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Author name code: brooks
ADS astronomy entries on 2022-09-14
author:"Brooks, David H." AND (aff:"Fairfax" OR aff:"Kyoto" OR aff:"Glasgow")
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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: Constraining Global Coronal Models with Multiple Independent
Observables
Authors: Badman, Samuel T.; Brooks, David H.; Poirier, Nicolas;
Warren, Harry P.; Petrie, Gordon; Rouillard, Alexis P.; Nick Arge,
C.; Bale, Stuart D.; de Pablos Agüero, Diego; Harra, Louise; Jones,
Shaela I.; Kouloumvakos, Athanasios; Riley, Pete; Panasenco, Olga;
Velli, Marco; Wallace, Samantha
2022ApJ...932..135B Altcode: 2022arXiv220111818B
Global coronal models seek to produce an accurate physical
representation of the Sun's atmosphere that can be used, for example, to
drive space-weather models. Assessing their accuracy is a complex task,
and there are multiple observational pathways to provide constraints
and tune model parameters. Here, we combine several such independent
constraints, defining a model-agnostic framework for standardized
comparison. We require models to predict the distribution of coronal
holes at the photosphere, and neutral line topology at the model's outer
boundary. We compare these predictions to extreme-ultraviolet (EUV)
observations of coronal hole locations, white-light Carrington maps of
the streamer belt, and the magnetic sector structure measured in situ
by Parker Solar Probe and 1 au spacecraft. We study these metrics for
potential field source surface (PFSS) models as a function of source
surface height and magnetogram choice, as well as comparing to the more
physical Wang-Sheeley-Arge (WSA) and the Magnetohydrodynamic Algorithm
outside a Sphere (MAS) models. We find that simultaneous optimization
of PFSS models to all three metrics is not currently possible, implying
a trade-off between the quality of representation of coronal holes
and streamer belt topology. WSA and MAS results show the additional
physics that they include address this by flattening the streamer belt
while maintaining coronal hole sizes, with MAS also improving coronal
hole representation relative to WSA. We conclude that this framework
is highly useful for inter- and intra-model comparisons. Integral to
the framework is the standardization of observables required of each
model, evaluating different model aspects.
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Title: Detection of Stellar-like Abundance Anomalies in the Slow
Solar Wind
Authors: Brooks, David H.; Baker, Deborah; van Driel-Gesztelyi, Lidia;
Warren, Harry P.; Yardley, Stephanie L.
2022ApJ...930L..10B Altcode: 2022arXiv220409332B
The elemental composition of the Sun's hot atmosphere, the corona,
shows a distinctive pattern that is different from the underlying
surface or photosphere. Elements that are easy to ionize in the
chromosphere are enhanced in abundance in the corona compared to
their photospheric values. A similar pattern of behavior is often
observed in the slow-speed (<500 km s<SUP>-1</SUP>) solar wind
and in solar-like stellar coronae, while a reversed effect is seen
in M dwarfs. Studies of the inverse effect have been hampered in the
past because only unresolved (point-source) spectroscopic data were
available for these stellar targets. Here we report the discovery of
several inverse events observed in situ in the slow solar wind using
particle-counting techniques. These very rare events all occur during
periods of high solar activity that mimic conditions more widespread
on M dwarfs. The detections allow a new way of connecting the slow
wind to its solar source and are broadly consistent with theoretical
models of abundance variations due to chromospheric fast-mode waves
with amplitudes of 8-10 km s<SUP>-1</SUP>, sufficient to accelerate
the solar wind. The results imply that M-dwarf winds are dominated
by plasma depleted in easily ionized elements and lend credence to
previous spectroscopic measurements.
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Title: Multiwavelength optical and NIR variability analysis of the
Blazar PKS 0027-426
Authors: Guise, E.; Hönig, S. F.; Almeyda, T.; Horne, K.; Kishimoto,
M.; Aguena, M.; Allam, S.; Andrade-Oliveira, F.; Asorey, J.; Banerji,
M.; Bertin, E.; Boulderstone, B.; Brooks, D.; Burke, D. L.; Carnero
Rosell, A.; Carollo, D.; Carrasco Kind, M.; Carretero, J.; Costanzi,
M.; da Costa, L. N.; Davis, T. M.; De Vicente, J.; Doel, P.; Everett,
S.; Ferrero, I.; Flaugher, B.; Frieman, J.; Gandhi, P.; Goad, M.;
Gruen, D.; Gruendl, R. A.; Gschwend, J.; Gutierrez, G.; Hinton, S. R.;
Hollowood, D. L.; Honscheid, K.; James, D. J.; Johnson, M. A. C.;
Kuehn, K.; Lewis, G. F.; Lidman, C.; Lima, M.; Maia, M. A. G.; Malik,
U.; Menanteau, F.; Miquel, R.; Morgan, R.; Ogando, R. L. C.; Palmese,
A.; Paz-Chinchón, F.; Pereira, M. E. S.; Pieres, A.; Plazas Malagón,
A. A.; Sanchez, E.; Scarpine, V.; Serrano, S.; Sevilla-Noarbe, I.;
Seymour, N.; Smith, M.; Soares-Santos, M.; Suchyta, E.; Swanson,
M. E. C.; Tarle, G.; To, C.; Tucker, B. E.
2022MNRAS.510.3145G Altcode: 2021arXiv210813386G; 2021MNRAS.tmp.3142G
We present multiwavelength spectral and temporal variability analysis
of PKS 0027-426 using optical griz observations from Dark Energy Survey
between 2013 and 2018 and VEILS Optical Light curves of Extragalactic
TransienT Events (VOILETTE) between 2018 and 2019 and near-infrared
(NIR) JKs observations from Visible and Infrared Survey Telescope for
Astronomy Extragalactic Infrared Legacy Survey (VEILS) between 2017 and
2019. Multiple methods of cross-correlation of each combination of light
curve provides measurements of possible lags between optical-optical,
optical-NIR, and NIR-NIR emission, for each observation season and for
the entire observational period. Inter-band time lag measurements
consistently suggest either simultaneous emission or delays
between emission regions on time-scales smaller than the cadences of
observations. The colour-magnitude relation between each combination
of filters was also studied to determine the spectral behaviour of
PKS 0027-426. Our results demonstrate complex colour behaviour that
changes between bluer when brighter, stable when brighter, and redder
when brighter trends over different time-scales and using different
combinations of optical filters. Additional analysis of the optical
spectra is performed to provide further understanding of this complex
spectral behaviour.
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Title: Evolution of Plasma Composition in an Eruptive Flux Rope
Authors: Baker, D.; Green, L. M.; Brooks, D. H.; Démoulin, P.;
van Driel-Gesztelyi, L.; Mihailescu, T.; To, A. S. H.; Long, D. M.;
Yardley, S. L.; Janvier, M.; Valori, G.
2022ApJ...924...17B Altcode: 2021arXiv211011714B
Magnetic flux ropes are bundles of twisted magnetic field enveloping a
central axis. They harbor free magnetic energy and can be progenitors
of coronal mass ejections (CMEs). However, identifying flux ropes on
the Sun can be challenging. One of the key coronal observables that
has been shown to indicate the presence of a flux rope is a peculiar
bright coronal structure called a sigmoid. In this work, we show Hinode
EUV Imaging Spectrometer observations of sigmoidal active region (AR)
10977. We analyze the coronal plasma composition in the AR and its
evolution as a sigmoid (flux rope) forms and erupts as a CME. Plasma
with photospheric composition was observed in coronal loops close to
the main polarity inversion line during episodes of significant flux
cancellation, suggestive of the injection of photospheric plasma into
these loops driven by photospheric flux cancellation. Concurrently,
the increasingly sheared core field contained plasma with coronal
composition. As flux cancellation decreased and a sigmoid/flux
rope formed, the plasma evolved to an intermediate composition in
between photospheric and typical AR coronal compositions. Finally,
the flux rope contained predominantly photospheric plasma during and
after a failed eruption preceding the CME. Hence, plasma composition
observations of AR 10977 strongly support models of flux rope formation
by photospheric flux cancellation forcing magnetic reconnection first
at the photospheric level then at the coronal level.
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Title: Investigating the origin of magnetic perturbations associated
with the FIP Effect
Authors: Murabito, M.; Stangalini, M.; Baker, D.; Valori, G.; Jess,
D. B.; Jafarzadeh, S.; Brooks, D. H.; Ermolli, I.; Giorgi, F.; Grant,
S. D. T.; Long, D. M.; van Driel-Gesztelyi, L.
2021A&A...656A..87M Altcode: 2021arXiv210811164M
Recently, magnetic oscillations were detected in the chromosphere
of a large sunspot and found to be linked to the coronal locations
where a first ionization potential (FIP) effect was observed. In
an attempt to shed light on the possible excitation mechanisms
of these localized waves, we further investigate the same data
by focusing on the relation between the spatial distribution of
the magnetic wave power and the overall field geometry and plasma
parameters obtained from multi-height spectropolarimetric non-local
thermodynamic equilibrium (NLTE) inversions of IBIS data. We find,
in correspondence with the locations where the magnetic wave energy
is observed at chromospheric heights, that the magnetic fields have
smaller scale heights, meaning faster expansions of the field lines,
which ultimately results in stronger vertical density stratification
and wave steepening. In addition, the acoustic spectrum of the
oscillations at the locations where magnetic perturbations are
observed is broader than that observed at other locations, which
suggests an additional forcing driver to the p-modes. Analysis of the
photospheric oscillations in the sunspot surroundings also reveals
a broader spectrum between the two opposite polarities of the active
region (the leading spot and the trailing opposite polarity plage),
and on the same side where magnetic perturbations are observed in
the umbra. We suggest that strong photospheric perturbations between
the two polarities are responsible for this broader spectrum of
oscillations, with respect to the p-mode spectrum, resulting in locally
excited acoustic waves that, after crossing the equipartition layer,
located close to the umbra-penumbra boundary at photopheric heights,
are converted into magnetic waves and steepen due to the strong
density gradient. <P />Movie associated to Fig. 1 is available at <A
href="https://www.aanda.org/10.1051/0004-6361/202141504/olm">https://www.aanda.org</A>
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Title: Signature and escape of highly fractionated plasma in an
active region
Authors: Brooks, David H.; Yardley, Stephanie L.
2021MNRAS.508.1831B Altcode: 2021MNRAS.tmp.2443B; 2021arXiv210911157B
Accurate forecasting of space weather requires knowledge of the source
regions where solar energetic particles (SEP) and eruptive events
originate. Recent work has linked several major SEP events in 2014,
January, to specific features in the host active region (AR 11944). In
particular, plasma composition measurements in and around the footpoints
of hot, coronal loops in the core of the active region were able to
explain the values later measured in situ by the Wind spacecraft. Due
to important differences in elemental composition between SEPs and
the solar wind, the magnitude of the Si/S elemental abundance ratio
emerged as a key diagnostic of SEP seed population and solar wind
source locations. We seek to understand if the results are typical
of other active regions, even if they are not solar wind sources or
SEP productive. In this paper, we use a novel composition analysis
technique, together with an evolutionary magnetic field model, in a
new approach to investigate a typical solar active region (AR 11150),
and identify the locations of highly fractionated (high Si/S abundance
ratio) plasma. Material confined near the footpoints of coronal loops,
as in AR 11944, that in this case have expanded to the AR periphery,
show the signature, and can be released from magnetic field opened by
reconnection at the AR boundary. Since the fundamental characteristics
of closed field loops being opened at the AR boundary is typical of
active regions, this process is likely to be general.
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Title: The Formation and Lifetime of Outflows in a Solar Active Region
Authors: Brooks, David H.; Harra, Louise; Bale, Stuart D.; Barczynski,
Krzysztof; Mandrini, Cristina; Polito, Vanessa; Warren, Harry P.
2021ApJ...917...25B Altcode: 2021arXiv210603318B
Active regions are thought to be one contributor to the slow solar
wind. Upflows in EUV coronal spectral lines are routinely observed at
their boundaries, and provide the most direct way for upflowing material
to escape into the heliosphere. The mechanisms that form and drive these
upflows, however, remain to be fully characterized. It is unclear how
quickly they form, or how long they exist during their lifetimes. They
could be initiated low in the atmosphere during magnetic flux emergence,
or as a response to processes occurring high in the corona when the
active region is fully developed. On 2019 March 31 a simple bipolar
active region (AR 12737) emerged and upflows developed on each side. We
used observations from Hinode, SDO, IRIS, and Parker Solar Probe (PSP)
to investigate the formation and development of the upflows from the
eastern side. We used the spectroscopic data to detect the upflow,
and then used the imaging data to try to trace its signature back to
earlier in the active region emergence phase. We find that the upflow
forms quickly, low down in the atmosphere, and that its initiation
appears associated with a small field-opening eruption and the onset
of a radio noise storm detected by PSP. We also confirmed that the
upflows existed for the vast majority of the time the active region
was observed. These results suggest that the contribution to the solar
wind occurs even when the region is small, and continues for most of
its lifetime.
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Title: Measurements of Coronal Magnetic Field Strengths in Solar
Active Region Loops
Authors: Brooks, David H.; Warren, Harry P.; Landi, Enrico
2021ApJ...915L..24B Altcode: 2021arXiv210610884B
The characteristic electron densities, temperatures, and thermal
distributions of 1 MK active region loops are now fairly well
established, but their coronal magnetic field strengths remain
undetermined. Here we present measurements from a sample of coronal
loops observed by the Extreme-ultraviolet Imaging Spectrometer on
Hinode. We use a recently developed diagnostic technique that involves
atomic radiation modeling of the contribution of a magnetically
induced transition to the Fe X 257.262 Å spectral line intensity. We
find coronal magnetic field strengths in the range of 60-150 G. We
discuss some aspects of these new results in the context of previous
measurements using different spectropolarimetric techniques, and their
influence on the derived Alfvén speeds and plasma β in coronal loops.
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Title: Comparison of active region upflow and core properties using
simultaneous spectroscopic observations from IRIS and Hinode
Authors: Barczynski, Krzysztof; Harra, Louise; Kleint, Lucia; Panos,
Brandon; Brooks, David H.
2021A&A...651A.112B Altcode: 2021arXiv210410234B
Context. The origin of the slow solar wind is still an open issue. It
has been suggested that upflows at the edge of active regions are
a possible source of the plasma outflow and therefore contribute
to the slow solar wind. <BR /> Aims: We investigate the origin and
morphology of the upflow regions and compare the upflow region and
the active region core properties. <BR /> Methods: We studied how the
plasma properties of flux, Doppler velocity, and non-thermal velocity
change throughout the solar atmosphere, from the chromosphere via the
transition region to the corona in the upflow region and the core
of an active region. We studied limb-to-limb observations of the
active region (NOAA 12687) obtained from 14 to 25 November 2017. We
analysed spectroscopic data simultaneously obtained from IRIS and
Hinode/EIS in the six emission lines Mg II 2796.4Å, C II 1335.71Å,
Si IV 1393.76Å, Fe XII 195.12Å, Fe XIII 202.04Å, and Fe XIV
270.52Å and 274.20Å. We studied the mutual relationships between the
plasma properties for each emission line, and we compared the plasma
properties between the neighbouring formation temperature lines. To
find the most characteristic spectra, we classified the spectra in
each wavelength using the machine learning technique k-means. <BR />
Results: We find that in the upflow region the Doppler velocities of
the coronal lines are strongly correlated, but the transition region
and coronal lines show no correlation. However, their fluxes are
strongly correlated. The upflow region has a lower density and lower
temperature than the active region core. In the upflow region, the
Doppler velocity and non-thermal velocity show a strong correlation in
the coronal lines, but the correlation is not seen in the active region
core. At the boundary between the upflow region and the active region
core, the upflow region shows an increase in the coronal non-thermal
velocity, the emission obtained from the DEM, and the domination
of the redshifted regions in the chromosphere. <BR /> Conclusions:
The obtained results suggest that at least three parallel mechanisms
generate the plasma upflow: (1) The reconnection between closed loops
and open magnetic field lines in the lower corona or upper chromosphere;
(2) the reconnection between the chromospheric small-scale loops and
open magnetic field; and (3) the expansion of the magnetic field lines
that allows the chromospheric plasma to escape to the solar corona.
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Title: Widespread occurrence of high-velocity upflows in solar
active regions
Authors: Yardley, S. L.; Brooks, D. H.; Baker, D.
2021A&A...650L..10Y Altcode: 2021arXiv210601396Y
<BR /> Aims: We performed a systematic study of 12 active regions
(ARs) with a broad range of areas, magnetic fluxes, and associated
solar activity in order to determine whether there are upflows present
at the AR boundaries and, if these upflows exist, whether there is
a high-speed asymmetric blue wing component present in them. <BR />
Methods: To identify the presence and locations of the AR upflows, we
derive relative Doppler velocity maps by fitting a Gaussian function
to Hinode/EIS Fe XII 192.394 Å line profiles. To determine whether
there is a high-speed asymmetric component present in the AR upflows,
we fit a double Gaussian function to the Fe XII 192.394 Å mean
spectrum that is computed in a region of interest situated in the
AR upflows. <BR /> Results: Upflows are observed at both the eastern
and western boundaries of all ARs in our sample, with average upflow
velocities ranging between −5 and −26 km s<SUP>−1</SUP>. A blue
wing asymmetry is present in every line profile. The intensity ratio
between the minor high-speed asymmetric Gaussian component compared
to the main component is relatively small for the majority of regions;
however, in a minority of cases (8/30) the ratios are large and range
between 20 and 56 %. <BR /> Conclusions: These results suggest that
upflows and the high-speed asymmetric blue wing component are a common
feature of all ARs.
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Title: The active region source of a type III radio storm observed
by Parker Solar Probe during encounter 2
Authors: Harra, L.; Brooks, D. H.; Bale, S. D.; Mandrini, C. H.;
Barczynski, K.; Sharma, R.; Badman, S. T.; Vargas Domínguez, S.;
Pulupa, M.
2021A&A...650A...7H Altcode: 2021arXiv210204964H
Context. We investigated the source of a type III radio burst storm
during encounter 2 of NASA's Parker Solar Probe (PSP) mission. <BR />
Aims: It was observed that in encounter 2 of NASA's PSP mission there
was a large amount of radio activity and, in particular, a noise storm
of frequent, small type III bursts from 31 March to 6 April 2019. Our
aim is to investigate the source of these small and frequent bursts. <BR
/> Methods: In order to do this, we analysed data from the Hinode EUV
Imaging Spectrometer, PSP FIELDS, and the Solar Dynamics Observatory
Atmospheric Imaging Assembly. We studied the behaviour of active region
12737, whose emergence and evolution coincides with the timing of the
radio noise storm and determined the possible origins of the electron
beams within the active region. To do this, we probed the dynamics,
Doppler velocity, non-thermal velocity, FIP bias, and densities,
and carried out magnetic modelling. <BR /> Results: We demonstrate
that although the active region on the disc produces no significant
flares, its evolution indicates it is a source of the electron beams
causing the radio storm. They most likely originate from the area
at the edge of the active region that shows strong blue-shifted
plasma. We demonstrate that as the active region grows and expands,
the area of the blue-shifted region at the edge increases, which is
also consistent with the increasing area where large-scale or expanding
magnetic field lines from our modelling are anchored. This expansion
is most significant between 1 and 4 April 2019, coinciding with the
onset of the type III storm and the decrease of the individual burst's
peak frequency, indicating that the height at which the peak radiation
is emitted increases as the active region evolves.
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Title: Plasma Upflows Induced by Magnetic Reconnection Above an
Eruptive Flux Rope
Authors: Baker, Deborah; Mihailescu, Teodora; Démoulin, Pascal;
Green, Lucie M.; van Driel-Gesztelyi, Lidia; Valori, Gherardo; Brooks,
David H.; Long, David M.; Janvier, Miho
2021SoPh..296..103B Altcode: 2021arXiv210616137B
One of the major discoveries of Hinode's Extreme-ultraviolet
Imaging Spectrometer (EIS) is the presence of upflows at the edges
of active regions. As active regions are magnetically connected
to the large-scale field of the corona, these upflows are a likely
contributor to the global mass cycle in the corona. Here we examine
the driving mechanism(s) of the very strong upflows with velocities
in excess of 70 km s<SUP>−1</SUP>, known as blue-wing asymmetries,
observed during the eruption of a flux rope in AR 10977 (eruptive flare
SOL2007-12-07T04:50). We use Hinode/EIS spectroscopic observations
combined with magnetic-field modeling to investigate the possible
link between the magnetic topology of the active region and the strong
upflows. A Potential Field Source Surface (PFSS) extrapolation of the
large-scale field shows a quadrupolar configuration with a separator
lying above the flux rope. Field lines formed by induced reconnection
along the separator before and during the flux-rope eruption are
spatially linked to the strongest blue-wing asymmetries in the upflow
regions. The flows are driven by the pressure gradient created when
the dense and hot arcade loops of the active region reconnect with
the extended and tenuous loops overlying it. In view of the fact
that separator reconnection is a specific form of the more general
quasi-separatrix (QSL) reconnection, we conclude that the mechanism
driving the strongest upflows is, in fact, the same as the one driving
the persistent upflows of ≈10 - 20 km s<SUP>−1</SUP> observed in
all active regions.
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Title: The Evolution of Plasma Composition during a Solar Flare
Authors: To, Andy S. H.; Long, David M.; Baker, Deborah; Brooks, David
H.; van Driel-Gesztelyi, Lidia; Laming, J. Martin; Valori, Gherardo
2021ApJ...911...86T Altcode: 2021arXiv210209985T
We analyze the coronal elemental abundances during a small flare using
Hinode/EIS observations. Compared to the preflare elemental abundances,
we observed a strong increase in coronal abundance of Ca XIV 193.84
Å, an emission line with low first ionization potential (FIP <
10 eV), as quantified by the ratio Ca/Ar during the flare. This is in
contrast to the unchanged abundance ratio observed using Si X 258.38
Å/S X 264.23 Å. We propose two different mechanisms to explain
the different composition results. First, the small flare-induced
heating could have ionized S, but not the noble gas Ar, so that the
flare-driven Alfvén waves brought up Si, S, and Ca in tandem via
the ponderomotive force which acts on ions. Second, the location of
the flare in strong magnetic fields between two sunspots may suggest
fractionation occurred in the low chromosphere, where the background
gas is neutral H. In this region, high-FIP S could behave more like a
low-FIP than a high-FIP element. The physical interpretations proposed
generate new insights into the evolution of plasma abundances in the
solar atmosphere during flaring, and suggests that current models must
be updated to reflect dynamic rather than just static scenarios.
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Title: Upflows in the Upper Solar Atmosphere
Authors: Tian, Hui; Harra, Louise; Baker, Deborah; Brooks, David H.;
Xia, Lidong
2021SoPh..296...47T Altcode: 2021arXiv210202429T
Spectroscopic observations at extreme- and far-ultraviolet wavelengths
have revealed systematic upflows in the solar transition region and
corona. These upflows are best seen in the network structures of
the quiet Sun and coronal holes, boundaries of active regions, and
dimming regions associated with coronal mass ejections. They have been
intensively studied in the past two decades because they are likely to
be closely related to the formation of the solar wind and heating of the
upper solar atmosphere. We present an overview of the characteristics
of these upflows, introduce their possible formation mechanisms, and
discuss their potential roles in the mass and energy transport in the
solar atmosphere. Although past investigations have greatly improved
our understanding of these upflows, they have left us with several
outstanding questions and unresolved issues that should be addressed
in the future. New observations from the Solar Orbiter mission, the
Daniel K. Inouye Solar Telescope, and the Parker Solar Probe will
likely provide critical information to advance our understanding of
the generation, propagation, and energization of these upflows.
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Title: Spectropolarimetric fluctuations in a sunspot chromosphere
Authors: Stangalini, M.; Baker, D.; Valori, G.; Jess, D. B.;
Jafarzadeh, S.; Murabito, M.; To, A. S. H.; Brooks, D. H.; Ermolli,
I.; Giorgi, F.; MacBride, C. D.
2021RSPTA.37900216S Altcode: 2020arXiv200905302S
The instrumental advances made in this new era of 4 m class solar
telescopes with unmatched spectropolarimetric accuracy and sensitivity
will enable the study of chromospheric magnetic fields and their
dynamics with unprecedented detail. In this regard, spectropolarimetric
diagnostics can provide invaluable insight into magneto-hydrodynamic
(MHD) wave processes. MHD waves and, in particular, Alfvénic
fluctuations associated with particular wave modes were recently
recognized as important mechanisms not only for the heating of the outer
layers of the Sun's atmosphere and the acceleration of the solar wind,
but also for the elemental abundance anomaly observed in the corona
of the Sun and other Sun-like stars (also known as first ionization
potential) effect. Here, we take advantage of state-of-the-art and
unique spectropolarimetric Interferometric BIdimensional Spectrometer
observations to investigate the relation between intensity and circular
polarization (CP) fluctuations in a sunspot chromosphere. Our results
show a clear link between the intensity and CP fluctuations in a patch
which corresponds to a narrow range of magnetic field inclinations. This
suggests the presence of Alfvénic perturbations in the sunspot. <P
/>This article is part of the Theo Murphy meeting issue `High-resolution
wave dynamics in the lower solar atmosphere'.
