explanation blue bibcodes open ADS page with paths to full text
Author name code: bethge
ADS astronomy entries on 2022-09-14
author:"Bethge, Christian"
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Title: Quiet Sun Center to Limb Variation of the Linear Polarization
Observed by CLASP2 Across the Mg II h and k Lines
Authors: Rachmeler, L. A.; Bueno, J. Trujillo; McKenzie, D. E.;
Ishikawa, R.; Auchère, F.; Kobayashi, K.; Kano, R.; Okamoto,
T. J.; Bethge, C. W.; Song, D.; Ballester, E. Alsina; Belluzzi,
L.; Pino Alemán, T. del; Ramos, A. Asensio; Yoshida, M.; Shimizu,
T.; Winebarger, A.; Kobelski, A. R.; Vigil, G. D.; Pontieu, B. De;
Narukage, N.; Kubo, M.; Sakao, T.; Hara, H.; Suematsu, Y.; Štěpán,
J.; Carlsson, M.; Leenaarts, J.
2022ApJ...936...67R Altcode: 2022arXiv220701788R
The CLASP2 (Chromospheric LAyer Spectro-Polarimeter 2) sounding rocket
mission was launched on 2019 April 11. CLASP2 measured the four Stokes
parameters of the Mg II h and k spectral region around 2800 Å along a
200″ slit at three locations on the solar disk, achieving the first
spatially and spectrally resolved observations of the solar polarization
in this near-ultraviolet region. The focus of the work presented here
is the center-to-limb variation of the linear polarization across these
resonance lines, which is produced by the scattering of anisotropic
radiation in the solar atmosphere. The linear polarization signals of
the Mg II h and k lines are sensitive to the magnetic field from the
low to the upper chromosphere through the Hanle and magneto-optical
effects. We compare the observations to theoretical predictions
from radiative transfer calculations in unmagnetized semiempirical
models, arguing that magnetic fields and horizontal inhomogeneities
are needed to explain the observed polarization signals and spatial
variations. This comparison is an important step in both validating and
refining our understanding of the physical origin of these polarization
signatures, and also in paving the way toward future space telescopes
for probing the magnetic fields of the solar upper atmosphere via
ultraviolet spectropolarimetry.
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Title: Magnetoseismology for the solar corona: from 10 Gauss to
coronal magnetograms
Authors: Yang, Zihao; Gibson, Sarah; He, Jiansen; Del Zanna, Giulio;
Tomczyk, Steven; Morton, Richard; McIntosh, Scott; Wang, Linghua;
Karak, Bidya Binay; Samanta, Tanmoy; Tian, Hui; Chen, Yajie; Bethge,
Christian; Bai, Xianyong
2022cosp...44.2490Y Altcode:
Magnetoseismology, a technique of magnetic field diagnostics based
on observations of magnetohydrodynamic (MHD) waves, has been widely
used to estimate the field strengths of oscillating structures in
the solar corona. However, previously magnetoseismology was mostly
applied to occasionally occurring oscillation events, providing
an estimate of only the average field strength or one-dimensional
distribution of field strength along an oscillating structure. This
restriction could be eliminated if we apply magnetoseismology to the
pervasive propagating transverse MHD waves discovered with the Coronal
Multi-channel Polarimeter (CoMP). Using several CoMP observations of
the Fe XIII 1074.7 nm and 1079.8 nm spectral lines, we obtained maps of
the plasma density and wave phase speed in the corona, which allow us
to map both the strength and direction of the coronal magnetic field
in the plane of sky. We also examined distributions of the electron
density and magnetic field strength, and compared their variations
with height in the quiet Sun and active regions. Such measurements
could provide critical information to advance our understanding of the
Sun's magnetism and the magnetic coupling of the whole solar atmosphere.
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Title: Magnetoseismology for the solar corona: from 10 Gauss to
coronal magnetograms
Authors: Yang, Zihao; Bethge, Christian; Tian, Hui; Tomczyk, Steven;
Morton, Richard; Del Zanna, Giulio; McIntosh, Scott; Karak, Bidya
Binay; Gibson, Sarah; Samanta, Tanmoy; He, Jiansen; Chen, Yajie; Bai,
Xianyong; Wang, Linghua
2021AGUFMSH12C..07Y Altcode:
Magnetoseismology, a technique of magnetic field diagnostics based
on observations of magnetohydrodynamic (MHD) waves, has been widely
used to estimate the field strengths of oscillating structures in
the solar corona. However, previously magnetoseismology was mostly
applied to occasionally occurring oscillation events, providing
an estimate of only the average field strength or one-dimensional
distribution of field strength along an oscillating structure. This
restriction could be eliminated if we apply magnetoseismology to the
pervasive propagating transverse MHD waves discovered with the Coronal
Multi-channel Polarimeter (CoMP). Using several CoMP observations of
the Fe XIII 1074.7 nm and 1079.8 nm spectral lines, we obtained maps of
the plasma density and wave phase speed in the corona, which allow us
to map both the strength and direction of the coronal magnetic field
in the plane of sky. We also examined distributions of the electron
density and magnetic field strength, and compared their variations
with height in the quiet Sun and active regions. Such measurements
could provide critical information to advance our understanding of the
Sun's magnetism and the magnetic coupling of the whole solar atmosphere.
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Title: Demonstration of Chromospheric Magnetic Mapping with CLASP2.1
Authors: McKenzie, David; Ishikawa, Ryohko; Trujillo Bueno, Javier;
Auchere, F.; Kobayashi, Ken; Winebarger, Amy; Kano, Ryouhei; Song,
Donguk; Okamoto, Joten; Rachmeler, Laurel; De Pontieu, Bart; Vigil,
Genevieve; Belluzzi, Luca; Alsina Ballester, Ernest; del Pino Aleman,
Tanausu; Bethge, Christian; Sakao, Taro; Stepan, Jiri
2021AGUFMSH52A..06M Altcode:
Probing the magnetic nature of the Suns atmosphere requires measurement
of the Stokes I, Q, U and V profiles of relevant spectral lines (of
which Q, U and V encode the magnetic field information). Many of the
magnetically sensitive lines formed in the chromosphere and transition
region are in the ultraviolet spectrum, necessitating observations
above the absorbing terrestrial atmosphere. The Chromospheric
Layer Spectro-Polarimeter (CLASP2) sounding rocket was flown
successfully in April 2019, as a follow-on to the successful flight in
September 2015 of the Chromospheric Lyman-Alpha Spectro-Polarimeter
(CLASP). Both projects were funded by NASAs Heliophysics Technology
and Instrument Development for Science (H-TIDeS) program to develop
and test a technique for observing the Sun in ultraviolet light,
and for quantifying the polarization of that light. By demonstrating
successful measurement and interpretation of the polarization in
hydrogen Lyman-alpha and the Mg II h and k spectral lines, the CLASP
and CLASP2 missions are vital first steps towards routine quantitative
characterization of the local thermal and magnetic conditions in the
solar chromosphere. In October of 2021, we re-flew the CLASP2 payload
with a modified observing program to further demonstrate the maturity
of the UV spectropolarimetry techniques, and readiness for development
into a satellite observatory. During the reflight, called CLASP2.1,
the spectrograph slit was scanned across an active region plage to
acquire a two-dimensional map of Stokes V/I, to demonstrate the ability
of UV spectropolarimetry to yield chromospheric magnetic fields over
a large area. This presentation will display preliminary results from
the flight of CLASP2.1.
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Title: Enhancements to Hinode/SOT-SP Vector Magnetic Field Data
Products
Authors: DeRosa, M. L.; Leka, K. D.; Barnes, G.; Wagner, E.; Centeno,
R.; De Wijn, A.; Bethge, C.
