.; Jiang, Y. L.
Bibcode: 2000graa.conf..112Z
Altcode:
No abstract at ADS
Title: Angular Distribution for 7Be(d, n)8B
Reaction at Ec.m. = 8.3 MeV and the Astrophysical
S17(0) Factor for 7Be(p, γ)8B
Reaction
Authors: Wang, You-bao; Liu, Wei-ping; Bai, Xi-xiang; Li, Zhi-chang;
Li, An-li; Zhou, Shu-hua; Zhu, Xiao-feng; Li, Xiao-mei; He, Gao-kui;
Guo, Gang; Lian, Gang; Tang, Xiao-dong
Bibcode: 1999ChPhL..16..873W
Altcode:
The differential cross section for 7Be(d, n)8B
reaction at Ec.m. = 8.3 MeV has been measured by using
a 7Be radioactive beam. The reaction cross section was
determined to be 28 ± 3 mb. The astrophysical S17(0)
factor for the 7Be(p,γ)8B reaction was derived
to be 24 ± 5 eV b through the asymptotic normalization constant of
8B extracted from the experimental data. This result is
found to be consistent with a previous value obtained from the same
reaction at Ec.m. = 5.8 MeV, implying the energy independence
of this indirect method within the uncertainty.
Title: CCD time-resolved photometry of four newly discovered CVs.
Authors: Liu, W.; Hu, J. Y.
Bibcode: 1999PYunO....S.386L
Altcode:
The authors present time-resolved optical light curves in R bands
obtained from differential photometry on sequential CCD frame of 4
new discovered high galactic latitude CVs, which are discovered by
spectroscopic observations of the optical identification of ROSAT X-ray
sources. The analysis of the light curves shows repeatable periodicity
in these objects. J020348.7+295921 exhibits 0.5 m variation with
orbital period of 258 min. J062518.2+733433 reveals a 0.3 mag modulation
with orbital period of 254 min. J230949.6+213523 shows probably both
orbital period of 207 min and WD spin period of 25 min. J232953.9+062814
present short period of 32 min, indicating a magnetic system.
Title: Optical Monitoring Sample of the GEV Gamma-Ray-loud Blazars
Authors: Xie, G. Z.; Li, K. H.; Zhang, X.; Bai, J. M.; Liu, W. W.
Bibcode: 1999ApJ...522..846X
Altcode:
We present optical monitoring between 1994 February and 1997 December of
10 γ-ray-loud blazars included in our blazar monitoring program. Most
of the monitored objects show significant rapid variations. The typical
minimum variability timescale in the optical range is about 1 hour. We
have analyzed the relationships between optical variability and γ-ray
variability, and discussed theoretical models for the γ-ray-loud
blazar emission.
Title: Internal acceleration of relativistic electrons by
large-amplitude ULF pulsations
Authors: Liu, W. W.; Rostoker, G.; Baker, D. N.
Bibcode: 1999JGR...10417391L
Altcode:
The flux of relativistic electrons in geostationary orbit exhibits a
variability closely regulated by the solar wind, but the acceleration
mechanism of relativistic electrons remains poorly understood. Recent
observational evidence has shown that the intensification of
relativistic electrons often takes place in a matter of several
hours. The rapidity is difficult to reconcile with traditional
diffusion-based models which often take days to produce appropriate
high-energy electron fluxes and motivates us to search for alternative
mechanisms of internal acceleration. Elaborating on the observation
in an earlier paper of Rostoker et al. [1998], we propose that
global oscillation of magnetosphere in the Pc4-5 range is capable
of accelerating electrons under the catalysis of random pitch angle
scattering. This view is developed theoretically and computationally
in this paper. The most noteworthy result of the investigation is
the demonstration that magnetic pumping by ULF waves can lead to the
observed high relativistic electron flux in a time as short as a few
hours under parameters appropriate for major magnetic storms. Further
development and test of this theory are discussed.
Title: Copper-Chloride Complexing in Hydrothermal Brines
Authors: McPhail, D. C.; Brugger, J.; Liu, W.; Spiccia, L.; Black, J.
Bibcode: 1999nag..conf.7354M
Altcode:
No abstract at ADS
Title: Photometric monitoring of three BL Lacertae objects in
1993-1998
Authors: Bai, J. M.; Xie, G. Z.; Li, K. H.; Zhang, X.; Liu, W. W.
Bibcode: 1999A&AS..136..455B
Altcode:
The results of optical photometric (BVRI) monitoring of three BL Lac
objects over a time interval of about four years are presented. The
sources are three classical radio-selected BL Lac objects, BL Lac, OJ
287 and PKS 0735+178. During our observation OJ 287 was in the stage of
a large periodic outburst which consisted of at least two peaks. Almost
all the observations obtained over consecutive nights detected
intranight variations. In 1995 and 1996 BL Lac kept in faint states,
with fewer and smaller rapid flares and fluctuations. On the contrary,
in late 1997 BL Lac was at the stage of a large outburst, accompanied
with much more large amplitude rapid flares and fluctuations. PKS
0735+178 was almost at its faint end from 1994 to early 1998. Over
this time interval, the intraday variations and microvariations in
PKS 0735+178 were rare and the amplitude was very small, except a
rapid darkening of ~ 0.4 mag on 24 January 1995. Previous work by
\cite[Webb et al. (1988);]{web88} \cite[Wagner et al. (1996);]{wag96}
\cite[Pian et al. (1997)]{pia97} also showed the same behaviour of
variability as BL Lac and PKS 0735+178 in BL Lac, S5 0716+714, PKS
2155-304, respectively. We propose that the motion of orientation
of the relativistic jet in a BL Lac object be responsible for these
variability behaviours. Table~1 is only available in electronic form
at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5)
or via http://cdsweb.u-strasbg.fr/Abstract.html
Title: Spacebased observations of the seasonal changes of south
Asian monsoons and oceanic responses
Authors: Liu, W. Timothy; Xie, Xiaosu
Bibcode: 1999GeoRL..26.1473L
Altcode:
The seasonal changes of monsoons in the South China Sea and the
Arabian Sea are compared, using observations by spaceborne microwave
scatterometers and radiometers. The oceanic responses to the forcing of
wind stress and latent heat flux resulting from the monsoon changes are
identified through surface temperature tendency and sea level changes.
Title: Australasian Tektites Found in Guangxi Province, China
Authors: Povenmire, H.; Liu, W.; Xianlin, L.
Bibcode: 1999LPI....30.1072P
Altcode:
Newly confirmed Australasian tektites have been found in Guangxi
Province, China. This is some 500 km NW of Guangdong and represents
an important extension of this strewn field.
Title: Condensation of Carbon in Supernovae: 1. Basic Chemistry
Authors: Liu, W.; Clayton, D. D.
Bibcode: 1999LPI....30.1108L
Altcode:
Contrary to the conventional wisdom on cosmic dust condensation based
on thermochemical equilibrium theory, kinetic chemistry demonstrates
that carbon condenses in supernovae even if C<O because radioactivity
destroys the CO trap.
Title: An Experiment Using NSCAT Winds in the Numerical Prediction
of Tropical Mesoscale Rainfall Systems under the influence of terrain
Authors: Chang, C. -P.; Lin, S. -C.; Liou, C. -S.; Liu, W. Timothy
Bibcode: 1999GeoRL..26..311C
Altcode:
The rich mesoscale information in NSCAT winds over tropical coastal
regions is used in numerical simulations of two June 1997 monsoonal
cases occurring over Taiwan. It is shown that transient NSCAT mesoscale
information over a localized area as small as 120 km × 240 km can
result in significant improvement in the 24 h heavy rainfall forecast
due to its effect on monsoonal convection and terrain effects.
Title: VizieR Online Data Catalog: BVRI photometry of 3 BL Lac objects
(Bai+, 1999)
Authors: Bai, J. M.; Xie, G. Z.; Li, K. H.; Zhang, X.; Liu, W. W.