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Title: Alfvénic Perturbations in a Sunspot Chromosphere Linked to
Fractionated Plasma in the Corona
Authors: Baker, Deborah; Stangalini, Marco; Valori, Gherardo; Brooks,
David H.; To, Andy S. H.; van Driel-Gesztelyi, Lidia; Démoulin,
Pascal; Stansby, David; Jess, David B.; Jafarzadeh, Shahin
2021ApJ...907...16B Altcode: 2020arXiv201204308B
In this study, we investigate the spatial distribution of highly
varying plasma composition around one of the largest sunspots of solar
cycle 24. Observations of the photosphere, chromosphere, and corona
are brought together with magnetic field modeling of the sunspot
in order to probe the conditions that regulate the degree of plasma
fractionation within loop populations of differing connectivities. We
find that, in the coronal magnetic field above the sunspot umbra,
the plasma has photospheric composition. Coronal loops rooted in the
penumbra contain fractionated plasma, with the highest levels observed
in the loops that connect within the active region. Tracing field
lines from regions of fractionated plasma in the corona to locations
of Alfvénic fluctuations detected in the chromosphere shows that they
are magnetically linked. These results indicate a connection between
sunspot chromospheric activity and observable changes in coronal
plasma composition.
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Title: Investigating the Chromospheric Footpoints of the Solar Wind
Authors: Bryans, Paul; McIntosh, Scott W.; Brooks, David H.; De
Pontieu, Bart
2020ApJ...905L..33B Altcode:
Coronal holes present the source of the fast solar wind. However,
the fast solar wind is not unimodal—there are discrete, but subtle,
compositional, velocity, and density structures that differentiate
different coronal holes as well as wind streams that originate within
one coronal hole. In this Letter we exploit full-disk observational
"mosaics" performed by the Interface Region Imaging Spectrograph
(IRIS) spacecraft to demonstrate that significant spectral variation
exists within the chromospheric plasma of coronal holes. The spectral
differences outline the boundaries of some—but not all—coronal
holes. In particular, we show that the "peak separation" of the Mg
II h line at 2803 Å illustrates changes in what appear to be open
magnetic features within a coronal hole. These observations point
to a chromospheric source for the inhomogeneities found in the fast
solar wind. These chromospheric signatures can provide additional
constraints on magnetic field extrapolations close to the source,
potentially on spatial scales smaller than from traditional coronal hole
detection methods based on intensity thresholding in the corona. This
is of increased importance with the advent of Parker Solar Probe and
Solar Orbiter and the ability to accurately establish the connectivity
between their in situ measurements and remote sensing observations of
the solar atmosphere.
---------------------------------------------------------
Title: IRIS Observations of the Low-atmosphere Counterparts of Active
Region Outflows
Authors: Polito, Vanessa; De Pontieu, Bart; Testa, Paola; Brooks,
David H.; Hansteen, Viggo
2020ApJ...903...68P Altcode: 2020arXiv201015945P
Active region (AR) outflows have been studied in detail since
the launch of Hinode/EIS and are believed to provide a possible
source of mass and energy to the slow solar wind. In this work, we
investigate the lower atmospheric counterpart of AR outflows using
observations from the Interface Region Imaging Spectrograph (IRIS). We
find that the IRIS Si IV, C II> and Mg II transition region (TR)
and chromospheric lines exhibit different spectral features in the
outflows as compared to neighboring regions at the footpoints ("moss")
of hot AR loops. The average redshift of Si IV in the outflow region
(≍5.5 km s<SUP>-1</SUP>) is smaller than typical moss (≍12-13
km s<SUP>-1</SUP>) and quiet Sun (≍7.5 km s<SUP>-1</SUP>) values,
while the C II line is blueshifted (≍-1.1-1.5 km s<SUP>-1</SUP>),
in contrast to the moss where it is observed to be redshifted by
about ≍2.5 km s<SUP>-1</SUP>. Further, we observe that the low
atmosphere underneath the coronal outflows is highly structured, with
the presence of blueshifts in Si IV and positive Mg II k2 asymmetries
(which can be interpreted as signatures of chromospheric upflows)
which are mostly not observed in the moss. These observations show a
clear correlation between the coronal outflows and the chromosphere
and TR underneath, which has not been shown before. Our work strongly
suggests that these regions are not separate environments and should
be treated together, and that current leading theories of AR outflows,
such as the interchange reconnection model, need to take into account
the dynamics of the low atmosphere.
---------------------------------------------------------
Title: Directly comparing coronal and solar wind elemental
fractionation
Authors: Stansby, D.; Baker, D.; Brooks, D. H.; Owen, C. J.
2020A&A...640A..28S Altcode: 2020arXiv200500371S
Context. As the solar wind propagates through the heliosphere, dynamical
processes irreversibly erase the signatures of the near-Sun heating
and acceleration processes. The elemental fractionation of the solar
wind should not change during transit, however, making it an ideal
tracer of these processes. <BR /> Aims: We aim to verify directly if
the solar wind elemental fractionation is reflective of the coronal
source region fractionation, both within and across different solar wind
source regions. <BR /> Methods: A backmapping scheme was used to predict
where solar wind measured by the Advanced Composition Explorer (ACE)
originated in the corona. The coronal composition measured by the Hinode
Extreme ultraviolet Imaging Spectrometer (EIS) at the source regions
was then compared with the in situ solar wind composition. <BR />
Results: On hourly timescales, there is no apparent correlation between
coronal and solar wind composition. In contrast, the distribution of
fractionation values within individual source regions is similar in
both the corona and solar wind, but distributions between different
sources have a significant overlap. <BR /> Conclusions: The matching
distributions directly verify that elemental composition is conserved
as the plasma travels from the corona to the solar wind, further
validating it as a tracer of heating and acceleration processes. The
overlap of fractionation values between sources means it is not possible
to identify solar wind source regions solely by comparing solar wind
and coronal composition measurements, but a comparison can be used to
verify consistency with predicted spacecraft-corona connections.
---------------------------------------------------------
Title: Directly Comparing Coronal and Solar Wind Elemental
Fractionation
Authors: Stansby, D.; Baker, D.; Owen, C.; Brooks, D.
2020SPD....5120801S Altcode:
The elemental fractionation of the quasi-collisionless solar wind
should not change during transit, making it an ideal tracer of coronal
heating and acceleration processes. We aimed to verify directly if the
solar wind elemental fractionation is reflective of the coronal source
region fractionation, both within and across different solar wind
source regions. A backmapping scheme was used to predict where solar
wind measured by the Advanced Composition Explorer (ACE) across 15 days
originated in the corona. The coronal composition measured by Hinode
Extreme ultraviolet Imaging Spectrometer (EIS) at the source regions
was then compared with the in-situ solar wind composition. On hourly
timescales there was no apparent correlation between coronal and solar
wind composition. In contrast, the distribution of fractionation values
within individual source regions was similar in both the corona and
solar wind, but distributions between different sources had significant
overlap. The overlap of fractionation values between sources means it is
not possible to identify solar wind source regions solely by comparing
solar wind and coronal composition measurements, but a comparison can be
used to verify consistency with predicted spacecraft-corona connections.
---------------------------------------------------------
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: Can Subphotospheric Magnetic Reconnection Change the Elemental
Composition in the Solar Corona?
Authors: Baker, Deborah; van Driel-Gesztelyi, Lidia; Brooks, David H.;
Démoulin, Pascal; Valori, Gherardo; Long, David M.; Laming, J. Martin;
To, Andy S. H.; James, Alexander W.
2020ApJ...894...35B Altcode: 2020arXiv200303325B
Within the coronae of stars, abundances of those elements with low
first ionization potential (FIP) often differ from their photospheric
values. The coronae of the Sun and solar-type stars mostly show
enhancements of low-FIP elements (the FIP effect) while more active
stars such as M dwarfs have coronae generally characterized by the
inverse-FIP effect (I-FIP). Here we observe patches of I-FIP effect
solar plasma in AR 12673, a highly complex βγδ active region. We
argue that the umbrae of coalescing sunspots, and more specifically
strong light bridges within the umbrae, are preferential locations for
observing I-FIP effect plasma. Furthermore, the magnetic complexity
of the active region and major episodes of fast flux emergence also
lead to repetitive and intense flares. The induced evaporation of
the chromospheric plasma in flare ribbons crossing umbrae enables
the observation of four localized patches of I-FIP effect plasma in
the corona of AR 12673. These observations can be interpreted in the
context of the ponderomotive force fractionation model which predicts
that plasma with I-FIP effect composition is created by the refraction
of waves coming from below the chromosphere. We propose that the waves
generating the I-FIP effect plasma in solar active regions are generated
by subphotospheric reconnection of coalescing flux systems. Although
we only glimpse signatures of I-FIP effect fractionation produced by
this interaction in patches on the Sun, on highly active M stars it
may be the dominant process.
---------------------------------------------------------
Title: A Solar Magnetic-fan Flaring Arch Heated by Nonthermal
Particles and Hot Plasma from an X-Ray Jet Eruption
Authors: Lee, Kyoung-Sun; Hara, Hirohisa; Watanabe, Kyoko; Joshi,
Anand D.; Brooks, David H.; Imada, Shinsuke; Prasad, Avijeet; Dang,
Phillip; Shimizu, Toshifumi; Savage, Sabrina L.; Moore, Ronald;
Panesar, Navdeep K.; Reep, Jeffrey W.
2020ApJ...895...42L Altcode: 2020arXiv200509875L
We have investigated an M1.3 limb flare, which develops as a magnetic
loop/arch that fans out from an X-ray jet. Using Hinode/EIS, we
found that the temperature increases with height to a value of over
10<SUP>7</SUP> K at the loop top during the flare. The measured Doppler
velocity (redshifts of 100-500 km s<SUP>-1</SUP>) and the nonthermal
velocity (≥100 km s<SUP>-1</SUP>) from Fe XXIV also increase with
loop height. The electron density increases from 0.3 × 10<SUP>9</SUP>
cm<SUP>-3</SUP> early in the flare rise to 1.3 × 10<SUP>9</SUP>
cm<SUP>-3</SUP> after the flare peak. The 3D structure of the loop
derived with Solar TErrestrial RElations Observatory/EUV Imager
indicates that the strong redshift in the loop-top region is due to
upflowing plasma originating from the jet. Both hard X-ray and soft
X-ray emission from the Reuven Ramaty High Energy Solar Spectroscopic
Imager were only seen as footpoint brightenings during the impulsive
phase of the flare, then, soft X-ray emission moved to the loop top in
the decay phase. Based on the temperature and density measurements and
theoretical cooling models, the temperature evolution of the flare arch
is consistent with impulsive heating during the jet eruption followed
by conductive cooling via evaporation and minor prolonged heating in
the top of the fan loop. Investigating the magnetic field topology and
squashing factor map from Solar Dynamics Observatory/HMI, we conclude
that the observed magnetic-fan flaring arch is mostly heated from low
atmospheric reconnection accompanying the jet ejection, instead of from
reconnection above the arch as expected in the standard flare model.
---------------------------------------------------------
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: 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 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: Active Region Modulation of Coronal Hole Solar Wind
Authors: Macneil, Allan R.; Owen, Christopher J.; Baker, Deborah;
Brooks, David H.; Harra, Louise K.; Long, David M.; Wicks, Robert T.
2019ApJ...887..146M Altcode:
Active regions (ARs) are a candidate source of the slow solar wind
(SW), the origins of which are a topic of ongoing research. We present
a case study that examines the processes by which SW is modulated in
the presence of an AR in the vicinity of the SW source. We compare
properties of SW associated with a coronal hole (CH)-quiet Sun boundary
to SW associated with the same CH but one Carrington rotation later,
when this region bordered the newly emerged NOAA AR 12532. Differences
found in a range of in situ parameters are compared between these
rotations in the context of source region mapping and remote sensing
observations. Marked changes exist in the structure and composition of
the SW, which we attribute to the influence of the AR on SW production
from the CH boundary. These unique observations suggest that the
features that emerge in the AR-associated wind are consistent with an
increased occurrence of interchange reconnection during SW production,
compared with the initial quiet Sun case.
---------------------------------------------------------
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: Structure and dynamics of the hot flaring loop-top source
observed by Hinode, SDO, RHESSI, and STEREO
Authors: Lee, Kyoung-Sun; Hara, Hirohisa; Watanabe, Kyoko; Joshi,
Anand D.; Imada, Shinsuke; Brooks, David H.; Dang, Phillip; Shimizu,
Toshifumi; Savage, Sabrina
2019AAS...23421605L Altcode:
We have investigated an M1.3 flare on 2014 January 13 around
21:48 UT observed at the west limb using the Hinode, SDO, RHESSI,
and STEREO. Especially, the Hinode/EIS scanned the flaring loop
covering the loop-top region over the limb, which is a good target to
investigate the dynamics of the flaring loop with their height. Using
the multi-wavelength observations from the Hinode/EIS and SDO/AIA,
we found a very hot emission above the loop-top observed in Fe XXIV
and 131Å channel. Measuring the intensity, Doppler velocity and line
width for the flaring loop, we found that hot emission observed at
the cusp-like shape of the loop-top region which shows strong redshift
about 500 km s<SUP>-1</SUP> in Doppler velocity and strong enhancement
of the non-thermal velocity (line width enhancement) larger than 100
km s<SUP>-1</SUP>. Combining with the STEREO observation, we have
examined the 3D structure with loop tilt angle and have investigated
the velocity distribution of the loop-top region. With the loop tilt
angle, we could identify the strong redshift at the loop-top region
may indicate an up-flow along the loop-top region. From RHESSI hard
X-ray (HXR), and soft X-ray (SXR) emission, we found that the footpoint
brightening region at the beginning of the flare has a both HXR (25-50
keV) and SXR (12-25 keV) emission in which imply that the region has
non-thermal emission or accelerated particles. Then, within 10 minutes
the soft X-ray (SXR) emission observed near the cusp shape region at
loop top. The temporal variation of the HXR and SXR emissions and the
Doppler velocity variation of the hot plasma component at the loop-top
imply that the strong flow in a hot component near loop-top could be
the evaporation flows which detected at the corona along the tilted
loop. Moreover, The temporal evolution of the temperature observed
by SDO/AIA and Hinode/EIS also shows the cooling process of the flare
plasma which is consistent with the impulsively heated flare model.
---------------------------------------------------------
Title: Comprehensive Determination of the Hinode/EIS Roll Angle
Authors: Pelouze, Gabriel; Auchère, Frédéric; Bocchialini, Karine;
Harra, Louise; Baker, Deborah; Warren, Harry P.; Brooks, David H.;
Mariska, John T.
2019SoPh..294...59P Altcode: 2019arXiv190311923P
We present a new coalignment method for the EUV Imaging Spectrometer
(EIS) on board the Hinode spacecraft. In addition to the pointing
offset and spacecraft jitter, this method determines the roll angle
of the instrument, which has never been systematically measured, and
which is therefore usually not corrected. The optimal pointing for EIS
is computed by maximizing the cross-correlations of the Fe XII 195.119
Å line with images from the 193 Å band of the Atmospheric Imaging
Assembly (AIA) on board the Solar Dynamics Observatory (SDO). By
coaligning 3336 rasters with high signal-to-noise ratio, we estimate
the rotation angle between EIS and AIA and explore the distribution
of its values. We report an average value of (−0.387<SUP>±0.007 )
∘</SUP>. We also provide a software implementation of this method
that can be used to coalign any EIS raster.
---------------------------------------------------------
Title: First Measurement of the Hubble Constant from a Dark Standard
Siren using the Dark Energy Survey Galaxies and the LIGO/Virgo
Binary-Black-hole Merger GW170814
Authors: Soares-Santos, M.; Palmese, A.; Hartley, W.; Annis, J.;
Garcia-Bellido, J.; Lahav, O.; Doctor, Z.; Fishbach, M.; Holz, D. E.;
Lin, H.; Pereira, M. E. S.; Garcia, A.; Herner, K.; Kessler, R.;
Peiris, H. V.; Sako, M.; Allam, S.; Brout, D.; Carnero Rosell, A.;
Chen, H. Y.; Conselice, C.; deRose, J.; deVicente, J.; Diehl, H. T.;
Gill, M. S. S.; Gschwend, J.; Sevilla-Noarbe, I.; Tucker, D. L.;
Wechsler, R.; Berger, E.; Cowperthwaite, P. S.; Metzger, B. D.;
Williams, P. K. G.; Abbott, T. M. C.; Abdalla, F. B.; Avila, S.;
Bechtol, K.; Bertin, E.; Brooks, D.; Buckley-Geer, E.; Burke, D. L.;
Carrasco Kind, M.; Carretero, J.; Castander, F. J.; Crocce, M.; Cunha,
C. E.; D'Andrea, C. B.; da Costa, L. N.; Davis, C.; Desai, S.; Doel,
P.; Drlica-Wagner, A.; Eifler, T. F.; Evrard, A. E.; Flaugher, B.;
Fosalba, P.; Frieman, J.; Gaztanaga, E.; Gerdes, D. W.; Gruen, D.;
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2019ApJ...876L...7S Altcode: 2019arXiv190101540T
We present a multi-messenger measurement of the Hubble constant
H <SUB>0</SUB> using the binary-black-hole merger GW170814 as a
standard siren, combined with a photometric redshift catalog from the
Dark Energy Survey (DES). The luminosity distance is obtained from
the gravitational wave signal detected by the Laser Interferometer
Gravitational-Wave Observatory (LIGO)/Virgo Collaboration (LVC) on 2017
August 14, and the redshift information is provided by the DES Year 3
data. Black hole mergers such as GW170814 are expected to lack bright
electromagnetic emission to uniquely identify their host galaxies and
build an object-by-object Hubble diagram. However, they are suitable
for a statistical measurement, provided that a galaxy catalog of
adequate depth and redshift completion is available. Here we present
the first Hubble parameter measurement using a black hole merger. Our
analysis results in {H}<SUB>0</SUB>={75}<SUB>-32</SUB><SUP>+40</SUP>
{km} {{{s}}}<SUP>-1</SUP> {Mpc}}<SUP>-1</SUP>, which is consistent
with both SN Ia and cosmic microwave background measurements of the
Hubble constant. The quoted 68% credible region comprises 60% of the
uniform prior range [20, 140] km s<SUP>-1</SUP> Mpc<SUP>-1</SUP>,
and it depends on the assumed prior range. If we take a broader
prior of [10, 220] km s<SUP>-1</SUP> Mpc<SUP>-1</SUP>, we
find {H}<SUB>0</SUB>={78}<SUB>-24</SUB><SUP>+96</SUP> {km}
{{{s}}}<SUP>-1</SUP> {Mpc}}<SUP>-1</SUP> (57% of the prior
range). Although a weak constraint on the Hubble constant from a single
event is expected using the dark siren method, a multifold increase in
the LVC event rate is anticipated in the coming years and combinations
of many sirens will lead to improved constraints on H <SUB>0</SUB>.
---------------------------------------------------------
Title: Transient Inverse-FIP Plasma Composition Evolution within a
Solar Flare
Authors: Baker, Deborah; van Driel-Gesztelyi, Lidia; Brooks, David
H.; Valori, Gherardo; James, Alexander W.; Laming, J. Martin; Long,
David M.; Démoulin, Pascal; Green, Lucie M.; Matthews, Sarah A.;
Oláh, Katalin; Kővári, Zsolt
2019ApJ...875...35B Altcode: 2019arXiv190206948B
Understanding elemental abundance variations in the solar corona
provides an insight into how matter and energy flow from the
chromosphere into the heliosphere. Observed variations depend on the
first ionization potential (FIP) of the main elements of the Sun’s
atmosphere. High-FIP elements (>10 eV) maintain photospheric
abundances in the corona, whereas low-FIP elements have enhanced
abundances. Conversely, inverse FIP (IFIP) refers to the enhancement of
high-FIP or depletion of low-FIP elements. We use spatially resolved
spectroscopic observations, specifically the Ar XIV/Ca XIV intensity
ratio, from Hinode’s Extreme-ultraviolet Imaging Spectrometer to
investigate the distribution and evolution of plasma composition
within two confined flares in a newly emerging, highly sheared
active region. During the decay phase of the first flare, patches
above the flare ribbons evolve from the FIP to the IFIP effect, while
the flaring loop tops show a stronger FIP effect. The patch and loop
compositions then evolve toward the preflare basal state. We propose
an explanation of how flaring in strands of highly sheared emerging
magnetic fields can lead to flare-modulated IFIP plasma composition
over coalescing umbrae which are crossed by flare ribbons. Subsurface
reconnection between the coalescing umbrae leads to the depletion of
low-FIP elements as a result of an increased wave flux from below. This
material is evaporated when the flare ribbons cross the umbrae. Our
results are consistent with the ponderomotive fractionation model for
the creation of IFIP-biased plasma.
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Title: Properties of the Diffuse Emission around Warm Loops in Solar
Active Regions
Authors: Brooks, David H.
2019ApJ...873...26B Altcode: 2019arXiv190107741B
Coronal loops in active regions are the subjects of intensive
investigation, but the important diffuse unresolved emission in which
they are embedded has received relatively little attention. Here
I measure the densities and emission measure (EM) distributions of
a sample of background-foreground regions surrounding warm (2 MK)
coronal loops, and introduce two new aspects to the analysis. First,
I infer the EM distributions only from temperatures that contribute
to the same background emission. Second, I measure the background
emission co-spatially with the loops so that the results are truly
representative of the immediate loop environment. The second aspect
also allows me to take advantage of the presence of embedded loops
to infer information about the (unresolvable) magnetic field in
the background. I find that about half of the regions in my sample
have narrow but not quite isothermal EM distributions with a peak
temperature of 1.4-2 MK. The other half have broad EM distributions
(Gaussian width >3 × 10<SUP>5</SUP> K), and the width of the
EM appears to be correlated with peak temperature. Densities in the
diffuse background are log (n/cm<SUP>-3</SUP>) = 8.5-9.0. Significantly,
these densities and temperatures imply that the co-spatial background
is broadly compatible with static equilibrium theory (RTV scaling laws)
provided that the unresolved field length is comparable to the embedded
loop length. For this agreement to break down, the field length in
most cases would have to be substantially longer than the loop length,
a factor of 2-3 on average, which for the sample in this work approaches
the dimensions of only the largest active regions.
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Title: A Diagnostic of Coronal Elemental Behavior during the Inverse
FIP Effect in Solar Flares
Authors: Brooks, David H.
2018ApJ...863..140B Altcode: 2018arXiv180704408B
The solar corona shows a distinctive pattern of elemental abundances
that is different from that of the photosphere. Low first ionization
potential (FIP) elements are enhanced by factors of several. A similar
effect is seen in the atmospheres of some solar-like stars, while
late-type M stars show an inverse FIP effect. This inverse effect
was recently detected on the Sun during solar flares, potentially
allowing a very detailed look at the spatial and temporal behavior
that is not possible from stellar observations. A key question for
interpreting these measurements is whether both effects act solely on
low-FIP elements (a true inverse effect predicted by some models),
or whether the inverse FIP effect arises because high-FIP elements
are enhanced. Here we develop a new diagnostic that can discriminate
between the two scenarios, based on modeling of the radiated power
loss, and apply the models to a numerical hydrodynamic simulation of
coronal loop cooling. We show that when low-/high-FIP elements are
depleted/enhanced, there is a significant difference in the cooling
lifetime of loops that is greatest at lower temperatures. We apply this
diagnostic to a post X1.8 flare loop arcade and inverse FIP region,
and show that for this event, low-FIP elements are depleted. We discuss
the results in the context of stellar observations, and models of the
FIP and inverse FIP effect. We also provide the radiated power-loss
functions for the two inverse FIP effect scenarios in machine readable
form to facilitate further modeling.
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Title: Solar Cycle Observations of the Neon Abundance in the
Sun-as-a-star
Authors: Brooks, David H.; Baker, Deborah; van Driel-Gesztelyi, Lidia;
Warren, Harry P.
2018ApJ...861...42B Altcode: 2018arXiv180507032B
Properties of the Sun’s interior can be determined accurately
from helioseismological measurements of solar oscillations. These
measurements, however, are in conflict with photospheric elemental
abundances derived using 3D hydrodynamic models of the solar
atmosphere. This divergence of theory and helioseismology is known as
the “solar modeling problem.” One possible solution is that the
photospheric neon abundance, which is deduced indirectly by combining
the coronal Ne/O ratio with the photospheric O abundance, is larger
than generally accepted. There is some support for this idea from
observations of cool stars. The Ne/O abundance ratio has also been
found to vary with the solar cycle in the slowest solar wind streams
and coronal streamers, and the variation from solar maximum to minimum
in streamers (∼0.1-0.25) is large enough to potentially bring some
of the solar models into agreement with the seismic data. Here we use
daily sampled observations from the EUV Variability Experiment on the
Solar Dynamics Observatory taken in 2010-2014, to investigate whether
the coronal Ne/O abundance ratio shows a variation with the solar cycle
when the Sun is viewed as a star. We find only a weak dependence on,
and moderate anti-correlation with, the solar cycle with the ratio
measured around 0.2-0.3 MK falling from 0.17 at solar minimum to
0.11 at solar maximum. The effect is amplified at higher temperatures
(0.3-0.6 MK) with a stronger anti-correlation and the ratio falling
from 0.16 at solar minimum to 0.08 at solar maximum. The values we
find at solar minimum are too low to solve the solar modeling problem.
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Title: Coronal Elemental Abundances in Solar Emerging Flux Regions
Authors: Baker, Deborah; Brooks, David H.; van Driel-Gesztelyi,
Lidia; James, Alexander W.; Démoulin, Pascal; Long, David M.; Warren,
Harry P.; Williams, David R.