2021AAS...23821305D Altcode:
The Solar Optical Telescope Spectro-Polarimeter (SOT-SP), on board the
Hinode spacecraft (launched in 2006), is a scanning-slit spectrograph
that continues to provide polarization spectra useful for inferring the
vector (three-component) magnetic field at the solar photosphere. SOT-SP
achieves this goal by obtaining line profiles of two magnetically
sensitive lines, namely the Fe I 6302 Angstrom doublet, using a
0.16"×164" slit as it scans a region of interest. Once the data are
merged, a Milne-Eddington based spectropolarimetric inversion scheme is
used to infer multiple physical parameters in the solar photosphere,
including the vector magnetic field, from the calibrated polarization
spectra. All of these data are publicly available once the processing
has occurred. <P />As of this year, the Hinode/SOT team is also making
available the disambiguated vector magnetic field and the re-projected
heliographic components of the field. In making the disambiguated vector
field data product, the 180° ambiguity in the plane-of-sky component
of the vector magnetic field inherent in the spectropolarimetric
inversion process has been resolved. This ambiguity is resolved
using the Minimum-Energy algorithm, which is the same algorithm used
within the pipeline producing the vector-magnetogram data product
for the Helioseismic and Magnetic Imager aboard the Solar Dynamics
Observatory. The heliographic field components (B<SUB>phi</SUB>,
B<SUB>theta</SUB>, B<SUB>r</SUB>) on the same grid as the inverted data
are also now provided. This poster provides more details about these
data product enhancements, and some examples on how the scientific
community may readily obtain these data.
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Title: Mapping of Solar Magnetic Fields from the Photosphere to the
Top of the Chromosphere with CLASP2
Authors: McKenzie, D.; Ishikawa, R.; Trujillo Bueno, J.; Auchere, F.;
del Pino Aleman, T.; Okamoto, T.; Kano, R.; Song, D.; Yoshida, M.;
Rachmeler, L.; Kobayashi, K.; Narukage, N.; Kubo, M.; Ishikawa, S.;
Hara, H.; Suematsu, Y.; Sakao, T.; Bethge, C.; De Pontieu, B.; Vigil,
G.; Winebarger, A.; Alsina Ballester, E.; Belluzzi, L.; Stepan, J.;
Asensio Ramos, A.; Carlsson, M.; Leenaarts, J.
2021AAS...23810603M Altcode:
Coronal heating, chromospheric heating, and the heating &
acceleration of the solar wind, are well-known problems in solar
physics. Additionally, knowledge of the magnetic energy that
powers solar flares and coronal mass ejections, important drivers
of space weather, is handicapped by imperfect determination of the
magnetic field in the sun's atmosphere. Extrapolation of photospheric
magnetic measurements into the corona is fraught with difficulties and
uncertainties, partly due to the vastly different plasma beta between
the photosphere and the corona. Better results in understanding
the coronal magnetic field should be derived from measurements of
the magnetic field in the chromosphere. To that end, we are pursuing
quantitative determination of the magnetic field in the chromosphere,
where plasma beta transitions from greater than unity to less than
unity, via ultraviolet spectropolarimetry. The CLASP2 mission, flown
on a sounding rocket in April 2019, succeeded in measuring all four
Stokes polarization parameters in UV spectral lines formed by singly
ionized Magnesium and neutral Manganese. Because these ions produce
spectral lines under different conditions, CLASP2 thus was able to
quantify the magnetic field properties at multiple heights in the
chromosphere simultaneously, as shown in the recent paper by Ishikawa
et al. In this presentation we will report the findings of CLASP2,
demonstrating the variation of magnetic fields along a track on
the solar surface and as a function of height in the chromosphere;
and we will illustrate what is next for the CLASP missions and the
demonstration of UV spectropolarimetry in the solar chromosphere.
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Title: Mapping the global magnetic field in the solar corona through
magnetoseismology
Authors: Yang, Zihao; Bethge, Christian; Tian, Hui; Tomczyk, Steven;
Morton, Richard; Del Zanna, Giulio; McIntosh, Scott; Karak, Bidya
Binay; Gibson, Sarah; Samanta, Tanmoy; He, Jiansen; Chen, Yajie;
Wang, Linghua; Bai, Xianyong
2021EGUGA..23..642Y Altcode:
Magnetoseismology, a technique of magnetic field diagnostics based
on observations of magnetohydrodynamic (MHD) waves, has been widely
used to estimate the field strengths of oscillating structures in
the solar corona. However, previously magnetoseismology was mostly
applied to occasionally occurring oscillation events, providing
an estimate of only the average field strength or one-dimensional
distribution of field strength along an oscillating structure. This
restriction could be eliminated if we apply magnetoseismology to the
pervasive propagating transverse MHD waves discovered with the Coronal
Multi-channel Polarimeter (CoMP). Using several CoMP observations of
the Fe XIII 1074.7 nm and 1079.8 nm spectral lines, we obtained maps of
the plasma density and wave phase speed in the corona, which allow us
to map both the strength and direction of the coronal magnetic field
in the plane of sky. We also examined distributions of the electron
density and magnetic field strength, and compared their variations
with height in the quiet Sun and active regions. Such measurements
could provide critical information to advance our understanding of the
Sun's magnetism and the magnetic coupling of the whole solar atmosphere.
---------------------------------------------------------
Title: Mapping solar magnetic fields from the photosphere to the
base of the corona
Authors: Ishikawa, Ryohko; Bueno, Javier Trujillo; del Pino Alemán,
Tanausú; Okamoto, Takenori J.; McKenzie, David E.; Auchère,
Frédéric; Kano, Ryouhei; Song, Donguk; Yoshida, Masaki; Rachmeler,
Laurel A.; Kobayashi, Ken; Hara, Hirohisa; Kubo, Masahito; Narukage,
Noriyuki; Sakao, Taro; Shimizu, Toshifumi; Suematsu, Yoshinori; Bethge,
Christian; De Pontieu, Bart; Dalda, Alberto Sainz; Vigil, Genevieve D.;
Winebarger, Amy; Ballester, Ernest Alsina; Belluzzi, Luca; Štěpán,
Jiří; Ramos, Andrés Asensio; Carlsson, Mats; Leenaarts, Jorrit
2021SciA....7.8406I Altcode: 2021arXiv210301583I
Routine ultraviolet imaging of the Sun's upper atmosphere shows the
spectacular manifestation of solar activity; yet we remain blind to
its main driver, the magnetic field. Here we report unprecedented
spectropolarimetric observations of an active region plage and
its surrounding enhanced network, showing circular polarization in
ultraviolet (Mg II $h$ & $k$ and Mn I) and visible (Fe I) lines. We
infer the longitudinal magnetic field from the photosphere to the
very upper chromosphere. At the top of the plage chromosphere the
field strengths reach more than 300 gauss, strongly correlated with
the Mg II $k$ line core intensity and the electron pressure. This
unique mapping shows how the magnetic field couples the different
atmospheric layers and reveals the magnetic origin of the heating in
the plage chromosphere.