Bibcode: 1999yCat..41360455B
Altcode:
The results of optical photometric (BVRI) monitoring of three BL Lac
objects over a time interval of about four years are presented. The
sources are three classical radio-selected BL Lac objects, BL Lac, OJ
287 and PKS 0735+178. During our observation OJ 287 was in the stage of
a large periodic outburst which consisted of at least two peaks. Almost
all the observations obtained over consecutive nights detected
intranight variations. In 1995 and 1996 BL Lac kept in faint states,
with fewer and smaller rapid flares and fluctuations. On the contrary,
in late 1997 BL Lac was at the stage of a large outburst, accompanied
with much more large amplitude rapid flares and fluctuations. PKS
0735+178 was almost at its faint end from 1994 to early 1998. Over
this time interval, the intraday variations and microvariations in
PKS 0735+178 were rare and the amplitude was very small, except a
rapid darkening of ~0.4mag on 24 January 1995. Previous work by Webb
et al. (1988AJ.....95..374W), Wagner et al. (1996AJ....111.2187W)
and Pian et al. (1997ApJ...486..784P) also showed the same behaviour
of variability as BL Lac and PKS 0735+178 in BL Lac, S5 0716+714,
PKS 2155-304, respectively. We propose that the motion of orientation
of the relativistic jet in a BL Lac object be responsible for these
variability behaviours. (1 data file).
Title: CCD Time-Resolved Photometry of Four Newly Discovered CVs
Authors: Liu, W.; Hu, J. Y.
Bibcode: 1999oaaf.conf..386L
Altcode:
No abstract at ADS
Title: β decay of 40Ti and 41Ti and implication
for solar-neutrino detection
Authors: Liu, W.; Hellström, M.; Collatz, R.; Benlliure, J.;
Chulkov, L.; Gil, D. Cortina; Farget, F.; Grawe, H.; Hu, Z.; Iwasa,
N.; Pfützner, M.; Piechaczek, A.; Raabe, R.; Reusen, I.; Roeckl,
E.; Vancraeynest, G.; Wöhr, A.
Bibcode: 1998PhRvC..58.2677L
Altcode:
The β decay of 40Ti and 41Ti was studied by
measuring the β-delayed proton and γ emission. The half-lives for
40Ti and 41Ti were determined to be 54(2)
and 82(3) ms, respectively. The experimental β-decay strengths
are compared with shell-model calculations and results from other
measurements. The integrated Gamow-Teller strengths for 40Ti
and 41Ti were found to be quenched, compared to the
calculations, by factors of 0.79(3) and 0.93(3), respectively. Based
on the experimental 40Ti β-decay strength, the neutrino
absorption cross section and induced neutrino event rates for
40Ar were determined to be 14.3(3)×10-43
cm2 and 9.4+/-0.2(stat)+1.3-1.6(syst)
SNU, respectively.
Title: A solitary wave packet in the atmosphere observed from space
Authors: Zheng, Quanan; Yan, Xiao-Hai; Liu, W. Timothy; Klemas, Vic;
Greger, Dietmar; Wang, Zongming
Bibcode: 1998GeoRL..25.3559Z
Altcode:
A group of parallel cloud lines was identified in seven successive
space shuttle photographs taken over the Pakistani offshore zone in
the northern Arabian Sea on April 29, 1993. There are a total of 19
lines aligned with the length of the leading line longer than 250 km
and an average separation distance (wavelength) of 1 km. We suggest
that the lines are generated by an atmospheric solitary wave packet
characterized by decreases in amplitudes and wavelengths from the front
to the rear. These features are comparable with the dnoidal soliton
solution to the Korteweg-de Vries (KdV) equation. The land breeze and
katabatic flow are proposed as a possible generation mechanism.
Title: The intraday variability in the radio-selected and
X-ray-selected BL Lacertae objects
Authors: Bai, J. M.; Xie, G. Z.; Li, K. H.; Zhang, X.; Liu, W. W.
Bibcode: 1998A&AS..132...83B
Altcode:
Seven BL Lac objects have been photometrically observed in an effort
to study the difference of optical intraday variability between the
radio-selected BL Lac objects (RBLs) and X-ray-selected BL Lac objects
(XBLs). The objects we observed are selected arbitrarily. They are four
RBLs, PKS 0735+178, PKS 0754+101, OJ 287 and BL Lac, and three XBLs,
H 0323+022, H 0548-322 and H 2154-304. During the observation all of
them exhibited microvariation, and H 0323+022 and H 0548-322 sometimes
showed brightness oscillation. PKS 0735+178 and BL Lac were in their
faint states and not very active. It seems that RBLs do not show
microvariability more frequently than XBLs. Table 2 is only available
in electronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr
(130.79.128.5)
Title: The impact of upper tropospheric humidity from microwave limb
sounder on the midlatitude greenhouse effect
Authors: Hu, Hua; Liu, W. Timothy
Bibcode: 1998GeoRL..25.3151H
Altcode:
This paper presents an analysis of upper tropospheric humidity,
as measured by the Microwave Limb Sounder, and the impact of the
humidity on the greenhouse effect in the midlatitudes. Enhanced upper
tropospheric humidity and an enhanced greenhouse effect occur over the
storm tracks in the North Pacific and North Atlantic. In these areas,
strong baroclinic activity and the large number of deep convective
clouds transport more water vapor to the upper troposphere, and hence
increase greenhouse trapping. The greenhouse effect increases with upper
tropospheric humidity in areas with a moist upper troposphere (such as
areas over storm tracks), but it is not sensitive to changes in upper
tropospheric humidity in regions with a dry upper troposphere, clearly
demonstrating that there are different mechanisms controlling the
geographical distribution of the greenhouse effect in the midlatitudes.
Title: VizieR Online Data Catalog: BVRI photometry of 7 BL Lac objects
(Bai+ 1998)
Authors: Bai, J. M.; Xie, G. Z.; Li, K. H.; Zhang, X.; Liu, W. W.
Bibcode: 1998yCat..41320083B
Altcode:
Seven BL Lac objects have been photometrically observed in an effort
to study the difference of optical intraday variability between the
radio-selected BL Lac objects (RBLs) and X-ray-selected BL Lac objects
(XBLs). The objects we observed are selected arbitrarily. They are
four RBLs, PKS 0735+178, PKS 0754+101, OJ 287 and BL Lac, and three
XBLs, H 0323+022, H 0548-322 and H 2154-304. During the observation
all of them exhibited microvariation, and H 0323+022 and H 0548-322
sometimes showed brightness oscillation. PKS 0735+178 and BL Lac were
in their faint states and not very active. It seems that RBLs do not
show microvariability more frequently than XBLs. (1 data file).
Title: NASA scatterometer provides global ocean-surface wind fields
with more structures than numerical weather prediction
Authors: Liu, W. Timothy; Tang, Wenqing; Polito, Paulo S.
Bibcode: 1998GeoRL..25..761L
Altcode:
The major differences between monthly-mean ocean-surface wind fields
derived from the observations of the National Aeronautics and Space
Administration (NASA) Scatterometer (NSCAT) and produced by the
operational numerical weather prediction (NWP) model of the European
Center for Medium-Range Weather Forecasts are found in coastal and
equatorial regions, where the sharp changes are smoothed over in NWP
products; these wind differences are explained to be the result of the
superior spatial resolution of NSCAT winds. Objective interpolation of
NSCAT data alleviates errors caused by the uneven satellite sampling
and retains greater energy content of NSCAT winds at high wavenumbers.
Title: Centrifugally driven instability of a rotationally dominated
magnetodisc
Authors: Liu, W. W.
Bibcode: 1998JGR...103.4707L
Altcode:
The dynamics of a rotationally dominated magnetodisc is considered
on the basis of linearized MHD. The treatment is prompted by the
concern that the dominant theoretical view on this subject is based
on the reduced framework of interchange motion, in which changes in
magnetic field are suppressed. A realistic perturbation of a magnetodisc
generally does not satisfy this constraint, and the changing magnetic
field is expected to stabilize any small-amplitude perturbation. We
reexamine the problem in an idealized slab magnetodisc geometry but
with dynamical terms fully installed in the MHD equations. We find that
the traditional interchange instability, essentially a centrifugal
buoyancy regulated by the ionosphere, is not a proper solution for
a thin magnetodisc. For short-wavelength modes the actual situation
of instability comes to resemble what is known in the literature as
magnetic buoyancy, i.e., a centrifugally driven motion moderated by
the strong local magnetic field. Physically, the instability results
as the rotational effects couple the Alfvén and slow modes; density
perturbations formed by the latter are in turn driven radially
by centrifugal buoyancy. The instability is manifest even for a
perfectly uniform density distribution and for the characteristic
parameters near the Io torus, dominates over the contribution from a
radial density gradient. The theory of centrifugally driven radial
diffusion is considered with this instability as the mechanism of
eddy formation. This consideration gives a mass transport rate of
~103kg/s and a density profile n~L-4 near the Io
torus, both in good agreement with observations. Further computational
works need to be carried out to compare our model with more detailed
in situ observations.
