explanation blue bibcodes open ADS page with paths to full text
Author name code: tiwari
ADS astronomy entries on 2022-09-14
author:"Tiwari, Sanjiv Kumar" AND (aff:"Lockheed" OR aff:"Udaipur")
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Title: Parallel Plasma Loops and the Energization of the Solar Corona
Authors: Peter, Hardi; Chitta, Lakshmi Pradeep; Chen, Feng; Pontin,
David I.; Winebarger, Amy R.; Golub, Leon; Savage, Sabrina L.;
Rachmeler, Laurel A.; Kobayashi, Ken; Brooks, David H.; Cirtain,
Jonathan W.; De Pontieu, Bart; McKenzie, David E.; Morton, Richard J.;
Testa, Paola; Tiwari, Sanjiv K.; Walsh, Robert W.; Warren, Harry P.
2022ApJ...933..153P Altcode: 2022arXiv220515919P
The outer atmosphere of the Sun is composed of plasma heated to
temperatures well in excess of the visible surface. We investigate
short cool and warm (<1 MK) loops seen in the core of an active
region to address the role of field-line braiding in energizing these
structures. We report observations from the High-resolution Coronal
imager (Hi-C) that have been acquired in a coordinated campaign with
the Interface Region Imaging Spectrograph (IRIS). In the core of the
active region, the 172 Å band of Hi-C and the 1400 Å channel of IRIS
show plasma loops at different temperatures that run in parallel. There
is a small but detectable spatial offset of less than 1″ between
the loops seen in the two bands. Most importantly, we do not see
observational signatures that these loops might be twisted around each
other. Considering the scenario of magnetic braiding, our observations
of parallel loops imply that the stresses put into the magnetic field
have to relax while the braiding is applied: the magnetic field never
reaches a highly braided state on these length scales comparable to
the separation of the loops. This supports recent numerical 3D models
of loop braiding in which the effective dissipation is sufficiently
large that it keeps the magnetic field from getting highly twisted
within a loop.
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Title: Bipolar Ephemeral Active Regions, Magnetic Flux Cancellation,
and Solar Magnetic Explosions
Authors: Moore, Ronald L.; Panesar, Navdeep K.; Sterling, Alphonse C.;
Tiwari, Sanjiv K.
2022ApJ...933...12M Altcode: 2022arXiv220313287M
We examine the cradle-to-grave magnetic evolution of 10 bipolar
ephemeral active regions (BEARs) in solar coronal holes, especially
aspects of the magnetic evolution leading to each of 43 obvious
microflare events. The data are from the Solar Dynamics Observatory: 211
Å coronal EUV images and line-of-sight photospheric magnetograms. We
find evidence that (1) each microflare event is a magnetic explosion
that results in a miniature flare arcade astride the polarity
inversion line (PIL) of the explosive lobe of the BEAR's anemone
magnetic field; (2) relative to the BEAR's emerged flux-rope Ω loop,
the anemone's explosive lobe can be an inside lobe, an outside lobe,
or an inside-and-outside lobe; (3) 5 events are confined explosions,
20 events are mostly confined explosions, and 18 events are blowout
explosions, which are miniatures of the magnetic explosions that
make coronal mass ejections (CMEs); (4) contrary to the expectation
of Moore et al., none of the 18 blowout events explode from inside
the BEAR's Ω loop during the Ω loop's emergence; and (5) before
and during each of the 43 microflare events, there is magnetic flux
cancellation at the PIL of the anemone's explosive lobe. From finding
evident flux cancellation at the underlying PIL before and during all
43 microflare events-together with BEARs evidently being miniatures of
all larger solar bipolar active regions-we expect that in essentially
the same way, flux cancellation in sunspot active regions prepares
and triggers the magnetic explosions for many major flares and CMEs.
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Title: SolO/EUI Observations of Ubiquitous Fine-scale Bright Dots
in an Emerging Flux Region: Comparison with a Bifrost MHD Simulation
Authors: Tiwari, Sanjiv K.; Hansteen, Viggo H.; De Pontieu, Bart;
Panesar, Navdeep K.; Berghmans, David
2022ApJ...929..103T Altcode: 2022arXiv220306161T
We report on the presence of numerous tiny bright dots in and around
an emerging flux region (an X-ray/coronal bright point) observed with
SolO's EUI/HRI<SUB>EUV</SUB> in 174 Å. These dots are roundish and have
a diameter of 675 ± 300 km, a lifetime of 50 ± 35 s, and an intensity
enhancement of 30% ± 10% above their immediate surroundings. About
half of the dots remain isolated during their evolution and move
randomly and slowly (<10 km s<SUP>-1</SUP>). The other half show
extensions, appearing as a small loop or surge/jet, with intensity
propagations below 30 km s<SUP>-1</SUP>. Many of the bigger and brighter
HRI<SUB>EUV</SUB> dots are discernible in the SDO/AIA 171 Å channel,
have significant emissivity in the temperature range of 1-2 MK, and
are often located at polarity inversion lines observed in SDO/HMI LOS
magnetograms. Although not as pervasive as in observations, a Bifrost
MHD simulation of an emerging flux region does show dots in synthetic
Fe IX/X images. These dots in the simulation show distinct Doppler
signatures-blueshifts and redshifts coexist, or a redshift of the
order of 10 km s<SUP>-1</SUP> is followed by a blueshift of similar
or higher magnitude. The synthetic images of O V/VI and Si IV lines,
which represent transition region radiation, also show the dots that
are observed in Fe IX/X images, often expanded in size, or extended
as a loop, and always with stronger Doppler velocities (up to 100
km s<SUP>-1</SUP>) than that in Fe IX/X lines. Our observation and
simulation results, together with the field geometry of dots in the
simulation, suggest that most dots in emerging flux regions form in the
lower solar atmosphere (at ≍ 1 Mm) by magnetic reconnection between
emerging and preexisting/emerged magnetic field. Some dots might be
manifestations of magnetoacoustic shocks through the line formation
region of Fe IX/X emission.
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Title: Birth and Evolution of a Jet-Base-Topology Solar Magnetic
Field with Four Consecutive Major Flare Explosions
Authors: Doran, Ilana; Panesar, Navdeep K.; Tiwari, Sanjiv; Moore,
Ron; Bobra, Monica; Sterling, Alphonse
2021AGUFMSH35B2039D Altcode:
During 2011 September 6-8, NOAA solar active region (AR) 11283
produced four consecutive major coronal mass ejections (CMEs) each
with a co-produced major flare (GOES class M5.3, X2.1, X1.8, and
M6.7). We examined the ARs magnetic field evolution leading to and
following each of these major solar magnetic explosions. We follow
flux emergence, flux cancellation and magnetic shear buildup leading
to each explosion, and look for sudden flux changes and shear changes
wrought by each explosion. We use AIA 193 A images and line-of-sight
HMI vector magnetograms from Solar Dynamics Observatory (SDO), and
SunPy, SHARPkeys, and IDL Solarsoft to prepare and analyze these
data. The observed evolution of the vector field informs how magnetic
field emergence and cancellation lead to and trigger the magnetic
explosions, and thus informs how major CMEs and their flares are
produced. We find that (1) all four flares are triggered by flux
cancellation, (2) the third and fourth explosions (X1.8 and M6.7)
begin with a filament eruption from the cancellation neutral line,
(3) in the first and second explosions a filament erupts in the core
of a secondary explosion that lags the main explosion and is probably
triggered by Hudson-effect field implosion under the adjacent main
exploding field, and (4) the transverse field suddenly strengthens along
each main explosions underlying neutral line during the explosion,
also likely due to Hudson-effect field implosion. Our observations
are consistent with flux cancellation at the explosions underlying
neutral line being essential in the buildup and triggering of each
of the four explosions in the same way as in smaller-scale magnetic
explosions that drive coronal jets.
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Title: Characterizing Steady and Bursty Coronal Heating of a Solar
Active Region
Authors: Wilkerson, Lucy; Tiwari, Sanjiv; Panesar, Navdeep K.;
Moore, Ronald
2021AGUFMSH15E2060W Altcode:
One of the biggest problems in solar physics today is our inability
to explain why the solar corona is so hot. In this project, we
aimed to quantify transient and background coronal heating for a
given active region in order to better understand coronal heating. We
used SDO/AIA data of the active region NOAA 12712 observed on May 29,
2018 over a period of 24 hours with a 3-minute cadence. We calculated
FeXVIII emission (hot component of AIA 94 Å channel) by removing
warm components using AIA 171 and 193 Å channels. From the maximum,
minimum, and mean brightness values of each pixel over the full 24 hour
period, we made maximum, minimum, and mean brightness maps. We repeated
this process in moving time windows of 16 hours, 8 hours, 5 hours, 3
hours, 1 hour, and 30 minutes. We used the total luminosity for each
of these maps over time to make lightcurves that show the evolution
of maximum, minimum, and mean brightness over time for each running
window. Finally, we took the ratio of the total maximum and total
minimum luminosity to total mean luminosity, and plotted these ratios
over time. The average maximum to mean ratio was 8.40±0.00, 6.36±0.46,
5.29±0.34, 4.73±0.24, 4.19±0.19, 3.21±0.17, and 2.64±0.15 and the
average minimum to mean ratio was 0.053±0.00, 0.08±0.00, 0.12±0.01,
0.14±0.02, 0.17±0.02, 0.26±0.02, and 0.33±0.03 for 24h, 16h, 8h,
5h, 3h, 1h, and 30m windows, respectively. As expected, the ratio of
background to mean luminosity increased as the time window decreased,
and the ratio of transient to mean luminosity decreased as the time
window decreased. As such, the ratio of background to mean luminosity
is a new and effective technique to quantify the background intensity
of the active region. Our 24h window result suggests that at most 5%
of the luminosity of the AR at a given time comes from the steady
background heating. This upper limit increases to 33% of the luminosity
of the AR for the 30 min running window.
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Title: The Magnetic Origin of Solar Campfires
Authors: Panesar, Navdeep K.; Tiwari, Sanjiv K.; Berghmans, David;
Cheung, Mark C. M.; Müller, Daniel; Auchere, Frederic; Zhukov, Andrei
2021ApJ...921L..20P Altcode: 2021arXiv211006846P
Solar campfires are fine-scale heating events, recently observed by
Extreme Ultraviolet Imager (EUI) on board Solar Orbiter. Here we use EUI
174 Å images, together with EUV images from Solar Dynamics Observatory
(SDO)/Atmospheric Imaging Assembly (AIA), and line-of-sight magnetograms
from SDO/Helioseismic and Magnetic Imager (HMI) to investigate the
magnetic origin of 52 randomly selected campfires in the quiet solar
corona. We find that (i) the campfires are rooted at the edges of
photospheric magnetic network lanes; (ii) most of the campfires reside
above the neutral line between majority-polarity magnetic flux patch and
a merging minority-polarity flux patch, with a flux cancelation rate of
~10<SUP>18</SUP> Mx hr<SUP>-1</SUP>; (iii) some of the campfires occur
repeatedly from the same neutral line; (iv) in the large majority of
instances, campfires are preceded by a cool-plasma structure, analogous
to minifilaments in coronal jets; and (v) although many campfires have
"complex" structure, most campfires resemble small-scale jets, dots,
or loops. Thus, "campfire" is a general term that includes different
types of small-scale solar dynamic features. They contain sufficient
magnetic energy (~10<SUP>26</SUP>-10<SUP>27</SUP> erg) to heat the solar
atmosphere locally to 0.5-2.5 MK. Their lifetimes range from about 1
minute to over 1 hr, with most of the campfires having a lifetime of
<10 minutes. The average lengths and widths of the campfires are 5400
± 2500 km and 1600 ± 640 km, respectively. Our observations suggest
that (a) the presence of magnetic flux ropes may be ubiquitous in the
solar atmosphere and not limited to coronal jets and larger-scale
eruptions that make CMEs, and (b) magnetic flux cancelation is the
fundamental process for the formation and triggering of most campfires.
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Title: Ti I lines at 2.2 μm as probes of the cooler regions of
sunspots
Authors: Smitha, H. N.; Castellanos Durán, J. S.; Solanki, S. K.;
Tiwari, S. K.
2021A&A...653A..91S Altcode: 2021arXiv210701247S
Context. The sunspot umbra harbours the coolest plasma on the solar
surface due to the presence of strong magnetic fields. The atomic
lines that are routinely used to observe the photosphere have weak
signals in the umbra and are often swamped by molecular lines. This
makes it harder to infer the properties of the umbra, especially in
the darkest regions. <BR /> Aims: The lines of the Ti I multiplet
at 2.2 μm are formed mainly at temperatures ≤4500 K and are not
known to be affected by molecular blends in sunspots. Since the first
systematic observations in the 1990s, these lines have been seldom
observed due to the instrumental challenges involved at these longer
wavelengths. We revisit these lines and investigate their formation
in different solar features. <BR /> Methods: We synthesized the
Ti I multiplet using a snapshot from 3D magnetohydrodynamic (MHD)
simulations of a sunspot and explored the properties of two of its
lines in comparison with two commonly used iron lines, at 6302.5 Å and
1.5648 μm. <BR /> Results: We find that the Ti I lines have stronger
signals than the Fe I lines in both intensity and polarization in the
sunspot umbra and in penumbral spines. They have little to no signal
in the penumbral filaments and the quiet Sun, at μ = 1. Their strong
and well-split profiles in the dark umbra are less affected by stray
light. Consequently, inside the sunspot, it is easier to invert these
lines and to infer the atmospheric properties as compared to the iron
lines. <BR /> Conclusions: The Cryo-NIRSP instrument at the DKIST will
provide the first-ever high-resolution observations in this wavelength
range. In this preparatory study, we demonstrate the unique temperature
and magnetic sensitivities of the Ti multiplet by probing the Sun's
coolest regions, which are not favourable for the formation of other
commonly used spectral lines. We thus expect such observations to
advance our understanding of sunspot properties.
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Title: On Making Magnetic-flux-rope Omega Loops For Solar Bipolar
Magnetic Regions Of All Sizes By Convection Cells
Authors: Moore, R.; Tiwari, S.; Panesar, N.; Sterling, A.
2021AAS...23831318M Altcode:
This poster gives an overview of Moore, R. L., Tiwari, S. K., Panesar,
N. K., & Sterling, A. C. 2020, ApJ Letters, 902:L35. We propose that
the magnetic-flux-rope omega loop that emerges to become any bipolar
magnetic region (BMR) is made by a convection cell of the omega-loop's
size from initially horizontal magnetic field ingested through the
cell's bottom. This idea is based on (1) observed characteristics of
BMRs of all spans (~1000 to ~200,000 km), (2) a well-known simulation
of the production of a BMR by a supergranule-sized convection cell
from horizontal field placed at cell bottom, and (3) a well-known
convection-zone simulation. From the observations and simulations,
we (1) infer that the strength of the field ingested by the biggest
convection cells (giant cells) to make the biggest BMR omega loops
is ~10<SUP>3</SUP> G, (2) plausibly explain why the span and flux of
the biggest observed BMRs are ~200,000 km and ~10<SUP>22</SUP> Mx,
(3) suggest how giant cells might also make "failed BMR" omega loops
that populate the upper convection zone with horizontal field, from
which smaller convection cells make BMR omega loops of their size,
(4) suggest why sunspots observed in a sunspot cycle's declining
phase tend to violate the hemispheric helicity rule, and (5) support a
previously proposed amended Babcock scenario (Moore, R. L., Cirtain,
J. W., & Sterling, A. C. 2016, arXiv:1606.05371) for the sunspot
cycle's dynamo process. Because the proposed convection-based heuristic
model for making a sunspot-BMR omega loop avoids having ~10<SUP>5</SUP>
G field in the initial flux rope at the bottom of the convection zone,
it is an appealing alternative to the present magnetic-buoyancy-based
standard scenario and warrants testing by high-enough-resolution
giant-cell magnetoconvection simulations.
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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
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.
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Title: Are the Brightest Coronal Loops Always Rooted in Mixed-polarity
Magnetic Flux?
Authors: Tiwari, Sanjiv K.; Evans, Caroline L.; Panesar, Navdeep K.;
Prasad, Avijeet; Moore, Ronald L.
2021ApJ...908..151T Altcode: 2021arXiv210210146T
A recent study demonstrated that freedom of convection and strength of
magnetic field in the photospheric feet of active-region (AR) coronal
loops, together, can engender or quench heating in them. Other studies
stress that magnetic flux cancellation at the loop-feet potentially
drives heating in loops. We follow 24 hr movies of a bipolar AR, using
extreme ultraviolet images from the Atmospheric Imaging Assembly/Solar
Dynamics Observatory (SDO) and line-of-sight (LOS) magnetograms from
the Helioseismic and Magnetic Imager (HMI)/SDO, to examine magnetic
polarities at the feet of 23 of the brightest coronal loops. We derived
Fe XVIII emission (hot-94) images (using the Warren et al. method)
to select the hottest/brightest loops, and confirm their footpoint
locations via non-force-free field extrapolations. From 6″ × 6″
boxes centered at each loop foot in LOS magnetograms we find that ∼40%
of the loops have both feet in unipolar flux, and ∼60% of the loops
have at least one foot in mixed-polarity flux. The loops with both feet
unipolar are ∼15% shorter lived on average than the loops having
mixed-polarity foot-point flux, but their peak-intensity averages
are equal. The presence of mixed-polarity magnetic flux in at least
one foot in the majority of the loops suggests that flux cancellation
at the footpoints may drive most of the heating. But the absence of
mixed-polarity magnetic flux (to the detection limit of HMI) in ∼40%
of the loops suggests that flux cancellation may not be necessary to
drive heating in coronal loops—magnetoconvection and field strength
at both loop feet possibly drive much of the heating, even in the
cases where a loop foot presents mixed-polarity magnetic flux.
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Title: Effects of Cowling Resistivity in the Weakly-Ionized
Chromosphere
Authors: Yalim, M. S.; Prasad, A.; Pogorelov, N. V.; Zank, G. P.;
Hu, Q.; Tiwari, S. K.
2020AGUFMSH0010015Y Altcode:
The physics of the solar chromosphere is complex from both theoretical
and modeling perspectives. The plasma temperature from the photosphere
to corona increases from ~5,000 K to ~1 million K over a distance of
only ~10,000 km from the chromosphere and the transition region. Certain
regions of the solar atmosphere have sufficiently low temperature and
ionization rates to be considered as weakly-ionized. In particular, this
is true at the lower chromosphere. As a result, the Cowling resistivity
is orders of magnitude greater than the Coulomb resistivity. Ohm's
law therefore includes anisotropic dissipation. To evaluate the
Cowling resistivity, we need to know the external magnetic field
strength and to estimate the neutral fraction as a function of the
bulk plasma density and temperature. In this study, we determine
the magnetic field topology using the non-force-free field (NFFF)
extrapolation technique based on SDO/HMI SHARP vector magnetogram
data, and the stratified density and temperature profiles from
the Maltby-M umbral core model for sunspots. We investigate the
variation and effects of Cowling resistivity on heating and magnetic
reconnection in the chromosphere as the flare-producing active region
(AR) 11166 evolves. In particular, we analyze a C2.0 flare emerging
from AR11166 and find a normalized reconnection rate of 0.051. <P />We
will also explore the possibility of using IRIS data in our analysis,
in particular spectral data calculated from the IRIS2 inversion scheme
to recover the thermodynamics of the chromosphere and high photosphere,
and slit-jaw images (SJIs) to capture and analyze solar flares.
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Title: Fine-scale explosive energy release at sites of magnetic
flux cancellation in the core of a solar active region: Hi-C 2.1,
IRIS and SDO observations
Authors: Tiwari, S. K.; Panesar, N. K.; Moore, R. L.; De Pontieu,
B.; Winebarger, A. R.
2020AGUFMSH0010007T Altcode:
The second sounding-rocket flight of the High-Resolution Coronal Imager
(Hi-C 2.1) provided unprecedentedly-high spatial and temporal resolution
(~250 km, 4.4 s) coronal EUV images of Fe IX/X emission at 172 Å, of
a solar active region (AR NOAA 12712) near solar disk center. Three
morphologically-different types (I: dot-like, II: loop-like, &
III: surge/jet-like) of fine-scale sudden brightening events (tiny
microflares) are seen within and at the ends of an arch filament system
in the core of the AR. Although type Is resemble IRIS bombs (in size,
and brightness with respect to surroundings), our dot-like events are
apparently much hotter, and shorter in span (70 s). Because Dot-like
brightenings are not as clearly discernible in AIA 171 Å as in Hi-C 172
Å, they were not reported before. We complement the 5-minute-duration
Hi-C 2.1 data with SDO/HMI magnetograms, SDO/AIA EUV and UV images,
and IRIS UV spectra and slit-jaw images to examine, at the sites of
these events, brightenings and flows in the transition region and corona
and evolution of magnetic flux in the photosphere. Most, if not all,
of the events are seated at sites of opposite-polarity magnetic flux
convergence (sometimes driven by adjacent flux emergence), implying
flux cancellation at the microflare's polarity inversion line. In the
IRIS spectra and images, we find confirming evidence of field-aligned
outflow from brightenings at the ends of loops of the arch filament
system. In types I and II the explosion is confined, while in type
III the explosion is ejective and drives jet-like outflow. The light
curves from Hi-C, AIA and IRIS peak nearly simultaneously for many
of these events and none of the events display a systematic cooling
sequence as seen in typical coronal flares, suggesting that these tiny
brightening events have chromospheric/transition-region origin.