2018ApJ...856...71B Altcode: 2018arXiv180108424B
The chemical composition of solar and stellar atmospheres differs from
the composition of their photospheres. Abundances of elements with low
first ionization potential (FIP) are enhanced in the corona relative
to high-FIP elements with respect to the photosphere. This is known as
the FIP effect and it is important for understanding the flow of mass
and energy through solar and stellar atmospheres. We used spectroscopic
observations from the Extreme-ultraviolet Imaging Spectrometer on board
the Hinode observatory to investigate the spatial distribution and
temporal evolution of coronal plasma composition within solar emerging
flux regions inside a coronal hole. Plasma evolved to values exceeding
those of the quiet-Sun corona during the emergence/early-decay phase
at a similar rate for two orders of magnitude in magnetic flux, a rate
comparable to that observed in large active regions (ARs) containing
an order of magnitude more flux. During the late-decay phase, the rate
of change was significantly faster than what is observed in large,
decaying ARs. Our results suggest that the rate of increase during the
emergence/early-decay phase is linked to the fractionation mechanism
that leads to the FIP effect, whereas the rate of decrease during
the later decay phase depends on the rate of reconnection with the
surrounding magnetic field and its plasma composition.
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Title: Spectroscopic Observations of Current Sheet Formation and
Evolution
Authors: Warren, Harry P.; Brooks, David H.; Ugarte-Urra, Ignacio;
Reep, Jeffrey W.; Crump, Nicholas A.; Doschek, George A.
2018ApJ...854..122W Altcode: 2017arXiv171110826W
We report on the structure and evolution of a current sheet that formed
in the wake of an eruptive X8.3 flare observed at the west limb of
the Sun on 2017 September 10. Using observations from the EUV Imaging
Spectrometer (EIS) on Hinode and the Atmospheric Imaging Assembly
(AIA) on the Solar Dynamics Observatory, we find that plasma in the
current sheet reaches temperatures of about 20 MK and that the range
of temperatures is relatively narrow. The highest temperatures occur
at the base of the current sheet, in the region near the top of the
post-flare loop arcade. The broadest high temperature line profiles,
in contrast, occur at the largest observed heights. Furthermore,
line broadening is strong very early in the flare and diminishes over
time. The current sheet can be observed in the AIA 211 and 171 channels,
which have a considerable contribution from thermal bremsstrahlung
at flare temperatures. Comparisons of the emission measure in these
channels with other EIS wavelengths and AIA channels dominated by
Fe line emission indicate a coronal composition and suggest that
the current sheet is formed by the heating of plasma already in the
corona. Taken together, these observations suggest that some flare
heating occurs in the current sheet, while additional energy is released
as newly reconnected field lines relax and become more dipolar.
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Title: The Origin of the Solar Wind
Authors: Lee, Kyoung-Sun; Brooks, David H.; Imada, Shinsuke
2018ASSL..449...95L Altcode:
No abstract at ADS
---------------------------------------------------------
Title: A gravitational-wave standard siren measurement of the
Hubble constant
Authors: Abbott, B. P.; Abbott, R.; Abbott, T. D.; Acernese, F.;
Ackley, K.; Adams, C.; Adams, T.; Addesso, P.; Adhikari, R. X.; Adya,
V. B.; Affeldt, C.; Afrough, M.; Agarwal, B.; Agathos, M.; Agatsuma,
K.; Aggarwal, N.; Aguiar, O. D.; Aiello, L.; Ain, A.; Ajith, P.;
Allen, B.; Allen, G.; Allocca, A.; Altin, P. A.; Amato, A.; Ananyeva,
A.; Anderson, S. B.; Anderson, W. G.; Angelova, S. V.; Antier, S.;
Appert, S.; Arai, K.; Araya, M. C.; Areeda, J. S.; Arnaud, N.; Arun,
K. G.; Ascenzi, S.; Ashton, G.; Ast, M.; Aston, S. M.; Astone, P.;
Atallah, D. V.; Aufmuth, P.; Aulbert, C.; Aultoneal, K.; Austin,
C.; Avila-Alvarez, A.; Babak, S.; Bacon, P.; Bader, M. K. M.; Bae,
S.; Baker, P. T.; Baldaccini, F.; Ballardin, G.; Ballmer, S. W.;
Banagiri, S.; Barayoga, J. C.; Barclay, S. E.; Barish, B. C.; Barker,
D.; Barkett, K.; Barone, F.; Barr, B.; Barsotti, L.; Barsuglia, M.;
Barta, D.; Bartlett, J.; Bartos, I.; Bassiri, R.; Basti, A.; Batch,
J. C.; Bawaj, M.; Bayley, J. C.; Bazzan, M.; Bécsy, B.; Beer, C.;
Bejger, M.; Belahcene, I.; Bell, A. S.; Berger, B. K.; Bergmann,
G.; Bero, J. J.; Berry, C. P. L.; Bersanetti, D.; Bertolini, A.;
Betzwieser, J.; Bhagwat, S.; Bhandare, R.; Bilenko, I. A.; Billingsley,
G.; Billman, C. R.; Birch, J.; Birney, R.; Birnholtz, O.; Biscans, S.;
Biscoveanu, S.; Bisht, A.; Bitossi, M.; Biwer, C.; Bizouard, M. A.;
Blackburn, J. K.; Blackman, J.; Blair, C. D.; Blair, D. G.; Blair,
R. M.; Bloemen, S.; Bock, O.; Bode, N.; Boer, M.; Bogaert, G.; Bohe,
A.; Bondu, F.; Bonilla, E.; Bonnand, R.; Boom, B. A.; Bork, R.; Boschi,
V.; Bose, S.; Bossie, K.; Bouffanais, Y.; Bozzi, A.; Bradaschia, C.;
Brady, P. R.; Branchesi, M.; Brau, J. E.; Briant, T.; Brillet, A.;
Brinkmann, M.; Brisson, V.; Brockill, P.; Broida, J. E.; Brooks, A. F.;
Brown, D. A.; Brown, D. D.; Brunett, S.; Buchanan, C. C.; Buikema,
A.; Bulik, T.; Bulten, H. J.; Buonanno, A.; Buskulic, D.; Buy, C.;
Byer, R. L.; Cabero, M.; Cadonati, L.; Cagnoli, G.; Cahillane, C.;
Bustillo, J. Calderón; Callister, T. A.; Calloni, E.; Camp, J. B.;
Canepa, M.; Canizares, P.; Cannon, K. C.; Cao, H.; Cao, J.; Capano,
C. D.; Capocasa, E.; Carbognani, F.; Caride, S.; Carney, M. F.; Diaz,
J. Casanueva; Casentini, C.; Caudill, S.; Cavaglià, M.; Cavalier, F.;
Cavalieri, R.; Cella, G.; Cepeda, C. B.; Cerdá-Durán, P.; Cerretani,
G.; Cesarini, E.; Chamberlin, S. J.; Chan, M.; Chao, S.; Charlton, P.;
Chase, E.; Chassande-Mottin, E.; Chatterjee, D.; Chatziioannou, K.;
Cheeseboro, B. D.; Chen, H. Y.; Chen, X.; Chen, Y.; Cheng, H. -P.;
Chia, H.; Chincarini, A.; Chiummo, A.; Chmiel, T.; Cho, H. S.; Cho,
M.; Chow, J. H.; Christensen, N.; Chu, Q.; Chua, A. J. K.; Chua, S.;
Chung, A. K. W.; Chung, S.; Ciani, G.; Ciolfi, R.; Cirelli, C. E.;
Cirone, A.; Clara, F.; Clark, J. A.; Clearwater, P.; Cleva, F.;
Cocchieri, C.; Coccia, E.; Cohadon, P. -F.; Cohen, D.; Colla, A.;
Collette, C. G.; Cominsky, L. R.; Constancio, M.; Conti, L.; Cooper,
S. J.; Corban, P.; Corbitt, T. R.; Cordero-Carrión, I.; Corley,
K. R.; Cornish, N.; Corsi, A.; Cortese, S.; Costa, C. A.; Coughlin,
M. W.; Coughlin, S. B.; Coulon, J. -P.; Countryman, S. T.; Couvares,
P.; Covas, P. B.; Cowan, E. E.; Coward, D. M.; Cowart, M. J.; Coyne,
D. C.; Coyne, R.; Creighton, J. D. E.; Creighton, T. D.; Cripe, J.;
Crowder, S. G.; Cullen, T. J.; Cumming, A.; Cunningham, L.; Cuoco,
E.; Dal Canton, T.; Dálya, G.; Danilishin, S. L.; D'Antonio, S.;
Danzmann, K.; Dasgupta, A.; da Silva Costa, C. F.; Datrier, L. E. H.;
Dattilo, V.; Dave, I.; Davier, M.; Davis, D.; Daw, E. J.; Day, B.;
de, S.; Debra, D.; Degallaix, J.; de Laurentis, M.; Deléglise,
S.; Del Pozzo, W.; Demos, N.; Denker, T.; Dent, T.; de Pietri, R.;
Dergachev, V.; De Rosa, R.; Derosa, R. T.; de Rossi, C.; Desalvo, R.;
de Varona, O.; Devenson, J.; Dhurandhar, S.; Díaz, M. C.; di Fiore,
L.; di Giovanni, M.; di Girolamo, T.; di Lieto, A.; di Pace, S.; di
Palma, I.; di Renzo, F.; Doctor, Z.; Dolique, V.; Donovan, F.; Dooley,
K. L.; Doravari, S.; Dorrington, I.; Douglas, R.; Dovale Álvarez,
M.; Downes, T. P.; Drago, M.; Dreissigacker, C.; Driggers, J. C.;
Du, Z.; Ducrot, M.; Dupej, P.; Dwyer, S. E.; Edo, T. B.; Edwards,
M. C.; Effler, A.; Eggenstein, H. -B.; Ehrens, P.; Eichholz, J.;
Eikenberry, S. S.; Eisenstein, R. A.; Essick, R. C.; Estevez, D.;
Etienne, Z. B.; Etzel, T.; Evans, M.; Evans, T. M.; Factourovich,
M.; Fafone, V.; Fair, H.; Fairhurst, S.; Fan, X.; Farinon, S.; Farr,
B.; Farr, W. M.; Fauchon-Jones, E. J.; Favata, M.; Fays, M.; Fee,
C.; Fehrmann, H.; Feicht, J.; Fejer, M. M.; Fernandez-Galiana, A.;
Ferrante, I.; Ferreira, E. C.; Ferrini, F.; Fidecaro, F.; Finstad,
D.; Fiori, I.; Fiorucci, D.; Fishbach, M.; Fisher, R. P.; Fitz-Axen,
M.; Flaminio, R.; Fletcher, M.; Fong, H.; Font, J. A.; Forsyth,
P. W. F.; Forsyth, S. S.; Fournier, J. -D.; Frasca, S.; Frasconi, F.;
Frei, Z.; Freise, A.; Frey, R.; Frey, V.; Fries, E. M.; Fritschel,
P.; Frolov, V. V.; Fulda, P.; Fyffe, M.; Gabbard, H.; Gadre, B. U.;
Gaebel, S. M.; Gair, J. R.; Gammaitoni, L.; Ganija, M. R.; Gaonkar,
S. G.; Garcia-Quiros, C.; Garufi, F.; Gateley, B.; Gaudio, S.; Gaur,
G.; Gayathri, V.; Gehrels, N.; Gemme, G.; Genin, E.; Gennai, A.;
George, D.; George, J.; Gergely, L.; Germain, V.; Ghonge, S.; Ghosh,
Abhirup; Ghosh, Archisman; Ghosh, S.; Giaime, J. A.; Giardina, K. D.;
Giazotto, A.; Gill, K.; Glover, L.; Goetz, E.; Goetz, R.; Gomes, S.;
Goncharov, B.; González, G.; Castro, J. M. Gonzalez; Gopakumar, A.;
Gorodetsky, M. L.; Gossan, S. E.; Gosselin, M.; Gouaty, R.; Grado,
A.; Graef, C.; Granata, M.; Grant, A.; Gras, S.; Gray, C.; Greco, G.;
Green, A. C.; Gretarsson, E. M.; Groot, P.; Grote, H.; Grunewald, S.;
Gruning, P.; Guidi, G. M.; Guo, X.; Gupta, A.; Gupta, M. K.; Gushwa,
K. E.; Gustafson, E. K.; Gustafson, R.; Halim, O.; Hall, B. R.; Hall,
E. D.; Hamilton, E. Z.; Hammond, G.; Haney, M.; Hanke, M. M.; Hanks,
J.; Hanna, C.; Hannam, M. D.; Hannuksela, O. A.; Hanson, J.; Hardwick,
T.; Harms, J.; Harry, G. M.; Harry, I. W.; Hart, M. J.; Haster, C. -J.;
Haughian, K.; Healy, J.; Heidmann, A.; Heintze, M. C.; Heitmann,
H.; Hello, P.; Hemming, G.; Hendry, M.; Heng, I. S.; Hennig, J.;
Heptonstall, A. W.; Heurs, M.; Hild, S.; Hinderer, T.; Hoak, D.;
Hofman, D.; Holt, K.; Holz, D. E.; Hopkins, P.; Horst, C.; Hough,
J.; Houston, E. A.; Howell, E. J.; Hreibi, A.; Hu, Y. M.; Huerta,
E. A.; Huet, D.; Hughey, B.; Husa, S.; Huttner, S. H.; Huynh-Dinh,
T.; Indik, N.; Inta, R.; Intini, G.; Isa, H. N.; Isac, J. -M.; Isi,
M.; Iyer, B. R.; Izumi, K.; Jacqmin, T.; Jani, K.; Jaranowski,
P.; Jawahar, S.; Jiménez-Forteza, F.; Johnson, W. W.; Jones,
D. I.; Jones, R.; Jonker, R. J. G.; Ju, L.; Junker, J.; Kalaghatgi,
C. V.; Kalogera, V.; Kamai, B.; Kandhasamy, S.; Kang, G.; Kanner,
J. B.; Kapadia, S. J.; Karki, S.; Karvinen, K. S.; Kasprzack, M.;
Katolik, M.; Katsavounidis, E.; Katzman, W.; Kaufer, S.; Kawabe, K.;
Kéfélian, F.; Keitel, D.; Kemball, A. J.; Kennedy, R.; Kent, C.;
Key, J. S.; Khalili, F. Y.; Khan, I.; Khan, S.; Khan, Z.; Khazanov,
E. A.; Kijbunchoo, N.; Kim, Chunglee; Kim, J. C.; Kim, K.; Kim, W.;
Kim, W. S.; Kim, Y. -M.; Kimbrell, S. J.; King, E. J.; King, P. J.;
Kinley-Hanlon, M.; Kirchhoff, R.; Kissel, J. S.; Kleybolte, L.;
Klimenko, S.; Knowles, T. D.; Koch, P.; Koehlenbeck, S. M.; Koley,
S.; Kondrashov, V.; Kontos, A.; Korobko, M.; Korth, W. Z.; Kowalska,
I.; Kozak, D. B.; Krämer, C.; Kringel, V.; Krishnan, B.; Królak,
A.; Kuehn, G.; Kumar, P.; Kumar, R.; Kumar, S.; Kuo, L.; Kutynia, A.;
Kwang, S.; Lackey, B. D.; Lai, K. H.; Landry, M.; Lang, R. N.; Lange,
J.; Lantz, B.; Lanza, R. K.; Lartaux-Vollard, A.; Lasky, P. D.; Laxen,
M.; Lazzarini, A.; Lazzaro, C.; Leaci, P.; Leavey, S.; Lee, C. H.;
Lee, H. K.; Lee, H. M.; Lee, H. W.; Lee, K.; Lehmann, J.; Lenon,
A.; Leonardi, M.; Leroy, N.; Letendre, N.; Levin, Y.; Li, T. G. F.;
Linker, S. D.; Littenberg, T. B.; Liu, J.; Liu, X.; Lo, R. K. L.;
Lockerbie, N. A.; London, L. T.; Lord, J. E.; Lorenzini, M.; Loriette,
V.; Lormand, M.; Losurdo, G.; Lough, J. D.; Lousto, C. O.; Lovelace,
G.; Lück, H.; Lumaca, D.; Lundgren, A. P.; Lynch, R.; Ma, Y.; Macas,
R.; Macfoy, S.; Machenschalk, B.; Macinnis, M.; MacLeod, D. M.;
Hernandez, I. Magaña; Magaña-Sandoval, F.; Zertuche, L. Magaña;
Magee, R. M.; Majorana, E.; Maksimovic, I.; Man, N.; Mandic, V.;
Mangano, V.; Mansell, G. L.; Manske, M.; Mantovani, M.; Marchesoni,
F.; Marion, F.; Márka, S.; Márka, Z.; Markakis, C.; Markosyan, A. S.;
Markowitz, A.; Maros, E.; Marquina, A.; Martelli, F.; Martellini, L.;
Martin, I. W.; Martin, R. M.; Martynov, D. V.; Mason, K.; Massera,
E.; Masserot, A.; Massinger, T. J.; Masso-Reid, M.; Mastrogiovanni,
S.; Matas, A.; Matichard, F.; Matone, L.; Mavalvala, N.; Mazumder,
N.; McCarthy, R.; McClelland, D. E.; McCormick, S.; McCuller, L.;
McGuire, S. C.; McIntyre, G.; McIver, J.; McManus, D. J.; McNeill, L.;
McRae, T.; McWilliams, S. T.; Meacher, D.; Meadors, G. D.; Mehmet, M.;
Meidam, J.; Mejuto-Villa, E.; Melatos, A.; Mendell, G.; Mercer, R. A.;
Merilh, E. L.; Merzougui, M.; Meshkov, S.; Messenger, C.; Messick, C.;
Metzdorff, R.; Meyers, P. M.; Miao, H.; Michel, C.; Middleton, H.;
Mikhailov, E. E.; Milano, L.; Miller, A. L.; Miller, B. B.; Miller,
J.; Millhouse, M.; Milovich-Goff, M. C.; Minazzoli, O.; Minenkov, Y.;
Ming, J.; Mishra, C.; Mitra, S.; Mitrofanov, V. P.; Mitselmakher,
G.; Mittleman, R.; Moffa, D.; Moggi, A.; Mogushi, K.; Mohan, M.;
Mohapatra, S. R. P.; Montani, M.; Moore, C. J.; Moraru, D.; Moreno,
G.; Morriss, S. R.; Mours, B.; Mow-Lowry, C. M.; Mueller, G.; Muir,
A. W.; Mukherjee, Arunava; Mukherjee, D.; Mukherjee, S.; Mukund, N.;
Mullavey, A.; Munch, J.; Muñiz, E. A.; Muratore, M.; Murray, P. G.;
Napier, K.; Nardecchia, I.; Naticchioni, L.; Nayak, R. K.; Neilson,
J.; Nelemans, G.; Nelson, T. J. N.; Nery, M.; Neunzert, A.; Nevin,
L.; Newport, J. M.; Newton, G.; Ng, K. K. Y.; Nguyen, T. T.; Nichols,
D.; Nielsen, A. B.; Nissanke, S.; Nitz, A.; Noack, A.; Nocera, F.;
Nolting, D.; North, C.; Nuttall, L. K.; Oberling, J.; O'Dea, G. D.;
Ogin, G. H.; Oh, J. J.; Oh, S. H.; Ohme, F.; Okada, M. A.; Oliver, M.;
Oppermann, P.; Oram, Richard J.; O'Reilly, B.; Ormiston, R.; Ortega,
L. F.; O'Shaughnessy, R.; Ossokine, S.; Ottaway, D. J.; Overmier, H.;
Owen, B. J.; Pace, A. E.; Page, J.; Page, M. A.; Pai, A.; Pai, S. A.;
Palamos, J. R.; Palashov, O.; Palomba, C.; Pal-Singh, A.; Pan, Howard;
Pan, Huang-Wei; Pang, B.; Pang, P. T. H.; Pankow, C.; Pannarale, F.;
Pant, B. C.; Paoletti, F.; Paoli, A.; Papa, M. A.; Parida, A.; Parker,
W.; Pascucci, D.; Pasqualetti, A.; Passaquieti, R.; Passuello, D.;
Patil, M.; Patricelli, B.; Pearlstone, B. L.; Pedraza, M.; Pedurand,
R.; Pekowsky, L.; Pele, A.; Penn, S.; Perez, C. J.; Perreca, A.;
Perri, L. M.; Pfeiffer, H. P.; Phelps, M.; Piccinni, O. J.; Pichot,
M.; Piergiovanni, F.; Pierro, V.; Pillant, G.; Pinard, L.; Pinto,
I. M.; Pirello, M.; Pitkin, M.; Poe, M.; Poggiani, R.; Popolizio,
P.; Porter, E. K.; Post, A.; Powell, J.; Prasad, J.; Pratt, J. W. W.;
Pratten, G.; Predoi, V.; Prestegard, T.; Prijatelj, M.; Principe, M.;
Privitera, S.; Prodi, G. A.; Prokhorov, L. G.; Puncken, O.; Punturo,
M.; Puppo, P.; Pürrer, M.; Qi, H.; Quetschke, V.; Quintero, E. A.;
Quitzow-James, R.; Raab, F. J.; Rabeling, D. S.; Radkins, H.; Raffai,
P.; Raja, S.; Rajan, C.; Rajbhandari, B.; Rakhmanov, M.; Ramirez,
K. E.; Ramos-Buades, A.; Rapagnani, P.; Raymond, V.; Razzano, M.;
Read, J.; Regimbau, T.; Rei, L.; Reid, S.; Reitze, D. H.; Ren, W.;
Reyes, S. D.; Ricci, F.; Ricker, P. M.; Rieger, S.; Riles, K.; Rizzo,
M.; Robertson, N. A.; Robie, R.; Robinet, F.; Rocchi, A.; Rolland,
L.; Rollins, J. G.; Roma, V. J.; Romano, J. D.; Romano, R.;
Romel, C. L.; Romie, J. H.; Rosińska, D.; Ross, M. P.; Rowan,
S.; Rüdiger, A.; Ruggi, P.; Rutins, G.; Ryan, K.; Sachdev, S.;
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D. A.; Shaffer, T. J.; Shah, A. A.; Shahriar, M. S.; Shaner, M. B.;
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P. J.; Swinkels, B. L.; Szczepańczyk, M. J.; Tacca, M.; Tait, S. C.;
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A. L.; Usman, S. A.; Vahlbruch, H.; Vajente, G.; Valdes, G.; van
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R. D.; Williamson, A. R.; Willis, J. L.; Willke, B.; Wimmer, M. H.;
Winkler, W.; Wipf, C. C.; Wittel, H.; Woan, G.; Woehler, J.; Wofford,
J.; Wong, K. W. K.; Worden, J.; Wright, J. L.; Wu, D. S.; Wysocki,
D. M.; Xiao, S.; Yamamoto, H.; Yancey, C. C.; Yang, L.; Yap, M. J.;
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M.; Zelenova, T.; Zendri, J. -P.; Zevin, M.; Zhang, L.; Zhang, M.;
Zhang, T.; Zhang, Y. -H.; Zhao, C.; Zhou, M.; Zhou, Z.; Zhu, S. J.;
Zhu, X. J.; Zimmerman, A. B.; Zucker, M. E.; Zweizig, J.; Foley, R. J.;
Coulter, D. A.; Drout, M. R.; Kasen, D.; Kilpatrick, C. D.; Madore,
B. F.; Murguia-Berthier, A.; Pan, Y. -C.; Piro, A. L.; Prochaska,
J. X.; Ramirez-Ruiz, E.; Rest, A.; Rojas-Bravo, C.; Shappee, B. J.;
Siebert, M. R.; Simon, J. D.; Ulloa, N.; Annis, J.; Soares-Santos,
M.; Brout, D.; Scolnic, D.; Diehl, H. T.; Frieman, J.; Berger, E.;
Alexander, K. D.; Allam, S.; Balbinot, E.; Blanchard, P.; Butler,
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A.; Drout, M. R.; Durret, F.; Eftekhari, T.; Finley, D. A.; Fong,
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R. A.; Hanna, C.; Hartley, W.; Herner, K.; Huterer, D.; Kasen,
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Rebolo, R.; Serra-Ricart, M.
2017Natur.551...85A Altcode: 2017arXiv171005835A
On 17 August 2017, the Advanced LIGO and Virgo detectors observed the
gravitational-wave event GW170817—a strong signal from the merger
of a binary neutron-star system. Less than two seconds after the
merger, a γ-ray burst (GRB 170817A) was detected within a region
of the sky consistent with the LIGO-Virgo-derived location of the
gravitational-wave source. This sky region was subsequently observed
by optical astronomy facilities, resulting in the identification of
an optical transient signal within about ten arcseconds of the galaxy
NGC 4993. This detection of GW170817 in both gravitational waves and
electromagnetic waves represents the first ‘multi-messenger’
astronomical observation. Such observations enable GW170817 to be
used as a ‘standard siren’ (meaning that the absolute distance
to the source can be determined directly from the gravitational-wave
measurements) to measure the Hubble constant. This quantity represents
the local expansion rate of the Universe, sets the overall scale of
the Universe and is of fundamental importance to cosmology. Here
we report a measurement of the Hubble constant that combines the
distance to the source inferred purely from the gravitational-wave
signal with the recession velocity inferred from measurements of
the redshift using the electromagnetic data. In contrast to previous
measurements, ours does not require the use of a cosmic ‘distance
ladder’: the gravitational-wave analysis can be used to estimate
the luminosity distance out to cosmological scales directly, without
the use of intermediate astronomical distance measurements. We
determine the Hubble constant to be about 70 kilometres per second
per megaparsec. This value is consistent with existing measurements,
while being completely independent of them. Additional standard siren
measurements from future gravitational-wave sources will enable the
Hubble constant to be constrained to high precision.