Title: Precipitation of hot protons from a stretched near-earth
current sheet
Authors: Liu, W. W.; Rostoker, G.; Samson, J. C.
Bibcode: 1998mrat.conf..165L
Altcode:
Recent observational evidences indicate that the near-Earth tail current
sheet at approximately ten earth radii often experiences substantial
and sudden changes which some researchers consider to be related to
the substorm expansive phase onset. Observations of the ionosphere
have revealed that auroral substorm activity is often preceded by
an enhancement of precipitation of >20 keV protons causing Hβ
emissions. Protons in this energy range are most likely to be found
in the near-Earth plasma sheet, giving support to the interpretation
of a near-Earth source of substorm onset. However, the reason why
proton precipitation intensifies during the auroral substorm has not
yet been clarified. We propose that a possible explanation of this
observation lies in the nonadiabatic dynamics of energetic protons in
the stretched near-Earth current sheet formed in the late growth phase
of the substorm. While pitch-angle scattering associated with such
nonadiabatic dynamics has been considered before, there have been few
studies which determine quantitatively how this process might contribute
to proton precipitation. We have carried out numerical integrations
of proton orbits in a magnetic field consisting of the Earth's main
field and that due to a Harris current sheet. We find that, in the
regime of highly nonadiabatic dynamics, the proton precipitation rate
can exceed the already strong limit of isotropically filled loss-cone
precipitation by an order of magnitude. This finding both contributes
to our understanding of nonadiabatic effects on precipitation and fits
nicely into the overall scheme of near-Earth onset theory.
Title: Atomic and molecular supernovae
Authors: Liu, W.
Bibcode: 1998sese.conf..649L
Altcode:
No abstract at ADS
Title: Atomic and Molecular Physics and Data Activities for
Astrophysics at Oak Ridge National Laboratory
Authors: Jeffery, D. J.; Krstic, P. S.; Liu, W.; Schultz, D. R.;
Stancil, P. C.
Bibcode: 1998lss..work..101J
Altcode:
No abstract at ADS
Title: Supernova Chemistry
Authors: Liu, W.
Bibcode: 1998ISAA....4..415L
Altcode: 1998masg.conf..415L
No abstract at ADS
Title: Supernova 1997dc in NGC 7678
Authors: Li, W. -D.; Liu, W.; Qiao, Q. -Y.; Esamdin, A.
Bibcode: 1997IAUC.6716....1L
Altcode: 1997IAUC.6716Q...1L; 1997IAUC.6716A...1L
W.-d. Li, Beijing Astronomical Observatory, reports that
a low-resolution spectrogram (20 nm/mm, range 380-830 nm) of SN
1997dc was obtained with the 2.16-m telescope at Xinglong station
by Li, W. Liu, Q.-y. Qiao, and A. Esamdin. The spectrum shows broad
emission and absorption lines typical of a type-Ic supernova at maximum
light. The whole spectrum is very similar to that of SN 1994I at maximum
light (Filippenko et al. 1995, Ap.J. 450, L11). Strong spectral lines
include the Ca II infrared triplet and H and K lines; O I at 774 nm;
Na I D/He I at 580 nm; Si II at 630 nm; and Fe II lines at 445, 490,
and 508 nm. There is no distinct evidence of H Balmer lines.
Title: Disruption of thin current sheets: A two-fluid theory
Authors: Liu, W. William
Bibcode: 1997JGR...10214331L
Altcode:
A growing list of observations and arguments has located the source
region of magnetospheric substorms at the near-Earth plasma sheet within
10RE. A popular descriptive paradigm conceptualizes the
substorm initiation as a sudden disruption of a severely stretched
magnetic field in the active region. The physical mechanism(s)
responsible for the disruption have evoked intense theoretical and
computational interests. In this paper we emphasize the macroscopic
aspect of substorm onsets and propose to tackle the problem as a
two-fluid instability of a plasma significantly polarized by an
intense current. It is found that, for a center-maximized current
distribution, a drift-wave instability with westward phase speed can
grow on a timescale -10s when the current sheet thins to 1500-3000
km. The phase speed, when mapped to the ionosphere, amounts to 3-5
km/s and is directed westward. The longitudinal size (wavelength)
of the fastest growing mode, when similarly mapped, is about 250-500
km. These numbers agree with the morphology of current disruptions
and westward traveling surges.
Title: Eg Cancri: A New Wz Sge Type Dwarf Nova
Authors: Liu, W.; Li, Z. Y.; Hu, J. Y.
Bibcode: 1997Ap&SS.257..183L
Altcode:
We present the optical light curve of EG Cancri during its outburst
in 1996-1997. It displayed some brightness fluctuations in the phase
of decline. Mini-outbursts were detected. Optical spectra obtained
during the decline showed it to be a dwarf nova on account of its broad
absorption lines superimposed on a blue continuum. Optical spectra near
minimum brightness revealed doubled Balmer lines in emission, over
broad absorptions, but no HeII4686. An additional heating presented
in the last stage of decline. CCD time-resolved photometry showed a
possible orbital period 0.0575(26) day. Superhumps was observed during
outburst byMatsumoto(1996). EG Cancri is a short-period CV which has
a large-amplitude outburst(∼ 7 mag), a slow decline from outburst,
and a long interval between outburst. From the above properties,
a classification as a WZ Sge type DN is plausible.
Title: Supernova 1997aa in IC 2102
Authors: Li, W. -D.; Qiu, Y. -L.; Qiaom, Q. -Y.; Hu, J. -Y.; Yuan,
Q. -R.; Liu, W.
Bibcode: 1997IAUC.6572....2L
Altcode: 1997IAUC.6572B...1L; 1997IAUC.6572R...1L
W.-d. Li, Y.-l. Qiu, Q.-y. Qiaom and J.-y. Hu, Beijing Astronomical
Observatory (BAO), on behalf of the BAO supernova survey, report the
discovery of a supernova on CCD images of IC 2102 taken on Mar. 1.5
UT with the BAO 0.60-m reflector. SN 1997aa is located at R.A. =
4h51m53s.6, Decl. = -4 57'36" (equinox 2000.0), which is 25" west
and 29" south of the center of IC 2102. Available unfiltered CCD
magnitudes: Mar. 1.5, about 17.0; 2.5, about 16.7. A low-resolution
spectrum (40 nm/mm, range 350-930 nm) obtained by Q.-r. Yuan (Nanjing
Normal University) and W. Liu and W.-d. Li (BAO) on Mar. 2.5 with the
BAO 2.16-m telescope at Xinglong station shows that this is an type-II
supernova prior to optical maximum. There are weak, yet conspicuous,
H Balmer lines superimposed on a very blue continuum. The expansion
velocity of the photosphere is 15 000 km/s (as derived from the H-alpha
line). H-beta could be seen only marginally.
Title: Physics of the explosive growth phase: Ballooning instability
revisited
Authors: Liu, W. William
Bibcode: 1997JGR...102.4927L
Altcode:
In situ observations have led to the notion of the explosive growth
phase when the cross-tail current sheet inside L~10 suddenly thins in a
time of ~1min. A theoretical explanation of the current intensification
envisages the ballooning instability of magnetospheric plasma. In this
paper, this theoretical notion is reanalyzed mathematically. In contrast
to some previous work, we find that for a high-plasma, the ballooning
instability can be excited easily by an earthward pressure gradient
of any magnitude and for perturbations having parallel wavenumbers
comparable to the field line curvature. The instability is compounded
by its own development, leading ultimately to the extreme condition
of a thin current sheet of a few ion gyroradius thick.
Title: Seasonal and interannual variability of atmospheric convergence
zones in the tropical Pacific observed with ERS-1 scatterometer
Authors: Zheng, Quanan; Yan, Xiao-Hai; Liu, W. Timothy; Tang, Wenqing;
Kurz, Dragan
Bibcode: 1997GeoRL..24..261Z
Altcode:
Monthly images of atmospheric convergence zones in the tropical Pacific
were produced with 1992-1994 ERS-1 scatterometer wind vectors. From the
images, the position, width, and intensity of the convergence zones can
be determined. Latitude-time sections of ocean surface wind divergence
show that the summer position of the ITCZ in the eastern Pacific during
the observed period exceeded the normal position northward by 3°-6°
latitude, and the annual cycle in the western Pacific for 1994 was
quite weak, implying a persistently unusual case.