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Title: Network Jets as the Driver of Counter-streaming Flows in a
Solar Filament
Authors: Panesar, N. K.; Tiwari, S. K.; Moore, R. L.; Sterling, A. C.
2020AGUFMSH0240004P Altcode:
We investigate the driving mechanism of counter-streaming flows
in a solar filament, using EUV images from SDO/AIA, line of sight
magnetograms from SDO/HMI, IRIS SJ images, and H-alpha data from
GONG. We find that: (i) persistent counter-streaming flows along
adjacent threads of a small (100" long) solar filament is present;
(ii) both ends of the solar filament are rooted at the edges of
magnetic network flux lanes; (iii) recurrent small-scale jets (also
known as network jets) occur at both ends of the filament; (iv) some
of the network jets occur at the sites of flux cancelation between the
majority-polarity flux and merging minority-polarity flux patches;
(v) these multiple network jets clearly drive the counter-streaming
flows along the adjacent threads of the solar filament for ~2 hours
with an average speed of 70 km s<SUP>-1</SUP>; (vi) some the network
jets show base brightenings, analogous to the base brightenings of
coronal jets; and (vii) the filament appears wider (4") in EUV images
than in H-alpha images (2.5"), consistent with previous studies. Thus,
our observations show that counter-streaming flows in the filament
are driven by network jets and possibly these driving network jet
eruptions are prepared and triggered by flux cancelation.
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Title: On Making Magnetic-flux-rope Ω Loops for Solar Bipolar
Magnetic Regions of All Sizes by Convection Cells
Authors: Moore, Ronald L.; Tiwari, Sanjiv K.; Panesar, Navdeep K.;
Sterling, Alphonse C.
2020ApJ...902L..35M Altcode: 2020arXiv200913694M
We propose that the flux-rope Ω loop that emerges to become any bipolar
magnetic region (BMR) is made by a convection cell of the Ω-loop's size
from initially horizontal magnetic field ingested through the cell's
bottom. This idea is based on (1) observed characteristics of BMRs
of all spans (∼1000 to ∼200,000 km), (2) a well-known simulation
of the production of a BMR by a supergranule-sized convection cell
from horizontal field placed at cell bottom, and (3) a well-known
convection-zone simulation. From the observations and simulations,
we (1) infer that the strength of the field ingested by the biggest
convection cells (giant cells) to make the biggest BMR Ω loops is
∼10<SUP>3</SUP> G, (2) plausibly explain why the span and flux of
the biggest observed BMRs are ∼200,000 km and ∼10<SUP>22</SUP>
Mx, (3) suggest how giant cells might also make "failed-BMR" Ω loops
that populate the upper convection zone with horizontal field, from
which smaller convection cells make BMR Ω loops of their size, (4)
suggest why sunspots observed in a sunspot cycle's declining phase
tend to violate the hemispheric helicity rule, and (5) support a
previously proposed amended Babcock scenario for the sunspot cycle's
dynamo process. Because the proposed convection-based heuristic model
for making a sunspot-BMR Ω loop avoids having ∼10<SUP>5</SUP> G
field in the initial flux rope at the bottom of the convection zone,
it is an appealing alternative to the present magnetic-buoyancy-based
standard scenario and warrants testing by high-enough-resolution
giant-cell magnetoconvection simulations.
---------------------------------------------------------
Title: Network Jets as the Driver of Counter-streaming Flows in a
Solar Filament/Filament Channel
Authors: Panesar, Navdeep K.; Tiwari, Sanjiv K.; Moore, Ronald L.;
Sterling, Alphonse C.
2020ApJ...897L...2P Altcode: 2020arXiv200604249P
Counter-streaming flows in a small (100″ long) solar filament/filament
channel are directly observed in high-resolution Solar Dynamics
Observatory (SDO)/Atmospheric Imaging Assembly (AIA) extreme-ultraviolet
(EUV) images of a region of enhanced magnetic network. We combine
images from SDO/AIA, SDO/Helioseismic and Magnetic Imager (HMI), and the
Interface Region Imaging Spectrograph (IRIS) to investigate the driving
mechanism of these flows. We find that: (I) counter-streaming flows are
present along adjacent filament/filament channel threads for ∼2 hr,
(II) both ends of the filament/filament channel are rooted at the
edges of magnetic network flux lanes along which there are impinging
fine-scale opposite-polarity flux patches, (III) recurrent small-scale
jets (known as network jets) occur at the edges of the magnetic network
flux lanes at the ends of the filament/filament channel, (IV) the
recurrent network jet eruptions clearly drive the counter-streaming
flows along threads of the filament/filament channel, (V) some
of the network jets appear to stem from sites of flux cancelation,
between network flux and merging opposite-polarity flux, and (VI) some
show brightening at their bases, analogous to the base brightening in
coronal jets. The average speed of the counter-streaming flows along the
filament/filament channel threads is 70 km s<SUP>-1</SUP>. The average
widths of the AIA filament/filament channel and the Hα filament are
4″ and 2"5, respectively, consistent with the earlier findings
that filaments in EUV images are wider than in Hα images. Thus,
our observations show that the continually repeated counter-streaming
flows come from network jets, and these driving network jet eruptions
are possibly prepared and triggered by magnetic flux cancelation.
---------------------------------------------------------
Title: Observation and Modeling of High-temperature Solar Active
Region Emission during the High-resolution Coronal Imager Flight of
2018 May 29
Authors: Warren, Harry P.; Reep, Jeffrey W.; Crump, Nicholas A.;
Ugarte-Urra, Ignacio; Brooks, David H.; Winebarger, Amy R.; Savage,
Sabrina; De Pontieu, Bart; Peter, Hardi; Cirtain, Jonathan W.; Golub,
Leon; Kobayashi, Ken; McKenzie, David; Morton, Richard; Rachmeler,
Laurel; Testa, Paola; Tiwari, Sanjiv; Walsh, Robert
2020ApJ...896...51W Altcode:
Excellent coordinated observations of NOAA active region 12712 were
obtained during the flight of the High-resolution Coronal Imager (Hi-C)
sounding rocket on 2018 May 29. This region displayed a typical active
region core structure with relatively short, high-temperature loops
crossing the polarity inversion line and bright "moss" located at the
footpoints of these loops. The differential emission measure (DEM) in
the active region core is very sharply peaked at about 4 MK. Further,
there is little evidence for impulsive heating events in the moss, even
at the high spatial resolution and cadence of Hi-C. This suggests that
active region core heating is occurring at a high frequency and keeping
the loops close to equilibrium. To create a time-dependent simulation of
the active region core, we combine nonlinear force-free extrapolations
of the measured magnetic field with a heating rate that is dependent
on the field strength and loop length and has a Poisson waiting time
distribution. We use the approximate solutions to the hydrodynamic
loop equations to simulate the full ensemble of active region core
loops for a range of heating parameters. In all cases, we find that
high-frequency heating provides the best match to the observed DEM. For
selected field lines, we solve the full hydrodynamic loop equations,
including radiative transfer in the chromosphere, to simulate transition
region and chromospheric emission. We find that for heating scenarios
consistent with the DEM, classical signatures of energy release,
such as transition region brightenings and chromospheric evaporation,
are weak, suggesting that they would be difficult to detect.
---------------------------------------------------------
Title: The Drivers of Active Region Outflows into the Slow Solar Wind
Authors: Brooks, David H.; Winebarger, Amy R.; Savage, Sabrina; Warren,
Harry P.; De Pontieu, Bart; Peter, Hardi; Cirtain, Jonathan W.; Golub,
Leon; Kobayashi, Ken; McIntosh, Scott W.; McKenzie, David; Morton,
Richard; Rachmeler, Laurel; Testa, Paola; Tiwari, Sanjiv; Walsh, Robert
2020ApJ...894..144B Altcode: 2020arXiv200407461B
Plasma outflows from the edges of active regions have been suggested as
a possible source of the slow solar wind. Spectroscopic measurements
show that these outflows have an enhanced elemental composition,
which is a distinct signature of the slow wind. Current spectroscopic
observations, however, do not have sufficient spatial resolution to
distinguish what structures are being measured or determine the driver
of the outflows. The High-resolution Coronal Imager (Hi-C) flew on a
sounding rocket in 2018 May and observed areas of active region outflow
at the highest spatial resolution ever achieved (250 km). Here we use
the Hi-C data to disentangle the outflow composition signatures observed
with the Hinode satellite during the flight. We show that there are
two components to the outflow emission: a substantial contribution
from expanded plasma that appears to have been expelled from closed
loops in the active region core and a second contribution from dynamic
activity in active region plage, with a composition signature that
reflects solar photospheric abundances. The two competing drivers of the
outflows may explain the variable composition of the slow solar wind.
---------------------------------------------------------
Title: Velocity Response of the Observed Explosive Events in the
Lower Solar Atmosphere. I. Formation of the Flowing Cool-loop System
Authors: Srivastava, A. K.; Rao, Yamini K.; Konkol, P.; Murawski,
K.; Mathioudakis, M.; Tiwari, Sanjiv K.; Scullion, E.; Doyle, J. G.;
Dwivedi, B. N.
2020ApJ...894..155S Altcode: 2020arXiv200402775S
We observe plasma flows in cool loops using the Slit-Jaw Imager on board
the Interface Region Imaging Spectrometer (IRIS). Huang et al. observed
unusually broadened Si IV 1403 Šline profiles at the footpoints of
such loops that were attributed to signatures of explosive events
(EEs). We have chosen one such unidirectional flowing cool-loop
system observed by IRIS where one of the footpoints is associated
with significantly broadened Si IV line profiles. The line-profile
broadening indirectly indicates the occurrence of numerous EEs below
the transition region (TR), while it directly infers a large velocity
enhancement/perturbation, further causing the plasma flows in the
observed loop system. The observed features are implemented in a
model atmosphere in which a low-lying bipolar magnetic field system
is perturbed in the chromosphere by a velocity pulse with a maximum
amplitude of 200 km s<SUP>-1</SUP>. The data-driven 2D numerical
simulation shows that the plasma motions evolve in a similar manner
as observed by IRIS in the form of flowing plasma filling the skeleton
of a cool-loop system. We compare the spatio-temporal evolution of the
cool-loop system in the framework of our model with the observations,
and conclude that their formation is mostly associated with the velocity
response of the transient energy release above their footpoints in
the chromosphere/TR. Our observations and modeling results suggest
that the velocity responses most likely associated to the EEs could
be one of the main candidates for the dynamics and energetics of the
flowing cool-loop systems in the lower solar atmosphere.
---------------------------------------------------------
Title: Is the High-Resolution Coronal Imager Resolving Coronal
Strands? Results from AR 12712
Authors: Williams, Thomas; Walsh, Robert W.; Winebarger, Amy R.;
Brooks, David H.; Cirtain, Jonathan W.; De Pontieu, Bart; Golub,
Leon; Kobayashi, Ken; McKenzie, David E.; Morton, Richard J.; Peter,
Hardi; Rachmeler, Laurel A.; Savage, Sabrina L.; Testa, Paola; Tiwari,
Sanjiv K.; Warren, Harry P.; Watkinson, Benjamin J.
2020ApJ...892..134W Altcode: 2020arXiv200111254W
Following the success of the first mission, the High-Resolution
Coronal Imager (Hi-C) was launched for a third time (Hi-C 2.1)
on 2018 May 29 from the White Sands Missile Range, NM, USA. On this
occasion, 329 s of 17.2 nm data of target active region AR 12712 were
captured with a cadence of ≈4 s, and a plate scale of 0.129 arcsec
pixel<SUP>-1</SUP>. Using data captured by Hi-C 2.1 and co-aligned
observations from SDO/AIA 17.1 nm, we investigate the widths of 49
coronal strands. We search for evidence of substructure within the
strands that is not detected by AIA, and further consider whether these
strands are fully resolved by Hi-C 2.1. With the aid of multi-scale
Gaussian normalization, strands from a region of low emission that can
only be visualized against the contrast of the darker, underlying moss
are studied. A comparison is made between these low-emission strands
and those from regions of higher emission within the target active
region. It is found that Hi-C 2.1 can resolve individual strands as
small as ≈202 km, though the more typical strand widths seen are
≈513 km. For coronal strands within the region of low emission, the
most likely width is significantly narrower than the high-emission
strands at ≈388 km. This places the low-emission coronal strands
beneath the resolving capabilities of SDO/AIA, highlighting the need
for a permanent solar observatory with the resolving power of Hi-C.
---------------------------------------------------------
Title: Propagation of waves above a plage as observed by IRIS and SDO
Authors: Kayshap, P.; Srivastava, A. K.; Tiwari, S. K.; Jelínek,
P.; Mathioudakis, M.
2020A&A...634A..63K Altcode: 2019arXiv191011557K
Context. Magnetohydrodynamic waves are proposed as the mechanism
that transport sufficient energy from the photosphere to heat the
transition region (TR) and corona. However, various aspects of these
waves, such as their nature, propagation characteristics, and role
in the atmospheric heating process, remain poorly understood and
require further investigation. <BR /> Aims: We aim to investigate
wave propagation within an active-region plage using IRIS and AIA
observations. The main motivation is to understand the relationship
between photospheric and TR oscillations. We identify the locations in
the plage region where magnetic flux tubes are essentially vertical,
and further we discuss the propagation and nature of these waves. <BR
/> Methods: We used photospheric observations from AIA (i.e., AIA
1700 Å) as well as TR imaging observations (IRIS SJI Si IV 1400.0
Å). We investigated the propagation of the waves into the TR from the
photosphere using wavelet analysis (e.g., cross power, coherence, and
phase difference) with the inclusion of a customized noise model. <BR />
Results: A fast Fourier transform algorithm shows the distribution of
wave power at photospheric and TR heights. Waves with periods between
2.0 and 9.0 min appear to be correlated between the photosphere and
TR. We exploited a customized noise model to estimate the 95% confidence
levels for the IRIS observations. On the basis of the sound speed in the
TR and estimated propagation speed, these waves are best interpreted
as slow magneto acoustic waves (SMAWs). It is found that almost all
locations show correlation and propagation of waves over a broad range
of periods from the photosphere to the TR. Our observations suggest
that the SMAWs spatial occurrence frequency is stronly correlated
between the photosphere and transition region within plage areas.
---------------------------------------------------------
Title: A CME-Producing Solar Eruption from the Interior of a Twisted
Emerging Bipole
Authors: Moore, R. L.; Adams, M.; Panesar, N. K.; Falconer, D. A.;
Tiwari, S. K.
2019AGUFMSH43D3355M Altcode:
In a negative-polarity coronal hole, magnetic flux emergence, seen by
the Solar Dynamics Observatory's (SDO) Helioseismic Magnetic Imager
(HMI), begins at approximately 19:00 UT on March 3, 2016. The emerged
magnetic field produced sunspots with penumbrae by 3:00 UT on March
4, which NOAA numbered 12514. The emerging magnetic field is largely
bipolar with the opposite-polarity fluxes spreading apart overall,
but there is simultaneously some convergence and cancellation of
opposite-polarity flux at the polarity inversion line (PIL) inside the
emerging bipole. The emerging bipole shows obvious overall left-handed
shear and/or twist in its magnetic field and corresponding clockwise
rotation of the two poles of the bipole about each other as the bipole
emerges. The eruption comes from inside the emerging bipole and blows
it open to produce a CME observed by SOHO/LASCO. That eruption is
preceded by flux cancellation at the emerging bipole's interior PIL,
cancellation that plausibly builds a sheared and twisted flux rope
above the interior PIL and finally triggers the blow-out eruption of
the flux rope via photospheric-convection-driven slow tether-cutting
reconnection of the legs of the sheared core field, low above the
interior PIL, as proposed by van Ballegooijen and Martens (1989, ApJ,
343, 971) and Moore and Roumeliotis (1992, in Eruptive Solar Flares,
ed. Z. Svestka, B.V. Jackson, and M.E. Machado [Berlin:Springer],
69). The production of this eruption is a (perhaps rare) counterexample
to solar eruptions that result from external collisional shearing
between opposite polarities from two distinct emerging and/or emerged
bipoles (Chintzoglou et al., 2019, ApJ, 871:67).
---------------------------------------------------------
Title: Are the brightest coronal loops always rooted in mixed-polarity
magnetic flux?
Authors: Evans, C.; Tiwari, S. K.; Panesar, N. K.; Prasad, A.; Moore,
R. L.
2019AGUFMSH41F3324E Altcode:
Magnetic energy dissipated in coronal loops heats the Sun's corona
to millions of Kelvin. Some recent investigations indicate that in
addition to the required magnetoconvection and field strength, heating
in the brightest coronal loops are driven by flux cancellation at
the loop-feet. To find coronal loop footpoints , we selected extreme
ultraviolet (EUV) data from the Atmospheric Imaging Assembly (AIA)
and line- of-sight (LOS) magnetograms from the Helioseismic and
Magnetic Imager (HMI), both on-board the Solar Dynamics Observatory
(SDO). We located the footpoints of 28 brightest coronal loops of
the bipolar active region NOAA 12712 on 28 May 2018 in hot 94 images
(calculated using the Warren et al. method) and confirm the location
of these footpoints via non-force free field extrapolations. We examine
the photospheric magnetic field in 6" boxes centered at each footpoint
and find that ~20% of loops have both feet in unipolar magnetic flux,
~10% loops have both feet in mixed-polarity flux, and ~70% of loops
have one foot in unipolar and one in mixed-polarity flux. The presence
of mixed-polarity magnetic flux in at least one foot of majority
of the brightest coronal loops suggests that flux cancellation at
the footpoints may drive heating in them. However, the absence of
mixed-polarity magnetic flux (to the detection limit of HMI) in a
significant number of the brightest coronal loops suggests that flux
cancellation may not be necessary to drive heating in the loops - the
combination of magnetoconvection and the magnetic field strength at the
footpoints could be responsible for much of the coronal loop heating
even in cases where a footpoint presents mixed-polarity magnetic flux.
---------------------------------------------------------
Title: Hi-C 2.1 Observations of Jetlet-like Events at Edges of Solar
Magnetic Network Lanes
Authors: Panesar, Navdeep K.; Sterling, Alphonse C.; Moore, Ronald L.;
Winebarger, Amy R.; Tiwari, Sanjiv K.; Savage, Sabrina L.; Golub, Leon
E.; Rachmeler, Laurel A.; Kobayashi, Ken; Brooks, David H.; Cirtain,
Jonathan W.; De Pontieu, Bart; McKenzie, David E.; Morton, Richard J.;
Peter, Hardi; Testa, Paola; Walsh, Robert W.; Warren, Harry P.
2019ApJ...887L...8P Altcode: 2019arXiv191102331P
We present high-resolution, high-cadence observations of six,
fine-scale, on-disk jet-like events observed by the High-resolution
Coronal Imager 2.1 (Hi-C 2.1) during its sounding-rocket flight. We
combine the Hi-C 2.1 images with images from the Solar Dynamics
Observatory (SDO)/Atmospheric Imaging Assembly (AIA) and the Interface
Region Imaging Spectrograph (IRIS), and investigate each event’s
magnetic setting with co-aligned line-of-sight magnetograms from the
SDO/Helioseismic and Magnetic Imager (HMI). We find that (i) all six
events are jetlet-like (having apparent properties of jetlets), (ii)
all six are rooted at edges of magnetic network lanes, (iii) four of
the jetlet-like events stem from sites of flux cancelation between
majority-polarity network flux and merging minority-polarity flux, and
(iv) four of the jetlet-like events show brightenings at their bases
reminiscent of the base brightenings in coronal jets. The average
spire length of the six jetlet-like events (9000 ± 3000 km) is three
times shorter than that for IRIS jetlets (27,000 ± 8000 km). While
not ruling out other generation mechanisms, the observations suggest
that at least four of these events may be miniature versions of both
larger-scale coronal jets that are driven by minifilament eruptions
and still-larger-scale solar eruptions that are driven by filament
eruptions. Therefore, we propose that our Hi-C events are driven by
the eruption of a tiny sheared-field flux rope, and that the flux rope
field is built and triggered to erupt by flux cancelation.
---------------------------------------------------------
Title: Fine-scale explosive energy release at sites of magnetic flux
cancellation in the core of the solar active region observed by Hi-C
2.1, IRIS and SDO
Authors: Tiwari, S. K.; Panesar, N. K.; Moore, R. L.; De Pontieu,
B.; Winebarger, A. R.
2019AGUFMSH31C3323T Altcode:
The second sounding-rocket flight of the High-Resolution Coronal Imager
(Hi-C 2.1) provided unprecedentedly-high spatial and temporal resolution
---------------------------------------------------------
Title: CME-Forecasting Performance of MAG4 with its HMI Vector
Magnetogram Database
Authors: Schragal, N. T.; Falconer, D. A.; Tiwari, S. K.; Moore, R. L.