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Title: Calibration of the MaGIXS Experiment. I. Calibration of the
X-Ray Source at the X-Ray and Cryogenic Facility
Authors: Athiray, P. S.; Winebarger, Amy R.; Champey, Patrick;
Kobayashi, Ken; Vigil, Genevieve D.; Haight, Harlan; Johnson, Steven;
Bethge, Christian; Rachmeler, Laurel A.; Savage, Sabrina; Beabout,
Brent; Beabout, Dyana; Hogue, William; Guillory, Anthony; Siler,
Richard; Wright, Ernest; Kegley, Jeffrey
2020ApJ...905...66A Altcode: 2020arXiv201009823A
The Marshall Grazing Incidence Spectrometer (MaGIXS) is a sounding
rocket experiment that will observe the soft X-ray spectrum of the
Sun from 24 to 6.0 Å (0.5-2.0 keV) and is scheduled for launch in
2021. Component- and instrument-level calibrations for the MaGIXS
instrument are carried out using the X-ray and Cryogenic Facility (XRCF)
at NASA Marshall Space Flight Center. In this paper, we present the
calibration of the incident X-ray flux from the electron impact source
with different targets at the XRCF using a CCD camera; the photon flux
at the CCD was low enough to enable its use as a "photon counter," i.e.,
the ability to identify individual photon hits and calculate their
energy. The goal of this paper is two-fold: (1) to confirm that the
flux measured by the XRCF beam normalization detectors is consistent
with the values reported in the literature and therefore reliable for
MaGIXS calibration and (2) to develop a method of counting photons in
CCD images that best captures their number and energy.
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Title: Global maps of the magnetic field in the solar corona
Authors: Yang, Zihao; Bethge, Christian; Tian, Hui; Tomczyk, Steven;
Morton, Richard; Del Zanna, Giulio; McIntosh, Scott W.; Karak, Bidya
Binay; Gibson, Sarah; Samanta, Tanmoy; He, Jiansen; Chen, Yajie;
Wang, Linghua
2020Sci...369..694Y Altcode: 2020arXiv200803136Y
Understanding many physical processes in the solar atmosphere requires
determination of the magnetic field in each atmospheric layer. However,
direct measurements of the magnetic field in the Sun’s corona are
difficult to obtain. Using observations with the Coronal Multi-channel
Polarimeter, we have determined the spatial distribution of the
plasma density in the corona and the phase speed of the prevailing
transverse magnetohydrodynamic waves within the plasma. We combined
these measurements to map the plane-of-sky component of the global
coronal magnetic field. The derived field strengths in the corona,
from 1.05 to 1.35 solar radii, are mostly 1 to 4 gauss. Our results
demonstrate the capability of imaging spectroscopy in coronal magnetic
field diagnostics.
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Title: Unfolding Overlapping Spectral Images to Determine the Plasma
Velocity During a Solar Flare
Authors: Treffner, B.; Winebarger, A. R.; Bethge, C.; Lee, K. S.;
Savage, S. L.
2019AGUFMSH31C3322T Altcode:
Spectroscopic images of the Sun can provide temperature and velocity
information when monitoring and detecting solar flares. Solar Flares
and the associated Coronal Mass Ejections (CMEs) can send fast
moving charged particles directly into the path of Earth and impact
space-borne instrumentation and astronauts. Strong CMEs can affect
power grids on the surface of Earth. Therefore, there is significant
interest and research is being conducted to try to predict these
events. <P />As most spectrometers have a comparatively small slit
width to avoid overlapping spectral images, their field of view is
limited and scanning slit spectrometers often miss rapidly evolving
events such as flares. Slot spectrometers measure both the imaging
and spectral information over a much larger field of view. However,
in these "overlappogram" images, the spectral and spatial information
is convolved, making the data difficult to interpret. <P />Recently,
a method to unfold slitless spectrometer data was developed for the
COronal Spectroscopic Imager in the EUV (COSIE) instrument. Building
upon this research, Extreme-ultraviolet Imaging Spectrometer (EIS)
and Atmospheric Imaging Assembly (AIA) data are used to determine the
best spatial, temperature, and velocity parameters for the preflare
data inversion, or unfolding. These parameters are then applied to the
flare data inversion with the goal of determining the velocity of the
plasma involved in a solar flare.
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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.
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Title: Unfolding Overlapped Slitless Imaging Spectrometer Data for
Extended Sources
Authors: Winebarger, Amy R.; Weber, Mark; Bethge, Christian; Downs,
Cooper; Golub, Leon; DeLuca, Edward; Savage, Sabrina; del Zanna,
Giulio; Samra, Jenna; Madsen, Chad; Ashraf, Afra; Carter, Courtney
2019ApJ...882...12W Altcode: 2018arXiv181108329W
Slitless spectrometers can provide simultaneous imaging and spectral
data over an extended field of view, thereby allowing rapid data
acquisition for extended sources. In some instances, when the object
is greatly extended or the spectral dispersion is too small, there
may be locations in the focal plane where emission lines at different
wavelengths contribute. It is then desirable to unfold the overlapped
regions in order to isolate the contributions from the individual
wavelengths. In this paper, we describe a method for such an unfolding,
using an inversion technique developed for an extreme ultraviolet
imaging spectrometer and coronagraph named the COronal Spectroscopic
Imager in the EUV (COSIE). The COSIE spectrometer wavelength range
(18.6-20.5 nm) contains a number of strong coronal emission lines and
several density sensitive lines. We focus on optimizing the unfolding
process to retrieve emission measure maps at constant temperature,
maps of spectrally pure intensity in the Fe XII and Fe XIII lines,
and density maps based on both Fe XII and Fe XIII diagnostics.
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Title: CLASP2: The Chromospheric LAyer Spectro-Polarimeter
Authors: McKenzie, D. E.; Ishikawa, R.; Trujillo Bueno, J.; Auchére,
F.; Rachmeler, L. A.; Kubo, M.; Kobayashi, K.; Winebarger, A. R.;
Bethge, C. W.; Narukage, N.; Kano, R.; Ishikawa, S.; de Pontieu,
B.; Carlsson, M.; Yoshida, M.; Belluzzi, L.; Štěpán, J.; del Pino
Alemán, T.; Alsina Ballester, E.; Asensio Ramos, A.
2019ASPC..526..361M Altcode:
The hydrogen Lyman-α line at 121.6 nm and the Mg k line at 279.5
nm are especially relevant for deciphering the magnetic structure
of the chromosphere since their line-center signals are formed in
the chromosphere and transition region, with unique sensitivities to
magnetic fields. We propose the Chromospheric LAyer Spectro-Polarimeter
(CLASP2), to build upon the success of the first CLASP flight, which
measured the linear polarization in H I Lyman-α. The existing CLASP
instrument will be refitted to measure all four Stokes parameters in
the 280 nm range, including variations due to the anisotropic radiation
pumping, the Hanle effect, and the Zeeman effect.