Title: Application of ERS scatterometer winds to typhoon, monsoon,
rain & EL Niño studies
Authors: Liu, W. T.; Tang, W. Q.
Bibcode: 1997ESASP.414.1585L
Altcode: 1997sse..symp.1585L
No abstract at ADS
Title: Laboratory Evaluations of a CCD System For the Balloon-borne
Solar Telescope
Authors: Song, Q.; Liu, W.; Ji, K.; Cao, W.; Huan, Z.
Bibcode: 1997IAUJD..19E..49S
Altcode:
The CCD camera, DALSA/CA-D7-1024, which is a commercial CCD system,
is selected as the main detector for the BAO's Balloon-borne Solar
Telescope. The principal parameters were tested by the YNAO, CCD-Testing
Laboratory in the early September, 1996. The equipment of the lab and
the method of the evaluations are described in the Poster. Evaluations
show that the overall behavior of the camera is superb among the
non-cooling commercial CCD systems. Nevertheless, there are some flaws
in the image-collecting system which must be solved before launch.
Title: A note on the interchange stability criterion
Authors: Liu, W. William
Bibcode: 1996JGR...10127443L
Altcode:
The correct stability criterion of interchange motions in the
magnetosphere has been a question of some controversy. Many researchers
hold the view first espoused by Gold [1959]. For a low-β plasma in a
dipole magnetic field, Gold argued that the gradient of pVγ,
where p is the plasma pressure, V is the unit flux tube volume, and
γ is the adiabatic polytropic index, determines the interchange
stability. This notion was further developed by Chandrasekhar
[1960]. This common belief was questioned by Cheng [1985], who was
subsequently questioned by Rogers and Sonnerup [1986] and Southwood and
Kivelson [1987] on the issue. Is Gold's criterion the necessary and
sufficient condition for interchange stability? We shall demonstrate
that the answer is ``no'' and provide a more accurate criterion for
the dipole magnetic field. We shall also discuss the interchange
instability in a plasma distribution with a longitudinal gradient.
Title: Effect of Hall conductivity on time-dependent convection
Authors: Liu, W. William
Bibcode: 1996GeoRL..23.2903L
Altcode:
Magnetospheric convection can be seen as a form of interchange motions,
but unlike in an ideal MHD system, is subject to the ionospheric
boundary condition. For general time-dependent interchanges, the Hall
current in the ionosphere generates a field-aligned current independent
of any background gradients. The effect of the Hall conductivity on
time-dependent convection is isolated through a simple box model where
pressure gradient and field line curvature are suppressed. Mathematical
analysis suggests that the Hall conductivity can destabilize interchange
modes with long longitudinal wavelength. The finding comes at the
expense of a high degree of geometrical idealization. More realistic
computations are needed to test the theory.
Title: Photoelectric properties of a voltage-tunable two-color
quantum well infrared photodetector
Authors: Cui, Liqiu; Jiang, De Sheng; Zhang, Yaohui; Wu, Wengang;
Song, Chunying; Liu, Wei; Wang, Ruozhen
Bibcode: 1996SPIE.2894...59C
Altcode:
A new voltage-tunable two-order GaAs/AlGaAs multistacks quantum
well infrared photodetector (QWIP) has been investigated in this
work. The infrared photodetector consists of GaAs/AlAs/AlGaAs double
barrier quantum wells (DBQWs) and GaAs/AlGaAs square quantum wells
(SQWs) with photovoltaic and photoconductive dual-mode operation
in the 3 approximately 5.3 micrometers and 7.5 approximately 12
atmosphere windows. Experimental and theoretical studies have been
conducted on the device physics of the intersubband transitions based
on photoexcitation from ground state to different upper subbands
including quasibound subband in DBQWs to virtual energy levels within
the continuum in SQWs. These allow a better understanding of the
optical and transport behaviors of the QWIP. The unique performance
and very simple voltage-tunable switching behavior of the two-color
GaAs/AlGaAs QWIP are expected to be quite competitive with HgCdTe
and InSb infrared photodetectors for large area staring array imaging
and two- color or multi-color detecting applications where material
uniformity and simple device technology are important.
Title: Optically coupled quantum well infrared detectors
Authors: Wu, Wengang; Cui, Liqiu; Jiang, De Sheng; Liu, Wei; Song,
Chunying
Bibcode: 1996SPIE.2894...48W
Altcode:
No abstract at ADS
Title: Low Energy Cosmic Ray Electrons and Diffuse Warm Ionized Medium
Authors: Liu, W.; Dalgarno, A.
Bibcode: 1996AAS...188.4306L
Altcode: 1996BAAS...28..889L
We propose that low energy cosmic ray electrons can maintain the
diffuse warm ionized medium (DWIM), the principal component of the
interstellar medium at high Galactic latitudes. We present a model
of propagation of these electrons in the vertical direction of the
Galactic disk and halo. These electrons lose energy by ionizing and
exciting H, He, and He(+) , and as heat in the Coulomb scattering
by the ambient thermal electrons as well as in the scattering by
hydromagnetic waves. The resulting ionization and thermal structure
is in good agreement with that of the interstellar medium indicated by
pulsar dispersion measures and by observations of diffuse optical and 21
cm emission and ultraviolet absorption. The gas is ionized and heated
mainly by the low energy secondary electrons produced as the energetic
electrons ionize the gas. Effects of the hydromagnetic waves on the
ionization structure are small, especially for clumpy medium. It is
predicted that helium is doubly ionized in the DWIM, consistent with
the recent negative search for the He I recombination line at 5876
Angstroms in the DWIM. The gas is cooled by electron-impact-induced
emission of abundant atoms and ions. At small distances from the
Galactic midplane, it is mainly by the forbidden line emission of S(+)
and by the fine structure line emission of C(+) and Si(+) , and at
large distances it is dominated by the two photon continuum emission
of neutral hydrogen and by the forbidden line emission of C(+) , N(+) ,
and O(+) . The temperature of the DWIM is determined to be about 10(4)
K, in agreement with observations. There appears to be a progression
toward reducing clumpiness from the Galactic disk to the halo.
Title: Some new perspectives on quasi-static convection formalism
Authors: Liu, W. William
Bibcode: 1996JGR...101.7891L
Altcode:
Magnetospheric convection occurs in response to a combination of
factors. It is driven by the solar wind-magnetosphere interaction,
causes Joule heating in the ionosphere, and energizes particles as
they convect earthward. While the equation governing magnetospheric
convection under the quasi-static condition is well known, there
is a lack of a formal proof that the energy processes named above
are properly balanced in the convection formalism. In particular,
the question has not been answered concerning the conservation of
energy in a steady state convection. In this paper, I prove that
energy conservation holds for steady state convection of an isotropic
plasma. The consideration of energetics also sheds light on the nature
of and relationship between region 1 and region 2 currents. It is
further proven that the quasistatic convection formalism is conformal
invariant, a property which can be exploited to develop more efficient
algorithms for modeling magnetospheric convection. Several examples
are presented to illustrate the conformal transformation method.
Title: Application of spaceborne scatterometer to study typhoon,
tropical hydrologic balance, and EL Nino
Authors: Liu, W. T.
Bibcode: 1995SPIE.2583..228L
Altcode:
The high spatial resolution and global coverage of a spaceborne
microwave scatterometer make it a powerful instrument to study
phenomena ranging from typhoons to El Nino Southern Oscillations
which have regional and short term economic and ecological impacts
as well as effects on long term and global climate changes. In this
report, the application of scatterometer data, by itself, to study
the intensity and the evolution of a typhoon is demonstrated. The
potential of combining wind vector and precipitable water derived
from two spaceborne sensors to study the hydrologic balance in the
tropics is discussed. The role of westerly wind bursts as a precursor
of anomalous warming in the equatorial Pacific is investigated with
coincident data from microwave scatterometer, altimeter, and radiometer.
Title: Energetic ring current particles generated by recurring
substorm cycles
Authors: Liu, W. W.; Rostoker, G.