2019AGUFMSH33C3354S Altcode:
Coronal mass ejections (CMEs), solar flares, and solar proton events
(SPEs) pose a threat to space-based infrastructure and astronauts. Many
years of developmental work on predicting these events from active
region (AR) magnetograms from MDI and HMI have led to MAG4 (MAGnetogram
FOREcasting), a large-database forecasting technique for near-real-time
forecasting of the next-day major flare, CME, and SPE productivity of
an AR. MAG4 uses a free-magnetic-energy proxy computed for the AR from
an HMI magnetogram and the AR's previous-day major-flare productivity in
conjunction with a pair of forecasting curves derived from MAG4's large
database of AR magnetograms to forecast these events. Previous work on
improving the major-flare forecasting performance of MAG4 by deriving
the forecasting curves from HMI vector magnetograms instead of from MDI
line-of-sight magnetograms has laid the groundwork for improving the
CME and SPE forecasting of MAG4. The present work is a first step in
similarly improving MAG4's CME forecasting performance. We use MAG4's
HMI AR vector magnetograms and a list of AR-produced CME events during
August 2010 - March 2014. As done previously for major flares, we carry
out 3000 random divisions of the observed set of ARs into a control
half-set and an experimental half-set to determine the forecasting
performance of each of 48 different parameters computed from the AR
magnetograms. Each control set gives the pair of CME forecasting curves
for each parameter. Then these curves are used to forecast the next-day
event rate from each AR magnetogram in the experimental set. We measure
forecasting performance by the Heidke Skill score which ranges from
-∞ to 1, where a score of 0 is for performance that is no better than
random chance, negative scores are for performance worse than random
chance, and 1 is for perfect performance. Preliminary results indicate
that the best-performing AR magnetogram parameters for predicting CMEs
are not the same as the ones for major flares.
---------------------------------------------------------
Title: Fine-scale Explosive Energy Release at Sites of Prospective
Magnetic Flux Cancellation in the Core of the Solar Active Region
Observed by Hi-C 2.1, IRIS, and SDO
Authors: Tiwari, Sanjiv K.; Panesar, Navdeep K.; Moore, Ronald L.;
De Pontieu, Bart; Winebarger, Amy R.; Golub, Leon; Savage, Sabrina L.;
Rachmeler, Laurel A.; Kobayashi, Ken; Testa, Paola; Warren, Harry P.;
Brooks, David H.; Cirtain, Jonathan W.; McKenzie, David E.; Morton,
Richard J.; Peter, Hardi; Walsh, Robert W.
2019ApJ...887...56T Altcode: 2019arXiv191101424T
The second Hi-C flight (Hi-C 2.1) provided unprecedentedly high spatial
and temporal resolution (∼250 km, 4.4 s) coronal EUV images of Fe IX/X
emission at 172 Å of AR 12712 on 2018 May 29, during 18:56:21-19:01:56
UT. Three morphologically different types (I: dot-like; II: loop-like;
III: surge/jet-like) of fine-scale sudden-brightening events (tiny
microflares) are seen within and at the ends of an arch filament system
in the core of the AR. Although type Is (not reported before) resemble
IRIS bombs (in size, and brightness with respect to surroundings),
our dot-like events are apparently much hotter and shorter in span
(70 s). We complement the 5 minute duration Hi-C 2.1 data with SDO/HMI
magnetograms, SDO/AIA EUV images, and IRIS UV spectra and slit-jaw
images to examine, at the sites of these events, brightenings and
flows in the transition region and corona and evolution of magnetic
flux in the photosphere. Most, if not all, of the events are seated
at sites of opposite-polarity magnetic flux convergence (sometimes
driven by adjacent flux emergence), implying likely flux cancellation
at the microflare’s polarity inversion line. In the IRIS spectra
and images, we find confirming evidence of field-aligned outflow from
brightenings at the ends of loops of the arch filament system. In types
I and II the explosion is confined, while in type III the explosion
is ejective and drives jet-like outflow. The light curves from Hi-C,
AIA, and IRIS peak nearly simultaneously for many of these events,
and none of the events display a systematic cooling sequence as seen in
typical coronal flares, suggesting that these tiny brightening events
have chromospheric/transition region origin.
---------------------------------------------------------
Title: The High-Resolution Coronal Imager, Flight 2.1
Authors: Rachmeler, Laurel A.; Winebarger, Amy R.; Savage, Sabrina L.;
Golub, Leon; Kobayashi, Ken; Vigil, Genevieve D.; Brooks, David H.;
Cirtain, Jonathan W.; De Pontieu, Bart; McKenzie, David E.; Morton,
Richard J.; Peter, Hardi; Testa, Paola; Tiwari, Sanjiv K.; Walsh,
Robert W.; Warren, Harry P.; Alexander, Caroline; Ansell, Darren;
Beabout, Brent L.; Beabout, Dyana L.; Bethge, Christian W.; Champey,
Patrick R.; Cheimets, Peter N.; Cooper, Mark A.; Creel, Helen K.;
Gates, Richard; Gomez, Carlos; Guillory, Anthony; Haight, Harlan;
Hogue, William D.; Holloway, Todd; Hyde, David W.; Kenyon, Richard;
Marshall, Joseph N.; McCracken, Jeff E.; McCracken, Kenneth; Mitchell,
Karen O.; Ordway, Mark; Owen, Tim; Ranganathan, Jagan; Robertson,
Bryan A.; Payne, M. Janie; Podgorski, William; Pryor, Jonathan; Samra,
Jenna; Sloan, Mark D.; Soohoo, Howard A.; Steele, D. Brandon; Thompson,
Furman V.; Thornton, Gary S.; Watkinson, Benjamin; Windt, David
2019SoPh..294..174R Altcode: 2019arXiv190905942R
The third flight of the High-Resolution Coronal Imager (Hi-C 2.1)
occurred on May 29, 2018; the Sounding Rocket was launched from White
Sands Missile Range in New Mexico. The instrument has been modified
from its original configuration (Hi-C 1) to observe the solar corona
in a passband that peaks near 172 Å, and uses a new, custom-built
low-noise camera. The instrument targeted Active Region 12712, and
captured 78 images at a cadence of 4.4 s (18:56:22 - 19:01:57 UT; 5
min and 35 s observing time). The image spatial resolution varies due
to quasi-periodic motion blur from the rocket; sharp images contain
resolved features of at least 0.47 arcsec. There are coordinated
observations from multiple ground- and space-based telescopes providing
an unprecedented opportunity to observe the mass and energy coupling
between the chromosphere and the corona. Details of the instrument
and the data set are presented in this paper.
---------------------------------------------------------
Title: Achievements of Hinode in the first eleven years
Authors: Hinode Review Team; Al-Janabi, Khalid; Antolin, Patrick;
Baker, Deborah; Bellot Rubio, Luis R.; Bradley, Louisa; Brooks,
David H.; Centeno, Rebecca; Culhane, J. Leonard; Del Zanna, Giulio;
Doschek, George A.; Fletcher, Lyndsay; Hara, Hirohisa; Harra,
Louise K.; Hillier, Andrew S.; Imada, Shinsuke; Klimchuk, James A.;
Mariska, John T.; Pereira, Tiago M. D.; Reeves, Katharine K.; Sakao,
Taro; Sakurai, Takashi; Shimizu, Toshifumi; Shimojo, Masumi; Shiota,
Daikou; Solanki, Sami K.; Sterling, Alphonse C.; Su, Yingna; Suematsu,
Yoshinori; Tarbell, Theodore D.; Tiwari, Sanjiv K.; Toriumi, Shin;
Ugarte-Urra, Ignacio; Warren, Harry P.; Watanabe, Tetsuya; Young,
Peter R.
2019PASJ...71R...1H Altcode:
Hinode is Japan's third solar mission following Hinotori (1981-1982)
and Yohkoh (1991-2001): it was launched on 2006 September 22 and is in
operation currently. Hinode carries three instruments: the Solar Optical
Telescope, the X-Ray Telescope, and the EUV Imaging Spectrometer. These
instruments were built under international collaboration with the
National Aeronautics and Space Administration and the UK Science and
Technology Facilities Council, and its operation has been contributed
to by the European Space Agency and the Norwegian Space Center. After
describing the satellite operations and giving a performance evaluation
of the three instruments, reviews are presented on major scientific
discoveries by Hinode in the first eleven years (one solar cycle long)
of its operation. This review article concludes with future prospects
for solar physics research based on the achievements of Hinode.
---------------------------------------------------------
Title: Invisibility of Solar Active Region Umbra-to-Umbra Coronal
Loops: New Evidence that Magnetoconvection Drives Solar-Stellar
Coronal Heating
Authors: Moore, Ronald L.; Tiwari, Sanjiv; Thalmann, Julia; Panesar,
Navdeep; Winebarger, Amy
2019AAS...23410603M Altcode:
How magnetic energy is injected and released in the solar corona,
keeping it heated to several million degrees, remains elusive. The
corona is shaped by the magnetic field that fills it and the heating
of the corona generally increases with increasing strength of the
field. For each of two bipolar solar active regions having one or
more sunspots in each of the two main opposite-polarity domains of
magnetic flux, from comparison of a nonlinear force-free model of the
active region's three-dimensional coronal magnetic field to observed
extreme-ultraviolet coronal loops, we find that (1) umbra-to-umbra
loops, despite being rooted in the strongest magnetic flux at both ends,
are invisible, and (2) the brightest loops have one foot in a sunspot
umbra or penumbra and the other foot in another sunspot's penumbra or
in unipolar or mixed-polarity plage. The invisibility of umbra-to-umbra
loops is new evidence that magnetoconvetion drives solar-stellar coronal
heating: evidently, the strong umbral field at both ends quenches the
magnetoconvection and hence the heating. Broadly, our results indicate
that depending on the field strength in both feet, the photospheric feet
of a coronal loop on any convective star can either engender or quench
coronal heating in the body of the loop. <P />This work was supported
by funding from the Heliophysics Division of NASA's Science Mission
Directorate, from NASA's Postdoctoral Program, and from the Austrian
Science Fund. The results have been published in The Astrophysical
Journal Letters (Tiwari, S. K., Thalmann, J. K., Panesar, N. K., Moore,
R. L., & Winebarger, A. R. 2017, ApJ Letters, 843:L20).
---------------------------------------------------------
Title: Improving Forecasting of Drivers of Severe Space Weather with
the New MAG4 HMI Vector Magnetogram Database
Authors: Falconer, David; Tiwari, Sanjiv; Moore, Ronald; Fisher, Megan
2019AAS...23431705F Altcode:
Major solar flares and Coronal Mass Ejections (CMEs) are drivers of
severe space weather. The strongest ones come from active regions
(ARs). They are powered by explosive release of magnetic energy. MAG4
(Magnetogram Forecast) is a large-database near-real-time tool that
measures an AR's free-energy proxy from the AR's deprojected HMI
vector magnetograms. MAG4 converts the free-energy proxy to the AR's
predicted event rate (and event probability) using a forecasting
curve. MAG4 forecasts the event rate and probability for each AR
on the disk, as well as for the full disk. The forecasting curves
presently used by MAG4 are derived from a large sample of SOHO/MDI AR
magnetograms. This requires the HMI vector magnetograms to be degraded
in spatial resolution to approximate what MDI would have measured,
in order to use the MDI forecasting curves. We report on the improved
performance of MAG4 that results from using forecasting curves based
on MAG4's new database of HMI vector magnetograms instead of using
the present forecasting curves that are based on MDI line-of-sight
magnetograms. MAG4's forecasting skill score significantly improves
for major flares (M1 or greater). We present MAG4's improvement in
forecasting SPEs (Solar Particle Events) and X-class flares as well. The
improvement in forecasting CMEs will be evaluated in the future. These
new forecasting curves are being implemented in the near-real-time
operational MAG4, though forecasts from the old curves will still
be given. This work is funded by NSF's Solar Terrestrial Program,
and NASA/SRAG.
---------------------------------------------------------
Title: Evidence of Twisting and Mixed-polarity Solar Photospheric
Magnetic Field in Large Penumbral Jets: IRIS and Hinode Observations
Authors: Tiwari, Sanjiv K.; Moore, Ronald L.; De Pontieu, Bart;
Tarbell, Theodore D.; Panesar, Navdeep K.; Winebarger, Amy R.;
Sterling, Alphonse C.
2018ApJ...869..147T Altcode: 2018arXiv181109554T
A recent study using Hinode (Solar Optical Telescope/Filtergraph
[SOT/FG]) data of a sunspot revealed some unusually large penumbral
jets that often repeatedly occurred at the same locations in the
penumbra, namely, at the tail of a penumbral filament or where the
tails of multiple penumbral filaments converged. These locations had
obvious photospheric mixed-polarity magnetic flux in Na I 5896 Stokes-V
images obtained with SOT/FG. Several other recent investigations have
found that extreme-ultraviolet (EUV)/X-ray coronal jets in quiet-Sun
regions (QRs), in coronal holes (CHs), and near active regions (ARs)
have obvious mixed-polarity fluxes at their base, and that magnetic
flux cancellation prepares and triggers a minifilament flux-rope
eruption that drives the jet. Typical QR, CH, and AR coronal jets are
up to 100 times bigger than large penumbral jets, and in EUV/X-ray
images they show a clear twisting motion in their spires. Here,
using Interface Region Imaging Spectrograph (IRIS) Mg II k λ2796 SJ
images and spectra in the penumbrae of two sunspots, we characterize
large penumbral jets. We find redshift and blueshift next to each
other across several large penumbral jets, and we interpret these as
untwisting of the magnetic field in the jet spire. Using Hinode/SOT
(FG and SP) data, we also find mixed-polarity magnetic flux at the
base of these jets. Because large penumbral jets have a mixed-polarity
field at their base and have a twisting motion in their spires, they
might be driven the same way as QR, CH, and AR coronal jets.
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Title: IRIS and SDO Observations of Solar Jetlets Resulting from
Network-edge Flux Cancelation
Authors: Panesar, Navdeep K.; Sterling, Alphonse C.; Moore, Ronald L.;
Tiwari, Sanjiv K.; De Pontieu, Bart; Norton, Aimee A.
2018ApJ...868L..27P Altcode: 2018arXiv181104314P
Recent observations show that the buildup and triggering of minifilament
eruptions that drive coronal jets result from magnetic flux cancelation
at the neutral line between merging majority- and minority-polarity
magnetic flux patches. We investigate the magnetic setting of 10
on-disk small-scale UV/EUV jets (jetlets, smaller than coronal X-ray
jets but larger than chromospheric spicules) in a coronal hole by using
IRIS UV images and SDO/AIA EUV images and line-of-sight magnetograms
from SDO/HMI. We observe recurring jetlets at the edges of magnetic
network flux lanes in the coronal hole. From magnetograms coaligned
with the IRIS and AIA images, we find, clearly visible in nine cases,
that the jetlets stem from sites of flux cancelation proceeding at
an average rate of ∼1.5 × 10<SUP>18</SUP> Mx hr<SUP>-1</SUP>, and
show brightenings at their bases reminiscent of the base brightenings
in larger-scale coronal jets. We find that jetlets happen at many
locations along the edges of network lanes (not limited to the base
of plumes) with average lifetimes of 3 minutes and speeds of 70 km
s<SUP>-1</SUP>. The average jetlet-base width (4000 km) is three
to four times smaller than for coronal jets (∼18,000 km). Based on
these observations of 10 obvious jetlets, and our previous observations
of larger-scale coronal jets in quiet regions and coronal holes, we
infer that flux cancelation is an essential process in the buildup and
triggering of jetlets. Our observations suggest that network jetlet
eruptions might be small-scale analogs of both larger-scale coronal
jets and the still-larger-scale eruptions producing CMEs.
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Title: Combining sparsity DEM inversions with event tracking for
AIA data
Authors: Bethge, Christian; Winebarger, Amy; Tiwari, Sanjiv
2018csc..confE.108B Altcode:
We apply a modified event tracking code (ASGARD - Automated Selection
and Grouping of events in AIA Regional Data) to the results from
sparsity DEM inversions (Cheung et al, 2015) using AIA EUV data. Outputs
are grouped regions (x/y/t) in multiple defined temperature bins
that can then be correlated in space and time to track the thermal
evolution of coronal structures. We show examples and an overview of
the methodology.
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Title: Critical Magnetic Field Strengths for Solar Coronal Plumes
in Quiet Regions and Coronal Holes?
Authors: Avallone, Ellis A.; Tiwari, Sanjiv K.; Panesar, Navdeep K.;
Moore, Ronald L.; Winebarger, Amy
2018ApJ...861..111A Altcode: 2018arXiv180511188A
Coronal plumes are bright magnetic funnels found in quiet regions (QRs)
and coronal holes (CHs). They extend high into the solar corona and last
from hours to days. The heating processes of plumes involve dynamics
of the magnetic field at their base, but the processes themselves
remain mysterious. Recent observations suggest that plume heating is
a consequence of magnetic flux cancellation and/or convergence at
the plume base. These studies suggest that the base flux in plumes
is of mixed polarity, either obvious or hidden in Solar Dynamics
Observatory (SDO)/HMI data, but do not quantify it. To investigate the
magnetic origins of plume heating, we select 10 unipolar network flux
concentrations, four in CHs, four in QRs, and two that do not form a
plume, and track plume luminosity in SDO/AIA 171 Å images along with
the base flux in SDO/HMI magnetograms, over each flux concentration’s
lifetime. We find that plume heating is triggered when convergence of
the base flux surpasses a field strength of ∼200-600 G. The luminosity
of both QR and CH plumes respond similarly to the field in the plume
base, suggesting that the two have a common formation mechanism. Our
examples of non-plume-forming flux concentrations, reaching field
strengths of 200 G for a similar number of pixels as for a couple of our
plumes, suggest that a critical field might be necessary to form a plume
but is not sufficient for it, thus advocating for other mechanisms,
e.g., flux cancellation due to hidden opposite-polarity field, at play.
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Title: MAG4's New Database of HMI Active-Region Vector Magnetograms:
Sample Size and Initial Results for Major-Flare Forecasting
Authors: Falconer, David Allen; Tiwari, Sanjiv K.; Moore, Ron L.
2018tess.conf41406F Altcode:
We have developed a large-database method of forecasting an active
region's (AR's) chance of producing a major flare (GOES M- or X-class)
and its chance of producing a major CME (speed > 800 km/s) in the
coming few days from a free-energy proxy - a proxy of the AR's free
magnetic energy - measured from a magnetogram of the AR. We have
named this forecasting tool MAG4 (for Magnetogram Forecast). In its
present near-real-time operation mode, MAG4 forecasts each on-disk
AR's rates of production of major flares and major CMEs in the
coming few days, based on the observed major-flare and major-CME
histories of 1,300 ARs observed within 30 degrees of disk center
in MDI line-of-sight magnetograms. From the passages of these ARs
across the 30-degree central disk, the presently-used MAG4 MDI
database has the value of a free-energy proxy measured from 40,000
MDI magnetograms of these 1,300 ARs. We are now compiling a similar
database of the about the same size for MAG4, but for HMI vector
magnetograms that are of ARs observed within 45 degrees of disk
center and that have been deprojected to disk center. This new MAG4
HMI database now has a wide variety of AR parameters measured from
each of 40,000 deprojected HMI vector magnetograms of 900 ARs within
45 degrees of disk center (15 magnetograms of each AR per day during
its passage across the 45-degree central disk). We present the MAG4
major-flare forecasting curves obtained from this new database for a few
alternative free-energy proxies measured from either the vertical-field
component or the horizontal-field component of the deprojected AR
vector magnetograms. (The magnetogram's horizontal-field component
more directly reflects the AR's free magnetic energy than does the
magnetogram's vertical-field component.) By using our statistical method
of measuring, via a skill score, whether the forecasting performance
of one AR magnetogram parameter is significantly better than that
of another, we show which free-energy proxy is the best major-flare
predictor that we have found so far.
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Title: Observations of Large Penumbral Jets from IRIS and Hinode
Authors: Tiwari, Sanjiv K.; Moore, Ronald Lee; De Pontieu, Bart;
Tarbell, Theodore D.; Panesar, Navdeep Kaur; Winebarger, Amy R.;
Sterling, Alphonse C.
2018tess.conf40807T Altcode:
Recent observations from Hinode (SOT/FG) revealed the presence of
large penumbral jets (widths ≥ 500 km, larger than normal penumbral
microjets, which have widths < 400 km) repeatedly occurring at
the same locations in a sunspot penumbra, at the tail of a penumbral
filament or where the tails of several penumbral filaments apparently
converge (Tiwari et al. 2016, ApJ). These locations were observed
to have mixed-polarity flux in Stokes-V images from SOT/FG. Large
penumbral jets displayed direct signatures in AIA 1600, 304, 171,
and 193 channels; thus they were heated to at least transition region
temperatures. Because large jets could not be detected in AIA 94 Å,
whether they had any coronal-temperature plasma remains unclear. In
the present work, for another sunspot, we use IRIS Mg II k 2796
slit jaw images and spectra and magnetograms from Hinode SOT/FG and
SOT/SP to examine: whether penumbral jets spin, similar to spicules
and coronal jets in the quiet Sun and coronal holes; whether they stem
from mixed-polarity flux; and whether they produce discernible coronal
emission, especially in AIA 94 Å images.
---------------------------------------------------------
Title: Theory and Transport of Nearly Incompressible
Magnetohydrodynamic Turbulence. IV. Solar Coronal Turbulence
Authors: Zank, G. P.; Adhikari, L.; Hunana, P.; Tiwari, S. K.; Moore,
R.; Shiota, D.; Bruno, R.; Telloni, D.