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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: Current State of UV Spectro-Polarimetry and its Future
Direction
Authors: Ishikawa, Ryohko; Sakao, Taro; Katsukawa, Yukio; Hara,
Hirohisa; Ichimoto, Kiyoshi; Shimizu, Toshifumi; Kubo, Masahito;
Auchere, Frederic; De Pontieu, Bart; Winebarger, Amy; Kobayashi,
. Ken; Kano, Ryouhei; Narukage, Noriyuki; Trujillo Bueno, Javier;
Song, Dong-uk; Manso Sainz, Rafael; Asensio Ramos, Andres; Leenaarts,
Jorritt; Carlsson, Mats; Bando, Takamasa; Ishikawa, Shin-nosuke;
Tsuneta, Saku; Belluzzi, Luca; Suematsu, Yoshinori; Giono, Gabriel;
Yoshida, Masaki; Goto, Motoshi; Del Pino Aleman, Tanausu; Stepan,
Jiri; Okamoto, Joten; Tsuzuki, Toshihiro; Uraguchi, Fumihiro; Champey,
Patrick; Alsina Ballester, Ernest; Casini, Roberto; McKenzie, David;
Rachmeler, Laurel; Bethge, Christian
2018cosp...42E1564I Altcode:
To obtain quantitative information on the magnetic field in low beta
regions (i.e., upper chromosphere and above) has been increasingly
important to understand the energetic phenomena of the outer
solar atmosphere such as flare, coronal heating, and the solar wind
acceleration. In the UV range, there are abundant spectral lines that
originate in the upper chromosphere and transition region. However,
the Zeeman effect in these spectral lines does not give rise to easily
measurable polarization signals because of the weak magnetic field
strength and the larger Doppler broadening compared with the Zeeman
effect. Instead, the Hanle effect in UV lines is expected to be a
suitable diagnostic tool of the magnetic field in the upper atmospheric
layers. To investigate the validity of UV spectro-polarimetry and
the Hanle effect, the Chromospheric Lyman-Alpha Spectro-Polarimeter
(CLASP), which is a NASA sounding- rocket experiment, was launched at
White Sands in US on September 3, 2015. During its 5 minutes ballistic
flight, it successfully performed spectro-polarimetric observations
of the hydrogen Lyman-alpha line (121.57 nm) with an unprecedentedly
high polarization sensitivity of 0.1% in this wavelength range. CLASP
observed the linear polarization produced by scattering process in VUV
lines for the first time and detected the polarization signals which
indicate the operation of the Hanle effect. Following the success
of CLASP, we are confident that UV spectro-polarimetry is the way
to proceed, and we are planning the second flight of CLASP (CLASP2:
Chromospheric LAyer SpectroPolarimeter 2). For this second flight we
will carry out spectro-polarimetry in the Mg II h and k lines around
280 nm, with minimum modifications of the CLASP1 instrument. The linear
polarization in the Mg II k line is induced by scattering processes and
the Hanle effect, being sensitive to magnetic field strengths of 5 to 50
G. In addition, the circular polarizations in the Mg II h and k lines
induced by the Zeeman effect can be measurable in at least plage and
active regions. The combination of the Hanle and Zeeman effects could
help us to more reliably infer the magnetic fields of the upper solar
chromosphere. CLASP2 was selected for flight and is being developed for
launch in the spring of 2019.Based on these sounding rocket experiments
(CLASP1 and 2), we aim at establishing the strategy and refining the
instrument concept for future space missions to explore the enigmatic
atmospheric layers via UV spectro-polarimetry.
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Title: Linearity Analysis and Efficiency Testing of The Chromospheric
Lyman-Alpha Spectro-Polarimeter (CLASP) Science Cameras for Flight
Authors: Walker, S. C.; Rachmeler, L.; Winebarger, A. R.; Champey,
P. R.; Bethge, C.
2017AGUFMSH51C2503W Altcode:
To unveil the complexity of the solar atmosphere, measurement of the
magnetic field in the upper chromosphere and transition region is
fundamentally important, as this is where the forces transition from
plasma to magnetic field dominated. Measurements of the field are also
needed to shed light on the energy transport from the lower atmospheric
regions to the corona beyond. Such an advance in heliospheric knowledge
became possible with the first flight of the international solar
sounding rocket mission, CLASP. For the first time, linear polarization
was measured in H Lyman-Alpha at 121.60 nm in September 2015. For linear
polarization measurements in this line, high sensitivity is required due
to the relatively weak polarization signal compared to the intensity. To
achieve this high sensitivity, a low-noise sensor is required with
good knowledge of its characterization, including linearity. This work
presents further refinement of the linearity characterization of the
cameras flown in 2015. We compared the current from a photodiode in
the light path to the digital response of the detectors. Pre-flight
CCD linearity measurements were taken for all three flight cameras and
calculations of the linear fits and residuals were performed. However,
the previous calculations included a smearing pattern and a digital
saturation region on the detectors which were not properly taken
into account. The calculations have been adjusted and were repeated
for manually chosen sub-regions on the detectors that were found not
to be affected. We present a brief overview of the instrument, the
calibration data and procedures, and a comparison of the old and new
linearity results. The CLASP cameras will be reused for the successor
mission, CLASP2, which will measure the Mg II h & k lines between
279.45 nm and 280.35 nm. The new approach will help to better prepare
for and to improve the camera characterization for CLASP2.
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Title: Comparison of Solar Fine Structure Observed Simultaneously
in Lyα and Mg II h
Authors: Schmit, D.; Sukhorukov, A. V.; De Pontieu, B.; Leenaarts,
J.; Bethge, C.; Winebarger, A.; Auchère, F.; Bando, T.; Ishikawa,
R.; Kano, R.; Kobayashi, K.; Narukage, N.; Trujillo Bueno, J.
2017ApJ...847..141S Altcode: 2017arXiv170900035S
The Chromospheric Lyman Alpha Spectropolarimeter (CLASP) observed the
Sun in H I Lyα during a suborbital rocket flight on 2015 September
3. The Interface Region Imaging Telescope (IRIS) coordinated with the
CLASP observations and recorded nearly simultaneous and co-spatial
observations in the Mg II h and k lines. The Mg II h and Lyα lines
are important transitions, energetically and diagnostically, in the
chromosphere. The canonical solar atmosphere model predicts that these
lines form in close proximity to each other and so we expect that the
line profiles will exhibit similar variability. In this analysis, we
present these coordinated observations and discuss how the two profiles
compare over a region of quiet Sun at viewing angles that approach the
limb. In addition to the observations, we synthesize both line profiles
using a 3D radiation-MHD simulation. In the observations, we find that
the peak width and the peak intensities are well correlated between the
lines. For the simulation, we do not find the same relationship. We
have attempted to mitigate the instrumental differences between IRIS
and CLASP and to reproduce the instrumental factors in the synthetic
profiles. The model indicates that formation heights of the lines
differ in a somewhat regular fashion related to magnetic geometry. This
variation explains to some degree the lack of correlation, observed
and synthesized, between Mg II and Lyα. Our analysis will aid in the
definition of future observatories that aim to link dynamics in the
chromosphere and transition region.
---------------------------------------------------------
Title: Introduction of the ASGARD code (Automated Selection and
Grouping of events in AIA Regional Data)
Authors: Bethge, Christian; Winebarger, Amy; Tiwari, Sanjiv K.;
Fayock, Brian
2017SPD....4810623B Altcode:
We have developed the ASGARD code to automatically detect and group
brightenings ("events") in AIA data. The event selection and grouping
can be optimized to the respective dataset with a multitude of control
parameters. The code was initially written for IRIS data, but has since
been optimized for AIA. However, the underlying algorithm is not limited
to either and could be used for other data as well.Results from datasets
in various AIA channels show that brightenings are reliably detected and
that coherent coronal structures can be isolated by using the obtained
information about the start, peak, and end times of events. We are
presently working on a follow-up algorithm to automatically determine
the heating and cooling timescales of coronal structures. This will
be done by correlating the information from different AIA channels
with different temperature responses. We will present the code and
preliminary results.