Bibcode: 1995JGR...10021897L
Altcode:
It is now generally accepted that substorm expansive phase activity
involves a release of magnetotail energy, part of which is available
for the acceleration of highly energetic particles (E>100 keV) that
play a role in ring current and radiation belt formation. However, the
physical process whereby this acceleration takes place is not yet fully
understood. In this paper we consider the physics of the acceleration
process based on the tenet that acceleration of particles to E>100
keV occurs as a cumulative process involving a sequence of substorm
expansive phases. In our view, nonadiabatic particle dynamics plays
a key role in the energization process. We present both a qualitative
description and quantitative treatment which starts with a consideration
of a single particle and is then extended to track the evolution of the
particle distribution function over several substorm expansive phase
cycles. We stress two salient features of the evolution of particle
distribution function, namely the rapid formation of a non-Maxwellian
high-energy tail and the saturation of this tail distribution toward
a kappa distribution in the asymptotic limit.
Title: The Ultraviolet Spectrum of the Jovian Dayglow
Authors: Liu, W.; Dalgarno, A.
Bibcode: 1995DPS....27.3013L
Altcode: 1995BAAS...27R1141L
No abstract at ADS
Title: The Ultraviolet Spectrum of the Jovian Dayglow
Authors: Liu, W.; Dalgarno, A.
Bibcode: 1995AAS...186.3303L
Altcode: 1995BAAS...27..857L
The ultraviolet spectra of the molecules H2 and HD by
solar fluorescence and photoelectron excitation are calculated and
compared with the Jovian equatorial dayglow spectrum obtained by
the Hopkins Ultraviolet Telescope at 3 Angstroms resolution near the
maximicrons of solar cycle 22. The Jovian dayglow is accounted for
in both the brightness and the spectral shape by solar fluorescence
and photoelectron excitation, and no additional energy source is
required. It is characterized by an H2 rotational-vibrational
temperature of 540 K and an H2 column density of 7 times
10(19) cm(-2) . The dayglow spectrum is in agreement with the presence
of cascade contribution to the Lyman band emission from the high-lying
E,F(1) Sigma_ {g}(+) states. The incorrectly perceived absence of
appreciable cascade effects from comparison of the dayglow spectrum
with the room-temperature laboratory spectrum of H2 is
caused by the fact that the spectrum of H2 is sensitive
to the temperature and the Jovian atmosphere is hotter. The observed
weakness of the dayglow emission at short wavelengths is mainly caused
by self-absorption by H2. The dayglow spectrum suggests
minimal absorption by hydrocarbon on Jupiter. Wavelength coincidences
of solar emission lines and absorption lines of H2 and HD
occur, resulting in strong fluorescence of H2 and HD. The
strong coincidence of the solar Lyman-beta line at 1025.72 Angstroms
and the P(1) line of the (6,0) Lyman band of H2 at 1025.93
Angstroms together with other line coincidences produce unique line
spectra which are identified in the dayglow spectrum. The fluorescence
due to absorption of the solar O VI line at 1031.91 Angstroms by
the vibrationally excited H2 via the Q(3) line of the
(1,1) Werner band at 1031.86 Angstroms is a sensitive measure of the
atmospheric temperature. Despite strong coincidence of the solar O VI
line at 1031.91 Angstroms and the R(0) line of the (6,0) Lyman band of
HD at 1031.91 Angstroms, the molecule HD remains to be detected due to
the weakness of the HD signature and the dominance of the H2
emission.
Title: Theory and observation of auroral substorms: A
magnetohydrodynamic approach
Authors: Liu, W. W.; Xu, B. -L.; Samson, J. C.; Rostoker, G.
Bibcode: 1995JGR...100...79L
Altcode:
A theory of auroral substorm dynamics is constructed on the basis
of MHD wave processes in the ionosphere-magnetosphere system. The
basic view is that the substorm commences in the nightside near-Earth
magnetosphere through a collapse of plasma equilibrium. The collapse
releases a significant amount of free energy embedded initially in
a collection of compressional waves. It is suggested that substorm
dynamics after the collapse are determined by the evolution of these
waves. We first investigate the quantitative ramifications of the
waves in a two-dimensional box in the GSM yz cross section of the
magnetotail. The model is constructed to allow the study of radiation
of substorm wave energy into the solar wind and also encompasses the
essential elements of resonant interaction in the plasma sheet boundary
layer. The natural boundary condition leading to radiative loss is
introduced. It is found that wave radiation into the solar wind can
relax the magnetospheric system in less than a hour. The resonant
Alfvén models driven by the normal compressional modes in the box
are studied through the construction of proper dispersion equation. By
studying the field-aligned current generated by resonances, we establish
the auroral pattern expected to result from the coupling. Following
the theoretical study, we examine an auroral substorm observed by
the CANOPUS photometer array on February 20, 1990. It is found that,
among the testable theoretical predictions, there exists a general
agreement with the observations. We did find, however, that electron-
and proton-induced aurora oscillate essentially in phase, thus implying
a more complicated precipitation process.
Title: The Oxygen Temperature of SN 1987A
Authors: Liu, W.; Dalgarno, A.
Bibcode: 1994AAS...185.3304L
Altcode: 1994BAAS...26.1362L
The temperature of the oxygen core of SN 1987A is determined
by analyzing the processes that heat and cool the gas and the
processes that form and destroy carbon monoxide. The heating and
ionization rates are calculated by examining the processes by which
the energetic electrons created following the radioactive decay of
(56) Co lose energy in a mixed gas of atomic oxygen and carbon and
carbon monoxide. The effects of non-uniform energy distribution in the
supernova ejecta at early times due to the large optical depths of
the gamma -rays of (56) Co are accounted for by reducing the energy
input rate in the oxygen core according to the observed emission of
CO. There is a large inhomogeneity in the thermal structure of the
oxygen core because different cooling mechanisms are operative in
different regions with different chemical compositions. The oxygen
core contains a cold CO-emitting region which is effectively cooled
by the vibrational emission of CO but heated by the O and C atoms
as the result of nonthermal excitations by the energetic electrons,
and a hot O-emitting region which contains neither CO nor SiO and
is cooled by the metastable transitions of O. The temperature of the
CO-emitting region is roughly a constant of 1800 K in the first year
and drops to 700 K at 800 days, consistent with the observed spectral
shapes of CO. The temperature of the O-emitting region is relatively
high and ranges from 4800 K at 100 days to 2200 K at 800 days, in
agreement with that inferred from the observations of the [OI]lambda
lambda 6300,6364 emission doublet. The masses of CO predicted by the
thermal-chemical model and derived from the observations agree well and
permit no microscopic mixing of helium into the oxygen core. This work
was supported by NSF grant AST-89-21939 and by NASA grant NAGW-1561.
Title: Supernova 1994Y in NGC 5371
Authors: Clocchiatti, A.; Garcia-Lopez, R.; Barker, E. S.; Wren,
W.; Wheeler, J. C.; Jiang, X. J.; Liu, W.; Hu, J. Y.; Boattini, A.;
Tombelli, M.
Bibcode: 1994IAUC.6065....1C
Altcode:
A. Clocchiatti, R. Garcia-Lopez, E. S. Barker, W. Wren,
and J. C. Wheeler, University of Texas, report: "A fully-reduced
spectrogram (range 380-640 nm, resolution 1.3 nm) of SN 1994Y, obtained
on Aug. 27.15 UT at the 2.7-m telescope of McDonald Observatory, shows
the lines of the Balmer series and Na D in emission superimposed on
a blue continuum. In the low-S/N spectrum, the emission lines do not
show a P-Cyg absorption counterpart with the possible exception of
Na D, but consist of a narrow core and a broad base, both centered at
the velocity of NGC 5371. The FWHM of the broader components implies
an expansion velocity of about 2600 km/s, while the FWZI implies a
maximum expansion of about 7000 km/s. SN 1994Y apparently belongs to the
'Seyfert 1' subclass of type-II supernovae (Filippenko 1989, A.J. 97,
726), called type-IIn by Schlegel (1990, MNRAS 244, 269). Continuous
monitoring of this event is strongly recommended." X. J. Jiang,
W. Liu, and J. Y. Hu, Beijing Observatory, communicate: "A spectrogram
(range 450-700 nm, resolution 0.53 nm/pixel) of SN 1994Y has been
obtained using the 2.2-m telescope at Beijing Observatory, Xinglong,
on Aug. 25. The spectrum shows strong Balmer emission, confirming it
to be a type-II supernova. The wavelengths of the H-alpha and H-beta
emission lines coincide with the radial velocity of the host galaxy
NGC 5371 (2550 km/s). The emission lines are narrow compared with
normal type-II supernovae; the FWHM of H-alpha and H-beta are about
1200 km/s. Another dominating wide emission feature peaks at 592.9
nm, possibly due to He I (587.6 nm) and Na I (589.3 nm). A feature at
673.0 nm is from He I (667.8 nm). The spectrum is similar to that of
SN 1994W, but without narrow absorption features at the blue side of
the Balmer emission lines." A. Boattini and M. Tombelli, Florence,
provide an accurate position for this object: R.A. = 13h53m30s.57,
Decl. = +40o42'32".8 (equinox 1950.0).