2018ApJ...854...32Z Altcode:
A new model describing the transport and evolution of turbulence in the
quiet solar corona is presented. In the low plasma beta environment,
transverse photospheric convective fluid motions drive predominantly
quasi-2D (nonpropagating) turbulence in the mixed-polarity “magnetic
carpet,” together with a minority slab (Alfvénic) component. We use
a simplified sub-Alfvénic flow velocity profile to solve transport
equations describing the evolution and dissipation of turbulence from
1\hspace{0.5em}{{t}}{{o}} 15 {R}<SUB>⊙ </SUB> (including the Alfvén
surface). Typical coronal base parameters are used, although one model
uses correlation lengths derived observationally by Abramenko et al.,
and the other assumes values 10 times larger. The model predicts that
(1) the majority quasi-2D turbulence evolves from a balanced state
at the coronal base to an imbalanced state, with outward fluctuations
dominating, at and beyond the Alfvén surface, i.e., inward turbulent
fluctuations are dissipated preferentially; (2) the initially imbalanced
slab component remains imbalanced throughout the solar corona, being
dominated by outwardly propagating Alfvén waves, and wave reflection
is weak; (3) quasi-2D turbulence becomes increasingly magnetized,
and beyond ∼ 6 {R}<SUB>⊙ </SUB>, the kinetic energy is mainly
in slab fluctuations; (4) there is no accumulation of inward energy
at the Alfvén surface; (5) inertial range quasi-2D rather than slab
fluctuations are preferentially dissipated within ∼ 3 {R}<SUB>⊙
</SUB>; and (6) turbulent dissipation of quasi-2D fluctuations is
sufficient to heat the corona to temperatures ∼ 2× {10}<SUP>6</SUP>
K within 2 {R}<SUB>⊙ </SUB>, consistent with observations that suggest
that the fast solar wind is accelerated most efficiently between ∼
2\hspace{0.5em}{{a}}{{n}}{{d}} 4 {R}<SUB>⊙ </SUB>.
---------------------------------------------------------
Title: Critical Magnetic Field Strengths for Unipolar Solar Coronal
Plumes in Quiet Regions and Coronal Holes?
Authors: Avallone, E. A.; Tiwari, S. K.; Panesar, N. K.; Moore, R. L.
2017AGUFMSH43A2797A Altcode:
Coronal plumes are sporadic fountain-like structures that are bright
in coronal emission. Each is a magnetic funnel rooted in a strong
patch of dominant-polarity photospheric magnetic flux surrounded by
a predominantly-unipolar magnetic network, either in a quiet region
or a coronal hole. The heating processes that make plumes bright
evidently involve the magnetic field in the base of the plume, but
remain mysterious. Raouafi et al. (2014) inferred from observations
that plume heating is a consequence of magnetic reconnection in the
base, whereas Wang et al. (2016) showed that plume heating turns
on/off from convection-driven convergence/divergence of the base
flux. While both papers suggest that the base magnetic flux in their
plumes is of mixed polarity, these papers provide no measurements
of the abundance and strength of the evolving base flux or consider
whether a critical magnetic field strength is required for a plume to
become noticeably bright. To address plume production and evolution,
we track the plume luminosity and the abundance and strength of the
base magnetic flux over the lifetimes of six coronal plumes, using
Solar Dynamics Observatory (SDO)/Atmospheric Imaging Assembly (AIA) 171
Å images and SDO/Helioseismic and Magnetic Imager (HMI) line-of-sight
magnetograms. Three of these plumes are in coronal holes, three are in
quiet regions, and each plume exhibits a unipolar base flux. We track
the base magnetic flux over each plume's lifetime to affirm that its
convergence and divergence respectively coincide with the appearance
and disappearance of the plume in 171 Å images. We tentatively find
that plume formation requires enough convergence of the base flux to
surpass a field strength of ∼300-500 Gauss, and that quiet Sun and
coronal-hole plumes both exhibit the same behavior in the response of
their luminosity in 171 Å to the strength of the magnetic field in
the base.
---------------------------------------------------------
Title: Invisibility of Solar Active Region Umbra-to-Umbra Coronal
Loops: New Evidence that Magnetoconvection Drives Solar-Stellar
Coronal Heating
Authors: Tiwari, S. K.; Thalmann, J. K.; Panesar, N. K.; Moore, R. L.;
Winebarger, A. R.
2017AGUFMSH43A2789T Altcode:
Coronal heating generally increases with increasing magnetic field
strength: the EUV/X-ray corona in active regions is 10-100 times more
luminous and 2-4 times hotter than that in quiet regions and coronal
holes, which are heated to only about 1.5 MK, and have fields that are
10-100 times weaker than that in active regions. From a comparison of
a nonlinear force-free model of the three-dimensional active region
coronal field to observed extreme-ultraviolet loops, we find that (1)
umbra-to-umbra coronal loops, despite being rooted in the strongest
magnetic flux, are invisible, and (2) the brightest loops have one
foot in an umbra or penumbra and the other foot in another sunspot's
penumbra or in unipolar or mixed-polarity plage. The invisibility of
umbra-to-umbra loops is new evidence that magnetoconvection drives
solar-stellar coronal heating: evidently, the strong umbral field at
both ends quenches the magnetoconvection and hence the heating. Our
results from EUV observations and nonlinear force-free modeling of
coronal magnetic field imply that, for any coronal loop on the Sun or
on any other convective star, as long as the field can be braided by
convection in at least one loop foot, the stronger the field in the
loop, the stronger the coronal heating.
---------------------------------------------------------
Title: Evidence from IRIS that Sunspot Large Penumbral Jets Spin
Authors: Tiwari, Sanjiv K.; Moore, Ronald L.; De Pontieu, Bart;
Tarbell, Theodore D.; Panesar, Navdeep K.; Winebarger, Amy; Sterling,
Alphonse C.
2017SPD....4810506T Altcode:
Recent observations from {\it Hinode} (SOT/FG) revealed the presence of
large penumbral jets (widths $\ge$500 km, larger than normal penumbral
microjets, which have widths $<$ 400 km) repeatedly occurring at the
same locations in a sunspot penumbra, at the tail of a filament or where
the tails of several penumbral filaments apparently converge (Tiwari et
al. 2016, ApJ). These locations were observed to have mixed-polarity
flux in Stokes-V images from SOT/FG. Large penumbral jets displayed
direct signatures in AIA 1600, 304, 171, and 193 channels; thus they
were heated to at least transition region temperatures. Because
large jets could not be detected in AIA 94 \AA, whether they had
any coronal-temperature plasma remains unclear. In the present work,
for another sunspot, we use IRIS Mg II k 2796 Å slit jaw images and
spectra and magnetograms from Hinode SOT/FG and SOT/SP to examine:
whether penumbral jets spin, similar to spicules and coronal jets in the
quiet Sun and coronal holes; whether they stem from mixed-polarity flux;
and whether they produce discernible coronal emission, especially in
AIA 94 Å images. The few large penumbral jets for which we have IRIS
spectra show evidence of spin. If these have mixed-polarity at their
base, then they might be driven the same way as coronal jets and CMEs.
---------------------------------------------------------
Title: New Evidence that Magnetoconvection Drives Solar-Stellar
Coronal Heating
Authors: Tiwari, Sanjiv K.; Thalmann, Julia K.; Panesar, Navdeep K.;
Moore, Ronald L.; Winebarger, Amy R.
2017ApJ...843L..20T Altcode: 2017arXiv170608035T
How magnetic energy is injected and released in the solar
corona, keeping it heated to several million degrees, remains
elusive. Coronal heating generally increases with increasing magnetic
field strength. From a comparison of a nonlinear force-free model
of the three-dimensional active region coronal field to observed
extreme-ultraviolet loops, we find that (1) umbra-to-umbra coronal
loops, despite being rooted in the strongest magnetic flux, are
invisible, and (2) the brightest loops have one foot in an umbra or
penumbra and the other foot in another sunspot’s penumbra or in
unipolar or mixed-polarity plage. The invisibility of umbra-to-umbra
loops is new evidence that magnetoconvection drives solar-stellar
coronal heating: evidently, the strong umbral field at both ends
quenches the magnetoconvection and hence the heating. Broadly, our
results indicate that depending on the field strength in both feet,
the photospheric feet of a coronal loop on any convective star can
either engender or quench coronal heating in the loop’s body.
---------------------------------------------------------
Title: The importance of high-resolution observations of the solar
corona
Authors: Winebarger, A. R.; Cirtain, J. W.; Golub, L.; Walsh, R. W.;
De Pontieu, B.; Savage, S. L.; Rachmeler, L.; Kobayashi, K.; Testa,
P.; Brooks, D.; Warren, H.; Mcintosh, S. W.; Peter, H.; Morton, R. J.;
Alexander, C. E.; Tiwari, S. K.
2016AGUFMSH31B2577W Altcode:
The spatial and temporal resolutions of the available coronal
observatories are inadequate to resolve the signatures of coronal
heating. High-resolution and high-cadence observations available with
the Interface Region Imaging Spectrograph (IRIS) and the High-resolution
Coronal Imager (Hi-C) instrument hint that 0.3 arcsec resolution images
and < 10 s cadence provide the necessary resolution to detect
heating events. Hi-C was launched from White Sands Missile Range on
July 11, 2012 (before the launch with IRIS) and obtained images of
a solar active region in the 19.3 nm passband. In this presentation,
I will discuss the potential of combining a flight in Hi-C with a 17.1
nm passband, in conjunction with IRIS. This combination will provide,
for the first time, a definitive method of tracing the energy flow
between the chromosphere and corona and vice versa.
---------------------------------------------------------
Title: Supplement: “Localization and Broadband Follow-up of the
Gravitational-wave Transient GW150914” (2016, ApJL, 826, L13)
Authors: Abbott, B. P.; Abbott, R.; Abbott, T. D.; Abernathy, M. R.;
Acernese, F.; Ackley, K.; Adams, C.; Adams, T.; Addesso, P.; Adhikari,
R. X.; Adya, V. B.; Affeldt, C.; Agathos, M.; Agatsuma, K.; Aggarwal,
N.; Aguiar, O. D.; Aiello, L.; Ain, A.; Ajith, P.; Allen, B.; Allocca,
A.; Altin, P. A.; Anderson, S. B.; Anderson, W. G.; Arai, K.; Araya,
M. C.; Arceneaux, C. C.; Areeda, J. S.; Arnaud, N.; Arun, K. G.;
Ascenzi, S.; Ashton, G.; Ast, M.; Aston, S. M.; Astone, P.; Aufmuth,
P.; Aulbert, C.; Babak, S.; Bacon, P.; Bader, M. K. M.; Baker, P. T.;
Baldaccini, F.; Ballardin, G.; Ballmer, S. W.; Barayoga, J. C.;
Barclay, S. E.; Barish, B. C.; Barker, D.; Barone, F.; Barr, B.;
Barsotti, L.; Barsuglia, M.; Barta, D.; Barthelmy, S.; Bartlett, J.;
Bartos, I.; Bassiri, R.; Basti, A.; Batch, J. C.; Baune, C.; Bavigadda,
V.; Bazzan, M.; Behnke, B.; Bejger, M.; Bell, A. S.; Bell, C. J.;
Berger, B. K.; Bergman, J.; Bergmann, G.; Berry, C. P. L.; Bersanetti,
D.; Bertolini, A.; Betzwieser, J.; Bhagwat, S.; Bhandare, R.; Bilenko,
I. A.; Billingsley, G.; Birch, J.; Birney, R.; Biscans, S.; Bisht,
A.; Bitossi, M.; Biwer, C.; Bizouard, M. A.; Blackburn, J. K.; Blair,
C. D.; Blair, D. G.; Blair, R. M.; Bloemen, S.; Bock, O.; Bodiya,
T. P.; Boer, M.; Bogaert, G.; Bogan, C.; Bohe, A.; Bojtos, P.; Bond,
C.; 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.; Brooks, A. F.; Brown, D. A.; Brown,
D. D.; Brown, N. M.; Buchanan, C. C.; Buikema, A.; Bulik, T.; Bulten,
H. J.; Buonanno, A.; Buskulic, D.; Buy, C.; Byer, R. L.; Cadonati, L.;
Cagnoli, G.; Cahillane, C.; Bustillo, J. C.; Callister, T.; Calloni,
E.; Camp, J. B.; Cannon, K. C.; Cao, J.; Capano, C. D.; Capocasa,
E.; Carbognani, F.; Caride, S.; Diaz, J. C.; Casentini, C.; Caudill,
S.; Cavagliá, M.; Cavalier, F.; Cavalieri, R.; Cella, G.; Cepeda,
C. B.; Baiardi, L. C.; Cerretani, G.; Cesarini, E.; Chakraborty, R.;
Chalermsongsak, T.; Chamberlin, S. J.; Chan, M.; Chao, S.; Charlton,
P.; Chassande-Mottin, E.; Chen, H. Y.; Chen, Y.; Cheng, C.; Chincarini,
A.; Chiummo, A.; Cho, H. S.; Cho, M.; Chow, J. H.; Christensen, N.;
Chu, Q.; Chua, S.; Chung, S.; Ciani, G.; Clara, F.; Clark, J. A.;
Cleva, F.; Coccia, E.; Cohadon, P. -F.; Colla, A.; Collette, C. G.;
Cominsky, L.; Constancio, M., Jr.; Conte, A.; Conti, L.; Cook, D.;
Corbitt, T. R.; Cornish, N.; Corsi, A.; Cortese, S.; Costa, C. A.;
Coughlin, M. W.; Coughlin, S. B.; Coulon, J. -P.; Countryman, S. T.;
Couvares, P.; Cowan, E. E.; Coward, D. M.; Cowart, M. J.; Coyne, D. C.;
Coyne, R.; Craig, K.; Creighton, J. D. E.; Cripe, J.; Crowder, S. G.;
Cumming, A.; Cunningham, L.; Cuoco, E.; Dal Canton, T.; Danilishin,
S. L.; D'Antonio, S.; Danzmann, K.; Darman, N. S.; Dattilo, V.; Dave,
I.; Daveloza, H. P.; Davier, M.; Davies, G. S.; Daw, E. J.; Day, R.;
DeBra, D.; Debreczeni, G.; Degallaix, J.; De Laurentis, M.; Deléglise,
S.; Del Pozzo, W.; Denker, T.; Dent, T.; Dereli, H.; Dergachev, V.;
DeRosa, R. T.; De Rosa, R.; DeSalvo, R.; Dhurandhar, S.; Díaz, M. C.;
Di Fiore, L.; Di Giovanni, M.; Di Lieto, A.; Di Pace, S.; Di Palma,
I.; Di Virgilio, A.; Dojcinoski, G.; Dolique, V.; Donovan, F.; Dooley,
K. L.; Doravari, S.; Douglas, R.; Downes, T. P.; Drago, M.; Drever,
R. W. P.; Driggers, J. C.; Du, Z.; Ducrot, M.; Dwyer, S. E.; Edo,
T. B.; Edwards, M. C.; Effler, A.; Eggenstein, H. -B.; Ehrens, P.;
Eichholz, J.; Eikenberry, S. S.; Engels, W.; Essick, R. C.; Etzel,
T.; Evans, M.; Evans, T. M.; Everett, R.; Factourovich, M.; Fafone,
V.; Fair, H.; Fairhurst, S.; Fan, X.; Fang, Q.; Farinon, S.; Farr,
B.; Farr, W. M.; Favata, M.; Fays, M.; Fehrmann, H.; Fejer, M. M.;
Ferrante, I.; Ferreira, E. C.; Ferrini, F.; Fidecaro, F.; Fiori, I.;
Fiorucci, D.; Fisher, R. P.; Flaminio, R.; Fletcher, M.; Fournier,
J. -D.; Franco, S.; Frasca, S.; Frasconi, F.; Frei, Z.; Freise, A.;
Frey, R.; Frey, V.; Fricke, T. T.; Fritschel, P.; Frolov, V. V.;
Fulda, P.; Fyffe, M.; Gabbard, H. A. G.; Gair, J. R.; Gammaitoni,
L.; Gaonkar, S. G.; Garufi, F.; Gatto, A.; Gaur, G.; Gehrels, N.;
Gemme, G.; Gendre, B.; Genin, E.; Gennai, A.; George, J.; Gergely, L.;
Germain, V.; Ghosh, A.; Ghosh, S.; Giaime, J. A.; Giardina, K. D.;
Giazotto, A.; Gill, K.; Glaefke, A.; Goetz, E.; Goetz, R.; Gondan,
L.; González, G.; Castro, J. M. G.; Gopakumar, A.; Gordon, N. A.;
Gorodetsky, M. L.; Gossan, S. E.; Gosselin, M.; Gouaty, R.; Graef,
C.; Graff, P. B.; Granata, M.; Grant, A.; Gras, S.; Gray, C.; Greco,
G.; Green, A. C.; Groot, P.; Grote, H.; Grunewald, S.; Guidi, G. M.;
Guo, X.; Gupta, A.; Gupta, M. K.; Gushwa, K. E.; Gustafson, E. K.;
Gustafson, R.; Hacker, J. J.; Hall, B. R.; Hall, E. D.; Hammond, G.;
Haney, M.; Hanke, M. M.; Hanks, J.; Hanna, C.; Hannam, M. D.; Hanson,
J.; Hardwick, T.; Haris, K.; Harms, J.; Harry, G. M.; Harry, I. W.;
Hart, M. J.; Hartman, M. T.; Haster, C. -J.; Haughian, K.; 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.; Hoak, D.; Hodge, K. A.; Hofman, D.; Hollitt, S. E.; Holt, K.;
Holz, D. E.; Hopkins, P.; Hosken, D. J.; Hough, J.; Houston, E. A.;
Howell, E. J.; Hu, Y. M.; Huang, S.; Huerta, E. A.; Huet, D.; Hughey,
B.; Husa, S.; Huttner, S. H.; Huynh-Dinh, T.; Idrisy, A.; Indik, N.;
Ingram, D. R.; Inta, R.; Isa, H. N.; Isac, J. -M.; Isi, M.; Islas,
G.; Isogai, T.; Iyer, B. R.; Izumi, K.; Jacqmin, T.; Jang, H.; Jani,
K.; Jaranowski, P.; Jawahar, S.; Jiménez-Forteza, F.; Johnson, W. W.;
Jones, D. I.; Jones, R.; Jonker, R. J. G.; Ju, L.; Kalaghatgi, C. V.;
Kalogera, V.; Kandhasamy, S.; Kang, G.; Kanner, J. B.; Karki, S.;
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M.; Zhang, F.; Zhang, L.; Zhang, M.; Zhang, Y.; Zhao, C.; Zhou, M.;