---------------------------------------------------------
Title: Multi-messenger Observations of a Binary Neutron Star Merger
Authors: Abbott, B. P.; Abbott, R.; Abbott, T. D.; Acernese, F.;
Ackley, K.; Adams, C.; Adams, T.; Addesso, P.; Adhikari, R. X.; Adya,
V. B.; Affeldt, C.; Afrough, M.; Agarwal, B.; Agathos, M.; Agatsuma,
K.; Aggarwal, N.; Aguiar, O. D.; Aiello, L.; Ain, A.; Ajith, P.;
Allen, B.; Allen, G.; Allocca, A.; Altin, P. A.; Amato, A.; Ananyeva,
A.; Anderson, S. B.; Anderson, W. G.; Angelova, S. V.; Antier, S.;
Appert, S.; Arai, K.; Araya, M. C.; Areeda, J. S.; Arnaud, N.; Arun,
K. G.; Ascenzi, S.; Ashton, G.; Ast, M.; Aston, S. M.; Astone, P.;
Atallah, D. V.; Aufmuth, P.; Aulbert, C.; AultONeal, K.; Austin,
C.; Avila-Alvarez, A.; Babak, S.; Bacon, P.; Bader, M. K. M.; Bae,
S.; Baker, P. T.; Baldaccini, F.; Ballardin, G.; Ballmer, S. W.;
Banagiri, S.; Barayoga, J. C.; Barclay, S. E.; Barish, B. C.; Barker,
D.; Barkett, K.; Barone, F.; Barr, B.; Barsotti, L.; Barsuglia,
M.; Barta, D.; Barthelmy, S. D.; Bartlett, J.; Bartos, I.; Bassiri,
R.; Basti, A.; Batch, J. C.; Bawaj, M.; Bayley, J. C.; Bazzan, M.;
Bécsy, B.; Beer, C.; Bejger, M.; Belahcene, I.; Bell, A. S.; Berger,
B. K.; Bergmann, G.; Bero, J. J.; Berry, C. P. L.; Bersanetti, D.;
Bertolini, A.; Betzwieser, J.; Bhagwat, S.; Bhandare, R.; Bilenko,
I. A.; Billingsley, G.; Billman, C. R.; Birch, J.; Birney, R.;
Birnholtz, O.; Biscans, S.; Biscoveanu, S.; Bisht, A.; Bitossi, M.;
Biwer, C.; Bizouard, M. A.; Blackburn, J. K.; Blackman, J.; Blair,
C. D.; Blair, D. G.; Blair, R. M.; Bloemen, S.; Bock, O.; Bode, N.;
Boer, M.; Bogaert, G.; Bohe, A.; Bondu, F.; Bonilla, E.; Bonnand, R.;
Boom, B. A.; Bork, R.; Boschi, V.; Bose, S.; Bossie, K.; Bouffanais,
Y.; Bozzi, A.; Bradaschia, C.; Brady, P. R.; Branchesi, M.; Brau,
J. E.; Briant, T.; Brillet, A.; Brinkmann, M.; Brisson, V.; Brockill,
P.; Broida, J. E.; Brooks, A. F.; Brown, D. A.; Brown, D. D.; Brunett,
S.; Buchanan, C. C.; Buikema, A.; Bulik, T.; Bulten, H. J.; Buonanno,
A.; Buskulic, D.; Buy, C.; Byer, R. L.; Cabero, M.; Cadonati, L.;
Cagnoli, G.; Cahillane, C.; Calderón Bustillo, J.; Callister, T. A.;
Calloni, E.; Camp, J. B.; Canepa, M.; Canizares, P.; Cannon, K. C.;
Cao, H.; Cao, J.; Capano, C. D.; Capocasa, E.; Carbognani, F.; Caride,
S.; Carney, M. F.; Casanueva Diaz, J.; Casentini, C.; Caudill, S.;
Cavaglià, M.; Cavalier, F.; Cavalieri, R.; Cella, G.; Cepeda, C. B.;
Cerdá-Durán, P.; Cerretani, G.; Cesarini, E.; Chamberlin, S. J.;
Chan, M.; Chao, S.; Charlton, P.; Chase, E.; Chassande-Mottin, E.;
Chatterjee, D.; Chatziioannou, K.; Cheeseboro, B. D.; Chen, H. Y.;
Chen, X.; Chen, Y.; Cheng, H. -P.; Chia, H.; Chincarini, A.; Chiummo,
A.; Chmiel, T.; Cho, H. S.; Cho, M.; Chow, J. H.; Christensen, N.;
Chu, Q.; Chua, A. J. K.; Chua, S.; Chung, A. K. W.; Chung, S.; Ciani,
G.; Ciolfi, R.; Cirelli, C. E.; Cirone, A.; Clara, F.; Clark, J. A.;
Clearwater, P.; Cleva, F.; Cocchieri, C.; Coccia, E.; Cohadon,
P. -F.; Cohen, D.; Colla, A.; Collette, C. G.; Cominsky, L. R.;
Constancio, M., Jr.; Conti, L.; Cooper, S. J.; Corban, P.; Corbitt,
T. R.; Cordero-Carrión, I.; Corley, K. R.; Cornish, N.; Corsi, A.;
Cortese, S.; Costa, C. A.; Coughlin, M. W.; Coughlin, S. B.; Coulon,
J. -P.; Countryman, S. T.; Couvares, P.; Covas, P. B.; Cowan, E. E.;
Coward, D. M.; Cowart, M. J.; Coyne, D. C.; Coyne, R.; Creighton,
J. D. E.; Creighton, T. D.; Cripe, J.; Crowder, S. G.; Cullen, T. J.;
Cumming, A.; Cunningham, L.; Cuoco, E.; Dal Canton, T.; Dálya,
G.; Danilishin, S. L.; D'Antonio, S.; Danzmann, K.; Dasgupta, A.;
Da Silva Costa, C. F.; Dattilo, V.; Dave, I.; Davier, M.; Davis, D.;
Daw, E. J.; Day, B.; De, S.; DeBra, D.; Degallaix, J.; De Laurentis,
M.; Deléglise, S.; Del Pozzo, W.; Demos, N.; Denker, T.; Dent, T.;
De Pietri, R.; Dergachev, V.; De Rosa, R.; DeRosa, R. T.; De Rossi,
C.; DeSalvo, R.; de Varona, O.; Devenson, J.; Dhurandhar, S.; Díaz,
M. C.; Di Fiore, L.; Di Giovanni, M.; Di Girolamo, T.; Di Lieto, A.;
Di Pace, S.; Di Palma, I.; Di Renzo, F.; Doctor, Z.; Dolique, V.;
Donovan, F.; Dooley, K. L.; Doravari, S.; Dorrington, I.; Douglas,
R.; Dovale Álvarez, M.; Downes, T. P.; Drago, M.; Dreissigacker,
C.; Driggers, J. C.; Du, Z.; Ducrot, M.; Dupej, P.; Dwyer, S. E.;
Edo, T. B.; Edwards, M. C.; Effler, A.; Ehrens, P.; Eichholz, J.;
Eikenberry, S. S.; Eisenstein, R. A.; Essick, R. C.; Estevez, D.;
Etienne, Z. B.; Etzel, T.; Evans, M.; Evans, T. M.; Factourovich,
M.; Fafone, V.; Fair, H.; Fairhurst, S.; Fan, X.; Farinon, S.; Farr,
B.; Farr, W. M.; Fauchon-Jones, E. J.; Favata, M.; Fays, M.; Fee,
C.; Fehrmann, H.; Feicht, J.; Fejer, M. M.; Fernandez-Galiana, A.;
Ferrante, I.; Ferreira, E. C.; Ferrini, F.; Fidecaro, F.; Finstad, D.;
Fiori, I.; Fiorucci, D.; Fishbach, M.; Fisher, R. P.; Fitz-Axen, M.;
Flaminio, R.; Fletcher, M.; Fong, H.; Font, J. A.; Forsyth, P. W. F.;
Forsyth, S. S.; Fournier, J. -D.; Frasca, S.; Frasconi, F.; Frei, Z.;
Freise, A.; Frey, R.; Frey, V.; Fries, E. M.; Fritschel, P.; Frolov,
V. V.; Fulda, P.; Fyffe, M.; Gabbard, H.; Gadre, B. U.; Gaebel,
S. M.; Gair, J. R.; Gammaitoni, L.; Ganija, M. R.; Gaonkar, S. G.;
Garcia-Quiros, C.; Garufi, F.; Gateley, B.; Gaudio, S.; Gaur, G.;
Gayathri, V.; Gehrels, N.; Gemme, G.; Genin, E.; Gennai, A.; George,
D.; George, J.; Gergely, L.; Germain, V.; Ghonge, S.; Ghosh, Abhirup;
Ghosh, Archisman; Ghosh, S.; Giaime, J. A.; Giardina, K. D.; Giazotto,
A.; Gill, K.; Glover, L.; Goetz, E.; Goetz, R.; Gomes, S.; Goncharov,
B.; González, G.; Gonzalez Castro, J. M.; Gopakumar, A.; Gorodetsky,
M. L.; Gossan, S. E.; Gosselin, M.; Gouaty, R.; Grado, A.; Graef, C.;
Granata, M.; Grant, A.; Gras, S.; Gray, C.; Greco, G.; Green, A. C.;
Gretarsson, E. M.; Griswold, B.; Groot, P.; Grote, H.; Grunewald, S.;
Gruning, P.; Guidi, G. M.; Guo, X.; Gupta, A.; Gupta, M. K.; Gushwa,
K. E.; Gustafson, E. K.; Gustafson, R.; Halim, O.; Hall, B. R.; Hall,
E. D.; Hamilton, E. Z.; Hammond, G.; Haney, M.; Hanke, M. M.; Hanks,
J.; Hanna, C.; Hannam, M. D.; Hannuksela, O. A.; Hanson, J.; Hardwick,
T.; Harms, J.; Harry, G. M.; Harry, I. W.; Hart, M. J.; Haster, C. -J.;
Haughian, K.; Healy, J.; Heidmann, A.; Heintze, M. C.; Heitmann,
H.; Hello, P.; Hemming, G.; Hendry, M.; Heng, I. S.; Hennig, J.;
Heptonstall, A. W.; Heurs, M.; Hild, S.; Hinderer, T.; Hoak, D.;
Hofman, D.; Holt, K.; Holz, D. E.; Hopkins, P.; Horst, C.; Hough,
J.; Houston, E. A.; Howell, E. J.; Hreibi, A.; Hu, Y. M.; Huerta,
E. A.; Huet, D.; Hughey, B.; Husa, S.; Huttner, S. H.; Huynh-Dinh,
T.; Indik, N.; Inta, R.; Intini, G.; Isa, H. N.; Isac, J. -M.; Isi,
M.; Iyer, B. R.; Izumi, K.; Jacqmin, T.; Jani, K.; Jaranowski,
P.; Jawahar, S.; Jiménez-Forteza, F.; Johnson, W. W.; Jones,
D. I.; Jones, R.; Jonker, R. J. G.; Ju, L.; Junker, J.; Kalaghatgi,
C. V.; Kalogera, V.; Kamai, B.; Kandhasamy, S.; Kang, G.; Kanner,
J. B.; Kapadia, S. J.; Karki, S.; Karvinen, K. S.; Kasprzack, M.;
Katolik, M.; Katsavounidis, E.; Katzman, W.; Kaufer, S.; Kawabe, K.;
Kéfélian, F.; Keitel, D.; Kemball, A. J.; Kennedy, R.; Kent, C.;
Key, J. S.; Khalili, F. Y.; Khan, I.; Khan, S.; Khan, Z.; Khazanov,
E. A.; Kijbunchoo, N.; Kim, Chunglee; Kim, J. C.; Kim, K.; Kim, W.;
Kim, W. S.; Kim, Y. -M.; Kimbrell, S. J.; King, E. J.; King, P. J.;
Kinley-Hanlon, M.; Kirchhoff, R.; Kissel, J. S.; Kleybolte, L.;
Klimenko, S.; Knowles, T. D.; Koch, P.; Koehlenbeck, S. M.; Koley,
S.; Kondrashov, V.; Kontos, A.; Korobko, M.; Korth, W. Z.; Kowalska,
I.; Kozak, D. B.; Krämer, C.; Kringel, V.; Krishnan, B.; Królak,
A.; Kuehn, G.; Kumar, P.; Kumar, R.; Kumar, S.; Kuo, L.; Kutynia,
A.; Kwang, S.; Lackey, B. D.; Lai, K. H.; Landry, M.; Lang, R. N.;
Lange, J.; Lantz, B.; Lanza, R. K.; Larson, S. L.; Lartaux-Vollard,
A.; Lasky, P. D.; Laxen, M.; Lazzarini, A.; Lazzaro, C.; Leaci, P.;
Leavey, S.; Lee, C. H.; Lee, H. K.; Lee, H. M.; Lee, H. W.; Lee, K.;
Lehmann, J.; Lenon, A.; Leonardi, M.; Leroy, N.; Letendre, N.; Levin,
Y.; Li, T. G. F.; Linker, S. D.; Littenberg, T. B.; Liu, J.; Lo,
R. K. L.; Lockerbie, N. A.; London, L. T.; Lord, J. E.; Lorenzini,
M.; Loriette, V.; Lormand, M.; Losurdo, G.; Lough, J. D.; Lousto,
C. O.; Lovelace, G.; Lück, H.; Lumaca, D.; Lundgren, A. P.; Lynch,
R.; Ma, Y.; Macas, R.; Macfoy, S.; Machenschalk, B.; MacInnis, M.;
Macleod, D. M.; Magaña Hernandez, I.; Magaña-Sandoval, F.; Magaña
Zertuche, L.; Magee, R. M.; Majorana, E.; Maksimovic, I.; Man, N.;
Mandic, V.; Mangano, V.; Mansell, G. L.; Manske, M.; Mantovani, M.;
Marchesoni, F.; Marion, F.; Márka, S.; Márka, Z.; Markakis, C.;
Markosyan, A. S.; Markowitz, A.; Maros, E.; Marquina, A.; Marsh,
P.; Martelli, F.; Martellini, L.; Martin, I. W.; Martin, R. M.;
Martynov, D. V.; Mason, K.; Massera, E.; Masserot, A.; Massinger,
T. J.; Masso-Reid, M.; Mastrogiovanni, S.; Matas, A.; Matichard, F.;
Matone, L.; Mavalvala, N.; Mazumder, N.; McCarthy, R.; McClelland,
D. E.; McCormick, S.; McCuller, L.; McGuire, S. C.; McIntyre, G.;
McIver, J.; McManus, D. J.; McNeill, L.; McRae, T.; McWilliams, S. T.;
Meacher, D.; Meadors, G. D.; Mehmet, M.; Meidam, J.; Mejuto-Villa, E.;
Melatos, A.; Mendell, G.; Mercer, R. A.; Merilh, E. L.; Merzougui, M.;
Meshkov, S.; Messenger, C.; Messick, C.; Metzdorff, R.; Meyers, P. M.;
Miao, H.; Michel, C.; Middleton, H.; Mikhailov, E. E.; Milano, L.;
Miller, A. L.; Miller, B. B.; Miller, J.; Millhouse, M.; Milovich-Goff,
M. C.; Minazzoli, O.; Minenkov, Y.; Ming, J.; Mishra, C.; Mitra, S.;
Mitrofanov, V. P.; Mitselmakher, G.; Mittleman, R.; Moffa, D.; Moggi,
A.; Mogushi, K.; Mohan, M.; Mohapatra, S. R. P.; Montani, M.; Moore,
C. J.; Moraru, D.; Moreno, G.; Morriss, S. R.; Mours, B.; Mow-Lowry,
C. M.; Mueller, G.; Muir, A. W.; Mukherjee, Arunava; Mukherjee, D.;
Mukherjee, S.; Mukund, N.; Mullavey, A.; Munch, J.; Muñiz, E. A.;
Muratore, M.; Murray, P. G.; Napier, K.; Nardecchia, I.; Naticchioni,
L.; Nayak, R. K.; Neilson, J.; Nelemans, G.; Nelson, T. J. N.; Nery,
M.; Neunzert, A.; Nevin, L.; Newport, J. M.; Newton, G.; Ng, K. K. Y.;
Nguyen, P.; Nguyen, T. T.; Nichols, D.; Nielsen, A. B.; Nissanke,
S.; Nitz, A.; Noack, A.; Nocera, F.; Nolting, D.; North, C.; Nuttall,
L. K.; Oberling, J.; O'Dea, G. D.; Ogin, G. H.; Oh, J. J.; Oh, S. H.;
Ohme, F.; Okada, M. A.; Oliver, M.; Oppermann, P.; Oram, Richard J.;
O'Reilly, B.; Ormiston, R.; Ortega, L. F.; O'Shaughnessy, R.; Ossokine,
S.; Ottaway, D. J.; Overmier, H.; Owen, B. J.; Pace, A. E.; Page,
J.; Page, M. A.; Pai, A.; Pai, S. A.; Palamos, J. R.; Palashov, O.;
Palomba, C.; Pal-Singh, A.; Pan, Howard; Pan, Huang-Wei; Pang, B.;
Pang, P. T. H.; Pankow, C.; Pannarale, F.; Pant, B. C.; Paoletti,
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Pasqualetti, A.; Passaquieti, R.; Passuello, D.; Patil, M.; Patricelli,
B.; Pearlstone, B. L.; Pedraza, M.; Pedurand, R.; Pekowsky, L.; Pele,
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Phelps, M.; Piccinni, O. J.; Pichot, M.; Piergiovanni, F.; Pierro,
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Poe, M.; Poggiani, R.; Popolizio, P.; Porter, E. K.; Post, A.; Powell,
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Momenté, G.; Montaruli, T.; Moore, R. W.; Moulai, M.; Nahnhauer,
R.; Nakarmi, P.; Naumann, U.; Neer, G.; Niederhausen, H.; Nowicki,
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Imager Team; Svinkin, D. S.; Hurley, K.; Aptekar, R. L.; Frederiks,
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Y. B.; Chen, Y. P.; Cui, W.; Cui, W. W.; Deng, J. K.; Dong, Y. W.; Du,
Y. Y.; Fu, M. X.; Gao, G. H.; Gao, H.; Gao, M.; Ge, M. Y.; Gu, Y. D.;
Guan, J.; Guo, C. C.; Han, D. W.; Hu, W.; Huang, Y.; Huo, J.; Jia,
S. M.; Jiang, L. H.; Jiang, W. C.; Jin, J.; Jin, Y. J.; Li, B.; Li,
C. K.; Li, G.; Li, M. S.; Li, W.; Li, X.; Li, X. B.; Li, X. F.; Li,
Y. G.; Li, Z. J.; Li, Z. W.; Liang, X. H.; Liao, J. Y.; Liu, C. Z.;
Liu, G. Q.; Liu, H. W.; Liu, S. Z.; Liu, X. J.; Liu, Y.; Liu, Y. N.;
Lu, B.; Lu, X. F.; Luo, T.; Ma, X.; Meng, B.; Nang, Y.; Nie, J. Y.;
Ou, G.; Qu, J. L.; Sai, N.; Sun, L.; Tan, Y.; Tao, L.; Tao, W. H.;
Tuo, Y. L.; Wang, G. F.; Wang, H. Y.; Wang, J.; Wang, W. S.; Wang,
Y. S.; Wen, X. Y.; Wu, B. B.; Wu, M.; Xiao, G. C.; Xu, H.; Xu, Y. P.;
Yan, L. L.; Yang, J. W.; Yang, S.; Yang, Y. J.; Zhang, A. M.; Zhang,
C. L.; Zhang, C. M.; Zhang, F.; Zhang, H. M.; Zhang, J.; Zhang, Q.;
Zhang, S.; Zhang, T.; Zhang, W.; Zhang, W. C.; Zhang, W. Z.; Zhang,
Y.; Zhang, Y.; Zhang, Y. F.; Zhang, Y. J.; Zhang, Z.; Zhang, Z. L.;
Zhao, H. S.; Zhao, J. L.; Zhao, X. F.; Zheng, S. J.; Zhu, Y.; Zhu,
Y. X.; Zou, C. L.; Insight-HXMT Collaboration; Albert, A.; André,
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T.; Baret, B.; Barrios-Martí, J.; Basa, S.; Belhorma, B.; Bertin, V.;
Biagi, S.; Bormuth, R.; Bourret, S.; Bouwhuis, M. C.; Brânzaş, H.;
Bruijn, R.; Brunner, J.; Busto, J.; Capone, A.; Caramete, L.; Carr,
J.; Celli, S.; Cherkaoui El Moursli, R.; Chiarusi, T.; Circella,
M.; Coelho, J. A. B.; Coleiro, A.; Coniglione, R.; Costantini, H.;
Coyle, P.; Creusot, A.; Díaz, A. F.; Deschamps, A.; De Bonis,
G.; Distefano, C.; Di Palma, I.; Domi, A.; Donzaud, C.; Dornic,
D.; Drouhin, D.; Eberl, T.; El Bojaddaini, I.; El Khayati, N.;
Elsässer, D.; Enzenhöfer, A.; Ettahiri, A.; Fassi, F.; Felis, I.;
Fusco, L. A.; Gay, P.; Giordano, V.; Glotin, H.; Grégoire, T.; Ruiz,
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C.; Illuminati, G.; James, C. W.; de Jong, M.; Jongen, M.; Kadler,
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Marinelli, A.; Martínez-Mora, J. A.; Mele, R.; Melis, K.; Michael,
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M.; Tayalati, Y.; Trovato, A.; Turpin, D.; Tönnis, C.; Vallage, B.;
Van Elewyck, V.; Versari, F.; Vivolo, D.; Vizzoca, A.; Wilms, J.;
Zornoza, J. D.; Zúñiga, J.; ANTARES Collaboration; Beardmore, A. P.;
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de Pasquale, M.; Emery, S. W. K.; Evans, P. A.; Giommi, P.; Gronwall,
C.; Kennea, J. A.; Krimm, H. A.; Kuin, N. P. M.; Lien, A.; Marshall,
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Marisaldi, M.; Minervini, G.; Fioretti, V.; Parmiggiani, N.; Gianotti,
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F.; Ferrari, A.; Morselli, A.; Paoletti, F.; Picozza, P.; Pilia,
M.; Rappoldi, A.; Soffitta, P.; Vercellone, S.; AGILE Team; Foley,
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Soares-Santos, M.; Annis, J.; Alexander, K. D.; Allam, S.; Balbinot,
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M. R.; Durret, F.; Eftekhari, T.; Finley, D. A.; Fong, W.; Frieman,
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Metzger, B. D.; Muñoz, R. R.; Muir, J.; Nicholl, M.; Nugent, P.;
Palmese, A.; Paz-Chinchón, F.; Quataert, E.; Sako, M.; Sauseda, M.;
Schlegel, D. J.; Scolnic, D.; Secco, L. F.; Smith, N.; Sobreira, F.;
Villar, V. A.; Vivas, A. K.; Wester, W.; Williams, P. K. G.; Yanny,
B.; Zenteno, A.; Zhang, Y.; Abbott, T. M. C.; Banerji, M.; Bechtol,
K.; Benoit-Lévy, A.; Bertin, E.; Brooks, D.; Buckley-Geer, E.; Burke,
D. L.; Capozzi, D.; Carnero Rosell, A.; Carrasco Kind, M.; Castander,
F. J.; Crocce, M.; Cunha, C. E.; D'Andrea, C. B.; da Costa, L. N.;
Davis, C.; DePoy, D. L.; Desai, S.; Dietrich, J. P.; Eifler, T. F.;
Fernandez, E.; Flaugher, B.; Fosalba, P.; Gaztanaga, E.; Gerdes,
D. W.; Giannantonio, T.; Goldstein, D. A.; Gruen, D.; Gschwend, J.;
Gutierrez, G.; Honscheid, K.; James, D. J.; Jeltema, T.; Johnson,
M. W. G.; Johnson, M. D.; Kent, S.; Krause, E.; Kron, R.; Kuehn, K.;
Lahav, O.; Lima, M.; Maia, M. A. G.; March, M.; Martini, P.; McMahon,
R. G.; Menanteau, F.; Miller, C. J.; Miquel, R.; Mohr, J. J.; Nichol,
R. C.; Ogando, R. L. C.; Plazas, A. A.; Romer, A. K.; Roodman, A.;
Rykoff, E. S.; Sanchez, E.; Scarpine, V.; Schindler, R.; Schubnell,
M.; Sevilla-Noarbe, I.; Sheldon, E.; Smith, M.; Smith, R. C.; Stebbins,
A.; Suchyta, E.; Swanson, M. E. C.; Tarle, G.; Thomas, R. C.; Troxel,
M. A.; Tucker, D. L.; Vikram, V.; Walker, A. R.; Wechsler, R. H.;
Weller, J.; Carlin, J. L.; Gill, M. S. S.; Li, T. S.; Marriner, J.;
Neilsen, E.; Dark Energy Camera GW-EM Collaboration; DES Collaboration;
Haislip, J. B.; Kouprianov, V. V.; Reichart, D. E.; Sand, D. J.;
Tartaglia, L.; Valenti, S.; Yang, S.; DLT40 Collaboration; Benetti,
S.; Brocato, E.; Campana, S.; Cappellaro, E.; Covino, S.; D'Avanzo,
P.; D'Elia, V.; Getman, F.; Ghirlanda, G.; Ghisellini, G.; Limatola,
L.; Nicastro, L.; Palazzi, E.; Pian, E.; Piranomonte, S.; Possenti,
A.; Rossi, A.; Salafia, O. S.; Tomasella, L.; Amati, L.; Antonelli,
L. A.; Bernardini, M. G.; Bufano, F.; Capaccioli, M.; Casella, P.;
Dadina, M.; De Cesare, G.; Di Paola, A.; Giuffrida, G.; Giunta,
A.; Israel, G. L.; Lisi, M.; Maiorano, E.; Mapelli, M.; Masetti,
N.; Pescalli, A.; Pulone, L.; Salvaterra, R.; Schipani, P.; Spera,
M.; Stamerra, A.; Stella, L.; Testa, V.; Turatto, M.; Vergani, D.;
Aresu, G.; Bachetti, M.; Buffa, F.; Burgay, M.; Buttu, M.; Caria,
T.; Carretti, E.; Casasola, V.; Castangia, P.; Carboni, G.; Casu,
S.; Concu, R.; Corongiu, A.; Deiana, G. L.; Egron, E.; Fara, A.;
Gaudiomonte, F.; Gusai, V.; Ladu, A.; Loru, S.; Leurini, S.; Marongiu,
L.; Melis, A.; Melis, G.; Migoni, Carlo; Milia, Sabrina; Navarrini,
Alessandro; Orlati, A.; Ortu, P.; Palmas, S.; Pellizzoni, A.; Perrodin,
D.; Pisanu, T.; Poppi, S.; Righini, S.; Saba, A.; Serra, G.; Serrau,
M.; Stagni, M.; Surcis, G.; Vacca, V.; Vargiu, G. P.; Hunt, L. K.;
Jin, Z. P.; Klose, S.; Kouveliotou, C.; Mazzali, P. A.; Møller, P.;
Nava, L.; Piran, T.; Selsing, J.; Vergani, S. D.; Wiersema, K.; Toma,
K.; Higgins, A. B.; Mundell, C. G.; di Serego Alighieri, S.; Gótz,
D.; Gao, W.; Gomboc, A.; Kaper, L.; Kobayashi, S.; Kopac, D.; Mao,
J.; Starling, R. L. C.; Steele, I.; van der Horst, A. J.; GRAWITA:
GRAvitational Wave Inaf TeAm; Acero, F.; Atwood, W. B.; Baldini,
L.; Barbiellini, G.; Bastieri, D.; Berenji, B.; Bellazzini, R.;
Bissaldi, E.; Blandford, R. D.; Bloom, E. D.; Bonino, R.; Bottacini,
E.; Bregeon, J.; Buehler, R.; Buson, S.; Cameron, R. A.; Caputo, R.;
Caraveo, P. A.; Cavazzuti, E.; Chekhtman, A.; Cheung, C. C.; Chiang,
J.; Ciprini, S.; Cohen-Tanugi, J.; Cominsky, L. R.; Costantin, D.;
Cuoco, A.; D'Ammando, F.; de Palma, F.; Digel, S. W.; Di Lalla,
N.; Di Mauro, M.; Di Venere, L.; Dubois, R.; Fegan, S. J.; Focke,
W. B.; Franckowiak, A.; Fukazawa, Y.; Funk, S.; Fusco, P.; Gargano,