Title: An explicit bounce average calculation of adiabatic particle
drifts
Authors: Liu, W. William
Bibcode: 1994JGR....99.2383L
Altcode:
The explicit method of bounce averaging the adiabatic drift of a
charged particle is generalized, and the relationship of this method
to earlier results derived from more implicitly based approaches is
briefly discussed.
Title: On the origin of auroral fingers
Authors: Liu, W. W.; Rostoker, G.
Bibcode: 1993JGR....9817401L
Altcode:
During the development of large-scale magnetospheric substorm expansive
phase activity, the auroral oval may become very wide. During such
episodes, clear discrete arc structures appear from time to time in
the equatorward portion of the evening sector oval in a region of space
normally thought to feature structureless diffuse auroras. On occasion,
these discrete auroral forms acquire a north-south orientation and
remain as identifiable forms for up to several minutes. Most auroral
theories attempt to describe the origin of the normally east-west
aligned features. In this paper we propose that the particles
responsible for north-south aligned arc structures originate as plasma
blobs injected into the central plasma sheet (CPS) from the adjacent
low-latitude boundary layer, as a result of enhanced wave activity
at the interface between the two regions during active times. We show
that the characteristics geometric forms of the CPS auroral structures
follow from tracking the drift paths of the particles in the injected
plasma blob as they convect earthward, heating adiabatically in the
process. We also outline outstanding issues pertaining to the proposal
as motivation for a continued study.
Title: Field-aligned flow in a centrifugally confined magnetodisc
Authors: Liu, W. W.
Bibcode: 1993JGR....9815365L
Altcode:
Significant magnetic field-aligned flows were detected by Voyager 1
during its encounter with Jupiter. We try to understand the origin and
dynamics of the field-aligned flow in the presence of a slow corotating
convection. We find that the field-aligned flow is a necessary part
in the preservation of the magnetodisc geometry and mass conservation
in the disc. We further investigate the dynamical origin of the flow
on the basis of a phenomenological equation, which indicates that the
field-aligned dynamics is likely to be chaotic.
Title: Observations of optical aurora modulated by resonant Alfvén
waves
Authors: Xu, B. -L.; Samson, J. C.; Liu, W. W.; Creutzberg, F.;
Hughes, T. J.
Bibcode: 1993JGR....9811531X
Altcode:
Optical aurora and magnetometer data from the Canadian Auroral Network
for the OPEN Unified Study (CANOPUS) array in Canada are used in the
study of the modulation of optical aurora in the 5577-Å and 4709-Å
emission lines, by resonant shear Alfvén waves, in the frequency
range of 1-4 mHz. A total of four events, carefully chosen to represent
different characteristics of timing and location, are analyzed. Typical
of these events, the power spectra featured discrete spectral peaks
usually near 1.3, 1.9, and 3.1 mHz. Furthermore, latitudinal phase
shifts of about 180° were typically observed across the latitudinal
maximum of a given frequency peak. These observations point irrevocably
to the field line resonance as a major factor in the modulation of
precipitation and possibly in the acceleration of electrons in forming
auroral arcs. Our study demonstrates that the modulation phenomena
are common features occurring in the auroral oval, observable in an
extensive latitude range, from 66° to 73° invariant latitude. Of the
events, one shows the modulation process accompanied by an inverted V
structure of electron precipitation in the evening sector near 72°. Two
events are observed in the equatorward region of the auroral oval just
before substorms onset, and maybe related to the energetic electron arcs
which are the precursor of substorm intensification. The fourth event is
seen in the morning sector at an equatorward latitude and occurs in the
recovery phase of a substorm. The diversity of these modulation events
allows us to further infer that resonant Alfvén waves play a direct
role in controlling the luminosity variation of the optical aurora.
Title: Ambipolar limit of electron precipitation
Authors: Liu, W. W.
Bibcode: 1993GeoRL..20..343L
Altcode:
In a magnetospheric condition, particles are often precipitated into
the ionosphere of the host planet. When a flux tube is not interacting
with those neighboring it, charge lost through its open ends to the
ionosphere must vanish to ensure charge quasi-neutrality in the flux
tube as a whole. To achieve this, a parallel electric field must
be present to impede the faster electron motion. Electric fields so
arisen are usually referred to as ambipolar fields. In this paper,
we discuss a number of specific aspects of the ambipolar coupling,
including the value of the ambipolar potential drop, the effects of
loss cone depletion, the outflow of ionospheric electrons extracted
by the ambipolar field, and point-to-point distribution of the
potential. Although the noninteractive assumption for the flux tube
restricts the validity of the treatment to cases where field-aligned
currents are very weak, the construction of the model sheds new light
on an important problem in magnetospheric physics.
Title: Reaction rates for 8Li(p, α) and 8Li(p,
n, α) and their effect on primordial nucleosynthesis
Authors: Becchetti, F. D.; Brown, J. A.; Liu, W. Z.; Jänecke, J. W.;
Roberts, D. A.; Kolata, J. J.; Smith, R. J.; Lamkin, K.; Morsad, A.;
Warner, R. E.; Boyd, R. N.; Kalen, J. D.
Bibcode: 1992NuPhA.550..507B
Altcode:
Differential-cross-section data are presented for the 8Li(p,
α)5He reaction at 1.5 MeV center-of-mass energy, measured
with a (radioactive) 8Li beam. The data are used to calculate
one of the terms of the thermonuclear reaction rate for destruction of
8Li. In addition, other data are used to estimate the total
reaction rate for p+8Li, which is found to be comparable
to that used in previous calculations of abundances from primordial
nucleosynthesis.
Title: Rotating magnetic anomalies as a possible accelerator of
charged particles
Authors: Liu, W. W.
Bibcode: 1992JGR....97.8145L
Altcode:
We show, through the formulation of a simple theoretical model,
that there exists a possibility that a significant number of a
energetic ions in the Jovian magnetosphere, and presumably in other
astrophysical environments beyond our direct access, owe their origin to
a large-scale longitudinal magnetic anomaly corotating with the central
body anchoring the magnetosphere, if the invoked magnetic anomaly has
a typical boundary thickness comparable to an ion gyroradius, which
for a preheated 10-kev heavy ion in the outer Jovian magnetosphere
may be of the order of a few Jovian radii. The energy source for
the acceleration is a torque from the central planet arising from a
differential rotation between the ionosphere and the magnetosphere. The
premise and outstanding issues pertaining to the present proposal are
further discussed as motivating points for future studies.
Title: Molecules in the Ejecta of Supernova 1987A
Authors: Dalgarno, A.; Liu, W.; Lepp, S.
Bibcode: 1992csim.conf..221D
Altcode:
No abstract at ADS
Title: Radioactive Ion Beam Rates from Inverse Kinematics Reaction
Yields at 0DEGREE
Authors: Tribble, R. E.; Liu, W.; Lui, Y. W.
Bibcode: 1992unia.work..245T
Altcode:
No abstract at ADS
Title: Molecules in Supernova 1987A
Authors: Liu, W.; Dalgarno, A.
Bibcode: 1991BAAS...23.1352L
Altcode:
No abstract at ADS
Title: Chaos driven by kinetic Alfven waves
Authors: Liu, W. W.