Zhou, Z.; Zhu, X. J.; Zucker, M. E.; Zuraw, S. E.; Zweizig, J.; LIGO
Scientific Collaboration; Virgo Collaboration; Allison, J.; Bannister,
K.; Bell, M. E.; Chatterjee, S.; Chippendale, A. P.; Edwards, P. G.;
Harvey-Smith, L.; Heywood, Ian; Hotan, A.; Indermuehle, B.; Marvil, J.;
McConnell, D.; Murphy, T.; Popping, A.; Reynolds, J.; Sault, R. J.;
Voronkov, M. A.; Whiting, M. T.; Australian Square Kilometer Array
Pathfinder (ASKAP Collaboration); Castro-Tirado, A. J.; Cunniffe, R.;
Jelínek, M.; Tello, J. C.; Oates, S. R.; Hu, Y. -D.; Kubánek, P.;
Guziy, S.; Castellón, A.; García-Cerezo, A.; Muñoz, V. F.; Pérez
del Pulgar, C.; Castillo-Carrión, S.; Castro Cerón, J. M.; Hudec,
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R.; Yock, P. C.; Rattenbury, N.; Allen, W. H.; Querel, R.; Jeong, S.;
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W. H.; Claret, A.; Sánchez-Ramírez, R.; Pandey, S. B.; Mediavilla,
T.; Sabau-Graziati, L.; BOOTES Collaboration; Abbott, T. M. C.;
Abdalla, F. B.; Allam, S.; Annis, J.; Armstrong, R.; Benoit-Lévy, A.;
Berger, E.; Bernstein, R. A.; Bertin, E.; Brout, D.; Buckley-Geer, E.;
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C. L.; Gaztanaga, E.; Gerdes, D. W.; Goldstein, D. A.; Gruen, D.;
Gruendl, R. A.; Gutierrez, G.; Herner, K.; Honscheid, K.; James, D. J.;
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R.; Marriner, J.; Martini, P.; Matheson, T.; Melchior, P.; Metzger,
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B.; Nugent, P.; Ogando, R.; Petravick, D.; Plazas, A. A.; Quataert,
E.; Roe, N.; Romer, A. K.; Roodman, A.; Rosell, A. C.; Rykoff, E. S.;
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M. E. C.; Tarle, G.; Thaler, J.; Thomas, D.; Thomas, R. C.; Tucker,
D. L.; Vikram, V.; Walker, A. R.; Wechsler, R. H.; Wester, W.; Yanny,
B.; Zhang, Y.; Zuntz, J.; Dark Energy Survey Collaboration; Dark Energy
Camera GW-EM Collaboration; Connaughton, V.; Burns, E.; Goldstein, A.;
Briggs, M. S.; Zhang, B. -B.; Hui, C. M.; Jenke, P.; Wilson-Hodge,
C. A.; Bhat, P. N.; Bissaldi, E.; Cleveland, W.; Fitzpatrick, G.;
Giles, M. M.; Gibby, M. H.; Greiner, J.; von Kienlin, A.; Kippen,
R. M.; McBreen, S.; Mailyan, B.; Meegan, C. A.; Paciesas, W. S.;
Preece, R. D.; Roberts, O.; Sparke, L.; Stanbro, M.; Toelge, K.; Veres,
P.; Yu, H. -F.; Blackburn, L.; Fermi GBM Collaboration; Ackermann,
M.; Ajello, M.; Albert, A.; Anderson, B.; Atwood, W. B.; Axelsson,
M.; Baldini, L.; Barbiellini, G.; Bastieri, D.; Bellazzini, R.;
Bissaldi, E.; Blandford, R. D.; Bloom, E. D.; Bonino, R.; Bottacini,
E.; Brandt, T. J.; Bruel, P.; Buson, S.; Caliandro, G. A.; Cameron,
R. A.; Caragiulo, M.; Caraveo, P. A.; Cavazzuti, E.; Charles, E.;
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J.; Cominsky, L. R.; Costanza, F.; Cuoco, A.; D'Ammando, F.; de
Palma, F.; Desiante, R.; Digel, S. W.; Di Lalla, N.; Di Mauro, M.;
Di Venere, L.; Domínguez, A.; Drell, P. S.; Dubois, R.; Favuzzi, C.;
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D.; Grenier, I. A.; Grove, J. E.; Guiriec, S.; Hadasch, D.; Harding,
A. K.; Hays, E.; Hewitt, J. W.; Hill, A. B.; Horan, D.; Jogler, T.;
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M.; La Mura, G.; Larsson, S.; Latronico, L.; Li, J.; Li, L.; Longo,
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J. E.; Meyer, M.; Michelson, P. F.; Mirabal, N.; Mizuno, T.; Moiseev,
A. A.; Monzani, M. E.; Moretti, E.; Morselli, A.; Moskalenko, I. V.;
Negro, M.; Nuss, E.; Ohsugi, T.; Omodei, N.; Orienti, M.; Orlando,
E.; Ormes, J. F.; Paneque, D.; Perkins, J. S.; Pesce-Rollins, M.;
Piron, F.; Pivato, G.; Porter, T. A.; Racusin, J. L.; Rainò, S.;
Rando, R.; Razzaque, S.; Reimer, A.; Reimer, O.; Salvetti, D.; Saz
Parkinson, P. M.; Sgrò, C.; Simone, D.; Siskind, E. J.; Spada, F.;
Spandre, G.; Spinelli, P.; Suson, D. J.; Tajima, H.; Thayer, J. B.;
Thompson, D. J.; Tibaldo, L.; Torres, D. F.; Troja, E.; Uchiyama,
Y.; Venters, T. M.; Vianello, G.; Wood, K. S.; Wood, M.; Zhu, S.;
Zimmer, S.; Fermi LAT Collaboration; Brocato, E.; Cappellaro, E.;
Covino, S.; Grado, A.; Nicastro, L.; Palazzi, E.; Pian, E.; Amati, L.;
Antonelli, L. A.; Capaccioli, M.; D'Avanzo, P.; D'Elia, V.; Getman,
F.; Giuffrida, G.; Iannicola, G.; Limatola, L.; Lisi, M.; Marinoni,
S.; Marrese, P.; Melandri, A.; Piranomonte, S.; Possenti, A.; Pulone,
L.; Rossi, A.; Stamerra, A.; Stella, L.; Testa, V.; Tomasella, L.;
Yang, S.; GRAvitational Wave Inaf TeAm (GRAWITA); Bazzano, A.; Bozzo,
E.; Brandt, S.; Courvoisier, T. J. -L.; Ferrigno, C.; Hanlon, L.;
Kuulkers, E.; Laurent, P.; Mereghetti, S.; Roques, J. P.; Savchenko,
V.; Ubertini, P.; INTEGRAL Collaboration; Kasliwal, M. M.; Singer,
L. P.; Cao, Y.; Duggan, G.; Kulkarni, S. R.; Bhalerao, V.; Miller,
A. A.; Barlow, T.; Bellm, E.; Manulis, I.; Rana, J.; Laher, R.; Masci,
F.; Surace, J.; Rebbapragada, U.; Cook, D.; Van Sistine, A.; Sesar,
B.; Perley, D.; Ferreti, R.; Prince, T.; Kendrick, R.; Horesh, A.;
Intermediate Palomar Transient Factory (iPTF Collaboration); Hurley,
K.; Golenetskii, S. V.; Aptekar, R. L.; Frederiks, D. D.; Svinkin,
D. S.; Rau, A.; von Kienlin, A.; Zhang, X.; Smith, D. M.; Cline,
T.; Krimm, H.; InterPlanetary Network; Abe, F.; Doi, M.; Fujisawa,
K.; Kawabata, K. S.; Morokuma, T.; Motohara, K.; Tanaka, M.; Ohta,
K.; Yanagisawa, K.; Yoshida, M.; J-GEM Collaboration; Baltay, C.;
Rabinowitz, D.; Ellman, N.; Rostami, S.; La Silla-QUEST Survey;
Bersier, D. F.; Bode, M. F.; Collins, C. A.; Copperwheat, C. M.;
Darnley, M. J.; Galloway, D. K.; Gomboc, A.; Kobayashi, S.; Mazzali,
P.; Mundell, C. G.; Piascik, A. S.; Pollacco, Don; Steele, I. A.;
Ulaczyk, K.; Liverpool Telescope Collaboration; Broderick, J. W.;
Fender, R. P.; Jonker, P. G.; Rowlinson, A.; Stappers, B. W.;
Wijers, R. A. M. J.; Low Frequency Array (LOFAR Collaboration);
Lipunov, V.; Gorbovskoy, E.; Tyurina, N.; Kornilov, V.; Balanutsa, P.;
Kuznetsov, A.; Buckley, D.; Rebolo, R.; Serra-Ricart, M.; Israelian,
G.; Budnev, N. M.; Gress, O.; Ivanov, K.; Poleshuk, V.; Tlatov, A.;
Yurkov, V.; MASTER Collaboration; Kawai, N.; Serino, M.; Negoro,
H.; Nakahira, S.; Mihara, T.; Tomida, H.; Ueno, S.; Tsunemi, H.;
Matsuoka, M.; MAXI Collaboration; Croft, S.; Feng, L.; Franzen,
T. M. O.; Gaensler, B. M.; Johnston-Hollitt, M.; Kaplan, D. L.;
Morales, M. F.; Tingay, S. J.; Wayth, R. B.; Williams, A.; Murchison
Wide-field Array (MWA Collaboration); Smartt, S. J.; Chambers, K. C.;
Smith, K. W.; Huber, M. E.; Young, D. R.; Wright, D. E.; Schultz, A.;
Denneau, L.; Flewelling, H.; Magnier, E. A.; Primak, N.; Rest, A.;
Sherstyuk, A.; Stalder, B.; Stubbs, C. W.; Tonry, J.; Waters, C.;
Willman, M.; Pan-STARRS Collaboration; Olivares E., F.; Campbell,
H.; Kotak, R.; Sollerman, J.; Smith, M.; Dennefeld, M.; Anderson,
J. P.; Botticella, M. T.; Chen, T. -W.; Della Valle, M.; Elias-Rosa,
N.; Fraser, M.; Inserra, C.; Kankare, E.; Kupfer, T.; Harmanen,
J.; Galbany, L.; Le Guillou, L.; Lyman, J. D.; Maguire, K.; Mitra,
A.; Nicholl, M.; Razza, A.; Terreran, G.; Valenti, S.; Gal-Yam, A.;
PESSTO Collaboration; Ćwiek, A.; Ćwiok, M.; Mankiewicz, L.; Opiela,
R.; Zaremba, M.; Żarnecki, A. F.; Pi of Sky Collaboration; Onken,
C. A.; Scalzo, R. A.; Schmidt, B. P.; Wolf, C.; Yuan, F.; SkyMapper
Collaboration; Evans, P. A.; Kennea, J. A.; Burrows, D. N.; Campana,
S.; Cenko, S. B.; Giommi, P.; Marshall, F. E.; Nousek, J.; O'Brien,
P.; Osborne, J. P.; Palmer, D.; Perri, M.; Siegel, M.; Tagliaferri,
G.; Swift Collaboration; Klotz, A.; Turpin, D.; Laugier, R.; TAROT
Collaboration; Zadko Collaboration; Algerian National Observatory,
Algerian Collaboration; C2PU Collaboration; Beroiz, M.; Peñuela,
T.; Macri, L. M.; Oelkers, R. J.; Lambas, D. G.; Vrech, R.; Cabral,
J.; Colazo, C.; Dominguez, M.; Sanchez, B.; Gurovich, S.; Lares,
M.; Marshall, J. L.; DePoy, D. L.; Padilla, N.; Pereyra, N. A.;
Benacquista, M.; TOROS Collaboration; Tanvir, N. R.; Wiersema, K.;
Levan, A. J.; Steeghs, D.; Hjorth, J.; Fynbo, J. P. U.; Malesani, D.;
Milvang-Jensen, B.; Watson, D.; Irwin, M.; Fernandez, C. G.; McMahon,
R. G.; Banerji, M.; Gonzalez-Solares, E.; Schulze, S.; de Ugarte
Postigo, A.; Thoene, C. C.; Cano, Z.; Rosswog, S.; VISTA Collaboration
2016ApJS..225....8A Altcode: 2016arXiv160407864A
This Supplement provides supporting material for Abbott et
al. (2016a). We briefly summarize past electromagnetic (EM) follow-up
efforts as well as the organization and policy of the current EM
follow-up program. We compare the four probability sky maps produced
for the gravitational-wave transient GW150914, and provide additional
details of the EM follow-up observations that were performed in the
different bands.
---------------------------------------------------------
Title: Localization and Broadband Follow-up of the Gravitational-wave
Transient GW150914
Authors: Abbott, B. P.; Abbott, R.; Abbott, T. D.; Abernathy, M. R.;
Acernese, F.; Ackley, K.; Adams, C.; Adams, T.; Addesso, P.; Adhikari,
R. X.; Adya, V. B.; Affeldt, C.; Agathos, M.; Agatsuma, K.; Aggarwal,
N.; Aguiar, O. D.; Aiello, L.; Ain, A.; Ajith, P.; Allen, B.; Allocca,
A.; Altin, P. A.; Anderson, S. B.; Anderson, W. G.; Arai, K.; Araya,
M. C.; Arceneaux, C. C.; Areeda, J. S.; Arnaud, N.; Arun, K. G.;
Ascenzi, S.; Ashton, G.; Ast, M.; Aston, S. M.; Astone, P.; Aufmuth,
P.; Aulbert, C.; Babak, S.; Bacon, P.; Bader, M. K. M.; Baker, P. T.;
Baldaccini, F.; Ballardin, G.; Ballmer, S. W.; Barayoga, J. C.;
Barclay, S. E.; Barish, B. C.; Barker, D.; Barone, F.; Barr, B.;
Barsotti, L.; Barsuglia, M.; Barta, D.; Barthelmy, S.; Bartlett, J.;
Bartos, I.; Bassiri, R.; Basti, A.; Batch, J. C.; Baune, C.; Bavigadda,
V.; Bazzan, M.; Behnke, B.; Bejger, M.; Bell, A. S.; Bell, C. J.;
Berger, B. K.; Bergman, J.; Bergmann, G.; Berry, C. P. L.; Bersanetti,
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I. A.; Billingsley, G.; Birch, J.; Birney, R.; Biscans, S.; Bisht,
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C. D.; Blair, D. G.; Blair, R. M.; Bloemen, S.; Bock, O.; Bodiya,
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V. B.; Branchesi, M.; Brau, J. E.; Briant, T.; Brillet, A.; Brinkmann,
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D. D.; Brown, N. M.; Buchanan, C. C.; Buikema, A.; Bulik, T.; Bulten,
H. J.; Buonanno, A.; Buskulic, D.; Buy, C.; Byer, R. L.; Cadonati, L.;
Cagnoli, G.; Cahillane, C.; Bustillo, J. C.; Callister, T.; Calloni,
E.; Camp, J. B.; Cannon, K. C.; Cao, J.; Capano, C. D.; Capocasa,
E.; Carbognani, F.; Caride, S.; Diaz, J. C.; Casentini, C.; Caudill,
S.; Cavagliá, M.; Cavalier, F.; Cavalieri, R.; Cella, G.; Cepeda,
C. B.; Baiardi, L. C.; Cerretani, G.; Cesarini, E.; Chakraborty, R.;
Chalermsongsak, T.; Chamberlin, S. J.; Chan, M.; Chao, S.; Charlton,
P.; Chassande-Mottin, E.; Chen, H. Y.; Chen, Y.; Cheng, C.; Chincarini,
A.; Chiummo, A.; Cho, H. S.; Cho, M.; Chow, J. H.; Christensen, N.;
Chu, Q.; Chua, S.; Chung, S.; Ciani, G.; Clara, F.; Clark, J. A.;
Cleva, F.; Coccia, E.; Cohadon, P. -F.; Colla, A.; Collette, C. G.;
Cominsky, L.; Constancio, M., Jr.; Conte, A.; Conti, L.; Cook, D.;
Corbitt, T. R.; Cornish, N.; Corsi, A.; Cortese, S.; Costa, C. A.;
Coughlin, M. W.; Coughlin, S. B.; Coulon, J. -P.; Countryman, S. T.;
Couvares, P.; Cowan, E. E.; Coward, D. M.; Cowart, M. J.; Coyne, D. C.;
Coyne, R.; Craig, K.; Creighton, J. D. E.; Cripe, J.; Crowder, S. G.;
Cumming, A.; Cunningham, L.; Cuoco, E.; Dal Canton, T.; Danilishin,
S. L.; D'Antonio, S.; Danzmann, K.; Darman, N. S.; Dattilo, V.; Dave,
I.; Daveloza, H. P.; Davier, M.; Davies, G. S.; Daw, E. J.; Day, R.;
Debra, D.; Debreczeni, G.; Degallaix, J.; de Laurentis, M.; Deléglise,
S.; Del Pozzo, W.; Denker, T.; Dent, T.; Dereli, H.; Dergachev, V.;
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di Fiore, L.; di Giovanni, M.; di Lieto, A.; di Pace, S.; di Palma,
I.; di Virgilio, A.; Dojcinoski, G.; Dolique, V.; Donovan, F.; Dooley,
K. L.; Doravari, S.; Douglas, R.; Downes, T. P.; Drago, M.; Drever,
R. W. P.; Driggers, J. C.; Du, Z.; Ducrot, M.; Dwyer, S. E.; Edo,
T. B.; Edwards, M. C.; Effler, A.; Eggenstein, H. -B.; Ehrens, P.;
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T.; Evans, M.; Evans, T. M.; Everett, R.; Factourovich, M.; Fafone,
V.; Fair, H.; Fairhurst, S.; Fan, X.; Fang, Q.; Farinon, S.; Farr,
B.; Farr, W. M.; Favata, M.; Fays, M.; Fehrmann, H.; Fejer, M. M.;
Ferrante, I.; Ferreira, E. C.; Ferrini, F.; Fidecaro, F.; Fiori, I.;
Fiorucci, D.; Fisher, R. P.; Flaminio, R.; Fletcher, M.; Fournier,
J. -D.; Franco, S.; Frasca, S.; Frasconi, F.; Frei, Z.; Freise, A.;
Frey, R.; Frey, V.; Fricke, T. T.; Fritschel, P.; Frolov, V. V.;
Fulda, P.; Fyffe, M.; Gabbard, H. A. G.; Gair, J. R.; Gammaitoni,
L.; Gaonkar, S. G.; Garufi, F.; Gatto, A.; Gaur, G.; Gehrels, N.;
Gemme, G.; Gendre, B.; Genin, E.; Gennai, A.; George, J.; Gergely, L.;
Germain, V.; Ghosh, A.; Ghosh, S.; Giaime, J. A.; Giardina, K. D.;
Giazotto, A.; Gill, K.; Glaefke, A.; Goetz, E.; Goetz, R.; Gondan,
L.; González, G.; Castro, J. M. G.; Gopakumar, A.; Gordon, N. A.;
Gorodetsky, M. L.; Gossan, S. E.; Gosselin, M.; Gouaty, R.; Graef,
C.; Graff, P. B.; Granata, M.; Grant, A.; Gras, S.; Gray, C.; Greco,
G.; Green, A. C.; Groot, P.; Grote, H.; Grunewald, S.; Guidi, G. M.;
Guo, X.; Gupta, A.; Gupta, M. K.; Gushwa, K. E.; Gustafson, E. K.;
Gustafson, R.; Hacker, J. J.; Hall, B. R.; Hall, E. D.; Hammond, G.;
Haney, M.; Hanke, M. M.; Hanks, J.; Hanna, C.; Hannam, M. D.; Hanson,
J.; Hardwick, T.; Haris, K.; Harms, J.; Harry, G. M.; Harry, I. W.;
Hart, M. J.; Hartman, M. T.; Haster, C. -J.; Haughian, K.; 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.; Hoak, D.; Hodge, K. A.; Hofman, D.; Hollitt, S. E.; Holt, K.;
Holz, D. E.; Hopkins, P.; Hosken, D. J.; Hough, J.; Houston, E. A.;
Howell, E. J.; Hu, Y. M.; Huang, S.; Huerta, E. A.; Huet, D.; Hughey,
B.; Husa, S.; Huttner, S. H.; Huynh-Dinh, T.; Idrisy, A.; Indik, N.;
Ingram, D. R.; Inta, R.; Isa, H. N.; Isac, J. -M.; Isi, M.; Islas,
G.; Isogai, T.; Iyer, B. R.; Izumi, K.; Jacqmin, T.; Jang, H.; Jani,
K.; Jaranowski, P.; Jawahar, S.; Jiménez-Forteza, F.; Johnson, W. W.;
Jones, D. I.; Jones, R.; Jonker, R. J. G.; Ju, L.; Kalaghatgi, C. V.;
Kalogera, V.; Kandhasamy, S.; Kang, G.; Kanner, J. B.; Karki, S.;
Kasprzack, M.; Katsavounidis, E.; Katzman, W.; Kaufer, S.; Kaur,
T.; Kawabe, K.; Kawazoe, F.; Kéfélian, F.; Kehl, M. S.; Keitel,
D.; Kelley, D. B.; Kells, W.; Kennedy, R.; Key, J. S.; Khalaidovski,
A.; Khalili, F. Y.; Khan, I.; Khan, S.; Khan, Z.; Khazanov, E. A.;
Kijbunchoo, N.; Kim, C.; Kim, J.; Kim, K.; Kim, N.; Kim, N.; Kim,
Y. -M.; King, E. J.; King, P. J.; Kinzel, D. L.; Kissel, J. S.;
Kleybolte, L.; Klimenko, S.; Koehlenbeck, S. M.; Kokeyama, K.; Koley,
S.; Kondrashov, V.; Kontos, A.; Korobko, M.; Korth, W. Z.; Kowalska,
I.; Kozak, D. B.; Kringel, V.; Królak, A.; Krueger, C.; Kuehn, G.;
Kumar, P.; Kuo, L.; Kutynia, A.; Lackey, B. D.; Landry, M.; Lange,
J.; Lantz, B.; Lasky, P. D.; Lazzarini, A.; Lazzaro, C.; Leaci,
P.; Leavey, S.; Lebigot, E. O.; Lee, C. H.; Lee, H. K.; Lee, H. M.;
Lee, K.; Lenon, A.; Leonardi, M.; Leong, J. R.; Leroy, N.; Letendre,
N.; Levin, Y.; Levine, B. M.; Li, T. G. F.; Libson, A.; Littenberg,
T. B.; Lockerbie, N. A.; Logue, J.; Lombardi, A. L.; Lord, J. E.;
Lorenzini, M.; Loriette, V.; Lormand, M.; Losurdo, G.; Lough, J. D.;
Lück, H.; Lundgren, A. P.; Luo, J.; Lynch, R.; Ma, Y.; MacDonald, T.;
Machenschalk, B.; Macinnis, M.; MacLeod, D. M.; Magaña-Sandoval, F.;
Magee, R. M.; Mageswaran, M.; Majorana, E.; Maksimovic, I.; Malvezzi,
V.; Man, N.; Mandel, I.; Mandic, V.; Mangano, V.; Mansell, G. L.;
Manske, M.; Mantovani, M.; Marchesoni, F.; Marion, F.; Márka, S.;