---------------------------------------------------------
Title: CLASP2: The Chromospheric LAyer Spectro-Polarimeter
Authors: Rachmeler, Laurel; E McKenzie, David; Ishikawa, Ryohko;
Trujillo Bueno, Javier; Auchère, Frédéric; Kobayashi, Ken;
Winebarger, Amy; Bethge, Christian; Kano, Ryouhei; Kubo, Masahito;
Song, Donguk; Narukage, Noriyuki; Ishikawa, Shin-nosuke; De Pontieu,
Bart; Carlsson, Mats; Yoshida, Masaki; Belluzzi, Luca; Stepan, Jiri;
del Pino Alemná, Tanausú; Ballester, Ernest Alsina; Asensio Ramos,
Andres
2017SPD....4811010R Altcode:
We present the instrument, science case, and timeline of the CLASP2
sounding rocket mission. The successful CLASP (Chromospheric Lyman-Alpha
Spectro-Polarimeter) sounding rocket flight in 2015 resulted in
the first-ever linear polarization measurements of solar hydrogen
Lyman-alpha line, which is sensitive to the Hanle effect and can be used
to constrain the magnetic field and geometric complexity of the upper
chromosphere. Ly-alpha is one of several upper chromospheric lines that
contain magnetic information. In the spring of 2019, we will re-fly
the modified CLASP telescope to measure the full Stokes profile of Mg
II h & k near 280 nm. This set of lines is sensitive to the upper
chromospheric magnetic field via both the Hanle and the Zeeman effects.
---------------------------------------------------------
Title: CLASP2: The Chromospheric LAyer Spectro-Polarimeter
Authors: Rachmeler, Laurel A.; McKenzie, D. E.; Ishikawa, R.;
Trujillo-Bueno, J.; Auchere, F.; Kobayashi, K.; Winebarger, A.;
Bethge, C.; Kano, R.; Kubo, M.; Song, D.; Narukage, N.; Ishikawa, S.;
De Pontieu, B.; Carlsson, M.; Yoshida, M.; Belluzzi, L.; Stepan, J.;
del Pino Alemán, T.; Alsina Ballester, E.; Asensio Ramos, A.
2017shin.confE..79R Altcode:
We present the instrument, science case, and timeline of the CLASP2
sounding rocket mission. The successful CLASP (Chromospheric Lyman-Alpha
Spectro-Polarimeter) sounding rocket flight in 2015 resulted in
the first-ever linear polarization measurements of solar hydrogen
Lyman-alpha line, which is sensitive to the Hanle effect and can be used
to constrain the magnetic field and geometric complexity of the upper
chromosphere. Ly-alpha is one of several upper chromospheric lines that
contain magnetic information. In the spring of 2019, we will re-fly
the modified CLASP telescope to measure the full Stokes profile of Mg
II h & k near 280 nm. This set of lines is sensitive to the upper
chromospheric magnetic field via both the Hanle and the Zeeman effects.
---------------------------------------------------------
Title: Magnetic fields of opposite polarity in sunspot penumbrae
Authors: Franz, M.; Collados, M.; Bethge, C.; Schlichenmaier, R.;
Borrero, J. M.; Schmidt, W.; Lagg, A.; Solanki, S. K.; Berkefeld,
T.; Kiess, C.; Rezaei, R.; Schmidt, D.; Sigwarth, M.; Soltau, D.;
Volkmer, R.; von der Luhe, O.; Waldmann, T.; Orozco, D.; Pastor Yabar,
A.; Denker, C.; Balthasar, H.; Staude, J.; Hofmann, A.; Strassmeier,
K.; Feller, A.; Nicklas, H.; Kneer, F.; Sobotka, M.
2016A&A...596A...4F Altcode: 2016arXiv160800513F
Context. A significant part of the penumbral magnetic field returns
below the surface in the very deep photosphere. For lines in the
visible, a large portion of this return field can only be detected
indirectly by studying its imprints on strongly asymmetric and
three-lobed Stokes V profiles. Infrared lines probe a narrow layer
in the very deep photosphere, providing the possibility of directly
measuring the orientation of magnetic fields close to the solar
surface. <BR /> Aims: We study the topology of the penumbral magnetic
field in the lower photosphere, focusing on regions where it returns
below the surface. <BR /> Methods: We analyzed 71 spectropolarimetric
datasets from Hinode and from the GREGOR infrared spectrograph. We
inferred the quality and polarimetric accuracy of the infrared data
after applying several reduction steps. Techniques of spectral
inversion and forward synthesis were used to test the detection
algorithm. We compared the morphology and the fractional penumbral
area covered by reversed-polarity and three-lobed Stokes V profiles for
sunspots at disk center. We determined the amount of reversed-polarity
and three-lobed Stokes V profiles in visible and infrared data of
sunspots at various heliocentric angles. From the results, we computed
center-to-limb variation curves, which were interpreted in the context
of existing penumbral models. <BR /> Results: Observations in visible
and near-infrared spectral lines yield a significant difference in the
penumbral area covered by magnetic fields of opposite polarity. In
the infrared, the number of reversed-polarity Stokes V profiles is
smaller by a factor of two than in the visible. For three-lobed Stokes
V profiles the numbers differ by up to an order of magnitude.
---------------------------------------------------------
Title: Statistical Evidence for the Existence of Alfvénic Turbulence
in Solar Coronal Loops
Authors: Liu, Jiajia; McIntosh, Scott W.; De Moortel, Ineke; Threlfall,
James; Bethge, Christian
2014ApJ...797....7L Altcode: 2014arXiv1411.5094L
Recent observations have demonstrated that waves capable of
carrying large amounts of energy are ubiquitous throughout the solar
corona. However, the question of how this wave energy is dissipated
(on which timescales and length scales) and released into the plasma
remains largely unanswered. Both analytic and numerical models have
previously shown that Alfvénic turbulence may play a key role not
only in the generation of the fast solar wind, but in the heating
of coronal loops. In an effort to bridge the gap between theory and
observations, we expand on a recent study by analyzing 37 clearly
isolated coronal loops using data from the Coronal Multi-channel
Polarimeter instrument. We observe Alfvénic perturbations with phase
speeds which range from 250 to 750 km s<SUP>-1</SUP> and periods from
140 to 270 s for the chosen loops. While excesses of high-frequency wave
power are observed near the apex of some loops (tentatively supporting
the onset of Alfvénic turbulence), we show that this excess depends on
loop length and the wavelength of the observed oscillations. In deriving
a proportional relationship between the loop length/wavelength ratio
and the enhanced wave power at the loop apex, and from the analysis
of the line widths associated with these loops, our findings are
supportive of the existence of Alfvénic turbulence in coronal loops.
---------------------------------------------------------
Title: Observations of a Hybrid Double-streamer/Pseudostreamer in
the Solar Corona
Authors: Rachmeler, L. A.; Platten, S. J.; Bethge, C.; Seaton, D. B.;
Yeates, A. R.
2014ApJ...787L...3R Altcode: 2013arXiv1312.3153R
We report on the first observation of a single hybrid magnetic structure
that contains both a pseudostreamer and a double streamer. This
structure was originally observed by the SWAP instrument on board
the PROBA2 satellite between 2013 May 5 and 10. It consists of a pair
of filament channels near the south pole of the Sun. On the western
edge of the structure, the magnetic morphology above the filaments
is that of a side-by-side double streamer, with open field between
the two channels. On the eastern edge, the magnetic morphology is
that of a coronal pseudostreamer without the central open field. We
investigated this structure with multiple observations and modeling
techniques. We describe the topology and dynamic consequences of such
a unified structure.
---------------------------------------------------------
Title: Potential Evidence for the Onset of Alfvénic Turbulence in
Trans-equatorial Coronal Loops
Authors: De Moortel, I.; McIntosh, S. W.; Threlfall, J.; Bethge, C.;
Liu, J.
2014ApJ...782L..34D Altcode:
This study investigates Coronal Multi-channel Polarimeter Doppler-shift
observations of a large, off-limb, trans-equatorial loop system observed
on 2012 April 10-11. Doppler-shift oscillations with a broad range of
frequencies are found to propagate along the loop with a speed of about
500 km s<SUP>-1</SUP>. The power spectrum of perturbations travelling
up from both loop footpoints is remarkably symmetric, probably due to
the almost perfect north-south alignment of the loop system. Compared
to the power spectrum at the footpoints of the loop, the Fourier power
at the apex appears to be higher in the high-frequency part of the
spectrum than expected from theoretical models. We suggest this excess
high-frequency power could be tentative evidence for the onset of a
cascade of the low-to-mid frequency waves into (Alfvénic) turbulence.