F.; Gasparrini, D.; Giglietto, N.; Giordano, F.; Giroletti, M.;
Glanzman, T.; Green, D.; Grondin, M. -H.; Guillemot, L.; Guiriec,
S.; Harding, A. K.; Horan, D.; Jóhannesson, G.; Kamae, T.; Kensei,
S.; Kuss, M.; La Mura, G.; Latronico, L.; Lemoine-Goumard, M.;
Longo, F.; Loparco, F.; Lovellette, M. N.; Lubrano, P.; Magill,
J. D.; Maldera, S.; Manfreda, A.; Mazziotta, M. N.; McEnery, J. E.;
Meyer, M.; Michelson, P. F.; Mirabal, N.; Monzani, M. E.; Moretti,
E.; Morselli, A.; Moskalenko, I. V.; Negro, M.; Nuss, E.; Ojha, R.;
Omodei, N.; Orienti, M.; Orlando, E.; Palatiello, M.; Paliya, V. S.;
Paneque, D.; Pesce-Rollins, M.; Piron, F.; Porter, T. A.; Principe, G.;
Rainò, S.; Rando, R.; Razzano, M.; Razzaque, S.; Reimer, A.; Reimer,
O.; Reposeur, T.; Rochester, L. S.; Saz Parkinson, P. M.; Sgrò, C.;
Siskind, E. J.; Spada, F.; Spandre, G.; Suson, D. J.; Takahashi, M.;
Tanaka, Y.; Thayer, J. G.; Thayer, J. B.; Thompson, D. J.; Tibaldo,
L.; Torres, D. F.; Torresi, E.; Troja, E.; Venters, T. M.; Vianello,
G.; Zaharijas, G.; Fermi Large Area Telescope Collaboration; Allison,
J. R.; Bannister, K. W.; Dobie, D.; Kaplan, D. L.; Lenc, E.; Lynch,
C.; Murphy, T.; Sadler, E. M.; Australia Telescope Compact Array,
ATCA:; Hotan, A.; James, C. W.; Oslowski, S.; Raja, W.; Shannon,
R. M.; Whiting, M.; Australian SKA Pathfinder, ASKAP:; Arcavi,
I.; Howell, D. A.; McCully, C.; Hosseinzadeh, G.; Hiramatsu, D.;
Poznanski, D.; Barnes, J.; Zaltzman, M.; Vasylyev, S.; Maoz, D.; Las
Cumbres Observatory Group; Cooke, J.; Bailes, M.; Wolf, C.; Deller,
A. T.; Lidman, C.; Wang, L.; Gendre, B.; Andreoni, I.; Ackley, K.;
Pritchard, T. A.; Bessell, M. S.; Chang, S. -W.; Möller, A.; Onken,
C. A.; Scalzo, R. A.; Ridden-Harper, R.; Sharp, R. G.; Tucker, B. E.;
Farrell, T. J.; Elmer, E.; Johnston, S.; Venkatraman Krishnan, V.;
Keane, E. F.; Green, J. A.; Jameson, A.; Hu, L.; Ma, B.; Sun, T.;
Wu, X.; Wang, X.; Shang, Z.; Hu, Y.; Ashley, M. C. B.; Yuan, X.; Li,
X.; Tao, C.; Zhu, Z.; Zhang, H.; Suntzeff, N. B.; Zhou, J.; Yang, J.;
Orange, B.; Morris, D.; Cucchiara, A.; Giblin, T.; Klotz, A.; Staff,
J.; Thierry, P.; Schmidt, B. P.; OzGrav; (Deeper, DWF; Wider; program,
Faster; AST3; CAASTRO Collaborations; Tanvir, N. R.; Levan, A. J.;
Cano, Z.; de Ugarte-Postigo, A.; González-Fernández, C.; Greiner,
J.; Hjorth, J.; Irwin, M.; Krühler, T.; Mandel, I.; Milvang-Jensen,
B.; O'Brien, P.; Rol, E.; Rosetti, S.; Rosswog, S.; Rowlinson, A.;
Steeghs, D. T. H.; Thöne, C. C.; Ulaczyk, K.; Watson, D.; Bruun,
S. H.; Cutter, R.; Figuera Jaimes, R.; Fujii, Y. I.; Fruchter, A. S.;
Gompertz, B.; Jakobsson, P.; Hodosan, G.; Jèrgensen, U. G.; Kangas,
T.; Kann, D. A.; Rabus, M.; Schrøder, S. L.; Stanway, E. R.; Wijers,
R. A. M. J.; VINROUGE Collaboration; Lipunov, V. M.; Gorbovskoy, E. S.;
Kornilov, V. G.; Tyurina, N. V.; Balanutsa, P. V.; Kuznetsov, A. S.;
Vlasenko, D. M.; Podesta, R. C.; Lopez, C.; Podesta, F.; Levato,
H. O.; Saffe, C.; Mallamaci, C. C.; Budnev, N. M.; Gress, O. A.;
Kuvshinov, D. A.; Gorbunov, I. A.; Vladimirov, V. V.; Zimnukhov,
D. S.; Gabovich, A. V.; Yurkov, V. V.; Sergienko, Yu. P.; Rebolo,
R.; Serra-Ricart, M.; Tlatov, A. G.; Ishmuhametova, Yu. V.; MASTER
Collaboration; Abe, F.; Aoki, K.; Aoki, W.; Asakura, Y.; Baar, S.;
Barway, S.; Bond, I. A.; Doi, M.; Finet, F.; Fujiyoshi, T.; Furusawa,
H.; Honda, S.; Itoh, R.; Kanda, N.; Kawabata, K. S.; Kawabata, M.; Kim,
J. H.; Koshida, S.; Kuroda, D.; Lee, C. -H.; Liu, W.; Matsubayashi,
K.; Miyazaki, S.; Morihana, K.; Morokuma, T.; Motohara, K.; Murata,
K. L.; Nagai, H.; Nagashima, H.; Nagayama, T.; Nakaoka, T.; Nakata,
F.; Ohsawa, R.; Ohshima, T.; Ohta, K.; Okita, H.; Saito, T.; Saito,
Y.; Sako, S.; Sekiguchi, Y.; Sumi, T.; Tajitsu, A.; Takahashi,
J.; Takayama, M.; Tamura, Y.; Tanaka, I.; Tanaka, M.; Terai, T.;
Tominaga, N.; Tristram, P. J.; Uemura, M.; Utsumi, Y.; Yamaguchi,
M. S.; Yasuda, N.; Yoshida, M.; Zenko, T.; J-GEM; Adams, S. M.;
Anupama, G. C.; Bally, J.; Barway, S.; Bellm, E.; Blagorodnova, N.;
Cannella, C.; Chandra, P.; Chatterjee, D.; Clarke, T. E.; Cobb, B. E.;
Cook, D. O.; Copperwheat, C.; De, K.; Emery, S. W. K.; Feindt, U.;
Foster, K.; Fox, O. D.; Frail, D. A.; Fremling, C.; Frohmaier, C.;
Garcia, J. A.; Ghosh, S.; Giacintucci, S.; Goobar, A.; Gottlieb, O.;
Grefenstette, B. W.; Hallinan, G.; Harrison, F.; Heida, M.; Helou,
G.; Ho, A. Y. Q.; Horesh, A.; Hotokezaka, K.; Ip, W. -H.; Itoh, R.;
Jacobs, Bob; Jencson, J. E.; Kasen, D.; Kasliwal, M. M.; Kassim,
N. E.; Kim, H.; Kiran, B. S.; Kuin, N. P. M.; Kulkarni, S. R.;
Kupfer, T.; Lau, R. M.; Madsen, K.; Mazzali, P. A.; Miller, A. A.;
Miyasaka, H.; Mooley, K.; Myers, S. T.; Nakar, E.; Ngeow, C. -C.;
Nugent, P.; Ofek, E. O.; Palliyaguru, N.; Pavana, M.; Perley, D. A.;
Peters, W. M.; Pike, S.; Piran, T.; Qi, H.; Quimby, R. M.; Rana, J.;
Rosswog, S.; Rusu, F.; Sadler, E. M.; Van Sistine, A.; Sollerman, J.;
Xu, Y.; Yan, L.; Yatsu, Y.; Yu, P. -C.; Zhang, C.; Zhao, W.; GROWTH;
JAGWAR; Caltech-NRAO; TTU-NRAO; NuSTAR Collaborations; Chambers,
K. C.; Huber, M. E.; Schultz, A. S. B.; Bulger, J.; Flewelling, H.;
Magnier, E. A.; Lowe, T. B.; Wainscoat, R. J.; Waters, C.; Willman,
M.; Pan-STARRS; Ebisawa, K.; Hanyu, C.; Harita, S.; Hashimoto, T.;
Hidaka, K.; Hori, T.; Ishikawa, M.; Isobe, N.; Iwakiri, W.; Kawai,
H.; Kawai, N.; Kawamuro, T.; Kawase, T.; Kitaoka, Y.; Makishima,
K.; Matsuoka, M.; Mihara, T.; Morita, T.; Morita, K.; Nakahira, S.;
Nakajima, M.; Nakamura, Y.; Negoro, H.; Oda, S.; Sakamaki, A.; Sasaki,
R.; Serino, M.; Shidatsu, M.; Shimomukai, R.; Sugawara, Y.; Sugita,
S.; Sugizaki, M.; Tachibana, Y.; Takao, Y.; Tanimoto, A.; Tomida, H.;
Tsuboi, Y.; Tsunemi, H.; Ueda, Y.; Ueno, S.; Yamada, S.; Yamaoka,
K.; Yamauchi, M.; Yatabe, F.; Yoneyama, T.; Yoshii, T.; MAXI Team;
Coward, D. M.; Crisp, H.; Macpherson, D.; Andreoni, I.; Laugier,
R.; Noysena, K.; Klotz, A.; Gendre, B.; Thierry, P.; Turpin, D.;
Consortium, TZAC; Im, M.; Choi, C.; Kim, J.; Yoon, Y.; Lim, G.; Lee,
S. -K.; Lee, C. -U.; Kim, S. -L.; Ko, S. -W.; Joe, J.; Kwon, M. -K.;
Kim, P. -J.; Lim, S. -K.; Choi, J. -S.; KU Collaboration; Fynbo,
J. P. U.; Malesani, D.; Xu, D.; Optical Telescope, Nordic; Smartt,
S. J.; Jerkstrand, A.; Kankare, E.; Sim, S. A.; Fraser, M.; Inserra,
C.; Maguire, K.; Leloudas, G.; Magee, M.; Shingles, L. J.; Smith,
K. W.; Young, D. R.; Kotak, R.; Gal-Yam, A.; Lyman, J. D.; Homan,
D. S.; Agliozzo, C.; Anderson, J. P.; Angus, C. R.; Ashall, C.;
Barbarino, C.; Bauer, F. E.; Berton, M.; Botticella, M. T.; Bulla,
M.; Cannizzaro, G.; Cartier, R.; Cikota, A.; Clark, P.; De Cia,
A.; Della Valle, M.; Dennefeld, M.; Dessart, L.; Dimitriadis, G.;
Elias-Rosa, N.; Firth, R. E.; Flörs, A.; Frohmaier, C.; Galbany, L.;
González-Gaitán, S.; Gromadzki, M.; Gutiérrez, C. P.; Hamanowicz,
A.; Harmanen, J.; Heintz, K. E.; Hernandez, M. -S.; Hodgkin, S. T.;
Hook, I. M.; Izzo, L.; James, P. A.; Jonker, P. G.; Kerzendorf, W. E.;
Kostrzewa-Rutkowska, Z.; Kromer, M.; Kuncarayakti, H.; Lawrence,
A.; Manulis, I.; Mattila, S.; McBrien, O.; Müller, A.; Nordin, J.;
O'Neill, D.; Onori, F.; Palmerio, J. T.; Pastorello, A.; Patat, F.;
Pignata, G.; Podsiadlowski, P.; Razza, A.; Reynolds, T.; Roy, R.;
Ruiter, A. J.; Rybicki, K. A.; Salmon, L.; Pumo, M. L.; Prentice,
S. J.; Seitenzahl, I. R.; Smith, M.; Sollerman, J.; Sullivan, M.;
Szegedi, H.; Taddia, F.; Taubenberger, S.; Terreran, G.; Van Soelen,
B.; Vos, J.; Walton, N. A.; Wright, D. E.; Wyrzykowski, Ł.; Yaron,
O.; pre="(">ePESSTO, <author; Chen, T. -W.; Krühler, T.; Schady,
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Nicuesa Guelbenzu, A.; GROND; Palliyaguru, N. T.; Tech University,
Texas; Shara, M. M.; Williams, T.; Vaisanen, P.; Potter, S. B.; Romero
Colmenero, E.; Crawford, S.; Buckley, D. A. H.; Mao, J.; SALT Group;
Díaz, M. C.; Macri, L. M.; García Lambas, D.; Mendes de Oliveira,
C.; Nilo Castellón, J. L.; Ribeiro, T.; Sánchez, B.; Schoenell,
W.; Abramo, L. R.; Akras, S.; Alcaniz, J. S.; Artola, R.; Beroiz,
M.; Bonoli, S.; Cabral, J.; Camuccio, R.; Chavushyan, V.; Coelho,
P.; Colazo, C.; Costa-Duarte, M. V.; Cuevas Larenas, H.; Domínguez
Romero, M.; Dultzin, D.; Fernández, D.; García, J.; Girardini, C.;
Gonçalves, D. R.; Gonçalves, T. S.; Gurovich, S.; Jiménez-Teja, Y.;
Kanaan, A.; Lares, M.; Lopes de Oliveira, R.; López-Cruz, O.; Melia,
R.; Molino, A.; Padilla, N.; Peñuela, T.; Placco, V. M.; Quiñones,
C.; Ramírez Rivera, A.; Renzi, V.; Riguccini, L.; Ríos-López, E.;
Rodriguez, H.; Sampedro, L.; Schneiter, M.; Sodré, L.; Starck, M.;
Torres-Flores, S.; Tornatore, M.; Zadrożny, A.; Castillo, M.; TOROS:
Transient Robotic Observatory of South Collaboration; Castro-Tirado,
A. J.; Tello, J. C.; Hu, Y. -D.; Zhang, B. -B.; Cunniffe, R.;
Castellón, A.; Hiriart, D.; Caballero-García, M. D.; Jelínek,
M.; Kubánek, P.; Pérez del Pulgar, C.; Park, I. H.; Jeong, S.;
Castro Cerón, J. M.; Pandey, S. B.; Yock, P. C.; Querel, R.; Fan,
Y.; Wang, C.; BOOTES Collaboration; Beardsley, A.; Brown, I. S.;
Crosse, B.; Emrich, D.; Franzen, T.; Gaensler, B. M.; Horsley,
L.; Johnston-Hollitt, M.; Kenney, D.; Morales, M. F.; Pallot, D.;
Sokolowski, M.; Steele, K.; Tingay, S. J.; Trott, C. M.; Walker, M.;
Wayth, R.; Williams, A.; Wu, C.; Murchison Widefield Array, MWA:;
Yoshida, A.; Sakamoto, T.; Kawakubo, Y.; Yamaoka, K.; Takahashi,
I.; Asaoka, Y.; Ozawa, S.; Torii, S.; Shimizu, Y.; Tamura, T.;
Ishizaki, W.; Cherry, M. L.; Ricciarini, S.; Penacchioni, A. V.;
Marrocchesi, P. S.; CALET Collaboration; Pozanenko, A. S.; Volnova,
A. A.; Mazaeva, E. D.; Minaev, P. Yu.; Krugov, M. A.; Kusakin, A. V.;
Reva, I. V.; Moskvitin, A. S.; Rumyantsev, V. V.; Inasaridze, R.;
Klunko, E. V.; Tungalag, N.; Schmalz, S. E.; Burhonov, O.; IKI-GW
Follow-up Collaboration; Abdalla, H.; Abramowski, A.; Aharonian, F.;
Ait Benkhali, F.; Angüner, E. O.; Arakawa, M.; Arrieta, M.; Aubert,
P.; Backes, M.; Balzer, A.; Barnard, M.; Becherini, Y.; Becker Tjus,
J.; Berge, D.; Bernhard, S.; Bernlöhr, K.; Blackwell, R.; Böttcher,
M.; Boisson, C.; Bolmont, J.; Bonnefoy, S.; Bordas, P.; Bregeon, J.;
Brun, F.; Brun, P.; Bryan, M.; Büchele, M.; Bulik, T.; Capasso, M.;
Caroff, S.; Carosi, A.; Casanova, S.; Cerruti, M.; Chakraborty, N.;
Chaves, R. C. G.; Chen, A.; Chevalier, J.; Colafrancesco, S.; Condon,
B.; Conrad, J.; Davids, I. D.; Decock, J.; Deil, C.; Devin, J.; deWilt,
P.; Dirson, L.; Djannati-Ataï, A.; Donath, A.; O'C. Drury, L.; Dutson,
K.; Dyks, J.; Edwards, T.; Egberts, K.; Emery, G.; Ernenwein, J. -P.;
Eschbach, S.; Farnier, C.; Fegan, S.; Fernandes, M. V.; Fiasson, A.;
Fontaine, G.; Funk, S.; Füssling, M.; Gabici, S.; Gallant, Y. A.;
Garrigoux, T.; Gaté, F.; Giavitto, G.; Giebels, B.; Glawion, D.;
Glicenstein, J. F.; Gottschall, D.; Grondin, M. -H.; Hahn, J.;
Haupt, M.; Hawkes, J.; Heinzelmann, G.; Henri, G.; Hermann, G.;
Hinton, J. A.; Hofmann, W.; Hoischen, C.; Holch, T. L.; Holler, M.;
Horns, D.; Ivascenko, A.; Iwasaki, H.; Jacholkowska, A.; Jamrozy, M.;
Jankowsky, D.; Jankowsky, F.; Jingo, M.; Jouvin, L.; Jung-Richardt,
I.; Kastendieck, M. A.; Katarzyński, K.; Katsuragawa, M.; Kerszberg,
D.; Khangulyan, D.; Khélifi, B.; King, J.; Klepser, S.; Klochkov,
D.; Kluźniak, W.; Komin, Nu.; Kosack, K.; Krakau, S.; Kraus, M.;
Krüger, P. P.; Laffon, H.; Lamanna, G.; Lau, J.; Lees, J. -P.;
Lefaucheur, J.; Lemière, A.; Lemoine-Goumard, M.; Lenain, J. -P.;
Leser, E.; Lohse, T.; Lorentz, M.; Liu, R.; Lypova, I.; Malyshev,
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Moderski, R.; Mohamed, M.; Mohrmann, L.; Morå, K.; Moulin, E.; Murach,
T.; Nakashima, S.; de Naurois, M.; Ndiyavala, H.; Niederwanger, F.;
Niemiec, J.; Oakes, L.; O'Brien, P.; Odaka, H.; Ohm, S.; Ostrowski,
M.; Oya, I.; Padovani, M.; Panter, M.; Parsons, R. D.; Pekeur,
N. W.; Pelletier, G.; Perennes, C.; Petrucci, P. -O.; Peyaud, B.;
Piel, Q.; Pita, S.; Poireau, V.; Poon, H.; Prokhorov, D.; Prokoph,
H.; Pühlhofer, G.; Punch, M.; Quirrenbach, A.; Raab, S.; Rauth,
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Sahakian, V.; Saito, S.; Sanchez, D. A.; Santangelo, A.; Sasaki, M.;
Schlickeiser, R.; Schüssler, F.; Schulz, A.; Schwanke, U.; Schwemmer,
S.; Seglar-Arroyo, M.; Settimo, M.; Seyffert, A. S.; Shafi, N.; Shilon,
I.; Shiningayamwe, K.; Simoni, R.; Sol, H.; Spanier, F.; Spir-Jacob,
M.; Stawarz, Ł.; Steenkamp, R.; Stegmann, C.; Steppa, C.; Sushch,
I.; Takahashi, T.; Tavernet, J. -P.; Tavernier, T.; Taylor, A. M.;
Terrier, R.; Tibaldo, L.; Tiziani, D.; Tluczykont, M.; Trichard,
C.; Tsirou, M.; Tsuji, N.; Tuffs, R.; Uchiyama, Y.; van der Walt,
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G.; Veh, J.; Venter, C.; Viana, A.; Vincent, P.; Vink, J.; Voisin,
F.; Völk, H. J.; Vuillaume, T.; Wadiasingh, Z.; Wagner, S. J.;
Wagner, P.; Wagner, R. M.; White, R.; Wierzcholska, A.; Willmann,
P.; Wörnlein, A.; Wouters, D.; Yang, R.; Zaborov, D.; Zacharias, M.;
Zanin, R.; Zdziarski, A. A.; Zech, A.; Zefi, F.; Ziegler, A.; Zorn,
J.; Żywucka, N.; H. E. S. S. Collaboration; Fender, R. P.; Broderick,
J. W.; Rowlinson, A.; Wijers, R. A. M. J.; Stewart, A. J.; ter Veen,
S.; Shulevski, A.; LOFAR Collaboration; Kavic, M.; Simonetti, J. H.;
League, C.; Tsai, J.; Obenberger, K. S.; Nathaniel, K.; Taylor,
G. B.; Dowell, J. D.; Liebling, S. L.; Estes, J. A.; Lippert, M.;
Sharma, I.; Vincent, P.; Farella, B.; Wavelength Array, LWA: Long;
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Arteaga-Velázquez, J. C.; Avila Rojas, D.; Ayala Solares, H. A.;
Barber, A. S.; Becerra Gonzalez, J.; Becerril, A.; Belmont-Moreno,
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S.; Castillo, M.; Cotti, U.; Cotzomi, J.; Coutiño de León, S.;
De León, C.; De la Fuente, E.; Diaz Hernandez, R.; Dichiara, S.;
Dingus, B. L.; DuVernois, M. A.; Díaz-Vélez, J. C.; Ellsworth,
R. W.; Engel, K.; Enríquez-Rivera, O.; Fiorino, D. W.; Fleischhack,
H.; Fraija, N.; García-González, J. A.; Garfias, F.; Gerhardt, M.;
Gonzõlez Muñoz, A.; González, M. M.; Goodman, J. A.; Hampel-Arias,
Z.; Harding, J. P.; Hernandez, S.; Hernandez-Almada, A.; Hona, B.;
Hüntemeyer, P.; Iriarte, A.; Jardin-Blicq, A.; Joshi, V.; Kaufmann,
S.; Kieda, D.; Lara, A.; Lauer, R. J.; Lennarz, D.; León Vargas, H.;
Linnemann, J. T.; Longinotti, A. L.; Raya, G. Luis; Luna-García,
R.; López-Coto, R.; Malone, K.; Marinelli, S. S.; Martinez, O.;
Martinez-Castellanos, I.; Martínez-Castro, J.; Martínez-Huerta, H.;
Matthews, J. A.; Miranda-Romagnoli, P.; Moreno, E.; Mostafá, M.;
Nellen, L.; Newbold, M.; Nisa, M. U.; Noriega-Papaqui, R.; Pelayo,
R.; Pretz, J.; Pérez-Pérez, E. G.; Ren, Z.; Rho, C. D.; Rivière,
C.; Rosa-González, D.; Rosenberg, M.; Ruiz-Velasco, E.; Salazar,
H.; Salesa Greus, F.; Sandoval, A.; Schneider, M.; Schoorlemmer, H.;
Sinnis, G.; Smith, A. J.; Springer, R. W.; Surajbali, P.; Tibolla, O.;
Tollefson, K.; Torres, I.; Ukwatta, T. N.; Weisgarber, T.; Westerhoff,
S.; Wisher, I. G.; Wood, J.; Yapici, T.; Yodh, G. B.; Younk, P. W.;
Zhou, H.; Álvarez, J. D.; HAWC Collaboration; Aab, A.; Abreu,
P.; Aglietta, M.; Albuquerque, I. F. M.; Albury, J. M.; Allekotte,
I.; Almela, A.; Alvarez Castillo, J.; Alvarez-Muñiz, J.; Anastasi,
G. A.; Anchordoqui, L.; Andrada, B.; Andringa, S.; Aramo, C.; Arsene,
N.; Asorey, H.; Assis, P.; Avila, G.; Badescu, A. M.; Balaceanu, A.;
Barbato, F.; Barreira Luz, R. J.; Becker, K. H.; Bellido, J. A.; Berat,
C.; Bertaina, M. E.; Bertou, X.; Biermann, P. L.; Biteau, J.; Blaess,
S. G.; Blanco, A.; Blazek, J.; Bleve, C.; Boháčová, M.; Bonifazi,
C.; Borodai, N.; Botti, A. M.; Brack, J.; Brancus, I.; Bretz, T.;
Bridgeman, A.; Briechle, F. L.; Buchholz, P.; Bueno, A.; Buitink,
S.; Buscemi, M.; Caballero-Mora, K. S.; Caccianiga, L.; Cancio,
A.; Canfora, F.; Caruso, R.; Castellina, A.; Catalani, F.; Cataldi,
G.; Cazon, L.; Chavez, A. G.; Chinellato, J. A.; Chudoba, J.; Clay,
R. W.; Cobos Cerutti, A. C.; Colalillo, R.; Coleman, A.; Collica,
L.; Coluccia, M. R.; Conceição, R.; Consolati, G.; Contreras, F.;
Cooper, M. J.; Coutu, S.; Covault, C. E.; Cronin, J.; D'Amico, S.;
Daniel, B.; Dasso, S.; Daumiller, K.; Dawson, B. R.; Day, J. A.; de
Almeida, R. M.; de Jong, S. J.; De Mauro, G.; de Mello Neto, J. R. T.;
De Mitri, I.; de Oliveira, J.; de Souza, V.; Debatin, J.; Deligny,
O.; Díaz Castro, M. L.; Diogo, F.; Dobrigkeit, C.; D'Olivo, J. C.;
Dorosti, Q.; Dos Anjos, R. C.; Dova, M. T.; Dundovic, A.; Ebr, J.;
Engel, R.; Erdmann, M.; Erfani, M.; Escobar, C. O.; Espadanal, J.;
Etchegoyen, A.; Falcke, H.; Farmer, J.; Farrar, G.; Fauth, A. C.;
Fazzini, N.; Feldbusch, F.; Fenu, F.; Fick, B.; Figueira, J. M.;
Filipčič, A.; Freire, M. M.; Fujii, T.; Fuster, A.; Gaïor, R.;
García, B.; Gaté, F.; Gemmeke, H.; Gherghel-Lascu, A.; Ghia, P. L.;
Giaccari, U.; Giammarchi, M.; Giller, M.; Głas, D.; Glaser, C.; Golup,
G.; Gómez Berisso, M.; Gómez Vitale, P. F.; González, N.; Gorgi,
A.; Gottowik, M.; Grillo, A. F.; Grubb, T. D.; Guarino, F.; Guedes,
G. P.; Halliday, R.; Hampel, M. R.; Hansen, P.; Harari, D.; Harrison,
T. A.; Harvey, V. M.; Haungs, A.; Hebbeker, T.; Heck, D.; Heimann,
P.; Herve, A. E.; Hill, G. C.; Hojvat, C.; Holt, E.; Homola, P.;
Hörandel, J. R.; Horvath, P.; Hrabovský, M.; Huege, T.; Hulsman, J.;
Insolia, A.; Isar, P. G.; Jandt, I.; Johnsen, J. A.; Josebachuili,
M.; Jurysek, J.; Kääpä, A.; Kampert, K. H.; Keilhauer,
B.; Kemmerich, N.; Kemp, J.; Kieckhafer, R. M.; Klages, H. O.;
Kleifges, M.; Kleinfeller, J.; Krause, R.; Krohm, N.; Kuempel, D.;
Kukec Mezek, G.; Kunka, N.; Kuotb Awad, A.; Lago, B. L.; LaHurd,
D.; Lang, R. G.; Lauscher, M.; Legumina, R.; Leigui de Oliveira,
M. A.; Letessier-Selvon, A.; Lhenry-Yvon, I.; Link, K.; Lo Presti,
D.; Lopes, L.; López, R.; López Casado, A.; Lorek, R.; Luce, Q.;
Lucero, A.; Malacari, M.; Mallamaci, M.; Mandat, D.; Mantsch, P.;
Mariazzi, A. G.; Maris, I. C.; Marsella, G.; Martello, D.; Martinez,
H.; Martínez Bravo, O.; Masías Meza, J. J.; Mathes, H. J.; Mathys,
S.; Matthews, J.; Matthiae, G.; Mayotte, E.; Mazur, P. O.; Medina, C.;
Medina-Tanco, G.; Melo, D.; Menshikov, A.; Merenda, K. -D.; Michal,
S.; Micheletti, M. I.; Middendorf, L.; Miramonti, L.; Mitrica, B.;
Mockler, D.; Mollerach, S.; Montanet, F.; Morello, C.; Morlino,
G.; Müller, A. L.; Müller, G.; Muller, M. A.; Müller, S.; Mussa,
R.; Naranjo, I.; Nguyen, P. H.; Niculescu-Oglinzanu, M.; Niechciol,
M.; Niemietz, L.; Niggemann, T.; Nitz, D.; Nosek, D.; Novotny, V.;
Nožka, L.; Núñez, L. A.; Oikonomou, F.; Olinto, A.; Palatka,