Márka, Z.; Markosyan, A. S.; Maros, E.; Martelli, F.; Martellini, L.;
Martin, I. W.; Martin, R. M.; Martynov, D. V.; Marx, J. N.; Mason,
K.; Masserot, A.; Massinger, T. J.; Masso-Reid, M.; Matichard, F.;
Matone, L.; Mavalvala, N.; Mazumder, N.; Mazzolo, G.; McCarthy, R.;
McClelland, D. E.; McCormick, S.; McGuire, S. C.; McIntyre, G.; McIver,
J.; McManus, D. J.; McWilliams, S. T.; Meacher, D.; Meadors, G. D.;
Meidam, J.; Melatos, A.; Mendell, G.; Mendoza-Gandara, D.; Mercer,
R. A.; Merilh, E.; Merzougui, M.; Meshkov, S.; Messenger, C.; Messick,
C.; Meyers, P. M.; Mezzani, F.; Miao, H.; Michel, C.; Middleton, H.;
Mikhailov, E. E.; Milano, L.; Miller, J.; Millhouse, M.; Minenkov, Y.;
Ming, J.; Mirshekari, S.; 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.; Mossavi, K.; Mours, B.; Mow-Lowry, C. M.;
Mueller, C. L.; Mueller, G.; Muir, A. W.; Mukherjee, A.; Mukherjee,
D.; Mukherjee, S.; Mukund, N.; Mullavey, A.; Munch, J.; Murphy, D. J.;
Murray, P. G.; Mytidis, A.; Nardecchia, I.; Naticchioni, L.; Nayak,
R. K.; Necula, V.; Nedkova, K.; Nelemans, G.; Neri, M.; Neunzert, A.;
Newton, G.; Nguyen, T. T.; Nielsen, A. B.; Nissanke, S.; Nitz, A.;
Nocera, F.; Nolting, D.; Normandin, M. E. N.; Nuttall, L. K.; Oberling,
J.; Ochsner, E.; O'Dell, J.; Oelker, E.; Ogin, G. H.; Oh, J. J.; Oh,
S. H.; Ohme, F.; Oliver, M.; Oppermann, P.; Oram, R. J.; O'Reilly,
B.; O'Shaughnessy, R.; Ottaway, D. J.; Ottens, R. S.; Overmier,
H.; Owen, B. J.; Pai, A.; Pai, S. A.; Palamos, J. R.; Palashov, O.;
Palliyaguru, N.; Palomba, C.; Pal-Singh, A.; Pan, 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.; Patrick, Z.; Pearlstone, B. L.;
Pedraza, M.; Pedurand, R.; Pekowsky, L.; Pele, A.; Penn, S.; Perreca,
A.; Phelps, M.; Piccinni, O.; Pichot, M.; Piergiovanni, F.; Pierro,
V.; Pillant, G.; Pinard, L.; Pinto, I. M.; Pitkin, M.; Poggiani,
R.; Popolizio, P.; Post, A.; Powell, J.; Prasad, J.; Predoi, V.;
Premachandra, S. S.; Prestegard, T.; Price, L. R.; Prijatelj, M.;
Principe, M.; Privitera, S.; Prodi, G. A.; Prokhorov, L.; Puncken,
O.; Punturo, M.; Puppo, P.; Pürrer, M.; Qi, H.; Qin, J.; Quetschke,
V.; Quintero, E. A.; Quitzow-James, R.; Raab, F. J.; Rabeling, D. S.;
Radkins, H.; Raffai, P.; Raja, S.; Rakhmanov, M.; Rapagnani, P.;
Raymond, V.; Razzano, M.; Re, V.; Read, J.; Reed, C. M.; Regimbau,
T.; Rei, L.; Reid, S.; Reitze, D. H.; Rew, H.; Reyes, S. D.; Ricci,
F.; Riles, K.; Robertson, N. A.; Robie, R.; Robinet, F.; Rocchi, A.;
Rolland, L.; Rollins, J. G.; Roma, V. J.; Romano, R.; Romanov, G.;
Romie, J. H.; Rosińska, D.; Rowan, S.; Rüdiger, A.; Ruggi, P.; Ryan,
K.; Sachdev, S.; Sadecki, T.; Sadeghian, L.; Salconi, L.; Saleem,
M.; Salemi, F.; Samajdar, A.; Sammut, L.; Sanchez, E. J.; Sandberg,
V.; Sandeen, B.; Sanders, J. R.; Sassolas, B.; Sathyaprakash, B. S.;
Saulson, P. R.; Sauter, O.; Savage, R. L.; Sawadsky, A.; Schale, P.;
Schilling, R.; Schmidt, J.; Schmidt, P.; Schnabel, R.; Schofield,
R. M. S.; Schönbeck, A.; Schreiber, E.; Schuette, D.; Schutz,
B. F.; Scott, J.; Scott, S. M.; Sellers, D.; Sentenac, D.; Sequino,
V.; Sergeev, A.; Serna, G.; Setyawati, Y.; Sevigny, A.; Shaddock,
D. A.; Shah, S.; Shahriar, M. S.; Shaltev, M.; Shao, Z.; Shapiro,
B.; Shawhan, P.; Sheperd, A.; Shoemaker, D. H.; Shoemaker, D. M.;
Siellez, K.; Siemens, X.; Sigg, D.; Silva, A. D.; Simakov, D.; Singer,
A.; Singh, A.; Singh, R.; Singhal, A.; Sintes, A. M.; Slagmolen,
B. J. J.; Smith, J. R.; Smith, N. D.; Smith, R. J. E.; Son, E. J.;
Sorazu, B.; Sorrentino, F.; Souradeep, T.; Srivastava, A. K.; Staley,
A.; Steinke, M.; Steinlechner, J.; Steinlechner, S.; Steinmeyer, D.;
Stephens, B. C.; Stone, R.; Strain, K. A.; Straniero, N.; Stratta, G.;
Strauss, N. A.; Strigin, S.; Sturani, R.; Stuver, A. L.; Summerscales,
T. Z.; Sun, L.; Sutton, P. J.; Swinkels, B. L.; Szczepańczyk, M. J.;
Tacca, M.; Talukder, D.; Tanner, D. B.; Tápai, M.; Tarabrin, S. P.;
Taracchini, A.; Taylor, R.; Theeg, T.; Thirugnanasambandam, M. P.;
Thomas, E. G.; Thomas, M.; Thomas, P.; Thorne, K. A.; Thorne, K. S.;
Thrane, E.; Tiwari, S.; Tiwari, V.; Tokmakov, K. V.; Tomlinson, C.;
Tonelli, M.; Torres, C. V.; Torrie, C. I.; Töyrä, D.; Travasso,
F.; Traylor, G.; Trifirò, D.; Tringali, M. C.; Trozzo, L.; Tse, M.;
Turconi, M.; Tuyenbayev, D.; 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 Schaaf, L.; van Heijningen, J. V.;
van Veggel, A. A.; Vardaro, M.; Vass, S.; Vasúth, M.; Vaulin, R.;
Vecchio, A.; Vedovato, G.; Veitch, J.; Veitch, P. J.; Venkateswara, K.;
Verkindt, D.; Vetrano, F.; Viceré, A.; Vinciguerra, S.; Vine, D. J.;
Vinet, J. -Y.; Vitale, S.; Vo, T.; Vocca, H.; Vorvick, C.; Voss, D.;
Vousden, W. D.; Vyatchanin, S. P.; Wade, A. R.; Wade, L. E.; Wade,
M.; Walker, M.; Wallace, L.; Walsh, S.; Wang, G.; Wang, H.; Wang,
M.; Wang, X.; Wang, Y.; Ward, R. L.; Warner, J.; Was, M.; Weaver,
B.; Wei, L. -W.; Weinert, M.; Weinstein, A. J.; Weiss, R.; Welborn,
T.; Wen, L.; Weßels, P.; Westphal, T.; Wette, K.; Whelan, J. T.;
White, D. J.; Whiting, B. F.; Williams, R. D.; Williamson, A. R.;
Willis, J. L.; Willke, B.; Wimmer, M. H.; Winkler, W.; Wipf, C. C.;
Wittel, H.; Woan, G.; Worden, J.; Wright, J. L.; Wu, G.; Yablon, J.;
Yam, W.; Yamamoto, H.; Yancey, C. C.; Yap, M. J.; Yu, H.; Yvert, M.;
Zadrożny, A.; Zangrando, L.; Zanolin, M.; Zendri, J. -P.; Zevin,
M.; Zhang, F.; Zhang, L.; Zhang, M.; Zhang, Y.; Zhao, C.; Zhou, M.;
Zhou, Z.; Zhu, X. J.; Zucker, M. E.; Zuraw, S. E.; Zweizig, J.; Ligo
Scientific Collaboration; VIRGO Collaboration; Allison, J.; Bannister,
K.; Bell, M. E.; Chatterjee, S.; Chippendale, A. P.; Edwards, P. G.;
Harvey-Smith, L.; Heywood, Ian; Hotan, A.; Indermuehle, B.; Marvil, J.;
McConnell, D.; Murphy, T.; Popping, A.; Reynolds, J.; Sault, R. J.;
Voronkov, M. A.; Whiting, M. T.; Australian Square Kilometer Array
Pathfinder (Askap Collaboration); Castro-Tirado, A. J.; Cunniffe, R.;
Jelínek, M.; Tello, J. C.; Oates, S. R.; Hu, Y. -D.; Kubánek, P.;
Guziy, S.; Castellón, A.; García-Cerezo, A.; Muñoz, V. F.; Pérez
Del Pulgar, C.; Castillo-Carrión, S.; Castro Cerón, J. M.; Hudec,
R.; Caballero-García, M. D.; Páta, P.; Vitek, S.; Adame, J. A.;
Konig, S.; Rendón, F.; Mateo Sanguino, T. De J.; Fernández-Muñoz,
R.; Yock, P. C.; Rattenbury, N.; Allen, W. H.; Querel, R.; Jeong,
S.; Park, I. H.; Bai, J.; Cui, Ch.; Fan, Y.; Wang, Ch.; Hiriart,
D.; Lee, W. H.; Claret, A.; Sánchez-Ramírez, R.; Pandey, S. B.;
Mediavilla, T.; Sabau-Graziati, L.; Bootes Collaboration; Abbott,
T. M. C.; Abdalla, F. B.; Allam, S.; Annis, J.; Armstrong, R.;
Benoit-Lévy, A.; Berger, E.; Bernstein, R. A.; Bertin, E.; Brout, D.;
Buckley-Geer, E.; Burke, D. L.; Capozzi, D.; Carretero, J.; Castander,
F. J.; Chornock, R.; Cowperthwaite, P. S.; Crocce, M.; Cunha, C. E.;
D'Andrea, C. B.; da Costa, L. N.; Desai, S.; Diehl, H. T.; Dietrich,
J. P.; Doctor, Z.; Drlica-Wagner, A.; Drout, M. R.; Eifler, T. F.;
Estrada, J.; Evrard, A. E.; Fernandez, E.; Finley, D. A.; Flaugher,
B.; Foley, R. J.; Fong, W. -F.; Fosalba, P.; Fox, D. B.; Frieman, J.;
Fryer, C. L.; Gaztanaga, E.; Gerdes, D. W.; Goldstein, D. A.; Gruen,
D.; Gruendl, R. A.; Gutierrez, G.; Herner, K.; Honscheid, K.; James,
D. J.; Johnson, M. D.; Johnson, M. W. G.; Karliner, I.; Kasen, D.;
Kent, S.; Kessler, R.; Kim, A. G.; Kind, M. C.; Kuehn, K.; Kuropatkin,
N.; Lahav, O.; Li, T. S.; Lima, M.; Lin, H.; Maia, M. A. G.; Margutti,
R.; Marriner, J.; Martini, P.; Matheson, T.; Melchior, P.; Metzger,
B. D.; Miller, C. J.; Miquel, R.; Neilsen, E.; Nichol, R. C.; Nord,
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E.; Roe, N.; Romer, A. K.; Roodman, A.; Rosell, A. C.; Rykoff, E. S.;
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M. E. C.; Tarle, G.; Thaler, J.; Thomas, D.; Thomas, R. C.; Tucker,
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C. A.; Bhat, P. N.; Bissaldi, E.; Cleveland, W.; Fitzpatrick, G.;
Giles, M. M.; Gibby, M. H.; Greiner, J.; von Kienlin, A.; Kippen,
R. M.; McBreen, S.; Mailyan, B.; Meegan, C. A.; Paciesas, W. S.;
Preece, R. D.; Roberts, O.; Sparke, L.; Stanbro, M.; Toelge, K.; Veres,
P.; Yu, H. -F.; Blackburn, L.; Fermi Gbm Collaboration; Ackermann,
M.; Ajello, M.; Albert, A.; Anderson, B.; Atwood, W. B.; Axelsson,
M.; Baldini, L.; Barbiellini, G.; Bastieri, D.; Bellazzini, R.;
Bissaldi, E.; Blandford, R. D.; Bloom, E. D.; Bonino, R.; Bottacini,
E.; Brandt, T. J.; Bruel, P.; Buson, S.; Caliandro, G. A.; Cameron,
R. A.; Caragiulo, M.; Caraveo, P. A.; Cavazzuti, E.; Charles, E.;
Chekhtman, A.; Chiang, J.; Chiaro, G.; Ciprini, S.; Cohen-Tanugi,
J.; Cominsky, L. R.; Costanza, F.; Cuoco, A.; D'Ammando, F.; de
Palma, F.; Desiante, R.; Digel, S. W.; di Lalla, N.; di Mauro, M.;
di Venere, L.; Domínguez, A.; Drell, P. S.; Dubois, R.; Favuzzi, C.;
Ferrara, E. C.; Franckowiak, A.; Fukazawa, Y.; Funk, S.; Fusco, P.;
Gargano, F.; Gasparrini, D.; Giglietto, N.; Giommi, P.; Giordano, F.;
Giroletti, M.; Glanzman, T.; Godfrey, G.; Gomez-Vargas, G. A.; Green,
D.; Grenier, I. A.; Grove, J. E.; Guiriec, S.; Hadasch, D.; Harding,
A. K.; Hays, E.; Hewitt, J. W.; Hill, A. B.; Horan, D.; Jogler, T.;
Jóhannesson, G.; Johnson, A. S.; Kensei, S.; Kocevski, D.; Kuss,
M.; La Mura, G.; Larsson, S.; Latronico, L.; Li, J.; Li, L.; Longo,
F.; Loparco, F.; Lovellette, M. N.; Lubrano, P.; Magill, J.; Maldera,
S.; Manfreda, A.; Marelli, M.; Mayer, M.; Mazziotta, M. N.; McEnery,
J. E.; Meyer, M.; Michelson, P. F.; Mirabal, N.; Mizuno, T.; Moiseev,
A. A.; Monzani, M. E.; Moretti, E.; Morselli, A.; Moskalenko, I. V.;
Negro, M.; Nuss, E.; Ohsugi, T.; Omodei, N.; Orienti, M.; Orlando,
E.; Ormes, J. F.; Paneque, D.; Perkins, J. S.; Pesce-Rollins, M.;
Piron, F.; Pivato, G.; Porter, T. A.; Racusin, J. L.; Rainò, S.;
Rando, R.; Razzaque, S.; Reimer, A.; Reimer, O.; Salvetti, D.; Saz
Parkinson, P. M.; Sgrò, C.; Simone, D.; Siskind, E. J.; Spada, F.;
Spandre, G.; Spinelli, P.; Suson, D. J.; Tajima, H.; Thayer, J. B.;
Thompson, D. J.; Tibaldo, L.; Torres, D. F.; Troja, E.; Uchiyama,
Y.; Venters, T. M.; Vianello, G.; Wood, K. S.; Wood, M.; Zhu, S.;
Zimmer, S.; Fermi Lat Collaboration; Brocato, E.; Cappellaro, E.;
Covino, S.; Grado, A.; Nicastro, L.; Palazzi, E.; Pian, E.; Amati, L.;
Antonelli, L. A.; Capaccioli, M.; D'Avanzo, P.; D'Elia, V.; Getman,
F.; Giuffrida, G.; Iannicola, G.; Limatola, L.; Lisi, M.; Marinoni,
S.; Marrese, P.; Melandri, A.; Piranomonte, S.; Possenti, A.; Pulone,
L.; Rossi, A.; Stamerra, A.; Stella, L.; Testa, V.; Tomasella, L.;
Yang, S.; Gravitational Wave Inaf Team (Grawita); Bazzano, A.; Bozzo,
E.; Brandt, S.; Courvoisier, T. J. -L.; Ferrigno, C.; Hanlon, L.;
Kuulkers, E.; Laurent, P.; Mereghetti, S.; Roques, J. P.; Savchenko,
V.; Ubertini, P.; INTEGRAL Collaboration; Kasliwal, M. M.; Singer,
L. P.; Cao, Y.; Duggan, G.; Kulkarni, S. R.; Bhalerao, V.; Miller,
A. A.; Barlow, T.; Bellm, E.; Manulis, I.; Rana, J.; Laher, R.; Masci,
F.; Surace, J.; Rebbapragada, U.; Cook, D.; van Sistine, A.; Sesar,
B.; Perley, D.; Ferreti, R.; Prince, T.; Kendrick, R.; Horesh, A.;
Intermediate Palomar Transient Factory (Iptf Collaboration); Hurley,
K.; Golenetskii, S. V.; Aptekar, R. L.; Frederiks, D. D.; Svinkin,
D. S.; Rau, A.; von Kienlin, A.; Zhang, X.; Smith, D. M.; Cline,
T.; Krimm, H.; Network, Interplanetary; Abe, F.; Doi, M.; Fujisawa,
K.; Kawabata, K. S.; Morokuma, T.; Motohara, K.; Tanaka, M.; Ohta,
K.; Yanagisawa, K.; Yoshida, M.; J-Gem Collaboration; Baltay, C.;
Rabinowitz, D.; Ellman, N.; Rostami, S.; La Silla-Quest Survey;
Bersier, D. F.; Bode, M. F.; Collins, C. A.; Copperwheat, C. M.;
Darnley, M. J.; Galloway, D. K.; Gomboc, A.; Kobayashi, S.; Mazzali,
P.; Mundell, C. G.; Piascik, A. S.; Pollacco, Don; Steele, I. A.;
Ulaczyk, K.; Liverpool Telescope Collaboration; Broderick, J. W.;
Fender, R. P.; Jonker, P. G.; Rowlinson, A.; Stappers, B. W.;
Wijers, R. A. M. J.; Low Frequency Array (Lofar Collaboration);
Lipunov, V.; Gorbovskoy, E.; Tyurina, N.; Kornilov, V.; Balanutsa, P.;
Kuznetsov, A.; Buckley, D.; Rebolo, R.; Serra-Ricart, M.; Israelian,
G.; Budnev, N. M.; Gress, O.; Ivanov, K.; Poleshuk, V.; Tlatov, A.;
Yurkov, V.; Master Collaboration; Kawai, N.; Serino, M.; Negoro,
H.; Nakahira, S.; Mihara, T.; Tomida, H.; Ueno, S.; Tsunemi, H.;
Matsuoka, M.; Maxi Collaboration; Croft, S.; Feng, L.; Franzen,
T. M. O.; Gaensler, B. M.; Johnston-Hollitt, M.; Kaplan, D. L.;
Morales, M. F.; Tingay, S. J.; Wayth, R. B.; Williams, A.; Murchison
Wide-Field Array (Mwa Collaboration); Smartt, S. J.; Chambers, K. C.;
Smith, K. W.; Huber, M. E.; Young, D. R.; Wright, D. E.; Schultz, A.;
Denneau, L.; Flewelling, H.; Magnier, E. A.; Primak, N.; Rest, A.;
Sherstyuk, A.; Stalder, B.; Stubbs, C. W.; Tonry, J.; Waters, C.;
Willman, M.; Pan-Starrs Collaboration; Olivares E., F.; Campbell,
H.; Kotak, R.; Sollerman, J.; Smith, M.; Dennefeld, M.; Anderson,
J. P.; Botticella, M. T.; Chen, T. -W.; Della Valle, M.; Elias-Rosa,
N.; Fraser, M.; Inserra, C.; Kankare, E.; Kupfer, T.; Harmanen,
J.; Galbany, L.; Le Guillou, L.; Lyman, J. D.; Maguire, K.; Mitra,
A.; Nicholl, M.; Razza, A.; Terreran, G.; Valenti, S.; Gal-Yam, A.;
Pessto Collaboration; Ćwiek, A.; Ćwiok, M.; Mankiewicz, L.; Opiela,
R.; Zaremba, M.; Żarnecki, A. F.; Pi Of Sky Collaboration; Onken,
C. A.; Scalzo, R. A.; Schmidt, B. P.; Wolf, C.; Yuan, F.; Skymapper
Collaboration; Evans, P. A.; Kennea, J. A.; Burrows, D. N.; Campana,
S.; Cenko, S. B.; Giommi, P.; Marshall, F. E.; Nousek, J.; O'Brien,
P.; Osborne, J. P.; Palmer, D.; Perri, M.; Siegel, M.; Tagliaferri,
G.; Swift Collaboration; Klotz, A.; Turpin, D.; Laugier, R.; Tarot,
Zadko, Algerian National Observatory C2PU Collaboration; Beroiz, M.;
Peñuela, T.; Macri, L. M.; Oelkers, R. J.; Lambas, D. G.; Vrech,
R.; Cabral, J.; Colazo, C.; Dominguez, M.; Sanchez, B.; Gurovich, S.;
Lares, M.; Marshall, J. L.; Depoy, D. L.; Padilla, N.; Pereyra, N. A.;
Benacquista, M.; Toros Collaboration; Tanvir, N. R.; Wiersema, K.;
Levan, A. J.; Steeghs, D.; Hjorth, J.; Fynbo, J. P. U.; Malesani, D.;
Milvang-Jensen, B.; Watson, D.; Irwin, M.; Fernandez, C. G.; McMahon,
R. G.; Banerji, M.; Gonzalez-Solares, E.; Schulze, S.; de Ugarte
Postigo, A.; Thoene, C. C.; Cano, Z.; Rosswog, S.; Vista Collaboration
2016ApJ...826L..13A Altcode: 2016arXiv160208492A
A gravitational-wave (GW) transient was identified in data recorded
by the Advanced Laser Interferometer Gravitational-wave Observatory
(LIGO) detectors on 2015 September 14. The event, initially designated
G184098 and later given the name GW150914, is described in detail
elsewhere. By prior arrangement, preliminary estimates of the time,
significance, and sky location of the event were shared with 63 teams of
observers covering radio, optical, near-infrared, X-ray, and gamma-ray
wavelengths with ground- and space-based facilities. In this Letter we
describe the low-latency analysis of the GW data and present the sky
localization of the first observed compact binary merger. We summarize
the follow-up observations reported by 25 teams via private Gamma-ray
Coordinates Network circulars, giving an overview of the participating
facilities, the GW sky localization coverage, the timeline, and depth
of the observations. As this event turned out to be a binary black hole
merger, there is little expectation of a detectable electromagnetic
(EM) signature. Nevertheless, this first broadband campaign to search
for a counterpart of an Advanced LIGO source represents a milestone and
highlights the broad capabilities of the transient astronomy community
and the observing strategies that have been developed to pursue neutron
star binary merger events. Detailed investigations of the EM data and
results of the EM follow-up campaign are being disseminated in papers
by the individual teams.