Bibcode: 1991GeoRL..18.1611L
Altcode:
We present a simple model describing the effect of a kinetic Alfvén
wave on the motion of a test electron along a closed magnetic field
line. We show that the electron motion can be strongly chaotic for a
wide range of conditions. The chaos exhibits a broad-band power spectrum
in the frequency domain, although only three principal frequencies are
involved in the model. Phase space density of electrons exhibits complex
but physically interesting evolution in response to the KAW. Typical
of a chaotic situation, the scale of the electron distribution in
phase space descends rapidly over the scale hierarchy to give rise
to a growing set of irregularities, which may in turn generate strong
electrostatic turbulences. This chain of events suggests a fundamental
mechanism that couples physical processes of different scales.
Title: Effect of dawn-dusk pressure asymmetry on convection in the
central plasma sheet
Authors: Liu, W. W.; Rostoker, G.
Bibcode: 1991JGR....9611501L
Altcode:
The central plasma sheet (CPS) of the Earth's magnetosphere contains
a thermally differentiated plasma, whose ion temperature exceeds
severalfold its electron temperature. The gradient/curvature drift of
ions and electrons of the CPS plasma tend to separate the two species
in the dawn-dusk direction. Because of the temperature difference, the
dusk CPS, which gains a surplus of hotter ions, is expected to have
a larger plasma pressure than its dawnside counterpart. Preliminary
analysis of ISEE 1 plasma data confirmed the pressence of such a
pressure asymmetry in the CPS during the quiet and the growth-of-driven
conditions. The closure of the electric current created by this pressure
asymmetry usually requires the flow of a field-aligned current, whose
effects of the E×B drift of the CPS plasma are the central focus of
this paper. The dawn-dusk asymmetry in the magnetosphere generally
leads to an azimuthally asymmetric ionospheric convection, with close
resemblance to the streamline structure first identified by Heppner
(1977). The field-aligned current associated with the asymmetry has
a strong effect in shielding the inner magnetosphere, in which the
imposed electric field decreases exponentially for polytropic indices
greater than 1. The asymmetry also affects the location of the inner
edge of the plasma sheet. We present a simplified model in this paper,
using an analytic paradigm to portrary the general properties of the
asymmetry-induced effects. A limited attempt is made to examine how
a departure from the idealized condition would change the solution of
the problem.
Title: MARS: a status report
Authors: Tribble, R. E.; Gagliardi, C. A.; Liu, W.
Bibcode: 1991NIMPB..56..956T
Altcode:
We are building a momentum achromat recoil spectrometer (MARS)
for use with the new K500 superconducting cyclotron at Texas
A&M University. MARS uses a unique optical design utilizing two
dispersive planes to combine a momentum achromat with a recoil mass
spectrometer. This configuration makes MARS applicable to a broad range
of nuclear reaction studies utilizing inverse kinematics. It also leads
to a system that is well matched to the range of secondary particle
energies that will be produced in reactions with K500 beam. MARS
will have a typical mass resolution of δM/M ~ 1/300, with an energy
acceptance of +/- 9% ΔE/E and a geometric solid angle of up to 9
msr. A beam swinger system will allow reaction products in the angular
range 0° to 30° to be studied. MARS will be used to study both the
excited states and decay properties of very proton- and neutron-rich
nuclei. MARS will also be used to provide a reaction mechanism filter
to assist investigations of the dynamics of heavy ion collisions and
to produce secondary radioactive beams for reaction and spectroscopic
studies of particular interest for nuclear astrophysics. We briefly
describe the design of MARS, give a status report on its construction
and an overview of the scientific program planned for it.
Title: Synthetic Observation and Analysis of the Strong Flare
Events 1989AUG
Authors: Liu, W. T.; Huang, Z.; Zheng, R. M.
Bibcode: 1990PYunO...4..227L
Altcode:
No abstract at ADS
Title: Effect of plasma mantle injection on the dynamics of the
distant magnetotail
Authors: Liu, W. W.; Hill, T. W.
Bibcode: 1990JGR....9518849L
Altcode:
We investigate the role of the plasma mantle in the dynamics of the
Earth's distant magnetotail. The plasma mantle can exert a substantial
influence on the current-sheet force equilibrium by transporting both
momentum and mass from the dayside magnetopause to the tail current
sheet. Such influences are particularly strong when the interplanetary
magnetic field contains a significant southward component for a
prolonged period. We find that a number of processes characterizing a
substorm growth phase can be attributed, at least in part, to the plasma
mantle. Among these processes are the thinning of the plasma sheet,
storage of magnetic energy in the tail, and formation of plasmoids. The
rates of these processes are found to increase nonlinearly with the
momentum density of the mantle plasma. The present model applies only
to the distant magnetotail (x<~-30RE) because of various
approximations that we make to allow an analytical treatment of the
governing equations.
Title: Ionospheric outflow of plasma and compression relationship
in the plasma sheet
Authors: Liu, W. W.; Rostoker, G.
Bibcode: 1990GeoRL..17.1849L
Altcode:
We are concerned in this article with the curious finding of Huang
et al. [1989] which suggests a polytropic index of plasma compression
of about 0.7 in the quiet time central plasma sheet. We show that the
reduction of this index from its adiabatic value (=5/3) can be achieved
through an ionospheric outflow of plasma which lowers the plasma
temperature by virtue of energy partition. The observed correlation
between the plasma temperature and density is best reproduced by
an ionospheric source of ∼5×1025 ions/s, consistent
with independent experinental estimates and smaller than the average
solar wind source by a factor of two or more. Despite the change in
the polytropic relationship, we find that the global energy equation
PV5/3=constant (V=volume of a unit flux tube) still holds
approximately (in the absence of other energy-loss mechanisms).
Title: Radial diffusion of iogenic plasma in a centrifugally-driven
turbulence
Authors: Liu, W. W.
Bibcode: 1990P&SS...38..995L
Altcode:
A quantitative model of plasma diffusion from the Io torus, driven
by the centrifugal force of Jupiter's rotation, is developed. It is
argued that the unstable mode of perturbation, which would lead to a
system of deterministic motion of plasma, should be dominated by a more
turbulent mode of motion in order to effect a longer trapping time of
the Iogenic plasma as implied by the observations. The energy of the
turbulent motion is derived internally from the centrifugal potential
of the planetary rotation. The length scale of the turbulence cells is
determined by the interaction between the magnetospheric plasma and the
dissipative ionosphere, and found to be of order 0.1 RJ for
the Jovian magnetosphere. Since the cells are smaller than the dimension
of the system, the transport of the plasma can be studied as a problem
of eddy diffusion, governed by the Fokker-Planck equation. A specific
model is established based on the above considerations. Investigation of
this model shows that the nominal L-5 dependence of plasma
density can be reproduced in an appropriate limit. Other details
of the density distribution (e.g. the density ramp located at L =
7.5) can be attributed to the spatial variation of the ionospheric
Pedersen conductance. The density ramp implies a conductivity peak
in its magnetically conjugate ionosphere. The conductivity profile
consistent with the observed density distribution is solved. The inward
expansion of the Io torus effected by fringing electric field of the
outer torus is also briefly discussed.
Title: Convective transport of plasma in the inner Jovian
magnetosphere
Authors: Liu, W. W.; Hill, T. W.
Bibcode: 1990JGR....95.4017L
Altcode:
We investigate the transport of plasma in the inner Jovian magnetosphere
according to the corotating model of Hill et al. [1981], emphasizing
mathematical aspects of the theory. We employ a simplified but
physically plausible boundary condition at the inner Io torus,
representing a 5% density enhancement of S+ ions in an
``active sector'' that is fixed in Jovian (systems III) longitude. We
first investigate the convection electric field pattern resulting from
this longitudinal mass anomaly alone, and then generalize the theory
to include the effects of Coriolis force and plasma acceleration. We
find that even a small (~5%) longitudinal asymmetry of the inner torus
produces a convection system capable of removing torus plasma from
the magnetosphere on a time scale of order one month.
Title: Some Special Phenomena on Ionograms at Wuchang China
Authors: Liu, W.
Bibcode: 1990PYunO.199....1L
Altcode:
No abstract at ADS
Title: Corotation lag and magnetospheric energetics of Jupiter
Authors: Liu, W. W.