M.; Pallotta, J.; Papenbreer, P.; Parente, G.; Parra, A.; Paul, T.;
Pech, M.; Pedreira, F.; Pȩkala, J.; Peña-Rodriguez, J.; Pereira,
L. A. S.; Perlin, M.; Perrone, L.; Peters, C.; Petrera, S.; Phuntsok,
J.; Pierog, T.; Pimenta, M.; Pirronello, V.; Platino, M.; Plum, M.;
Poh, J.; Porowski, C.; Prado, R. R.; Privitera, P.; Prouza, M.; Quel,
E. J.; Querchfeld, S.; Quinn, S.; Ramos-Pollan, R.; Rautenberg, J.;
Ravignani, D.; Ridky, J.; Riehn, F.; Risse, M.; Ristori, P.; Rizi, V.;
Rodrigues de Carvalho, W.; Rodriguez Fernandez, G.; Rodriguez Rojo,
J.; Roncoroni, M. J.; Roth, M.; Roulet, E.; Rovero, A. C.; Ruehl,
P.; Saffi, S. J.; Saftoiu, A.; Salamida, F.; Salazar, H.; Saleh, A.;
Salina, G.; Sánchez, F.; Sanchez-Lucas, P.; Santos, E. M.; Santos,
E.; Sarazin, F.; Sarmento, R.; Sarmiento-Cano, C.; Sato, R.; Schauer,
M.; Scherini, V.; Schieler, H.; Schimp, M.; Schmidt, D.; Scholten,
O.; Schovánek, P.; Schröder, F. G.; Schröder, S.; Schulz, A.;
Schumacher, J.; Sciutto, S. J.; Segreto, A.; Shadkam, A.; Shellard,
R. C.; Sigl, G.; Silli, G.; Šmída, R.; Snow, G. R.; Sommers, P.;
Sonntag, S.; Soriano, J. F.; Squartini, R.; Stanca, D.; Stanič, S.;
Stasielak, J.; Stassi, P.; Stolpovskiy, M.; Strafella, F.; Streich,
A.; Suarez, F.; Suarez-Durán, M.; Sudholz, T.; Suomijärvi, T.;
Supanitsky, A. D.; Šupík, J.; Swain, J.; Szadkowski, Z.; Taboada, A.;
Taborda, O. A.; Timmermans, C.; Todero Peixoto, C. J.; Tomankova, L.;
Tomé, B.; Torralba Elipe, G.; Travnicek, P.; Trini, M.; Tueros, M.;
Ulrich, R.; Unger, M.; Urban, M.; Valdés Galicia, J. F.; Valiño,
I.; Valore, L.; van Aar, G.; van Bodegom, P.; van den Berg, A. M.;
van Vliet, A.; Varela, E.; Vargas Cárdenas, B.; Vázquez, R. A.;
Veberič, D.; Ventura, C.; Vergara Quispe, I. D.; Verzi, V.; Vicha,
J.; Villaseñor, L.; Vorobiov, S.; Wahlberg, H.; Wainberg, O.;
Walz, D.; Watson, A. A.; Weber, M.; Weindl, A.; Wiedeński, M.;
Wiencke, L.; Wilczyński, H.; Wirtz, M.; Wittkowski, D.; Wundheiler,
B.; Yang, L.; Yushkov, A.; Zas, E.; Zavrtanik, D.; Zavrtanik, M.;
Zepeda, A.; Zimmermann, B.; Ziolkowski, M.; Zong, Z.; Zuccarello,
F.; Pierre Auger Collaboration; Kim, S.; Schulze, S.; Bauer, F. E.;
Corral-Santana, J. M.; de Gregorio-Monsalvo, I.; González-López,
J.; Hartmann, D. H.; Ishwara-Chandra, C. H.; Martín, S.; Mehner,
A.; Misra, K.; Michałowski, M. J.; Resmi, L.; ALMA Collaboration;
Paragi, Z.; Agudo, I.; An, T.; Beswick, R.; Casadio, C.; Frey, S.;
Jonker, P.; Kettenis, M.; Marcote, B.; Moldon, J.; Szomoru, A.;
van Langevelde, H. J.; Yang, J.; Euro VLBI Team; Cwiek, A.; Cwiok,
M.; Czyrkowski, H.; Dabrowski, R.; Kasprowicz, G.; Mankiewicz, L.;
Nawrocki, K.; Opiela, R.; Piotrowski, L. W.; Wrochna, G.; Zaremba,
M.; Żarnecki, A. F.; Pi of Sky Collaboration; Haggard, D.; Nynka,
M.; Ruan, J. J.; Chandra Team at McGill University; Bland, P. A.;
Booler, T.; Devillepoix, H. A. R.; de Gois, J. S.; Hancock, P. J.;
Howie, R. M.; Paxman, J.; Sansom, E. K.; Towner, M. C.; Desert
Fireball Network, DFN:; Tonry, J.; Coughlin, M.; Stubbs, C. W.;
Denneau, L.; Heinze, A.; Stalder, B.; Weiland, H.; ATLAS; Eatough,
R. P.; Kramer, M.; Kraus, A.; Time Resolution Universe Survey, High;
Troja, E.; Piro, L.; Becerra González, J.; Butler, N. R.; Fox, O. D.;
Khandrika, H. G.; Kutyrev, A.; Lee, W. H.; Ricci, R.; Ryan, R. E.,
Jr.; Sánchez-Ramírez, R.; Veilleux, S.; Watson, A. M.; Wieringa,
M. H.; Burgess, J. M.; van Eerten, H.; Fontes, C. J.; Fryer, C. L.;
Korobkin, O.; Wollaeger, R. T.; RIMAS; RATIR; Camilo, F.; Foley,
A. R.; Goedhart, S.; Makhathini, S.; Oozeer, N.; Smirnov, O. M.;
Fender, R. P.; Woudt, P. A.; South Africa/MeerKAT, SKA
2017ApJ...848L..12A Altcode: 2017arXiv171005833L
On 2017 August 17 a binary neutron star coalescence candidate (later
designated GW170817) with merger time 12:41:04 UTC was observed
through gravitational waves by the Advanced LIGO and Advanced Virgo
detectors. The Fermi Gamma-ray Burst Monitor independently detected a
gamma-ray burst (GRB 170817A) with a time delay of ∼ 1.7 {{s}} with
respect to the merger time. From the gravitational-wave signal, the
source was initially localized to a sky region of 31 deg<SUP>2</SUP>
at a luminosity distance of {40}<SUB>-8</SUB><SUP>+8</SUP> Mpc and
with component masses consistent with neutron stars. The component
masses were later measured to be in the range 0.86 to 2.26 {M}<SUB>⊙
</SUB>. An extensive observing campaign was launched across the
electromagnetic spectrum leading to the discovery of a bright optical
transient (SSS17a, now with the IAU identification of AT 2017gfo) in
NGC 4993 (at ∼ 40 {{Mpc}}) less than 11 hours after the merger by the
One-Meter, Two Hemisphere (1M2H) team using the 1 m Swope Telescope. The
optical transient was independently detected by multiple teams
within an hour. Subsequent observations targeted the object and its
environment. Early ultraviolet observations revealed a blue transient
that faded within 48 hours. Optical and infrared observations showed
a redward evolution over ∼10 days. Following early non-detections,
X-ray and radio emission were discovered at the transient's position ∼
9 and ∼ 16 days, respectively, after the merger. Both the X-ray and
radio emission likely arise from a physical process that is distinct
from the one that generates the UV/optical/near-infrared emission. No
ultra-high-energy gamma-rays and no neutrino candidates consistent with
the source were found in follow-up searches. These observations support
the hypothesis that GW170817 was produced by the merger of two neutron
stars in NGC 4993 followed by a short gamma-ray burst (GRB 170817A)
and a kilonova/macronova powered by the radioactive decay of r-process
nuclei synthesized in the ejecta. <P />Any correspondence should be
addressed to .
---------------------------------------------------------
Title: A Solar cycle correlation of coronal element abundances in
Sun-as-a-star observations
Authors: Brooks, David H.; Baker, Deborah; van Driel-Gesztelyi, Lidia;
Warren, Harry P.
2017NatCo...8..183B Altcode: 2018arXiv180200563B
The elemental composition in the coronae of low-activity solar-like
stars appears to be related to fundamental stellar properties such as
rotation, surface gravity, and spectral type. Here we use full-Sun
observations from the Solar Dynamics Observatory, to show that when
the Sun is observed as a star, the variation of coronal composition
is highly correlated with a proxy for solar activity, the F10.7 cm
radio flux, and therefore with the solar cycle phase. Similar cyclic
variations should therefore be detectable spectroscopically in X-ray
observations of solar analogs. The plasma composition in full-disk
observations of the Sun is related to the evolution of coronal magnetic
field activity. Our observations therefore introduce an uncertainty
into the nature of any relationship between coronal composition and
fixed stellar properties. The results highlight the importance of
systematic full-cycle observations for understanding the elemental
composition of solar-like stellar coronae.
---------------------------------------------------------
Title: On-Disc Observations of Flux Rope Formation Prior to Its
Eruption
Authors: James, A. W.; Green, L. M.; Palmerio, E.; Valori, G.; Reid,
H. A. S.; Baker, D.; Brooks, D. H.; van Driel-Gesztelyi, L.; Kilpua,
E. K. J.
2017SoPh..292...71J Altcode: 2017arXiv170310837J
Coronal mass ejections (CMEs) are one of the primary manifestations of
solar activity and can drive severe space weather effects. Therefore,
it is vital to work towards being able to predict their
occurrence. However, many aspects of CME formation and eruption
remain unclear, including whether magnetic flux ropes are present
before the onset of eruption and the key mechanisms that cause CMEs
to occur. In this work, the pre-eruptive coronal configuration of
an active region that produced an interplanetary CME with a clear
magnetic flux rope structure at 1 AU is studied. A forward-S sigmoid
appears in extreme-ultraviolet (EUV) data two hours before the onset
of the eruption (SOL2012-06-14), which is interpreted as a signature
of a right-handed flux rope that formed prior to the eruption. Flare
ribbons and EUV dimmings are used to infer the locations of the flux
rope footpoints. These locations, together with observations of the
global magnetic flux distribution, indicate that an interaction between
newly emerged magnetic flux and pre-existing sunspot field in the days
prior to the eruption may have enabled the coronal flux rope to form
via tether-cutting-like reconnection. Composition analysis suggests
that the flux rope had a coronal plasma composition, supporting our
interpretation that the flux rope formed via magnetic reconnection in
the corona. Once formed, the flux rope remained stable for two hours
before erupting as a CME.
---------------------------------------------------------
Title: IRIS, Hinode, SDO, and RHESSI Observations of a White Light
Flare Produced Directly by Nonthermal Electrons
Authors: Lee, Kyoung-Sun; Imada, Shinsuke; Watanabe, Kyoko; Bamba,
Yumi; Brooks, David H.
2017ApJ...836..150L Altcode: 2017arXiv170106286L
An X1.6 flare occurred in active region AR 12192 on 2014 October 22
at 14:02 UT and was observed by Hinode, IRIS, SDO, and RHESSI. We
analyze a bright kernel that produces a white light (WL) flare with
continuum enhancement and a hard X-ray (HXR) peak. Taking advantage
of the spectroscopic observations of IRIS and Hinode/EIS, we measure
the temporal variation of the plasma properties in the bright kernel
in the chromosphere and corona. We find that explosive evaporation
was observed when the WL emission occurred, even though the intensity
enhancement in hotter lines is quite weak. The temporal correlation of
the WL emission, HXR peak, and evaporation flows indicates that the WL
emission was produced by accelerated electrons. To understand the WL
emission process, we calculated the energy flux deposited by non-thermal
electrons (observed by RHESSI) and compared it to the dissipated
energy estimated from a chromospheric line (Mg II triplet) observed
by IRIS. The deposited energy flux from the non-thermal electrons is
about (3-7.7) × 10<SUP>10</SUP> erg cm<SUP>-2</SUP> s<SUP>-1</SUP>
for a given low-energy cutoff of 30-40 keV, assuming the thick-target
model. The energy flux estimated from the changes in temperature in
the chromosphere measured using the Mg II subordinate line is about
(4.6-6.7) × 10<SUP>9</SUP> erg cm<SUP>-2</SUP> s<SUP>-1</SUP>:
∼6%-22% of the deposited energy. This comparison of estimated energy
fluxes implies that the continuum enhancement was directly produced
by the non-thermal electrons.
---------------------------------------------------------
Title: Properties and Modeling of Unresolved Fine Structure Loops
Observed in the Solar Transition Region by IRIS
Authors: Brooks, David H.; Reep, Jeffrey W.; Warren, Harry P.
2016ApJ...826L..18B Altcode: 2016arXiv160605440B
Recent observations from the Interface Region Imaging Spectrograph
(IRIS) have discovered a new class of numerous low-lying dynamic loop
structures, and it has been argued that they are the long-postulated
unresolved fine structures (UFSs) that dominate the emission of the
solar transition region. In this letter, we combine IRIS measurements
of the properties of a sample of 108 UFSs (intensities, lengths, widths,
lifetimes) with one-dimensional non-equilibrium ionization simulations,
using the HYDRAD hydrodynamic model to examine whether the UFSs are now
truly spatially resolved in the sense of being individual structures
rather than being composed of multiple magnetic threads. We find that
a simulation of an impulsively heated single strand can reproduce most
of the observed properties, suggesting that the UFSs may be resolved,
and the distribution of UFS widths implies that they are structured on
a spatial scale of 133 km on average. Spatial scales of a few hundred
kilometers appear to be typical for a range of chromospheric and
coronal structures, and we conjecture that this could be an important
clue for understanding the coronal heating process.
---------------------------------------------------------
Title: Transition Region Abundance Measurements During Impulsive
Heating Events
Authors: Warren, Harry P.; Brooks, David H.; Doschek, George A.;
Feldman, Uri
2016ApJ...824...56W Altcode: 2015arXiv151204447W
It is well established that elemental abundances vary in the solar
atmosphere and that this variation is organized by first ionization
potential (FIP). Previous studies have shown that in the solar corona,
low-FIP elements such as Fe, Si, Mg, and Ca, are generally enriched
relative to high-FIP elements such as C, N, O, Ar, and Ne. In this paper
we report on measurements of plasma composition made during impulsive
heating events observed at transition region temperatures with the
Extreme Ultraviolet Imaging Spectrometer (EIS) on Hinode. During these
events the intensities of O IV, v, and VI emission lines are enhanced
relative to emission lines from Mg v, VI, and vii and Si VI and vii,
and indicate a composition close to that of the photosphere. Long-lived
coronal fan structures, in contrast, show an enrichment of low-FIP
elements. We conjecture that the plasma composition is an important
signature of the coronal heating process, with impulsive heating leading
to the evaporation of unfractionated material from the lower layers of
the solar atmosphere and higher-frequency heating leading to long-lived
structures and the accumulation of low-FIP elements in the corona.
---------------------------------------------------------
Title: Measurements of Non-thermal Line Widths in Solar Active Regions
Authors: Brooks, David H.; Warren, Harry P.
2016ApJ...820...63B Altcode: 2015arXiv151102313B
Spectral line widths are often observed to be larger than can be
accounted for by thermal and instrumental broadening alone. This excess
broadening is a key observational constraint for both nanoflare and
wave dissipation models of coronal heating. Here we present a survey
of non-thermal velocities measured in the high temperature loops (1-4
MK) often found in the cores of solar active regions. This survey of
Hinode Extreme Ultraviolet Imaging Spectrometer (EIS) observations
covers 15 non-flaring active regions that span a wide range of solar
conditions. We find relatively small non-thermal velocities, with a
mean value of 17.6 ± 5.3 km s<SUP>-1</SUP>, and no significant trend
with temperature or active region magnetic flux. These measurements
appear to be inconsistent with those expected from reconnection jets in
the corona, chromospheric evaporation induced by coronal nanoflares,
and Alfvén wave turbulence models. Furthermore, because the observed
non-thermal widths are generally small, such measurements are difficult
and susceptible to systematic effects.
---------------------------------------------------------
Title: A Comparison of Global Magnetic Field Skeletons and
Active-Region Upflows
Authors: Edwards, S. J.; Parnell, C. E.; Harra, L. K.; Culhane, J. L.;
Brooks, D. H.
2016SoPh..291..117E Altcode: 2015SoPh..tmp..161E
Plasma upflows have been detected in active regions using Doppler
velocity maps. The origin and nature of these upflows is not well known
with many of their characteristics determined from the examination
of single events. In particular, some studies suggest these upflows
occur along open field lines and, hence, are linked to sources of
the solar wind. To investigate the relationship these upflows may
have with the solar wind, and to probe what may be driving them, this
paper considers seven active regions observed on the solar disc using
the Extreme ultraviolet Imaging Spectrometer aboard Hinode between
August 2011 and September 2012. Plasma upflows are observed in all
these active regions. The locations of these upflows are compared
to the global potential magnetic field extrapolated from the Solar
Dynamics Observatory, Helioseismic and Magnetic Imager daily synoptic
magnetogram taken on the day the upflows were observed. The structure
of the magnetic field is determined by constructing its magnetic
skeleton in order to help identify open-field regions and also sites
where magnetic reconnection at global features is likely to occur. As
a further comparison, measurements of the temperature, density and
composition of the plasma are taken from regions with active-region
upflows. In most cases the locations of the upflows in the active
regions do not correspond to areas of open field, as predicted by
a global coronal potential-field model, and therefore these upflows
are not always sources of the slow solar wind. The locations of the
upflows are, in general, intersected by separatrix surfaces associated
with null points located high in the corona; these could be important
sites of reconnection with global consequences.
---------------------------------------------------------
Title: Photospheric Abundances of Polar Jets on the Sun Observed
by Hinode
Authors: Lee, Kyoung-Sun; Brooks, David H.; Imada, Shinsuke
2015ApJ...809..114L Altcode: 2015arXiv150704075L
Many jets are detected at X-ray wavelengths in the Sun's polar
regions, and the ejected plasma along the jets has been suggested to
contribute mass to the fast solar wind. From in situ measurements
in the magnetosphere, it has been found that the fast solar wind
has photospheric abundances while the slow solar wind has coronal
abundances. Therefore, we investigated the abundances of polar jets
to determine whether they are the same as that of the fast solar
wind. For this study, we selected 22 jets in the polar region observed
by Hinode/EUV Imaging Spectroscopy (EIS) and X-ray Telescope (XRT)
simultaneously on 2007 November 1-3. We calculated the First Ionization
Potential (FIP) bias factor from the ratio of the intensity between high
(S) and low (Si, Fe) FIP elements using the EIS spectra. The values of
the FIP bias factors for the polar jets are around 0.7-1.9, and 75% of
the values are in the range of 0.7-1.5, which indicates that they have
photospheric abundances similar to the fast solar wind. The results
are consistent with the reconnection jet model where photospheric
plasma emerges and is rapidly ejected into the fast wind.