---------------------------------------------------------
Title: Solar Science with the Atacama Large Millimeter/Submillimeter
Array—A New View of Our Sun
Authors: Wedemeyer, S.; Bastian, T.; Brajša, R.; Hudson, H.;
Fleishman, G.; Loukitcheva, M.; Fleck, B.; Kontar, E. P.; De Pontieu,
B.; Yagoubov, P.; Tiwari, S. K.; Soler, R.; Black, J. H.; Antolin,
P.; Scullion, E.; Gunár, S.; Labrosse, N.; Ludwig, H. -G.; Benz,
A. O.; White, S. M.; Hauschildt, P.; Doyle, J. G.; Nakariakov, V. M.;
Ayres, T.; Heinzel, P.; Karlicky, M.; Van Doorsselaere, T.; Gary,
D.; Alissandrakis, C. E.; Nindos, A.; Solanki, S. K.; Rouppe van
der Voort, L.; Shimojo, M.; Kato, Y.; Zaqarashvili, T.; Perez, E.;
Selhorst, C. L.; Barta, M.
2016SSRv..200....1W Altcode: 2015SSRv..tmp..118W; 2015arXiv150406887W
The Atacama Large Millimeter/submillimeter Array (ALMA) is a new
powerful tool for observing the Sun at high spatial, temporal, and
spectral resolution. These capabilities can address a broad range
of fundamental scientific questions in solar physics. The radiation
observed by ALMA originates mostly from the chromosphere—a complex
and dynamic region between the photosphere and corona, which plays a
crucial role in the transport of energy and matter and, ultimately,
the heating of the outer layers of the solar atmosphere. Based on
first solar test observations, strategies for regular solar campaigns
are currently being developed. State-of-the-art numerical simulations
of the solar atmosphere and modeling of instrumental effects can help
constrain and optimize future observing modes for ALMA. Here we present
a short technical description of ALMA and an overview of past efforts
and future possibilities for solar observations at submillimeter and
millimeter wavelengths. In addition, selected numerical simulations
and observations at other wavelengths demonstrate ALMA's scientific
potential for studying the Sun for a large range of science cases.
---------------------------------------------------------
Title: SSALMON - The Solar Simulations for the Atacama Large
Millimeter Observatory Network
Authors: Wedemeyer, S.; Bastian, T.; Brajša, R.; Barta, M.; Hudson,
H.; Fleishman, G.; Loukitcheva, M.; Fleck, B.; Kontar, E.; De Pontieu,
B.; Tiwari, S.; Kato, Y.; Soler, R.; Yagoubov, P.; Black, J. H.;
Antolin, P.; Gunár, S.; Labrosse, N.; Benz, A. O.; Nindos, A.;
Steffen, M.; Scullion, E.; Doyle, J. G.; Zaqarashvili, T.; Hanslmeier,
A.; Nakariakov, V. M.; Heinzel, P.; Ayres, T.; Karlicky, M.
2015AdSpR..56.2679W Altcode: 2015arXiv150205601W
The Solar Simulations for the Atacama Large Millimeter Observatory
Network (SSALMON) was initiated in 2014 in connection with two ALMA
development studies. The Atacama Large Millimeter/submillimeter Array
(ALMA) is a powerful new tool, which can also observe the Sun at
high spatial, temporal, and spectral resolution. The international
SSALMONetwork aims at co-ordinating the further development of solar
observing modes for ALMA and at promoting scientific opportunities
for solar physics with particular focus on numerical simulations,
which can provide important constraints for the observing modes and
can aid the interpretation of future observations. The radiation
detected by ALMA originates mostly in the solar chromosphere - a
complex and dynamic layer between the photosphere and corona, which
plays an important role in the transport of energy and matter and the
heating of the outer layers of the solar atmosphere. Potential targets
include active regions, prominences, quiet Sun regions, flares. Here,
we give a brief overview over the network and potential science cases
for future solar observations with ALMA.
---------------------------------------------------------
Title: Near-Sun speed of CMEs and the magnetic nonpotentiality of
their source active regions
Authors: Tiwari, Sanjiv K.; Falconer, David A.; Moore, Ronald L.;
Venkatakrishnan, P.; Winebarger, Amy R.; Khazanov, Igor G.
2015GeoRL..42.5702T Altcode: 2015arXiv150801532T
We show that the speed of the fastest coronal mass ejections (CMEs)
that an active region (AR) can produce can be predicted from a
vector magnetogram of the AR. This is shown by logarithmic plots of
CME speed (from the SOHO Large Angle and Spectrometric Coronagraph
CME catalog) versus each of ten AR-integrated magnetic parameters
(AR magnetic flux, three different AR magnetic-twist parameters,
and six AR free-magnetic-energy proxies) measured from the vertical
and horizontal field components of vector magnetograms (from the
Solar Dynamics Observatory's Helioseismic and Magnetic Imager)
of the source ARs of 189 CMEs. These plots show the following: (1)
the speed of the fastest CMEs that an AR can produce increases with
each of these whole-AR magnetic parameters and (2) that one of the AR
magnetic-twist parameters and the corresponding free-magnetic-energy
proxy each determine the CME-speed upper limit line somewhat better
than any of the other eight whole-AR magnetic parameters.
---------------------------------------------------------
Title: Speed of CMEs and the magnetic non-potentiality of their
source active regions
Authors: Tiwari, S. K.; Falconer, D. A.; Moore, R. L.; Venkatakrishnan,
P.
2014AGUFMSH21C4134T Altcode:
Most fast coronal mass ejections (CMEs) originate from solar active
regions (ARs). Non-potentiality of ARs is expected to determine the
speed and size of CMEs in the outer corona. Several other unexplored
parameters might be important as well. To find out the correlation
between the initial speed of CMEs and the non-potentiality of source
ARs, we associated over a hundred of CMEs with source ARs via their
co-produced flares. The speed of the CMEs are collected from the SOHO
LASCO CME catalog. We have used vector magnetograms obtained mainly
with HMI/SDO, also with Hinode (SOT/SP) when available within an hour
of a CME occurence, to evaluate various magnetic non-potentiality
parameters, e.g. magnetic free-energy proxies, computed magnetic
free energy, twist, shear angle, signed shear angle etc. We have
also included several other parameters e.g. total unsigned flux, net
current, magnetic area of ARs, area of sunspots, to investigate their
correlation, if any, with the initial speeds of CMEs. Our preliminary
results show that the ARs with larger non-potentiality and area mostly
produce fast CMEs but they can also produce slower ones. The ARs with
lesser non-potentiality and area generally produce only slower CMEs,
however, there are a few exceptions. The total unsigned flux correlate
with the non-potentiality parameters and area of ARs but some ARs with
large unsigned flux are also found to be least non-potential. A more
detailed analysis is underway. SKT is supported by an appointment to
the NASA Postdoctoral Program at the NASA Marshall Space Flight Center,
administered by Oak Ridge Associated Universities through a contract
with NASA. RLM is supported by funding from the Living With a Star
Targeted Research and Technology Program of the Heliophysics Division
of NASA's Science Mission Directorate. Support for MAG4 development
comes from NASA's Game Changing Development Program, and Johnson Space
Center's Space Radiation Analysis Group (SRAG).
---------------------------------------------------------
Title: Impulsive Energy Release and Non-thermal Emission in a Confined
M4.0 Flare Triggered by Rapidly Evolving Magnetic Structures
Authors: Kushwaha, Upendra; Joshi, Bhuwan; Cho, Kyung-Suk; Veronig,
Astrid; Tiwari, Sanjiv Kumar; Mathew, S. K.
2014ApJ...791...23K Altcode: 2014arXiv1407.8115K
We present observations of a confined M4.0 flare from NOAA 11302
on 2011 September 26. Observations at high temporal, spatial, and
spectral resolution from the Solar Dynamics Observatory, Reuven Ramaty
High Energy Solar Spectroscopic Imager, and Nobeyama Radioheliograph
observations enabled us to explore the possible triggering and energy
release processes of this flare despite its very impulsive behavior
and compact morphology. The flare light curves exhibit an abrupt rise
of non-thermal emission with co-temporal hard X-ray (HXR) and microwave
(MW) bursts that peaked instantly without any precursor emission. This
stage was associated with HXR emission up to 200 keV that followed
a power law with photon spectral index (γ) ~ 3. Another non-thermal
peak, observed 32 s later, was more pronounced in the MW flux than the
HXR profiles. Dual peaked structures in the MW and HXR light curves
suggest a two-step magnetic reconnection process. Extreme ultraviolet
(EUV) images exhibit a sequential evolution of the inner and outer core
regions of magnetic loop systems while the overlying loop configuration
remained unaltered. Combined observations in HXR, (E)UV, and Hα
provide support for flare models involving the interaction of coronal
loops. The magnetograms obtained by the Helioseismic and Magnetic
Imager reveal emergence of magnetic flux that began ~five hr before the
flare. However, the more crucial changes in the photospheric magnetic
flux occurred about one minute prior to the flare onset with opposite
polarity magnetic transients appearing at the early flare location
within the inner core region. The spectral, temporal, and spatial
properties of magnetic transients suggest that the sudden changes
in the small-scale magnetic field have likely triggered the flare by
destabilizing the highly sheared pre-flare magnetic configuration.
---------------------------------------------------------
Title: Erratum: ”On the Force-free Nature of Photospheric
Sunspot Magnetic Fields as Observed from Hinode (SOT/SP)” <A
href="/abs/2012ApJ...744...65T">(2012, ApJ, 744, 65)</A>
Authors: Tiwari, Sanjiv Kumar
2012ApJ...759..148T Altcode:
No abstract at ADS
---------------------------------------------------------
Title: On the Force-free Nature of Photospheric Sunspot Magnetic
Fields as Observed from Hinode (SOT/SP)
Authors: Tiwari, Sanjiv Kumar
2012ApJ...744...65T Altcode: 2011arXiv1109.3156T
A magnetic field is force-free if there is no interaction between it and
the plasma in the surrounding atmosphere, i.e., electric currents are
aligned with the magnetic field, giving rise to zero Lorentz force. The
computation of various magnetic parameters, such as magnetic energy
(using the virial theorem), gradient of twist of sunspot magnetic
fields (computed from the force-free parameter α), and any kind of
extrapolation, heavily hinges on the force-free approximation of the
photospheric sunspot magnetic fields. Thus, it is of vital importance
to inspect the force-free behavior of sunspot magnetic fields. The
force-free nature of sunspot magnetic fields has been examined
earlier by some researchers, ending with incoherent results. Accurate
photospheric vector field measurements with high spatial resolution
are required to inspect the force-free nature of sunspots. For this
purpose, we use several vector magnetograms of high spatial resolution
obtained from the Solar Optical Telescope/Spectro-Polarimeter on board
Hinode. Both the necessary and sufficient conditions for force-free
nature are examined by checking the global and local nature of
equilibrium magnetic forces over sunspots. We find that sunspot
magnetic fields are not very far from the force-free configuration,
although they are not completely force-free on the photosphere. The
umbral and inner penumbral fields are more force-free than the
middle and outer penumbral fields. During their evolution, sunspot
magnetic fields are found to maintain their proximity to force-free
field behavior. Although a dependence of net Lorentz force components
is seen on the evolutionary stages of the sunspots, we do not find
a systematic relationship between the nature of sunspot magnetic
fields and the associated flare activity. Further, we examine whether
the fields at the photosphere follow linear or nonlinear force-free
conditions. After examining this in various complex and simple sunspots,
we conclude that, in either case, photospheric sunspot magnetic fields
are closer to satisfying the nonlinear force-free field approximation.
---------------------------------------------------------
Title: On the Flare-induced Seismicity in the Active Region NOAA
10930 and Related Enhancement of Global Waves in the Sun
Authors: Kumar, Brajesh; Venkatakrishnan, P.; Mathur, Savita; Tiwari,
Sanjiv Kumar; García, R. A.
2011ApJ...743...29K Altcode: 2011arXiv1110.6309K
A major flare (of class X3.4) occurred on 2006 December 13 in the active
region NOAA 10930. This flare event has remained interesting to solar
researchers for studies related to particle acceleration during the
flare process and the reconfiguration of magnetic fields as well as
fine-scale features in the active region. The energy released during
flares is also known to induce acoustic oscillations in the Sun. Here,
we analyze the line-of-sight velocity patterns in this active region
during the X3.4 flare using the Dopplergrams obtained by the Global
Oscillation Network Group (GONG) instrument. We have also analyzed the
disk-integrated velocity observations of the Sun obtained by the Global
Oscillation at Low Frequency (GOLF) instrument on board the Solar and
Heliospheric Observatory spacecraft as well as full-disk collapsed
velocity signals from GONG observations during this flare to study
any possible connection between the flare-related changes seen in the
local and global velocity oscillations in the Sun. We apply wavelet
transform to the time series of the localized velocity oscillations
as well as the global velocity oscillations in the Sun spanning the
flare event. The line-of-sight velocity shows significant enhancement
in some localized regions of the penumbra of this active region during
the flare. The affected region is seen to be away from the locations of
the flare ribbons and the hard X-ray footpoints. The sudden enhancement
of this velocity seems to be caused by the Lorentz force driven by
the "magnetic jerk" in the localized penumbral region. Application of
wavelet analysis to these flare-induced localized seismic signals shows
significant enhancement in the high-frequency domain (5 <ν < 8
mHz) and a feeble enhancement in the p-mode oscillations (2 <ν <
5 mHz) during the flare. On the other hand, the wavelet analysis of GOLF
velocity data and the full-disk collapsed GONG velocity data spanning
the flare event indicates significant post-flare enhancements in the
high-frequency global velocity oscillations in the Sun, as evident
from the wavelet power spectrum and the corresponding scale-average
variance. The present observations of the flare-induced seismic signals
in the active region in context of the driving force are different as
compared to previous reports on such cases. We also find indications
of a connection between flare-induced localized seismic signals and
the excitation of global high-frequency oscillations in the Sun.
---------------------------------------------------------
Title: Pre-flare Activity and Magnetic Reconnection during the
Evolutionary Stages of Energy Release in a Solar Eruptive Flare
Authors: Joshi, Bhuwan; Veronig, Astrid M.; Lee, Jeongwoo; Bong,
Su-Chan; Tiwari, Sanjiv Kumar; Cho, Kyung-Suk
2011ApJ...743..195J Altcode: 2011arXiv1109.3415J
In this paper, we present a multi-wavelength analysis of an eruptive
white-light M3.2 flare that occurred in active region NOAA 10486 on
2003 November 1. The excellent set of high-resolution observations
made by RHESSI and the TRACE provides clear evidence of significant
pre-flare activities for ~9 minutes in the form of an initiation
phase observed at EUV/UV wavelengths followed by an X-ray precursor
phase. During the initiation phase, we observed localized brightenings
in the highly sheared core region close to the filament and interactions
among short EUV loops overlying the filament, which led to the opening
of magnetic field lines. The X-ray precursor phase is manifested in
RHESSI measurements below ~30 keV and coincided with the beginning of
flux emergence at the flaring location along with early signatures of
the eruption. The RHESSI observations reveal that both plasma heating
and electron acceleration occurred during the precursor phase. The main
flare is consistent with the standard flare model. However, after the
impulsive phase, an intense hard X-ray (HXR) looptop source was observed
without significant footpoint emission. More intriguingly, for a brief
period, the looptop source exhibited strong HXR emission with energies
up to ~50-100 keV and significant non-thermal characteristics. The
present study indicates a causal relation between the activities in
the pre-flare and the main flare. We also conclude that pre-flare
activities, occurring in the form of subtle magnetic reorganization
along with localized magnetic reconnection, played a crucial role in
destabilizing the active region filament, leading to a solar eruptive
flare and associated large-scale phenomena.
---------------------------------------------------------
Title: Evolution of Currents of Opposite Signs in the Flare-productive
Solar Active Region NOAA 10930
Authors: Ravindra, B.; Venkatakrishnan, P.; Tiwari, Sanjiv Kumar;
Bhattacharyya, R.
2011ApJ...740...19R Altcode: 2011arXiv1108.5818R
Analysis of a time series of high spatial resolution vector magnetograms
of the active region NOAA 10930 available from the Solar Optical
Telescope SpectroPolarimeter on board Hinode revealed that there is
a mixture of upward and downward currents in the two footpoints of
an emerging flux rope. The flux emergence rate is almost the same
in both the polarities. We observe that along with an increase in
magnetic flux, the net current in each polarity increases initially
for about three days after which it decreases. This net current is
characterized by having exactly opposite signs in each polarity while
its magnitude remains almost the same most of the time. The decrease
of the net current in both the polarities is due to the increase of
current having a sign opposite to that of the net current. The dominant
current, with the same sign as the net current, is seen to increase
first and then decreases during the major X-class flares. Evolution
of non-dominant current appears to be a necessary condition for flare
initiation. The above observations can be plausibly explained in terms
of the superposition of two different force-free states resulting in a
non-zero Lorentz force in the corona. This Lorentz force then pushes the
coronal plasma and might facilitate the magnetic reconnection required
for flares. Also, the evolution of the net current is found to follow
the evolution of magnetic shear at the polarity inversion line.
---------------------------------------------------------
Title: Helicity of the solar magnetic field
Authors: Tiwari, Sanjiv Kumar
2011IAUS..273...21T Altcode: 2010arXiv1009.5163T
Helicity measures complexity in the field. Magnetic helicity is given
by a volume integral over the scalar product of magnetic field B and
its vector potential A. A direct computation of magnetic helicity
in the solar atmosphere is not possible due to unavailability of the
observations at different heights and also due to non-uniqueness of
A. The force-free parameter α has been used as a proxy of magnetic
helicity for a long time. We have clarified the physical meaning of
α and its relationship with the magnetic helicity. We have studied
the effect of polarimetric noise on estimation of various magnetic
parameters. Fine structures of sunspots in terms of vertical current
(J<SUB>z</SUB>) and α have been examined. We have introduced the
concept of signed shear angle (SSA) for sunspots and established its
importance for non force-free fields. We find that there is no net
current in sunspots even in presence of a significant twist, showing
consistency with their fibril-bundle nature. The finding of existence
of a lower limit of SASSA for a given class of X-ray flare will be
very useful for space weather forecasting. A good correlation is found
between the sign of helicity in the sunspots and the chirality of the
associated chromospheric and coronal features. We find that a large
number of sunspots observed in the declining phase of solar cycle
23 do not follow the hemispheric helicity rule whereas most of the
sunspots observed in the beginning of new solar cycle 24 do follow. This
indicates a long term behaviour of the hemispheric helicity patterns
in the Sun. The above sums up my PhD thesis.
---------------------------------------------------------
Title: Are the photospheric sunspots magnetically force-free in
nature?
Authors: Tiwari, Sanjiv Kumar
2011IAUS..273..333T Altcode: 2010arXiv1009.5164T
In a force-free magnetic field, there is no interaction of field and
the plasma in the surrounding atmosphere i.e., electric currents are
aligned with the magnetic field, giving rise to zero Lorentz force. The
computation of many magnetic parameters like magnetic energy, gradient
of twist of sunspot magnetic fields (computed from the force-free
parameter α), including any kind of extrapolations heavily hinge on
the force-free approximation of the photospheric magnetic fields. The
force-free magnetic behaviour of the photospheric sunspot fields has
been examined by Metcalf et al. (1995) and Moon et al. (2002) ending
with inconsistent results. Metcalf et al. (1995) concluded that the
photospheric magnetic fields are far from the force-free nature whereas
Moon et al. (2002) found the that the photospheric magnetic fields are
not so far from the force-free nature as conventionally regarded. The
accurate photospheric vector field measurements with high resolution
are needed to examine the force-free nature of sunspots. We use
high resolution vector magnetograms obtained from the Solar Optical
Telescope/Spectro-Polarimeter (SOT/SP) aboard Hinode to inspect the
force-free behaviour of the photospheric sunspot magnetic fields. Both
the necessary and sufficient conditions for force-freeness are examined
by checking global as well as as local nature of sunspot magnetic
fields. We find that the sunspot magnetic fields are very close to the
force-free approximation, although they are not completely force-free
on the photosphere.