---------------------------------------------------------
Title: The spatial relation between EUV cavities and linear
polarization signatures
Authors: Bak-Stȩślicka, Urszula; Gibson, Sarah E.; Fan, Yuhong;
Bethge, Christian; Forland, Blake; Rachmeler, Laurel A.
2014IAUS..300..395B Altcode:
Solar coronal cavities are regions of rarefied density and elliptical
cross-section. The Coronal Multi-channel Polarimeter (CoMP) obtains
daily full-Sun coronal observations in linear polarization, allowing
a systematic analysis of the coronal magnetic field in polar-crown
prominence cavities. These cavities commonly possess a characteristic
“lagomorphic” signature in linear polarization that may be explained
by a magnetic flux-rope model. We analyze the spatial relation between
the EUV cavity and the CoMP linear polarization signature.
---------------------------------------------------------
Title: Observations of Coronal Mass Ejections with the Coronal
Multichannel Polarimeter
Authors: Tian, H.; Tomczyk, S.; McIntosh, S. W.; Bethge, C.; de Toma,
G.; Gibson, S.
2013SoPh..288..637T Altcode: 2013arXiv1303.4647T
The Coronal Multichannel Polarimeter (CoMP) measures not only the
polarization of coronal emission, but also the full radiance profiles of
coronal emission lines. For the first time, CoMP observations provide
high-cadence image sequences of the coronal line intensity, Doppler
shift, and line width simultaneously over a large field of view. By
studying the Doppler shift and line width we may explore more of the
physical processes of the initiation and propagation of coronal mass
ejections (CMEs). Here we identify a list of CMEs observed by CoMP
and present the first results of these observations. Our preliminary
analysis shows that CMEs are usually associated with greatly increased
Doppler shift and enhanced line width. These new observations provide
not only valuable information to constrain CME models and probe
various processes during the initial propagation of CMEs in the low
corona, but also offer a possible cost-effective and low-risk means
of space-weather monitoring.
---------------------------------------------------------
Title: The Evolving Magnetic Scales of the Outer Solar Atmosphere
and Their Potential Impact on Heliospheric Turbulence
Authors: McIntosh, Scott W.; Bethge, Christian; Threlfall, James;
De Moortel, Ineke; Leamon, Robert J.; Tian, Hui
2013arXiv1311.2538M Altcode:
The presence of turbulent phenomena in the outer solar atmosphere
is a given. However, because we are reduced to remotely sensing the
atmosphere of a star with instruments of limited spatial and/or spectral
resolution, we can only infer the physical progression from macroscopic
to microscopic phenomena. Even so, we know that many, if not all,
of the turbulent phenomena that pervade interplanetary space have
physical origins at the Sun and so in this brief article we consider
some recent measurements which point to sustained potential source(s)
of heliospheric turbulence in the magnetic and thermal domains. In
particular, we look at the scales of magnetism that are imprinted on
the outer solar atmosphere by the relentless magneto-convection of the
solar interior and combine state-of-the-art observations from the Solar
Dynamics Observatory (SDO) and the Coronal Multi-channel Polarimeter
(CoMP) which are beginning to hint at the origins of the wave/plasma
interplay prevalent closer to the Earth. While linking these disparate
scales of observation and understanding of their connection is near
to impossible, it is clear that the constant evolution of subsurface
magnetism on a host of scales guides and governs the flow of mass
and energy at the smallest scales. In the near future significant
progress in this area will be made by linking observations from high
resolution platforms like the Interface Region Imaging Spectrograph
(IRIS) and Advanced Technology Solar Telescope (ATST) with full-disk
synoptic observations such as those presented herein.
---------------------------------------------------------
Title: First comparison of wave observations from CoMP and AIA/SDO
Authors: Threlfall, J.; De Moortel, I.; McIntosh, S. W.; Bethge, C.
2013A&A...556A.124T Altcode: 2013arXiv1306.3354T
Context. Waves have long been thought to contribute to the heating
of the solar corona and the generation of the solar wind. Recent
observations have demonstrated evidence of quasi-periodic longitudinal
disturbances and ubiquitous transverse wave propagation in many
different coronal environments. <BR /> Aims: This paper investigates
signatures of different types of oscillatory behaviour, both above
the solar limb and on-disk, by comparing findings from the Coronal
Multi-channel Polarimeter (CoMP) and the Atmospheric Imaging
Assembly (AIA) on-board the Solar Dynamics Observatory (SDO) for
the same active region. <BR /> Methods: We study both transverse and
longitudinal motion by comparing and contrasting time-distance images
of parallel and perpendicular cuts along/across active region fan
loops. Comparisons between parallel space-time diagram features in
CoMP Doppler velocity and transverse oscillations in AIA images are
made, together with space-time analysis of propagating quasi-periodic
intensity features seen near the base of loops in AIA. <BR /> Results:
Signatures of transverse motions are observed along the same magnetic
structure using CoMP Doppler velocity (v<SUB>phase</SUB> = 600 → 750
km s<SUP>-1</SUP>, P = 3 → 6 min) and in AIA/SDO above the limb (P =
3 → 8 min). Quasi-periodic intensity features (v<SUB>phase</SUB> =
100 → 200 km s<SUP>-1</SUP>, P = 6 → 11 min) also travel along the
base of the same structure. On the disk, signatures of both transverse
and longitudinal intensity features were observed by AIA, and both show
similar properties to signatures found along structures anchored in
the same active region three days earlier above the limb. Correlated
features are recovered by space-time analysis of neighbouring tracks
over perpendicular distances of ≲2.6 Mm.
---------------------------------------------------------
Title: The Magnetic Structure of Solar Prominence Cavities: New
Observational Signature Revealed by Coronal Magnetometry
Authors: Bąk-Stȩślicka, Urszula; Gibson, Sarah E.; Fan, Yuhong;
Bethge, Christian; Forland, Blake; Rachmeler, Laurel A.
2013ApJ...770L..28B Altcode: 2013arXiv1304.7388B
The Coronal Multi-Channel Polarimeter (CoMP) obtains daily full-Sun
above-the-limb coronal observations in linear polarization, allowing,
for the first time, a diagnostic of the coronal magnetic field
direction in quiescent prominence cavities. We find that these cavities
consistently possess a characteristic "lagomorphic" signature in linear
polarization indicating twist or shear extending up into the cavity
above the neutral line. We demonstrate that such a signature may be
explained by a magnetic flux-rope model, a topology with implications
for solar eruptions. We find corroborating evidence for a flux-rope
structure in the pattern of concentric rings within cavities seen in
CoMP line-of-sight velocity.