Bibcode: 1989P&SS...37.1393L
Altcode:
Jupiter exerts an enormous torque upon its magnetospheric plasma to
force the latter to corotate. However, the corotation is generally
not perfect due to internal production of plasma and/or its outward
transport. In a steady state in which the magnetosphere rotationally
lags behind the ionosphere, a Birkeland current system is formed to
couple the two regions. This current is found to play a dual role in
the magnetospheric energetics of Jupiter. On the one hand, it transfers
energy from the planetary rotation to the magnetosphere; on the other
hand, it returns part of this transferred energy back to the ionosphere
to drive the ionospheric current required for the maintenance of the
current system. Owing to this partition of energy, the magnetosphere
gets only about one third of the energy extracted from the planetary
rotation, with the rest going to the ionosphere as Joule heating. The
total energy delivery from the planetary rotation amounts to over 10
14 W, considerably larger than the solar wind contribution.
Title: A Radioactive Beam Facility Using a Large Superconducting
Solenoid
Authors: Becchetti, F. D.; Liu, W. Z.; Roberts, D. A.; Jänecke,
J. W.; Kolata, J. J.; Morsad, A.; Kong, X. J.; Warner, R. E.
Bibcode: 1989hipn.conf..277B
Altcode:
No abstract at ADS
Title: The Supporting Electronics System for New Hydrogen Maser H7
Authors: Lin, C. F.; Liu, W. J.; Wu, Y.
Bibcode: 1989AnShO..10..229L
Altcode:
No abstract at ADS
Title: Paleomagnetism of sedimentary rocks from and near the DOSECC
Cajon Pass Well, southern California
Authors: Liu, Wei; Kirschvink, Joseph L.; Weldon, Ray J.
Bibcode: 1988GeoRL..15.1065L
Altcode:
As part of a larger study of the geologic and tectonic history of the
Cajon Pass area, we conducted paleomagnetic studies on sedimentary
rocks recovered from the Cajon Pass DOSECC well, and adjacent surface
exposures from unit 5 of the late Early to Middle Miocene Cajon Fm. A
comparison of the magnetic polarity stratigraphy of the surface and
the core sections suggests that they do not match well, which may imply
that the rocks at depth have been deformed so that simple extrapolation
from the surficial geology to depth is not possible. Although tectonic
rotation cannot be inferred from the samples from the core, a clockwise
rotation of 30 ± 8.9° was found in unit 5 of the Cajon Fm near the
well site at the surface, which is consistent with the results from the
same unit 2 km to the west. In contrast, the early Late to late Early
Miocene Crowder Fm across the Squaw Peak fault and the youngest unit,
unit 6, of the Cajon Fm at the northwestern end of the formation have
not been rotated. The rotation of unit 5 near the Squaw Peak fault is
thus probably local, caused by drag associated with the fault.
Title: Quark-number susceptibility of high-temperature QCD
Authors: Gottlieb, Steven; Liu, W.; Toussaint, D.; Renken, R. L.;
Sugar, R. L.
Bibcode: 1987PhRvL..59.2247G
Altcode:
We measure the response of the quark number to an infinitesimal chemical
potential in high-temperature QCD with two light flavors of dynamical
fermions. In the chirally symmetric phase the susceptibilities for quark
number density and for the density of the third component of isospin are
large and equal within statistics, which is consistent with a plasma
of light quarks. In the broken-symmetry phase the susceptibility for
quark number density is small, as expected from quark confinement.
Title: Corotating convection revisited
Authors: Hill, T. W.; Liu, W. W.
Bibcode: 1987GeoRL..14..178H
Altcode:
The corotating convection model invokes a systematic large-scale
pattern of plasma motion through the Jovian magnetosphere, a pattern
fixed in corotating (System III) coordinates and established by an
observed longitudinal asymmetry of the S+ ion distribution
in the inner Io torus. In its various versions published to date,
the corotating convection model would preserve this longitudinal
asymmetry throughout the magnetospheric convection system; the model
is thus in conflict with the high degree of longitudinal symmetry
that is observed to exist in the hot outer Io torus and presumed to
exist also in the magnetosphere outside the torus. We propose to solve
this difficulty by superimposing on the corotating convection system
a strong retrograde flow confined to the torus region, representing
the corotation lag associated with ion production and charge exchange
in the Io torus. The addition of this azimuthal flow in the torus
region renders the plasma density distribution almost symmetric with
respect to longitude in the outer torus and beyond (as required by
direct observation), while retaining a corotating convection pattern
outside the torus (whose existence is supported indirectly by a number
of observations). Serendipitously, the condition of approximate
azimuthal symmetry of the plasma density distribution permits an
analytic solution of the otherwise intractable equations governing
the corotating convection pattern.
Title: Velocity filter effect and dynamics of distant magnetotail
Authors: Liu, W. W.; Hill, T. W.
Bibcode: 1986P&SS...34..197L
Altcode:
The velocity filter effect produces a persistent time variation
of the self-consistent magnetic-field configuration in the Earth's
distant magnetotail. In the presence of a mantle source of plasma,
a steady-state configuration cannot be attained, even if the source
supply is constant in time. The velocity filter effect produces an
evolution of the magnetotail such that the plasma sheet thins throughout
the region accessible to the incoming plasma. This thinning process,
widely observed and theoretically predicted, leads to current-sheet
disruption when the thickness of the plasma sheet shrinks to a critical
value. The whole process lasts 1-2 h, consistent with the observed
duration of a typical substorm growth phase.
Title: Synthetic aperture radar observation of ocean roughness from
rolls in an unstable marine boundary layer
Authors: Thompson, T. W.; Liu, W. T.; Weissman, D. E.
Bibcode: 1983GeoRL..10.1172T
Altcode:
Simultaneous synthetic aperture radar (SAR) and cloud photographic
observations of the Atlantic Ocean off the coast of Florida were made
from a high-altitude aircraft when there was an unstable marine boundary
layer. The synthetic aperture radar images show unusual kilometer-sized
features on the ocean surface which are related to clouds. The ocean
near shore was cloud-free and had no radar features, while from 30
to 330 km offshore there were clouds and prominent kilometer-sized
features in the SAR image. These radar features are most prominent
when the radar was looking upwind, are less prominent when the radar
was looking downwind, and disappear entirely when the radar was
looking crosswind. Since ocean radar echo strengths are believed to
be controlled primarily by ocean waves satisfying the Bragg relation,
these radar features most likely resulted from local enhancements of
short gravity waves with 17- to 34-cm wavelengths, which in turn are
surface expressions of roll convections in a kilometer-thick unstable
marine boundary layer.
Title: An Operational Large-Scale Marine Planetary Boundary Layer
Model.
Authors: Brown, R. A.; Liu, W. Timothy
Bibcode: 1982JApMe..21..261B
Altcode:
An operational planetary boundary layer model (Brown, 1974,1978, 1981)
for determining surface winds and stress from free-stream flow has been
modified for the marine layer by including surface roughness feedback,
variable humidity and interfacial layer effects. The surface winds
determined from synoptic-scale pressure and temperature fields are
compared to surface measurements in GOASEX and JASIN.
Title: Precise determination of the difference between path delays
in clock synchronization using TV signals.
Authors: Liu, W. -Z.; Luo, D. -C.
Bibcode: 1981ssa..confQ.366L
Altcode:
No abstract at ADS
Title: Precise Determination of the Difference between Path Delays
in Clock Synchronization Using TV Signal
Authors: Liu, W. Z.; et al.
Bibcode: 1980ssa..confQ.366L
Altcode:
No abstract at ADS
Title: A Frequency Calibrator by Subcarrier of PAL TV System
Authors: Zhang, M. Y.; Lo, D. C.; Liu, W. Z.
Bibcode: 1979PBeiO...4...64Z
Altcode:
No abstract at ADS
Title: An experimental determination of the gravitational constant
at distances around ten meters.
Authors: Yu, H. -T.; Ni, W. -T.; Hu, C. -C.; Liu, F. -H.; Yang,
C. -H.; Liu, W. -N.
Bibcode: 1979ChJPh..16..201Y
Altcode:
No abstract at ADS
Title: Temperature profile in the molecular sublayer near the
interface of a fluid in turbulent motion
Authors: Liu, W. Timothy; Businger, Joost A.
Bibcode: 1975GeoRL...2..403L
Altcode:
The molecular sublayers adjacent to the air-sea interface are assumed
to undergo cyclic growth and destruction in order to explain the
exponential temperature profiles measured by Khundzhua and Andreyev. The
duration of such cycles is taken to be randomly distributed in forced
convection and a constant period is used to determine the temperature
profile in free convection.