---------------------------------------------------------
Title: FIP Bias Evolution in a Decaying Active Region
Authors: Baker, D.; Brooks, D. H.; Démoulin, P.; Yardley, S. L.;
van Driel-Gesztelyi, L.; Long, D. M.; Green, L. M.
2015ApJ...802..104B Altcode: 2015arXiv150107397B
Solar coronal plasma composition is typically characterized by
first ionization potential (FIP) bias. Using spectra obtained by
Hinode’s EUV Imaging Spectrometer instrument, we present a series
of large-scale, spatially resolved composition maps of active region
(AR)11389. The composition maps show how FIP bias evolves within the
decaying AR during the period 2012 January 4-6. Globally, FIP bias
decreases throughout the AR. We analyzed areas of significant plasma
composition changes within the decaying AR and found that small-scale
evolution in the photospheric magnetic field is closely linked to the
FIP bias evolution observed in the corona. During the AR’s decay
phase, small bipoles emerging within supergranular cells reconnect
with the pre-existing AR field, creating a pathway along which
photospheric and coronal plasmas can mix. The mixing timescales are
shorter than those of plasma enrichment processes. Eruptive activity
also results in shifting the FIP bias closer to photospheric in the
affected areas. Finally, the FIP bias still remains dominantly coronal
only in a part of the AR’s high-flux density core. We conclude that
in the decay phase of an AR’s lifetime, the FIP bias is becoming
increasingly modulated by episodes of small-scale flux emergence,
i.e., decreasing the AR’s overall FIP bias. Our results show that
magnetic field evolution plays an important role in compositional
changes during AR development, revealing a more complex relationship
than expected from previous well-known Skylab results showing that
FIP bias increases almost linearly with age in young ARs.
---------------------------------------------------------
Title: Full-Sun observations for identifying the source of the slow
solar wind
Authors: Brooks, David H.; Ugarte-Urra, Ignacio; Warren, Harry P.
2015NatCo...6.5947B Altcode: 2016arXiv160509514B; 2015NatCo...6E5947B
Fast (>700 km s<SUP>-1</SUP>) and slow
(~400 km s<SUP>-1</SUP>) winds stream from the Sun, permeate
the heliosphere and influence the near-Earth environment. While the
fast wind is known to emanate primarily from polar coronal holes,
the source of the slow wind remains unknown. Here we identify possible
sites of origin using a slow solar wind source map of the entire Sun,
which we construct from specially designed, full-disk observations
from the Hinode satellite, and a magnetic field model. Our map
provides a full-Sun observation that combines three key ingredients
for identifying the sources: velocity, plasma composition and magnetic
topology and shows them as solar wind composition plasma outflowing on
open magnetic field lines. The area coverage of the identified sources
is large enough that the sum of their mass contributions can explain
a significant fraction of the mass loss rate of the solar wind.
---------------------------------------------------------
Title: Constraining hot plasma in a non-flaring solar active region
with FOXSI hard X-ray observations
Authors: Ishikawa, Shin-nosuke; Glesener, Lindsay; Christe, Steven;
Ishibashi, Kazunori; Brooks, David H.; Williams, David R.; Shimojo,
Masumi; Sako, Nobuharu; Krucker, Säm
2014PASJ...66S..15I Altcode: 2015arXiv150905288I; 2014PASJ..tmp..102I
We present new constraints on the high-temperature emission measure
of a non-flaring solar active region using observations from the
recently flown Focusing Optics X-ray Solar Imager (FOXSI) sounding
rocket payload. FOXSI has performed the first focused hard X-ray
(HXR) observation of the Sun in its first successful flight on 2012
November 2. Focusing optics, combined with small strip detectors,
enable high-sensitivity observations with respect to previous
indirect imagers. This capability, along with the sensitivity of
the HXR regime to high-temperature emission, offers the potential
to better characterize high-temperature plasma in the corona as
predicted by nanoflare heating models. We present a joint analysis of
the differential emission measure (DEM) of active region 11602 using
coordinated observations by FOXSI, Hinode/XRT, and Hinode/EIS. The
Hinode-derived DEM predicts significant emission measure between
1 MK and 3 MK, with a peak in the DEM predicted at 2.0-2.5 MK. The
combined XRT and EIS DEM also shows emission from a smaller population
of plasma above 8 MK. This is contradicted by FOXSI observations that
significantly constrain emission above 8 MK. This suggests that the
Hinode DEM analysis has larger uncertainties at higher temperatures and
that > 8 MK plasma above an emission measure of 3 × 10<SUP>44</SUP>
cm<SUP>-3</SUP> is excluded in this active region.
---------------------------------------------------------
Title: Hot Topic, Warm Loops, Cooling Plasma? Multithermal Analysis
of Active Region Loops
Authors: Schmelz, J. T.; Pathak, S.; Brooks, D. H.; Christian, G. M.;
Dhaliwal, R. S.
2014ApJ...795..171S Altcode:
We have found indications of a relationship between the differential
emission measure (DEM) weighted temperature and the cross-field DEM
width for coronal loops. The data come from the Hinode X-ray Telescope,
the Hinode EUV Imaging Spectrometer, and the Solar Dynamics Observatory
Atmospheric Imaging Assembly. These data show that cooler loops tend to
have narrower DEM widths. If most loops observed by these instruments
are composed of bundles of unresolved magnetic strands and are only
observed in their cooling phase, as some studies have suggested,
then this relationship implies that the DEM of a coronal loop narrows
as it cools. This could imply that fewer strands are seen emitting
in the later cooling phase, potentially resolving the long standing
controversy of whether the cross-field temperatures of coronal loops
are multithermal or isothermal.
---------------------------------------------------------
Title: Tracking Solar Active Region Outflow Plasma from Its Source
to the Near-Earth Environment
Authors: Culhane, J. L.; Brooks, D. H.; van Driel-Gesztelyi, L.;
Démoulin, P.; Baker, D.; DeRosa, M. L.; Mandrini, C. H.; Zhao, L.;
Zurbuchen, T. H.
2014SoPh..289.3799C Altcode: 2014SoPh..tmp...90C; 2014arXiv1405.2949C
Seeking to establish whether active-region upflow material contributes
to the slow solar wind, we examine in detail the plasma upflows from
Active Region (AR) 10978, which crossed the Sun's disc in the interval 8
to 16 December 2007 during Carrington rotation (CR) 2064. In previous
work, using data from the Hinode/EUV Imaging Spectrometer, upflow
velocity evolution was extensively studied as the region crossed the
disc, while a linear force-free-field magnetic extrapolation was used
to confirm aspects of the velocity evolution and to establish the
presence of quasi-separatrix layers at the upflow source areas. The
plasma properties, temperature, density, and first ionisation potential
bias [FIP-bias] were measured with the spectrometer during the disc
passage of the active region. Global potential-field source-surface
(PFSS) models showed that AR 10978 was completely covered by the
closed field of a helmet streamer that is part of the streamer
belt. Therefore it is not clear how any of the upflowing AR-associated
plasma could reach the source surface at 2.5 R<SUB>⊙</SUB> and
contribute to the slow solar wind. However, a detailed examination of
solar-wind in-situ data obtained by the Advanced Composition Explorer
(ACE) spacecraft at the L<SUB>1</SUB> point shows that increases in
O<SUP>7+</SUP>/O<SUP>6+</SUP>, C<SUP>6+</SUP>/C<SUP>5+</SUP>, and Fe/O -
a FIP-bias proxy - are present before the heliospheric current-sheet
crossing. These increases, along with an accompanying reduction in
proton velocity and an increase in density are characteristic of
both AR and slow-solar-wind plasma. Finally, we describe a two-step
reconnection process by which some of the upflowing plasma from the
AR might reach the heliosphere.
---------------------------------------------------------
Title: FIP bias in a sigmoidal active region
Authors: Baker, D.; Brooks, D. H.; Démoulin, P.; van Driel-Gesztelyi,
Lidia; Green, L. M.; Steed, K.; Carlyle, J.
2014IAUS..300..222B Altcode:
We investigate first ionization potential (FIP) bias levels in
an anemone active region (AR) - coronal hole (CH) complex using an
abundance map derived from Hinode/EIS spectra. The detailed, spatially
resolved abundance map has a large field of view covering 359” ×
485”. Plasma with high FIP bias, or coronal abundances, is concentrated
at the footpoints of the AR loops whereas the surrounding CH has a low
FIP bias, ~1, i.e. photospheric abundances. A channel of low FIP bias
is located along the AR's main polarity inversion line containing a
filament where ongoing flux cancellation is observed, indicating a
bald patch magnetic topology characteristic of a sigmoid/flux rope
configuration.
---------------------------------------------------------
Title: Plasma Composition in a Sigmoidal Anemone Active Region
Authors: Baker, D.; Brooks, D. H.; Démoulin, P.; van Driel-Gesztelyi,
L.; Green, L. M.; Steed, K.; Carlyle, J.
2013ApJ...778...69B Altcode: 2013arXiv1310.0999B
Using spectra obtained by the EUV Imaging Spectrometer (EIS) instrument
onboard Hinode, we present a detailed spatially resolved abundance map
of an active region (AR)-coronal hole (CH) complex that covers an area
of 359” × 485”. The abundance map provides first ionization potential
(FIP) bias levels in various coronal structures within the large EIS
field of view. Overall, FIP bias in the small, relatively young AR
is 2-3. This modest FIP bias is a consequence of the age of the AR,
its weak heating, and its partial reconnection with the surrounding
CH. Plasma with a coronal composition is concentrated at AR loop
footpoints, close to where fractionation is believed to take place in
the chromosphere. In the AR, we found a moderate positive correlation
of FIP bias with nonthermal velocity and magnetic flux density, both
of which are also strongest at the AR loop footpoints. Pathways of
slightly enhanced FIP bias are traced along some of the loops connecting
opposite polarities within the AR. We interpret the traces of enhanced
FIP bias along these loops to be the beginning of fractionated plasma
mixing in the loops. Low FIP bias in a sigmoidal channel above the
AR's main polarity inversion line, where ongoing flux cancellation is
taking place, provides new evidence of a bald patch magnetic topology
of a sigmoid/flux rope configuration.
---------------------------------------------------------
Title: High Spatial Resolution Observations of Loops in the Solar
Corona
Authors: Brooks, David H.; Warren, Harry P.; Ugarte-Urra, Ignacio;
Winebarger, Amy R.
2013ApJ...772L..19B Altcode: 2013arXiv1305.2246B
Understanding how the solar corona is structured is of fundamental
importance to determine how the Sun's upper atmosphere is heated to
high temperatures. Recent spectroscopic studies have suggested that an
instrument with a spatial resolution of 200 km or better is necessary
to resolve coronal loops. The High Resolution Coronal Imager (Hi-C)
achieved this performance on a rocket flight in 2012 July. We use Hi-C
data to measure the Gaussian widths of 91 loops observed in the solar
corona and find a distribution that peaks at about 270 km. We also
use Atmospheric Imaging Assembly data for a subset of these loops and
find temperature distributions that are generally very narrow. These
observations provide further evidence that loops in the solar corona
are often structured at a scale of several hundred kilometers, well
above the spatial scale of many proposed physical mechanisms.
---------------------------------------------------------
Title: Tracking Solar Active Region Outflow Plasma from its Source
to the near-Earth Environment
Authors: Culhane, J. L.; Brooks, D.; Zurbuchen, T.; van
Driel-Gesztelyi, L.; Fazakerley, A. N.; DeRosa, M. L.
2012AGUFMSH53A2255C Altcode:
In a recent study of persistent active region outflow from AR 10978 in
the period 10 - 15, December, 2007, Brooks and Warren (2011), using the
Hinode EUV Imaging Spectrometer (EIS) instrument showed the presence
of a strong low-FIP element enhancement in the outflowing plasma that
was replicated three days later in the in-situ solar wind measurements
made by the ACE/SWICS instrument. In the present work, we examine the
outflowing plasma properties (Te, Ne, v, abundances) as a function
of time in greater detail as AR 10978 passes the Earth-Sun line. The
structure of the magnetic field above the two outflow regions - E and
W of the AR, is also examined. Following an assessment of the relevant
magnetic structures between Sun and Earth, the properties of the solar
wind plasma arriving at ACE approximately three days later are measured
and compared with those of the outflowing AR plasma. The relationship
of these measurements to the in-situ magnetic field observed by the
ACE magnetometer is also studied. Finally the role of persistent AR
outflows in contributing to the slow solar wind is assessed.
---------------------------------------------------------
Title: Hinode/EIS measurements of Abundances in Solar Active Region
Outflows
Authors: Brooks, D.; Warren, H. P.
2012AGUFMSH52A..04B Altcode:
Peripheral outflows appear to be a common feature of active regions,
and may be a significant source of the slow speed solar wind. Spectral
line profiles from the Hinode EUV Imaging Spectrometer (EIS) show that
the bulk outflows reach speeds of ~50km/s with a much faster component
reaching hundreds of km/s. I will review recent measurements of the
elemental composition of the outflows obtained by EIS, with particular
attention paid to AR 10978 that was observed as it crossed the solar
disk in December 2007. EIS measurements show that the temperature
distribution of the outflows is dominated by coronal emission, and
that plasma with a slow wind-like composition flowed from the edge of
AR 10978 for at least five days. Furthermore, when the outflow from
the Western side was favorably oriented in the Earth direction, the
composition was found to match the value measured a few days later by
ACE/SWICS. The composition of the high speed component of the outflows
was also found to be similar to that of the slow speed wind, implying
that it may also be a contributor. Observations and models indicate
that it takes time for plasma to evolve to the enhanced composition
typical of the slow wind, suggesting that the material in the outflows
is trapped on closed loops before escaping, perhaps by interchange
reconnection. The results, therefore, also identify the high speed
component of the plasma as having a coronal origin. A significant
constraint on the mechanisms that drive the outflows.
---------------------------------------------------------
Title: Magnetic Topology of Active Regions and Coronal Holes:
Implications for Coronal Outflows and the Solar Wind
Authors: van Driel-Gesztelyi, L.; Culhane, J. L.; Baker, D.; Démoulin,
P.; Mandrini, C. H.; DeRosa, M. L.; Rouillard, A. P.; Opitz, A.;
Stenborg, G.; Vourlidas, A.; Brooks, D. H.
2012SoPh..281..237V Altcode: 2012SoPh..tmp..228V
During 2 - 18 January 2008 a pair of low-latitude opposite-polarity
coronal holes (CHs) were observed on the Sun with two active regions
(ARs) and the heliospheric plasma sheet located between them. We use
the Hinode/EUV Imaging Spectrometer (EIS) to locate AR-related outflows
and measure their velocities. Solar-Terrestrial Relations Observatory
(STEREO) imaging is also employed, as are the Advanced Composition
Explorer (ACE) in-situ observations, to assess the resulting impacts on
the solar wind (SW) properties. Magnetic-field extrapolations of the two
ARs confirm that AR plasma outflows observed with EIS are co-spatial
with quasi-separatrix layer locations, including the separatrix of a
null point. Global potential-field source-surface modeling indicates
that field lines in the vicinity of the null point extend up to the
source surface, enabling a part of the EIS plasma upflows access
to the SW. We find that similar upflow properties are also observed
within closed-field regions that do not reach the source surface. We
conclude that some of plasma upflows observed with EIS remain confined
along closed coronal loops, but that a fraction of the plasma may be
released into the slow SW. This suggests that ARs bordering coronal
holes can contribute to the slow SW. Analyzing the in-situ data, we
propose that the type of slow SW present depends on whether the AR is
fully or partially enclosed by an overlying streamer.
---------------------------------------------------------
Title: A Systematic Survey of High-temperature Emission in Solar
Active Regions
Authors: Warren, Harry P.; Winebarger, Amy R.; Brooks, David H.
2012ApJ...759..141W Altcode: 2012arXiv1204.3220W
The recent analysis of observations taken with the EUV Imaging
Spectrometer and X-Ray Telescope instruments on Hinode suggests that
well-constrained measurements of the temperature distribution in solar
active regions can finally be made. Such measurements are critical
for constraining theories of coronal heating. Past analysis, however,
has suffered from limited sample sizes and large uncertainties at
temperatures between 5 and 10 MK. Here we present a systematic study
of the differential emission measure distribution in 15 active region
cores. We focus on measurements in the "inter-moss" region, that is, the
region between the loop footpoints, where the observations are easier
to interpret. To reduce the uncertainties at the highest temperatures
we present a new method for isolating the Fe XVIII emission in the
AIA/SDO 94 Å channel. The resulting differential emission measure
distributions confirm our previous analysis showing that the temperature
distribution in an active region core is often strongly peaked near 4
MK. We characterize the properties of the emission distribution as a
function of the total unsigned magnetic flux. We find that the amount
of high-temperature emission in the active region core is correlated
with the total unsigned magnetic flux, while the emission at lower
temperatures, in contrast, is inversely related. These results provide
compelling evidence that high-temperature active region emission is
often close to equilibrium, although weaker active regions may be
dominated by evolving million degree loops in the core.
---------------------------------------------------------
Title: The Coronal Source of Extreme-ultraviolet Line Profile
Asymmetries in Solar Active Region Outflows
Authors: Brooks, David H.; Warren, Harry P.
2012ApJ...760L...5B Altcode: 2012arXiv1210.1274B
High-resolution spectra from the Hinode EUV Imaging Spectrometer have
revealed that coronal spectral line profiles are sometimes asymmetric,
with a faint enhancement in the blue wing on the order of 100 km
s<SUP>-1</SUP>. These asymmetries could be important since they may
be subtle yet diagnostically useful signatures of coronal heating or
solar wind acceleration processes. It has also been suggested that
they are signatures of chromospheric jets supplying mass and energy
to the corona. Until now, however, there have been no studies of the
physical properties of the plasma producing the asymmetries. Here we
identify regions of asymmetric profiles in the outflows of AR 10978
using an asymmetric Gaussian function and extract the intensities
of the faint component using multiple Gaussian fits. We then derive
the temperature structure and chemical composition of the plasma
producing the asymmetries. We find that the asymmetries are dependent
on temperature, and are clearer and stronger in coronal lines. The
temperature distribution peaks around 1.4-1.8 MK with an emission
measure at least an order of magnitude larger than that at 0.6
MK. The first ionization potential bias is found to be 3-5, implying
that the high-speed component of the outflows may also contribute to
the slow-speed wind. Observations and models indicate that it takes
time for plasma to evolve to a coronal composition, suggesting that
the material is trapped on closed loops before escaping, perhaps by
interchange reconnection. The results, therefore, identify the plasma
producing the asymmetries as having a coronal origin.
---------------------------------------------------------
Title: Solar Coronal Loops Resolved by Hinode and the Solar Dynamics
Observatory
Authors: Brooks, David H.; Warren, Harry P.; Ugarte-Urra, Ignacio
2012ApJ...755L..33B Altcode:
Despite decades of studying the Sun, the coronal heating problem remains
unsolved. One fundamental issue is that we do not know the spatial scale
of the coronal heating mechanism. At a spatial resolution of 1000 km or
more, it is likely that most observations represent superpositions of
multiple unresolved structures. In this Letter, we use a combination
of spectroscopic data from the Hinode EUV Imaging Spectrometer and
high-resolution images from the Atmospheric Imaging Assembly on the
Solar Dynamics Observatory to determine the spatial scales of coronal
loops. We use density measurements to construct multi-thread models of
the observed loops and confirm these models using the higher spatial
resolution imaging data. The results allow us to set constraints on the
number of threads needed to reproduce a particular loop structure. We
demonstrate that in several cases million degree loops are revealed to
be single monolithic structures that are fully spatially resolved by
current instruments. The majority of loops, however, must be composed
of a number of finer, unresolved threads, but the models suggest that
even for these loops the number of threads could be small, implying
that they are also close to being resolved. These results challenge
heating models of loops based on the reconnection of braided magnetic
fields in the corona.
---------------------------------------------------------
Title: Constraints on the Heating of High-temperature Active Region
Loops: Observations from Hinode and the Solar Dynamics Observatory
Authors: Warren, Harry P.; Brooks, David H.; Winebarger, Amy R.
2011ApJ...734...90W Altcode: 2010arXiv1009.5976W
We present observations of high-temperature emission in the core
of a solar active region using instruments on Hinode and the Solar
Dynamics Observatory (SDO). These multi-instrument observations allow
us to determine the distribution of plasma temperatures and follow the
evolution of emission at different temperatures. We find that at the
apex of the high-temperature loops the emission measure distribution
is strongly peaked near 4 MK and falls off sharply at both higher and
lower temperatures. Perhaps most significantly, the emission measure at
0.5 MK is reduced by more than two orders of magnitude from the peak at
4 MK. We also find that the temporal evolution in broadband soft X-ray
images is relatively constant over about 6 hr of observing. Observations
in the cooler SDO/Atmospheric Imaging Assembly (AIA) bandpasses
generally do not show cooling loops in the core of the active region,
consistent with the steady emission observed at high temperatures. These
observations suggest that the high-temperature loops observed in the
core of an active region are close to equilibrium. We find that it is
possible to reproduce the relative intensities of high-temperature
emission lines with a simple, high-frequency heating scenario where
heating events occur on timescales much less than a characteristic
cooling time. In contrast, low-frequency heating scenarios, which are
commonly invoked to describe nanoflare models of coronal heating, do
not reproduce the relative intensities of high-temperature emission
lines and predict low-temperature emission that is approximately an
order of magnitude too large. We also present an initial look at images
from the SDO/AIA 94 Å channel, which is sensitive to Fe XVIII.
---------------------------------------------------------
Title: EUV Spectral Line Formation and the Temperature Structure of
Active Region Fan Loops: Observations with Hinode/EIS and SDO/AIA
Authors: Brooks, David H.; Warren, Harry P.; Young, Peter R.
2011ApJ...730...85B Altcode: 2011arXiv1101.5240B
With the aim of studying active region fan loops using observations
from the Hinode EUV Imaging Spectrometer (EIS) and Solar Dynamics
Observatory Atmospheric Imaging Assembly (AIA), we investigate a number
of inconsistencies in modeling the absolute intensities of Fe VIII
and Si VII lines, and address why spectroheliograms formed from these
lines look very similar despite the fact that ionization equilibrium
calculations suggest that they have significantly different formation
temperatures: log(T<SUB>e</SUB> /K) = 5.6 and 5.8, respectively. It is
important to resolve these issues because confidence has been undermined
in their use for differential emission measure (DEM) analysis, and
Fe VIII is the main contributor to the AIA 131 Å channel at low
temperatures. Furthermore, the strong Fe VIII 185.213 Å and Si VII
275.368 Å lines are the best EIS lines to use for velocity studies
in the transition region, and for assigning the correct temperature
to velocity measurements in the fans. We find that the Fe VIII 185.213
Å line is particularly sensitive to the slope of the DEM, leading to
disproportionate changes in its effective formation temperature. If
the DEM has a steep gradient in the log(T<SUB>e</SUB> /K) = 5.6-5.8
temperature range, or is strongly peaked, Fe VIII 185.213 Å and Si VII
275.368 Å will be formed at the same temperature. We show that this
effect explains the similarity of these images in the fans. Furthermore,
we show that the most recent ionization balance compilations resolve the
discrepancies in absolute intensities. With these difficulties overcome,
we combine EIS and AIA data to determine the temperature structure of
a number of fan loops and find that they have peak temperatures of
0.8-1.2 MK. The EIS data indicate that the temperature distribution
has a finite (but narrow) width < log (σ_{T_e}/K) = 5.5 which,
in one detailed case, is found to broaden substantially toward the
loop base. AIA and EIS yield similar results on the temperature,
emission measure magnitude, and thermal distribution in the fans,
though sometimes the AIA data suggest a relatively larger thermal
width. The result is that both the Fe VIII 185.213 Å and Si VII
275.368 Å lines are formed at log(T<SUB>e</SUB> /K)~ 5.9 in the fans,
and the AIA 131 Å response also shifts to this temperature.
---------------------------------------------------------
Title: Establishing a Connection Between Active Region Outflows and
the Solar Wind: Abundance Measurements with EIS/Hinode
Authors: Brooks, David H.; Warren, Harry P.
2011ApJ...727L..13B Altcode: 2010arXiv1009.4291B
One of the most interesting discoveries from Hinode is the presence
of persistent high-temperature high-speed outflows from the edges
of active regions (ARs). EUV imaging spectrometer (EIS) measurements
indicate that the outflows reach velocities of 50 km s<SUP>-1</SUP>
with spectral line asymmetries approaching 200 km s<SUP>-1</SUP>. It
has been suggested that these outflows may lie on open field lines
that connect to the heliosphere, and that they could potentially
be a significant source of the slow speed solar wind. A direct link
has been difficult to establish, however. We use EIS measurements of
spectral line intensities that are sensitive to changes in the relative
abundance of Si and S as a result of the first ionization potential
(FIP) effect, to measure the chemical composition in the outflow
regions of AR 10978 over a 5 day period in 2007 December. We find that
Si is always enhanced over S by a factor of 3-4. This is generally
consistent with the enhancement factor of low FIP elements measured
in situ in the slow solar wind by non-spectroscopic methods. Plasma
with a slow wind-like composition was therefore flowing from the edge
of the AR for at least 5 days. Furthermore, on December 10 and 11,
when the outflow from the western side was favorably oriented in the
Earth direction, the Si/S ratio was found to match the value measured
a few days later by the Advanced Composition Explorer/Solar Wind Ion
Composition Spectrometer. These results provide strong observational
evidence for a direct connection between the solar wind, and the
coronal plasma in the outflow regions.