---------------------------------------------------------
Title: The Chromosphere and Prominence Magnetometer
Authors: de Wijn, Alfred; Bethge, Christian; McIntosh, Scott; Tomczyk,
Steven; Burkepile, Joan
2013EGUGA..1512765D Altcode:
The Chromosphere and Prominence Magnetometer (ChroMag) is a synoptic
instrument with the goal of quantifying the intertwined dynamics
and magnetism of the solar chromosphere and in prominences through
imaging spectro-polarimetry of the full solar disk in a synoptic
fashion. The picture of chromospheric magnetism and dynamics is
rapidly developing, and a pressing need exists for breakthrough
observations of chromospheric vector magnetic field measurements
at the true lower boundary of the heliospheric system. ChroMag will
provide measurements that will enable scientists to study and better
understand the energetics of the solar atmosphere, how prominences are
formed, how energy is stored in the magnetic field structure of the
atmosphere and how it is released during space weather events like
flares and coronal mass ejections. An essential part of the ChroMag
program is a commitment to develop and provide community access to the
`inversion' tools necessary to interpret the measurements and derive
the magneto-hydrodynamic parameters of the plasma. Measurements of an
instrument like ChroMag provide critical physical context for the Solar
Dynamics Observatory (SDO) and Interface Region Imaging Spectrograph
(IRIS) as well as ground-based observatories such as the future Advanced
Technology Solar Telescope (ATST). A prototype is currently under
construction at the High Altitude Observatory of the National Center
for Atmospheric Research in Boulder, CO, USA. The heart of the ChroMag
instrument is an electro-optically tunable wide-fielded narrow-band
birefringent six-stage Lyot filter with a built-in polarimeter. We
will present a progress update on the ChroMag design, and present
results from the prototype instrument.
---------------------------------------------------------
Title: The chromosphere and prominence magnetometer
Authors: de Wijn, Alfred G.; Bethge, Christian; Tomczyk, Steven;
McIntosh, Scott
2012SPIE.8446E..78D Altcode: 2012arXiv1207.0969D
The Chromosphere and Prominence Magnetometer (ChroMag) is conceived
with the goal of quantifying the intertwined dynamics and magnetism
of the solar chromosphere and in prominences through imaging spectro-
polarimetry of the full solar disk. The picture of chromospheric
magnetism and dynamics is rapidly developing, and a pressing need
exists for breakthrough observations of chromospheric vector magnetic
field measurements at the true lower boundary of the heliospheric
system. ChroMag will provide measurements that will enable scientists
to study and better understand the energetics of the solar atmosphere,
how prominences are formed, how energy is stored in the magnetic field
structure of the atmosphere and how it is released during space weather
events like flares and coronal mass ejections. An integral part of the
ChroMag program is a commitment to develop and provide community access
to the "inversion" tools necessary for the difficult interpretation
of the measurements and derive the magneto-hydrodynamic parameters of
the plasma. Measurements of an instrument like ChroMag provide critical
physical context for the Solar Dynamics Observatory (SDO) and Interface
Region Imaging Spectrograph (IRIS) as well as ground-based observatories
such as the future Advanced Technology Solar Telescope (ATST).
---------------------------------------------------------
Title: Magnetic Structure of Coronal Cavities
Authors: Gibson, Sarah; Bak-Steslicka, Urszula; Bethge, Christian;
de Toma, Giuliana; Dove, Jim; Fan, Yuhong; Forland, Blake; Rachmeler,
Laurel
2012shin.confE.209G Altcode:
Coronal cavities are dark, elliptical regions in which strong
and twisted magnetism dwells. Polar-crown-prominence cavities in
particular are excellent targets for coronal magnetometry, because
they are long-lived (on the order of weeks) and extended along the
line of sight. Using data from the Coronal Multichannel Polarimeter
(CoMP), we show a specific structure in linear polarization that
is very consistent from cavity to cavity, and that matches that of a
forward-modeled flux rope. We discuss how this structure scales with the
size of the cavity, and consider implications for future observations
(e.g., ATST and COSMO) in probing and indeed predicting topological
changes and instabilities leading up to eruptions.
---------------------------------------------------------
Title: New insight into CME processes revealed by CoMP observations
Authors: Tian, Hui; McIntosh, Scott W.; Bethge, Christian; Tomczyk,
Steve; Sitongia, Leonard E.
2012shin.confE..11T Altcode:
CoMP measures not only the polarization of coronal emission, but also
measures the full radiance profiles of coronal emission lines. For the
first time, CoMP observations provide high-cadence image sequences
of the coronal intensity, Doppler shift, line width and linear
polarization simultaneously. These measurements may help us explore
more of the physical processes at the onset of solar eruptions such
as CMEs and flares. They should also provide important constraints to
models of solar eruptions. Our preliminary analysis shows that CMEs are
usually associated with greatly increased Doppler shift and enhanced
line width. The linear polarization in CMEs measured by CoMP has also
been investigated.
---------------------------------------------------------
Title: The Chromospheric Magnetometer ChroMag
Authors: Bethge, Christian; de Wijn, A. G.; McIntosh, S. W.; Tomczyk,
S.; Casini, R.
2012AAS...22013506B Altcode:
We present the Chromosphere Magnetometer (ChroMag), which is part of
the Coronal Solar Magnetism Observatory (COSMO) proposed by the High
Altitude Observatory (HAO) in collaboration with the University of
Hawaii and the University of Michigan. ChroMag will perform routine
measurements of chromospheric magnetic fields in a synoptic manner. A <P
/>prototype is currently being assembled at HAO. The main component of
the instrument is a Lyot-type filtergraph polarimeter for both on-disk
and off-limb polarization measurements in <P />the spectral lines of
H alpha at 656.3 nm, Fe I 617.3 nm, Ca II 854.2 nm, He I 587.6 nm,
and He I 1083.0 nm. The Lyot filter is tunable at a fast rate. This
allows to determine line-of-sight <P />velocities in addition to the
magnetic field measurements. The instrument has a field-of-view of
up to 2.5 solar radii and will acquire data at a cadence of less than
1 minute and at a spatial resolution of 2 arcsec. The community will
have open access to the data as well as to a set of inversion tools
for an easier interpretation of the measurements. We show an overview
of the proposed instrument and first results from the protoype.
---------------------------------------------------------
Title: Recent Results from the Coronal Multi-Channel Polarimeter
Authors: Tomczyk, Steven; Bethge, C.; Gibson, S. E.; McIntosh, S. W.;
Rachmeler, L. A.; Tian, H.
2012AAS...22031001T Altcode:
The Coronal Multi-Channel Polarimeter (CoMP) instrument is a
ground-based filter/polarimeter which can image the solar corona at
wavelengths around the emission lines of FeXIII at 1074.7 and 1079.8
nm and the chromospheric emission line of HeI at 1083.0 nm. The
instrument consists of a 20-cm aperture coronagraph followed by a
Stokes polarimeter and a Lyot birefringent filter with a passband
of 0.14 nm width. Both the polarimeter and filter employ liquid
crystals for rapid electro-optical tuning. This instrument measures
the line-of-sight strength of the coronal magnetic field through the
Zeeman effect and the plane-of-sky direction of the magnetic field via
resonance scattering. The line-of-sight velocity can also be determined
from the Doppler shift. The CoMP has obtained daily observations from
the Mauna Loa Solar Observatory for almost one year. We will present
recent measurements of the polarization signatures seen with the
CoMP and a comparison with models that allow us to constrain coronal
structure. We also will present observations of coronal waves taken
with the CoMP and discuss their implications for the heating of the
solar corona and the acceleration of the solar wind.
---------------------------------------------------------
Title: The Chromosphere and Prominence Magnetometer
Authors: de Wijn, Alfred; Bethge, Christian; McIntosh, Scott; Tomczyk,
Steven; Casini, Roberto
2012decs.confE..63D Altcode:
ChroMag is an imaging polarimeter designed to measure on-disk
chromosphere and off-disk prominence magnetic fields using the
spectral lines of He I (587.6 and 1083 nm). It is part of the planned
CoSMO suite, which includes two more instruments: a large 1.5-m
refracting coronagraph for coronal magnetic field measurements, and
the K-Coronagraph for measurement of the coronal density. ChroMag
will provide insights in the energetics of the solar atmosphere,
how prominences are formed, and how energy is stored and released
in the magnetic field structure of the atmosphere. An essential
part of the ChroMag program is a commitment to develop and provide
community access to the "inversion" tools necessary to interpret the
measurements and derive the magneto-hydrodynamic parameters of the
plasma. A prototype instrument is currently under construction at the
High Altitude Observatory. We will present an overview of the ChroMag
instrument concept, target science, and prototype status.