---------------------------------------------------------
Title: Evolution of Magnetic Field Twist and Tilt in Active Region
NOAA 10930
Authors: Ravindra, B.; Venkatakrishnan, P.; Tiwari, Sanjiv Kumar
2011aogs...27..153R Altcode: 2010arXiv1012.0120R
Magnetic twist of the active region has been measured over a decade
using photospheric vector field data, chromospheric H<SUB>α</SUB>
data, and coronal loop data. The twist and tilt of the active regions
have been measured at the photospheric level with the vector magnetic
field measurements. The active region NOAA 10930 is a highly twisted
emerging region. The same active region produced several flares and has
been extensively observed by Hinode. In this paper, we will show the
evolution of twist and tilt in this active region leading up to the two
X-class flares. We find that the twist initially increases with time
for a few days with a simultaneous decrease in the tilt until before
the X3.4 class flare on December 13, 2006. The total twist acquired
by the active region is larger than one complete winding before the
X3.4 class flare and it decreases in later part of observations. The
injected helicity into the corona is negative and it is in excess of
10<SUP>43</SUP> Mx<SUP>2</SUP> before the flares.
---------------------------------------------------------
Title: Analysis of peculiar penumbral flows observed in the active
region NOAA 10930 during a major solar flare
Authors: Kumar, Brajesh; Venkatakrishnan, P.; Mathur, Savita; Tiwari,
Sanjiv Kumar; García, R. A.
2011JPhCS.271a2020K Altcode:
It is believed that the high energetic particles and tremendous amount
of energy released during the flares can induce velocity oscillations in
the Sun. Using the Dopplergrams obtained by Global Oscillation Network
Group (GONG) telescope, we analyze the velocity flows in the active
region NOAA 10930 during a major flare (of class X3.4) that occurred on
13 December 2006. We observe peculiar evolution of velocity flows in
some localized portions of the penumbra of this active region during
the flare. Application of Wavelet transform to these velocity flows
reveals that there is major enhancement of velocity oscillations in the
high-frequency regime (5-8 mHz), while there is feeble enhancement in
the p mode oscillations (2-5 mHz) in the aforementioned location. It
has been recently shown that flares can induce high-frequency global
oscillations in the Sun. Therefore, it appears that during the flare
process there might be a common origin for the excitation of local
and global high-frequency oscillations in the Sun.
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Title: Magnetic Non-potentiality of Solar Active Regions and Peak
X-ray Flux of the Associated Flares
Authors: Tiwari, Sanjiv Kumar; Venkatakrishnan, P.; Gosain, Sanjay
2010ApJ...721..622T Altcode: 2010arXiv1007.4876T
Predicting the severity of solar eruptive phenomena such as flares and
coronal mass ejections remains a great challenge despite concerted
efforts to do so over the past several decades. However, the advent
of high-quality vector magnetograms obtained from Hinode (SOT/SP) has
increased the possibility of meeting this challenge. In particular,
the spatially averaged signed shear angle (SASSA) seems to be a
unique parameter for quantifying the non-potentiality of active
regions. We demonstrate the usefulness of the SASSA for predicting
flare severity. For this purpose, we present case studies of the
evolution of magnetic non-potentiality using 115 vector magnetograms of
four active regions, namely, ARs NOAA 10930, 10960, 10961, and 10963
during 2006 December 8-15, 2007 June 3-10, 2007 June 28-July 5, and
2007 July 10-17, respectively. The NOAA ARs 10930 and 10960 were very
active and produced X and M class flares, respectively, along with many
smaller X-ray flares. On the other hand, the NOAA ARs 10961 and 10963
were relatively less active and produced only very small (mostly A-
and B-class) flares. For this study, we have used a large number of
high-resolution vector magnetograms obtained from Hinode (SOT/SP). Our
analysis shows that the peak X-ray flux of the most intense solar
flare emanating from the active regions depends on the magnitude of
the SASSA at the time of the flare. This finding of the existence of
a lower limit of the SASSA for a given class of X-ray flares will be
very useful for space weather forecasting. We have also studied another
non-potentiality parameter called the mean weighted shear angle (MWSA)
of the vector magnetograms along with the SASSA. We find that the MWSA
does not show such distinction as the SASSA for upper limits of the
GOES X-ray flux of solar flares; however, both the quantities show
similar trends during the evolution of all active regions studied.
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Title: On the Estimate of Magnetic Non-potentiality of Sunspots
Derived Using Hinode SOT/SP Observations: Effect of Polarimetric Noise
Authors: Gosain, Sanjay; Tiwari, Sanjiv Kumar; Venkatakrishnan, P.
2010ApJ...720.1281G Altcode: 2010arXiv1007.2505G
The accuracy of Milne-Eddington (ME) inversions, used to retrieve the
magnetic field vector, depends upon the signal-to-noise ratio (S/N)
of the spectro-polarimetric observations. The S/N in real observations
varies from pixel to pixel; therefore the accuracy of the field vector
also varies over the map. The aim of this work is to study the effect
of polarimetric noise on the inference of the magnetic field vector
and the magnetic non-potentiality of a real sunspot. To this end,
we use the Hinode SOT/SP vector magnetogram of a real sunspot NOAA
10933 as an input to generate synthetic Stokes profiles under ME model
assumptions. We then add normally distributed polarimetric noise of
the level 0.5% of continuum intensity to these synthetic profiles and
invert them again using the ME code. This process is repeated 100 times
with different realizations of noise. It is found that within most of
the sunspot areas (>90% area) the spread in the (1) field strength
is less than 8 G, (2) field inclination is less than 1°, and (3)
field azimuth is less than 5°. Further, we determine the uncertainty
in the magnetic non-potentiality of a sunspot as determined by the
force-free parameter α<SUB> g </SUB> and spatially averaged signed
shear angle (SASSA). It is found that for the sunspot studied here
these parameters are α<SUB> g </SUB> = -3.5 ± 0.37(×10<SUP>-9</SUP>
m<SUP>-1</SUP>) and SASSA = -1.68 ± 0fdg014. This suggests that the
SASSA is a less dispersed non-potentiality parameter as compared to
α<SUB> g </SUB>. Further, we examine the effect of increasing noise
levels, viz. 0.01%, 0.1%, 0.5%, and 1% of continuum intensity, and
find that SASSA is less vulnerable to noise as compared to the α<SUB>
g </SUB> parameter.
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Title: Magnetic tension of sunspot fine structures
Authors: Venkatakrishnan, P.; Tiwari, Sanjiv Kumar
2010A&A...516L...5V Altcode: 2010arXiv1005.3899V
Context. The equilibrium structure of sunspots depends critically on
its magnetic topology and is dominated by magnetic forces. Tension
force is one component of the Lorentz force, which balances the
gradient of magnetic pressure in force-free configurations. <BR />
Aims: We employ the tension term of the Lorentz force to clarify
the structure of sunspot features like penumbral filaments, umbral
light bridges, and outer penumbral fine structures. <BR /> Methods:
We computed the vertical component of the tension term of Lorentz force
over two active regions, NOAA AR 10933 and NOAA AR 10930 observed on 5
January 2007 and 12 December 2006, respectively. The former is a simple
active region while the latter is a complex one with highly sheared
polarity inversion line (PIL). We obtained the vector magnetograms from
Hinode(SOT/SP). <BR /> Results: We find an inhomogeneous distribution of
tension with both positive and negative signs in various features of the
sunspots. The existence of positive tension at locations of lower field
strength and higher inclination is compatible with the uncombed model
of the penumbral structure. Positive tension is also seen in umbral
light bridges, which could be indication of uncombed structure of the
light bridge. Likewise, the upwardly directed tension associated with
bipolar regions in the penumbra could be a direct confirmation of the
sea serpent model of penumbral structures. Upwardly directed tension
at the PIL of AR 10930 seems to be related to flux emergence. The
magnitude of the tension force is greater than the force of gravity
in some places, implying a nearly force-free configuration for these
sunspot features. <BR /> Conclusions: From our study, magnetic tension
emerges as a useful diagnostic of the local equilibrium of the sunspot
fine structures. <P />Figures A.1-A.3 are only available in electronic
form at <A href="http://www.aanda.org">http://www.aanda.org</A>
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Title: Helicity at Photospheric and Chromospheric Heights
Authors: Tiwari, S. K.; Venkatakrishnan, P.; Sankarasubramanian, K.
2010ASSP...19..443T Altcode: 2009arXiv0904.4353T; 2010mcia.conf..443T
In the solar atmosphere, the twist parameter α has the same sign as
magnetic helicity. It has been observed using photospheric vector
magnetograms that negative/positive helicity is dominant in the
northern/southern hemisphere of the Sun. Chromospheric features show
dextral/sinistral dominance in the northern/ southern hemisphere
and sigmoids observed in X-rays also have a dominant sense of
reverse-S/forward-S in the northern/southern hemisphere. It
is of interest whether individual features have one-to-one
correspondence in terms of helicity at different atmospheric
heights. We use UBF Hα images from the Dunn Solar Telescope (DST)
and other Hα data from Udaipur Solar Observatory and Big Bear Solar
Observatory. Near-simultaneous vector magnetograms from the DST are
used to establish one-to-one correspondence of helicity at photospheric
and chromospheric heights. We plan to extend this investigation with
more data including coronal intensities.
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Title: Helicity of the Solar Magnetic Field
Authors: Tiwari, Sanjiv Kumar
2009PhDT.........8T Altcode:
Magnetic helicity is a physical quantity that measures the degree of
linkages and twistedness in the field lines. It is given by a volume
integral over the scalar product of magnetic field B and its vector
potential A. Direct computation of magnetic helicity in the solar
atmosphere is not possible due to two reasons. First, we do not have the
observations at different heights in the solar atmosphere to compute
the volume integral. Second, the vector potential A is non-unique
owing to gauge variance. Many researchers incorrectly inferred twist,
a component of magnetic helicity, from the force-free parameter α. We
clarified the physical meaning of α and its relation with the magnetic
helicity. Also, a direct method is proposed for the computation of
global α values of sunspots. An analytical bipole was generated to
study the effect of polarimetric noise on the estimation of various
magnetic parameters. We find that the effect of polarimetric noise,
present in the recent vector magnetograms e.g., from Hinode (Solar
Optical Telescope/Spectro- Polarimeter (SOT/SP)), on the magnetic
parameters like α and magnetic energy, is negligible. We examined
the fine structures of local current and α in the sunspots. Local α
patches of opposite signs are present in the umbra of each sunspot. The
amplitude of the spatial variation of local α in the umbra is typically
of the order of the global α of the sunspot. We find that the local
α and current are distributed as alternately positive and negative
filaments in the penumbra. The amplitude of azimuthal variation of
the local α in the penumbra is approximately an order of magnitude
larger than that in the umbra. The contributions of the local positive
and negative currents and α in the penumbra cancel each other giving
almost no contribution for their global values for whole sunspot. We
have introduced the concept of signed shear angle (SSA) for sunspots
and establish its importance for non force-free fields. The spatially
averaged SSA (SASSA) gives the actual twist present in a sunspot
irrespective of the force-free nature and the shape of the sunspot. We
find that the sign of global α is well correlated with the SASSA of
the sunspots but the magnitudes are not. We find that there is no net
current in the sunspots, although there is significant twist present
in the photospheric magnetic field of the sunspots. The existence of
a global twist for a sunspot even in the absence of a net current is
consistent with the fibril-bundle structure of the sunspot magnetic
fields. We also discovered the curly interlocking combed structure
in the azimuthal component of sunspot magnetic field. We studied the
SASSA of sunspots to predict the flare activity of the associated
active regions. We studied the evolution of vector magnetic fields
using a large number of vector magnetograms of both, an eruptive
and a non-eruptive sunspot. We arrive at a critical threshold value
of the SASSA for each class of X-ray flare associated with these
two sunspots. Thus, the SASSA holds promise to be very useful in
predicting the probability of the occurrence of solar flares. A good
correlation is found between the sign of helicity in the sunspots at
the photosphere and the chirality of the associated chromospheric and
coronal features. This study will be very useful as a constraint while
modeling the Chromospheric and coronal features. We find that a large
number of sunspots observed in the declining phase of the solar cycle
23 follow the reverse hemispheric helicity rule. Most of the sunspots
observed in the beginning of new solar cycle 24 follow the conventional
hemispheric helicity rule. This indicates a long term behaviour of the
helicity patterns in the solar atmosphere. However, this needs to be
confirmed with the data sets spanning large number of years.
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Title: HINODE Observations of Coherent Lateral Motion of Penumbral
Filaments During an X-Class Flare
Authors: Gosain, S.; Venkatakrishnan, P.; Tiwari, Sanjiv Kumar
2009ApJ...706L.240G Altcode: 2009arXiv0910.5336G
The X-3.4 class flare of 2006 December 13 was observed with a high
cadence of 2 minutes at 0.2 arcsec resolution by HINODE/SOT FG
instrument. The flare ribbons could be seen in G-band images also. A
careful analysis of these observations after proper registration
of images shows flare-related changes in penumbral filaments of the
associated sunspot for the first time. The observations of sunspot
deformation, decay of penumbral area, and changes in magnetic flux
during large flares have been reported earlier in the literature. In
this Letter, we report lateral motion of the penumbral filaments in
a sheared region of the δ-sunspot during the X-class flare. Such
shifts have not been seen earlier. The lateral motion occurs in two
phases: (1) motion before the flare ribbons move across the penumbral
filaments and (2) motion afterward. The former motion is directed away
from expanding flare ribbons and lasts for about 4 minutes. The latter
motion is directed in the opposite direction and lasts for more than
40 minutes. Further, we locate a patch in adjacent opposite polarity
spot moving in opposite direction to the penumbral filaments. Together
these patches represent conjugate footpoints on either side of the
polarity inversion line, moving toward each other. This converging
motion could be interpreted as shrinkage of field lines.
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Title: Evolution of Fine Structures in an Eruptive Active Region:
Hinode (SOT/SP) Observations
Authors: Tiwari, S. K.; Venkatakrishnan, P.
2009AGUFMSH51A1268T Altcode:
We study the evolution of an active region NOAA 10930 by using a
large number of high resolution vector magnetograms obtained from
Hinode (SOT/SP). A X3.4 class solar flare was observed from the active
region NOAA 10930 (S06W35), which started at 02:14 UT on 13th December
2006. We have used HINODE (SOT/SP) data for 12, 13 and 14 December
2006 for studying spatial and temporal changes in pre and post eruption
cases. The evolution of twist (computed from signed shear angle (SSA))
in the vector magnetograms is studied. It is known that the magnetic
tension is reduced in highly sheared magnetic field regions e.g.,
polarity inversion lines. We study the evolution of magnetic tension
near the polarity inversion line to check if the loss of magnetic
tension was the possible cause of its eruption. We also study the
evolution of AR NOAA 10961 as a non-erupting case. The difference
between the evolution of fine structures in erupting and non-erupting
active regions is the main motivation of this study.
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Title: On the Absence of Photospheric Net Currents in Vector
Magnetograms of Sunspots Obtained from Hinode (Solar Optical
Telescope/Spectro-Polarimeter)
Authors: Venkatakrishnan, P.; Tiwari, Sanjiv Kumar
2009ApJ...706L.114V Altcode: 2009arXiv0910.3751V
Various theoretical and observational results have been reported
regarding the presence/absence of net electric currents in the
sunspots. The limited spatial resolution of the earlier observations
perhaps obscured the conclusions. We have analyzed 12 sunspots observed
from Hinode (Solar Optical Telescope/Spectro-polarimeter) to clarify
the issue. The azimuthal and radial components of magnetic fields and
currents have been derived. The azimuthal component of the magnetic
field of sunspots is found to vary in sign with azimuth. The radial
component of the field also varies in magnitude with azimuth. While the
latter pattern is a confirmation of the interlocking combed structure
of penumbral filaments, the former pattern shows that the penumbra is
made up of a "curly interlocking combed" magnetic field. The azimuthally
averaged azimuthal component is seen to decline much faster than 1/piv
in the penumbra, after an initial increase in the umbra, for all the
spots studied. This confirms the confinement of magnetic fields and
absence of a net current for sunspots as postulated by Parker. The
existence of a global twist for a sunspot even in the absence of a net
current is consistent with a fibril-bundle structure of the sunspot
magnetic fields.
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Title: Global Twist of Sunspot Magnetic Fields Obtained from
High-Resolution Vector Magnetograms
Authors: Tiwari, Sanjiv Kumar; Venkatakrishnan, P.; Sankarasubramanian,
K.
2009ApJ...702L.133T Altcode: 2009arXiv0907.5064T
The presence of fine structures in sunspot vector magnetic fields has
been confirmed from Hinode as well as other earlier observations. We
studied 43 sunspots based on the data sets taken from ASP/DLSP, Hinode
(SOT/SP), and SVM (USO). In this Letter, (1) we introduce the concept
of signed shear angle (SSA) for sunspots and establish its importance
for non-force-free fields. (2) We find that the sign of global α
(force-free parameter) is well correlated with that of the global SSA
and the photospheric chirality of sunspots. (3) Local α patches of
opposite signs are present in the umbra of each sunspot. The amplitude
of the spatial variation of local α in the umbra is typically of the
order of the global α of the sunspot. (4) We find that the local α
is distributed as alternately positive and negative filaments in the
penumbra. The amplitude of azimuthal variation of the local α in the
penumbra is approximately an order of magnitude larger than that in the
umbra. The contributions of the local positive and negative currents
and α in the penumbra cancel each other giving almost no contribution
for their global values for the whole sunspot. (5) Arc-like structures
(partial rings) with a sign opposite to that of the dominant sign of
α of the umbral region are seen at the umbral-penumbral boundaries
of some sunspots. (6) Most of the sunspots studied belong to the
minimum epoch of the 23rd solar cycle and do not follow the so-called
hemispheric helicity rule.
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Title: Effect of Polarimetric Noise on the Estimation of Twist and
Magnetic Energy of Force-Free Fields
Authors: Tiwari, Sanjiv Kumar; Venkatakrishnan, P.; Gosain, Sanjay;
Joshi, Jayant
2009ApJ...700..199T Altcode: 2009arXiv0904.4594T
The force-free parameter α, also known as helicity parameter or twist
parameter, bears the same sign as the magnetic helicity under some
restrictive conditions. The single global value of α for a whole active
region gives the degree of twist per unit axial length. We investigate
the effect of polarimetric noise on the calculation of global α value
and magnetic energy of an analytical bipole. The analytical bipole
has been generated using the force-free field approximation with a
known value of constant α and magnetic energy. The magnetic parameters
obtained from the analytical bipole are used to generate Stokes profiles
from the Unno-Rachkovsky solutions for polarized radiative transfer
equations. Then we add random noise of the order of 10<SUP>-3</SUP>
of the continuum intensity (I <SUB> c </SUB>) in these profiles to
simulate the real profiles obtained by modern spectropolarimeters such
as Hinode (SOT/SP), SVM (USO), ASP, DLSP, POLIS, and SOLIS etc. These
noisy profiles are then inverted using a Milne-Eddington inversion
code to retrieve the magnetic parameters. Hundred realizations of this
process of adding random noise and polarimetric inversion is repeated
to study the distribution of error in global α and magnetic energy
values. The results show that (1) the sign of α is not influenced
by polarimetric noise and very accurate values of global twist can
be calculated, and (2) accurate estimation of magnetic energy with
uncertainty as low as 0.5% is possible under the force-free condition.
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Title: Software for interactively visualizing solar vector
magnetograms of udaipur solar observatory
Authors: Gosain, Sanjay; Tiwari, Sanjiv; Joshi, Jayant;
Venkatakrishnan, P.
2008JApA...29..107G Altcode:
No abstract at ADS
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Title: Evolution of Magnetic Helicity in NOAA 10923 Over Three
Consecutive Solar Rotations
Authors: Tiwari, Sanjiv Kumar; Joshi, Jayant; Gosain, Sanjay;
Venkatakrishnan, P.
2008ASSP...12..329T Altcode: 2009arXiv0904.4024T; 2008tdad.conf..329T
We have studied the evolution of magnetic helicity and chirality
in an active region over three consecutive solar rotations. The
region where it first appeared was named NOAA10923 and in subsequent
rotations it was numbered NOAA 10930, 10935 and 10941. We compare the
chirality of these regions at photospheric, chromospheric and coronal
heights. The observations used for photospheric and chromospheric
heights are taken from Solar Vector Magnetograph (SVM) and H-α imaging
telescope of Udaipur Solar Observatory (USO), respectively. We discuss
the chirality of the sunspots and associated H-α filaments in these
regions. We find that the twistedness of superpenumbral filaments is
maintained in the photospheric transverse field vectors also. We also
compare the chirality at photospheric and chromospheric heights with
the chirality of the associated coronal loops, as observed from the
HINODE X-Ray Telescope.