---------------------------------------------------------
Title: Synoptic measurements of chromospheric and prominence magnetic
fields with the Chromosphere Magnetometer ChroMag
Authors: Bethge, C.; de Wijn, A. G.; McIntosh, S. W.; Tomczyk, S.;
Casini, R.
2012decs.confE..62B Altcode:
The Chromosphere Magnetometer is part of the Coronal Solar Magnetism
Observatory (COSMO) proposed by the High Altitude Observatory (HAO)
in collaboration with the University of Hawaii and the University of
Michigan. Routine measurements of chromospheric and coronal magnetic
fields are vital if we want to understand fundamental problems like
the energy and mass balance of the corona, the onset and acceleration
of the solar wind, the emergence of CMEs, and how these phenomena
influence space weather. ChroMag is designed as a Lyot-type filtergraph
polarimeter with an FOV of 2.5 solar radii, i.e., it will be capable of
both on-disk and off-limb polarimetric measurements. The Lyot filter
- currently being built at HAO - is tunable at a fast rate, which
allows to determine line-of-sight velocities. This will be done in
the spectral lines of H alpha at 656.3 nm, Fe I 617.3 nm, Ca II 854.2
nm, He I 587.6 nm, and He I 1083.0 nm at a high cadence of less than
1 minute, and at a moderate spatial resolution of 2 arcsec. ChroMag
data will be freely accessible to the community, along with inversion
tools for an easier interpretation of the data. A protoype instrument
for ChroMag is currently being assembled at HAO and is expected to
perform first measurements at the Boulder Mesa Lab in Summer 2012. We
present an overview of the ChroMag instrument and the current status
of the protoype.
---------------------------------------------------------
Title: Siphon flow in a cool magnetic loop
Authors: Bethge, C.; Beck, C.; Peter, H.; Lagg, A.
2012A&A...537A.130B Altcode: 2011arXiv1111.5564B
Context. Siphon flows that are driven by a gas pressure difference
between two photospheric footpoints of different magnetic field strength
connected by magnetic field lines are a well-studied phenomenon in
theory, but observational evidence is scarce. Aims. We investigate the
properties of a structure in the solar chromosphere in an active region
to find out whether the feature is consistent with a siphon flow in
a magnetic loop filled with chromospheric material. <P />Methods. We
derived the line-of-sight (LOS) velocity of several photospheric
spectral lines and two chromospheric spectral lines, Ca II H 3968.5
*Aring; and He I 10830 Å, in spectropolarimetric observations of
NOAA 10978 done with the Tenerife Infrared Polarimeter (TIP-II) and
the POlarimetric LIttrow Spectrograph (POLIS). The structure can be
clearly traced in the LOS velocity maps and the absorption depth of
He I. The magnetic field configuration in the photosphere is inferred
directly from the observed Stokes parameters and from inversions with
the HELIX<SUP>+</SUP> code. Data from the full-disk Chromospheric
Telescope (ChroTel) in He I in intensity and LOS velocity are used for
tracking the temporal evolution of the flow, along with TRACE Fe IX/X
171 Å data for additional information about coronal regions related to
the structure under investigation. <P />Results. The inner end of the
structure is located in the penumbra of a sunspot. It shows downflows
whose strength decreases with decreasing height in the atmosphere. The
flow velocity in He I falls abruptly from above 40 km s<SUP>-1</SUP>
to about zero further into the penumbra. A slight increase of emission
is seen in the Ca II H spectra at the endpoint. At the outer end of the
structure, the photospheric lines that form higher up in the atmosphere
show upflows that accelerate with height. The polarization signal near
the outer end shows a polarity opposite to that of the sunspot, the
magnetic field strength of 580 G is roughly half as large as at the
inner end. The structure exists for about 90 min. Its appearance is
preceeded by a brightening in its middle in the coronal TRACE data. <P
/>Conclusions. The observed flows match theoretical predictions of
chromospheric and coronal siphon flows, with accelerating upflowing
plasma at one footpoint with low field strength and decelerating
downflowing plasma at the other end. A tube shock at the inner end is
probable, but the evidence is not conclusive. The TRACE data suggest
that the structure forms because of a reorganization of field lines
after a reconnection event.
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Title: The Chromospheric Telescope
Authors: Bethge, C.; Peter, H.; Kentischer, T. J.; Halbgewachs, C.;
Elmore, D. F.; Beck, C.
2011A&A...534A.105B Altcode: 2011arXiv1108.4880B
<BR /> Aims: We introduce the Chromospheric Telescope (ChroTel) at the
Observatorio del Teide in Izaña on Tenerife as a new multi-wavelength
imaging telescope for full-disk synoptic observations of the solar
chromosphere. We describe the design of the instrument and summarize
its performance during the first one and a half years of operation. We
present a method to derive line-of-sight velocity maps of the full
solar disk from filtergrams taken in and near the He i infrared line
at 10 830 Å. <BR /> Methods: ChroTel observations are conducted
using Lyot-type filters for the chromospheric lines of Ca ii K,
Hα, and He i 10 830 Å. The instrument operates autonomically and
gathers imaging data in all three channels with a cadence of down to
one minute. The use of a tunable filter for the He i line allows us
to determine line-shifts by calibrating the line-of-sight velocity
maps derived from the filtergram intensities with spectrographic data
from the Tenerife Infrared Polarimeter at high spatial and spectral
resolution. <BR /> Results: The robotic operation and automated data
reduction have proven to operate reliably in the first one and and
half years. The achieved spatial resolution of the data is close to
the theoretical limit of 2 arcsec in Hα and Ca ii K and 3 arcsec in He
i. Line-of-sight velocities in He i can be determined with a precision
of better than 3-4 km s<SUP>-1</SUP> when co-temporal spectrographic
maps are available for calibration. <BR /> Conclusions: ChroTel offers a
unique combination of imaging in the most important chromospheric lines,
along with the possibility to determine line-of-sight velocities in
one of the lines. This is of interest for scientific investigations
of large-scale structures in the solar chromosphere, as well as for
context imaging of high-resolution solar observations.
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Title: The Slow Control System of the Auger Fluorescence Detectors
Authors: Barenthien, N.; Bethge, C.; Daumiller, K.; Gemmeke, H.;
Kampert, K. -H.; Wiebusch, C.
2003ICRC....2..895B Altcode: 2003ICRC...28..895B; 2003ICRC....2..895G
The fluorescence detector (FD) of the Pierre Auger experiment [1]
comprises 24 telescopes that will be situated in 4 remote buildings in
the Pampa Amarilla. It is planned to run the fluorescence detectors
in absence of operators on site. Therefore, the main task of the
Slow Control System (SCS) is to ensure a secure remote operation
of the FD system. The Slow Control System works autonomously and
continuously monitors those parameters which may disturb a secure
operation. Commands from the data-acquisition system or the remote
operator are accepted only if they do not violate safety rules that
depend on the actual experimental conditions (e.g. high-voltage,
wind-sp eed, light, etc.). In case of malfunctions (power failure,
communication breakdown, ...) the SCS performs an orderly shutdown and
subsequent startup of the fluorescence detector system. The concept
and the implementation of the Slow Control System are presented.