---------------------------------------------------------
Title: Characteristics and Evolution of the Magnetic Field and
Chromospheric Emission in an Active Region Core Observed by Hinode
Authors: Brooks, David H.; Warren, Harry P.; Winebarger, Amy R.
2010ApJ...720.1380B Altcode: 2010arXiv1006.5776B
We describe the characteristics and evolution of the magnetic field and
chromospheric emission in an active region core observed by the Solar
Optical Telescope (SOT) on Hinode. Consistent with previous studies,
we find that the moss is unipolar, the spatial distribution of magnetic
flux evolves slowly, and that the magnetic field is only moderately
inclined. We also show that the field-line inclination and horizontal
component are coherent, and that the magnetic field is mostly sheared
in the inter-moss regions where the highest magnetic flux variability
is seen. Using extrapolations from spectropolarimeter magnetograms,
we show that the magnetic connectivity in the moss is different from
that in the quiet Sun because most of the magnetic field extends to
significant coronal heights. The magnetic flux, field vector, and
chromospheric emission in the moss also appear highly dynamic but
actually show only small-scale variations in magnitude on timescales
longer than the cooling times for hydrodynamic loops computed from
our extrapolations, suggesting high-frequency (continuous) heating
events. Some evidence is found for flux (Ca II intensity) changes on
the order of 100-200 G (DN) on timescales of 20-30 minutes that could
be taken as indicative of low-frequency heating. We find, however,
that only a small fraction (10%) of our simulated loops would be
expected to cool on these timescales, and we do not find clear evidence
that the flux changes consistently produce intensity changes in the
chromosphere. Using observations from the EUV Imaging Spectrometer
(EIS), we also determine that the filling factor in the moss is ~16%,
consistent with previous studies and larger than the size of an SOT
pixel. The magnetic flux and chromospheric intensity in most individual
SOT pixels in the moss vary by less than ~20% and ~10%, respectively,
on loop cooling timescales. In view of the high energy requirements of
the chromosphere, we suggest that these variations could be sufficient
for the heating of "warm" EUV loops, but that the high basal levels
may be more important for powering the hot core loops rooted in the
moss. The magnetic field and chromospheric emission appear to evolve
gradually on spatial scales comparable to the cross-field scale of
the fundamental coronal structures inferred from EIS measurements.
---------------------------------------------------------
Title: Evidence for Steady Heating: Observations of an Active Region
Core with Hinode and TRACE
Authors: Warren, Harry P.; Winebarger, Amy R.; Brooks, David H.
2010ApJ...711..228W Altcode: 2009arXiv0910.0458W
The timescale for energy release is an important parameter for
constraining the coronal heating mechanism. Observations of "warm"
coronal loops (~1 MK) have indicated that the heating is impulsive and
that coronal plasma is far from equilibrium. In contrast, observations
at higher temperatures (~3 MK) have generally been consistent with
steady heating models. Previous observations, however, have not been
able to exclude the possibility that the high temperature loops are
actually composed of many small-scale threads that are in various stages
of heating and cooling and only appear to be in equilibrium. With new
observations from the EUV Imaging Spectrometer and X-ray Telescope
(XRT) on Hinode we have the ability to investigate the properties of
high temperature coronal plasma in extraordinary detail. We examine
the emission in the core of an active region and find three independent
lines of evidence for steady heating. We find that the emission observed
in XRT is generally steady for hours, with a fluctuation level of
approximately 15% in an individual pixel. Short-lived impulsive heating
events are observed, but they appear to be unrelated to the steady
emission that dominates the active region. Furthermore, we find no
evidence for warm emission that is spatially correlated with the hot
emission, as would be expected if the high temperature loops are the
result of impulsive heating. Finally, we also find that intensities in
the "moss," the footpoints of high temperature loops, are consistent
with steady heating models provided that we account for the local
expansion of the loop from the base of the transition region to the
corona. In combination, these results provide strong evidence that
the heating in the core of an active region is effectively steady,
that is, the time between heating events is short relative to the
relevant radiative and conductive cooling times.
---------------------------------------------------------
Title: Signatures of Coronal Heating Mechanisms
Authors: Antolin, P.; Shibata, K.; Kudoh, T.; Shiota, D.; Brooks, D.
2010ASSP...19..277A Altcode: 2010mcia.conf..277A; 2009arXiv0903.1766A
Alfvén waves created by sub-photospheric motions or by magnetic
reconnection in the low solar atmosphere seem good candidates for
coronal heating. However, the corona is also likely to be heated more
directly by magnetic reconnection, with dissipation taking place
in current sheets. Distinguishing observationally between these
two heating mechanisms is an extremely difficult task. We perform
1.5-dimensional MHD simulations of a coronal loop subject to each
type of heating and derive observational quantities that may allow
these to be differentiated. This work is presented in more detail in
Antolin et al. (2008).
---------------------------------------------------------
Title: Hinode/Extreme-Ultraviolet Imaging Spectrometer Observations
of the Temperature Structure of the Quiet Corona
Authors: Brooks, David H.; Warren, Harry P.; Williams, David R.;
Watanabe, Tetsuya
2009ApJ...705.1522B Altcode: 2009arXiv0905.3603B
We present a differential emission measure (DEM) analysis of the quiet
solar corona on disk using data obtained by the Extreme-ultraviolet
Imaging Spectrometer (EIS) on Hinode. We show that the expected
quiet-Sun DEM distribution can be recovered from judiciously selected
lines, and that their average intensities can be reproduced to
within 30%. We present a subset of these selected lines spanning the
temperature range log T = 5.6-6.4 K that can be used to derive the DEM
distribution reliably, including a subset of iron lines that can be used
to derive the DEM distribution free of the possibility of uncertainties
in the elemental abundances. The subset can be used without the need for
extensive measurements, and the observed intensities can be reproduced
to within the estimated uncertainty in the pre-launch calibration
of EIS. Furthermore, using this subset, we also demonstrate that
the quiet coronal DEM distribution can be recovered on size scales
down to the spatial resolution of the instrument (1” pixels). The
subset will therefore be useful for studies of small-scale spatial
inhomogeneities in the coronal temperature structure, for example,
in addition to studies requiring multiple DEM derivations in space or
time. We apply the subset to 45 quiet-Sun data sets taken in the period
2007 January to April, and show that although the absolute magnitude
of the coronal DEM may scale with the amount of released energy, the
shape of the distribution is very similar up to at least log T ~ 6.2 K
in all cases. This result is consistent with the view that the shape of
the quiet-Sun DEM is mainly a function of the radiating and conducting
properties of the plasma and is fairly insensitive to the location and
rate of energy deposition. This universal DEM may be sensitive to other
factors such as loop geometry, flows, and the heating mechanism, but
if so they cannot vary significantly from quiet-Sun region to region.
---------------------------------------------------------
Title: Flows and Motions in Moss in the Core of a Flaring Active
Region: Evidence for Steady Heating
Authors: Brooks, David H.; Warren, Harry P.
2009ApJ...703L..10B Altcode: 2009arXiv0905.3462B
We present new measurements of the time variability of intensity,
Doppler, and nonthermal velocities in moss in an active region core
observed by the EUV Imaging Spectrometer on Hinode in 2007 June. The
measurements are derived from spectral profiles of the Fe XII 195
Å line. Using the 2” slit, we repeatedly scanned 150” by 150”
in a few minutes. This is the first time it has been possible to
make such velocity measurements in the moss, and the data presented
are the highest cadence spatially resolved maps of moss Doppler and
nonthermal velocities ever obtained in the corona. The observed region
produced numerous C- and M-class flares with several occurring in
the core close to the moss. The magnetic field was therefore clearly
changing in the active region core, so we ought to be able to detect
dynamic signatures in the moss if they exist. Our measurements of
moss intensities agree with previous studies in that a less than 15%
variability is seen over a period of 16 hr. Our new measurements of
Doppler and nonthermal velocities reveal no strong flows or motions
in the moss, nor any significant variability in these quantities. The
results confirm that moss at the bases of high temperature coronal loops
is heated quasi-steadily. They also show that quasi-steady heating
can contribute significantly even in the core of a flare productive
active region. Such heating may be impulsive at high frequency, but
if so it does not give rise to large flows or motions.
---------------------------------------------------------
Title: The Temperature and Density Structure of the Solar
Corona. I. Observations of the Quiet Sun with the EUV Imaging
Spectrometer on Hinode
Authors: Warren, Harry P.; Brooks, David H.
2009ApJ...700..762W Altcode: 2009arXiv0901.1621W
Measurements of the temperature and density structure of the
solar corona provide critical constraints on theories of coronal
heating. Unfortunately, the complexity of the solar atmosphere,
observational uncertainties, and the limitations of current atomic
calculations, particularly those for Fe, all conspire to make this
task very difficult. A critical assessment of plasma diagnostics in
the corona is essential to making progress on the coronal heating
problem. In this paper, we present an analysis of temperature and
density measurements above the limb in the quiet corona using new
observations from the EUV Imaging Spectrometer (EIS) on Hinode. By
comparing the Si and Fe emission observed with EIS we are able to
identify emission lines that yield consistent emission measure
distributions. With these data we find that the distribution of
temperatures in the quiet corona above the limb is strongly peaked
near 1 MK, consistent with previous studies. We also find, however,
that there is a tail in the emission measure distribution that extends
to higher temperatures. EIS density measurements from several density
sensitive line ratios are found to be generally consistent with
each other and with previous measurements in the quiet corona. Our
analysis, however, also indicates that a significant fraction of the
weaker emission lines observed in the EIS wavelength ranges cannot be
understood with current atomic data.
---------------------------------------------------------
Title: Active Region Transition Region Loop Populations and Their
Relationship to the Corona
Authors: Ugarte-Urra, Ignacio; Warren, Harry P.; Brooks, David H.
2009ApJ...695..642U Altcode: 2009arXiv0901.1075U
The relationships among coronal loop structures at different
temperatures are not settled. Previous studies have suggested that
coronal loops in the core of an active region (AR) are not seen cooling
through lower temperatures and therefore are steadily heated. If loops
were cooling, the transition region would be an ideal temperature regime
to look for a signature of their evolution. The Extreme-ultraviolet
Imaging Spectrometer on Hinode provides monochromatic images of the
solar transition region and corona at an unprecedented cadence and
spatial resolution, making it an ideal instrument to shed light on
this issue. Analysis of observations of AR 10978 taken in 2007 December
8-19 indicates that there are two dominant loop populations in the AR:
(1) core multitemperature loops that undergo a continuous process of
heating and cooling in the full observed temperature range 0.4-2.5
MK and even higher as shown by the X-Ray Telescope and (2) peripheral
loops which evolve mostly in the temperature range 0.4-1.3 MK. Loops
at transition region temperatures can reach heights of 150 Mm in the
corona above the limb and develop downflows with velocities in the
range of 39-105 km s<SUP>-1</SUP>.
---------------------------------------------------------
Title: The Role of Transient Brightenings in Heating the Solar Corona
Authors: Brooks, David H.; Ugarte-Urra, Ignacio; Warren, Harry P.
2008ApJ...689L..77B Altcode:
Nanoflare reconnection events have been proposed as a mechanism for
heating the corona. Parker's original suggestion was that frequent
reconnection events occur in coronal loops due to the braiding of the
magnetic field. Many observational studies, however, have focused on the
properties of isolated transient brightenings unassociated with loops,
but their cause, role, and relevance for coronal heating have not
yet been established. Using Hinode SOT magnetograms and high-cadence
EIS spectral data we study the relationship between chromospheric,
transition region, and coronal emission and the evolution of the
magnetic field. We find that hot, relatively steadily emitting coronal
loops and isolated transient brightenings are both associated with
magnetic flux regions that are highly dynamic. An essential difference,
however, is that brightenings are typically found in regions of flux
collision and cancellation whereas coronal loops are generally rooted
in magnetic field regions that are locally unipolar with unmixed
flux. This suggests that the type of heating (transient vs. steady) is
related to the structure of the magnetic field, and that the heating
in transient events may be fundamentally different than in coronal
loops. This implies that they do not play an important role in heating
the "quiescent" corona.
---------------------------------------------------------
Title: Predicting Observational Signatures of Coronal Heating by
Alfvén Waves and Nanoflares
Authors: Antolin, P.; Shibata, K.; Kudoh, T.; Shiota, D.; Brooks, D.
2008ApJ...688..669A Altcode:
Alfvén waves can dissipate their energy by means of nonlinear
mechanisms, and constitute good candidates to heat and maintain the
solar corona to the observed few million degrees. Another appealing
candidate is nanoflare reconnection heating, in which energy is released
through many small magnetic reconnection events. Distinguishing the
observational features of each mechanism is an extremely difficult
task. On the other hand, observations have shown that energy release
processes in the corona follow a power-law distribution in frequency
whose index may tell us whether small heating events contribute
substantially to the heating or not. In this work we show a link
between the power-law index and the operating heating mechanism in
a loop. We set up two coronal loop models: in the first model Alfvén
waves created by footpoint shuffling nonlinearly convert to longitudinal
modes which dissipate their energy through shocks; in the second model
numerous heating events with nanoflare-like energies are input randomly
along the loop, either distributed uniformly or concentrated at the
footpoints. Both models are based on a 1.5-dimensional MHD code. The
obtained coronae differ in many aspects; for instance, in the flow
patterns along the loop and the simulated intensity profile that
Hinode XRT would observe. The intensity histograms display power-law
distributions whose indexes differ considerably. This number is found
to be related to the distribution of the shocks along the loop. We
thus test the observational signatures of the power-law index as a
diagnostic tool for the above heating mechanisms and the influence of
the location of nanoflares.
---------------------------------------------------------
Title: Modeling of the Extreme-Ultraviolet and Soft X-Ray Emission
in a Solar Coronal Bright Point
Authors: Brooks, David H.; Warren, Harry P.
2008ApJ...687.1363B Altcode:
Previous studies have been able to reproduce both the observed
intensities and the morphology of high-temperature solar plasma
using steady state heating models. These models, however, have
been unable to reproduce the lower temperature emission observed in
active regions. Here we present results from numerical simulations
of a coronal bright point. We use potential field extrapolations of a
Kitt Peak magnetogram to compute the coronal field lines and populate
them with solutions to the hydrostatic loop equations based on a
volumetric heating function that scales as bar B/L, where bar B is the
magnetic field strength averaged along a field line and L is the loop
length. We consider the effects of altering the magnitude and scale
height of the energy deposition and the effect of allowing the loop
cross sections to expand proportionally to 1/bar B. We then use the
computed densities and temperatures to calculate average intensities
and simulated EUV and soft X-ray images and compared them to Yohkoh
and SOHO observations. We find that our best-case model (apex heating
of expanding loops) can reproduce the high-temperature emission, the
general morphology of the lower temperature emission, and the majority
of the average intensities of reliable lines over a wide range of
temperatures to within ~20%. The morphology in the EUV visualizations,
however, shows some differences from the observations. These results
suggest the role of nonpotential or evolving magnetic fields, or
dynamic processes, but indicate that departures from the potential
field hydrostatic case may not be too large.
---------------------------------------------------------
Title: Observations of Active Region Loops with the EUV Imaging
Spectrometer on Hinode
Authors: Warren, Harry P.; Ugarte-Urra, Ignacio; Doschek, George A.;
Brooks, David H.; Williams, David R.
2008ApJ...686L.131W Altcode: 2008arXiv0808.3227W
Previous solar observations have shown that coronal loops near 1 MK
are difficult to reconcile with simple heating models. These loops have
lifetimes that are long relative to a radiative cooling time, suggesting
quasi-steady heating. The electron densities in these loops, however,
are too high to be consistent with thermodynamic equilibrium. Models
proposed to explain these properties generally rely on the existence
of smaller scale filaments within the loop that are in various stages
of heating and cooling. Such a framework implies that there should be
a distribution of temperatures within a coronal loop. In this paper
we analyze new observations from the EUV Imaging Spectrometer (EIS)
on Hinode. EIS is capable of observing active regions over a wide range
of temperatures (Fe VIII-Fe XVII) at relatively high spatial resolution
(1”). We find that most isolated coronal loops that are bright in Fe
XII generally have very narrow temperature distributions (σ<SUB>T</SUB>
lesssim 3 × 10<SUP>5</SUP> K), but are not isothermal. We also derive
volumetric filling factors in these loops of approximately 10%. Both
results lend support to the filament models.
---------------------------------------------------------
Title: Predicting observational signatures of coronal heating by
Alfvén waves and nanoflares
Authors: Antolin, Patrick; Shibata, Kazunari; Kudoh, Takahiro; Shiota,
Daiko; Brooks, David
2008IAUS..247..279A Altcode: 2007IAUS..247..279A
Alfvén waves can dissipate their energy by means of nonlinear
mechanisms, and constitute good candidates to heat and maintain the
solar corona to the observed few million degrees. Another appealing
candidate is the nanoflare-reconnection heating, in which energy is
released through many small magnetic reconnection events. Distinguishing
the observational features of each mechanism is an extremely difficult
task. On the other hand, observations have shown that energy release
processes in the corona follow a power law distribution in frequency
whose index may tell us whether small heating events contribute
substantially to the heating or not. In this work we show a link
between the power law index and the operating heating mechanism in
a loop. We set up two coronal loop models: in the first model Alfvén
waves created by footpoint shuffling nonlinearly convert to longitudinal
modes which dissipate their energy through shocks; in the second model
numerous heating events with nanoflare-like energies are input randomly
along the loop, either distributed uniformly or concentrated at the
footpoints. Both models are based on a 1.5-D MHD code. The obtained
coronae differ in many aspects, for instance, in the simulated intensity
profile that Hinode/XRT would observe. The intensity histograms display
power law distributions whose indexes differ considerably. This number
is found to be related to the distribution of the shocks along the
loop. We thus test the observational signatures of the power law index
as a diagnostic tool for the above heating mechanisms and the influence
of the location of nanoflares.
---------------------------------------------------------
Title: The Role of Isolated EUV Brightenings in Heating the Corona
Authors: Brooks, D. H.; Warren, H. P.; Ugarte-Urra, I.
2008AGUSMSP43C..04B Altcode:
Nanoflare reconnection events have been proposed as a mechanism for
heating the solar corona. Parker's original suggestion was that frequent
reconnection events occur in coronal loops due to the twisting and
braiding of the magnetic field. Many observational studies, however,
have focused on the radiating properties of isolated brightening
events, but their cause, role, and relevance for coronal heating
has not yet been established. Using Hinode Solar Optical Telescope
(SOT) magnetograms and high cadence EUV Imaging Spectrometer (EIS)
slot rasters we study the relationship between transition region and
coronal emission and the evolution of the magnetic field. We find that
hot, relatively steadily emitting coronal loops are generally rooted in
magnetic field regions that are locally unipolar yet highly dynamic,
whereas detailed analysis shows that ubiquitous EUV brightenings are
found in regions of magnetic flux cancellation in the photosphere. This
suggests that the heating in transient events may be fundamentally
different than the heating in coronal loops and that they play no
direct role in the heating of the quiescent corona.
---------------------------------------------------------
Title: Electron Densities in Active Region Loops Observed with
Hinode/EIS
Authors: Warren, H. P.; Winebarger, A. R.; Brooks, D. H.
2008AGUSMSP41C..02W Altcode:
Active region observations with the Transition Region and Coronal
Explorer (TRACE) showed that loops near 1 MK appear to have high
densities relative to the predictions of scaling laws based on steady
heating. These loops also persist much longer than a radiative cooling
time. This lead to the formation of models based on the impulsive
heating of small scale filaments. With the launch of the EUV Imaging
Spectrometer (EIS) on Hinode we now have a much more detailed view of
coronal loops at these temperatures. We find that the temperatures,
densities, and filling factors inferred from the new spectroscopic
data are largely consistent with our interpretation of the earlier
TRACE observations. The impulsive heating models also predict low
densities relative to the steady heating models at high temperatures,
and we will discuss the EIS evidence for hot, underdense loops in
solar active regions.
---------------------------------------------------------
Title: EIS: a new view of active region transition region loops
Authors: Ugarte-Urra, I.; Warren, H. P.; Brooks, D. H.
2008AGUSMSP41C..03U Altcode:
The EUV Imaging Spectrometer (EIS) on board Hinode is providing
unprecedented diagnostics of solar coronal plasmas. One of its less
exploited capabilities is the ability to make instantaneous spectrally
pure images with the 40” slot. Simultaneous transition region (Mg
VI, Mg VII, Si VII) and coronal (Fe XI - Fe XVI) images allow us
to observe active region loops as we have not been able to before,
given the spatial resolution (1arcsec pixels), cadence (70s) and,
most importantly, the broad temperature coverage. Under this scrutiny
two distinct populations of active region transition region loops can
be differentiated: core loops that result from the cooling of several
million degree plasma; and fan structures with their main contribution
in the 0.6-1 MK temperature range. These results suggest that the cores
of active regions are not as steady as commonly assumed and reinforce
the idea of coexistance of differentiated loop populations within the
active region topology. We present the properties of the loops and we
discuss the implications that these new observations have for current
transition region and coronal models.
---------------------------------------------------------
Title: Observations of Transient Active Region Heating with Hinode
Authors: Warren, Harry P.; Ugarte-Urra, Ignacio; Brooks, David H.;
Cirtain, Jonathan W.; Williams, David R.; Hara, Hirohisa
2007PASJ...59S.675W Altcode: 2007arXiv0711.0357W
We present observations of transient active region heating events
observed with the Extreme Ultraviolet Imaging Spectrometer (EIS) and
X-ray Telescope (XRT) on Hinode. This initial investigation focuses
on NOAA active region 10940 as observed by Hinode on 2007 February 1
between 12 and 19UT. In these observations we find numerous examples
of transient heating events within the active region. The high spatial
resolution and broad temperature coverage of these instruments allows
us to track the evolution of coronal plasma. The evolution of the
emission observed with XRT and EIS during these events is generally
consistent with loops that have been heated and are cooling. We have
analyzed the most energetic heating event observed during this period,
a small GOES B-class flare, in some detail and present some of the
spectral signatures of the event, such as relative Doppler shifts at
one of the loop footpoints and enhanced line widths during the rise
phase of the event. While the analysis of these transient events has
the potential to yield insights into the coronal heating mechanism,
these observations do not rule out the possibility that there is a
strong steady heating level in the active region. Detailed statistical
analysis will be required to address this question definitively.
---------------------------------------------------------
Title: Hinode EUV Imaging Spectrometer Observations of Solar Active
Region Dynamics
Authors: Mariska, John T.; Warren, Harry P.; Ugarte-Urra, Ignacio;
Brooks, David H.; Williams, David R.; Hara, Hirohisa
2007PASJ...59S.713M Altcode: 2007arXiv0708.4309M
The EUV Imaging Spectrometer (EIS) on the Hinode satellite is capable of
measuring emission line center positions for Gaussian line profiles to a
fraction of a spectral pixel, resulting in relative solar Doppler-shift
measurements with an accuracy of a less than a km s<SUP>-1</SUP> for
strong lines. We show an example of the application of that capability
to an active region sit-and-stare observation in which the EIS slit
is placed at one location on the Sun and many exposures are taken
while the spacecraft tracking keeps the same solar location within
the slit. For the active region examined (NOAA10930), we find that
significant intensity and Doppler-shift fluctuations as a function of
time are present at a number of locations. These fluctuations appear
to be similar to those observed in high-temperature emission lines
with other space-borne spectroscopic instruments. With its increased
sensitivity over earlier spectrometers and its ability to image many
emission lines simultaneously, EIS should provide significant new
constraints on Doppler-shift oscillations in the corona.
---------------------------------------------------------
Title: The X10 Flare on 29 October 2003: Was It Triggered by Magnetic
Reconnection between Counter-Helical Fluxes?
Authors: Liu, Yu; Kurokawa, Hiroki; Liu, Chang; Brooks, David H.;
Dun, Jingping; Ishii, Takako T.; Zhang, Hongqi
2007SoPh..240..253L Altcode: 2007astro.ph..1794L
Vector magnetograms taken at Huairou Solar Observing Station (HSOS)
and Mees Solar Observatory (MSO) reveal that the super active region
(AR) NOAA 10486 was a complex region containing current helicity flux of
opposite signs. The main positive sunspots were dominated by negative
helicity fields, while positive helicity patches persisted both inside
and around the main positive sunspots. Based on a comparison of two days
of deduced current helicity density, pronounced changes associated with
the occurrence of an X10 flare that peaked at 20:49 UT on 29 October
2003 were noticed. The average current helicity density (negative) of
the main sunspots decreased significantly by about 50%. Accordingly,
the helicity densities of counter-helical patches (positive) were also
found to decay by the same proportion or more. In addition, two hard
X-ray (HXR) "footpoints" were observed by the Reuven Ramaty High Energy
Solar Spectroscopic Imager (RHESSI) during the flare in the 50 - 100
keV energy range. The cores of these two HXR footpoints were adjacent
to the positions of two patches with positive current helicity that
disappeared after the flare. This strongly suggested that the X10
flare on 29 October 2003 resulted from reconnection between magnetic
flux tubes having opposite current helicity. Finally, the global
decrease of current helicity in AR 10486 by ∼50% can be understood
as the helicity launched away by the halo coronal mass ejection (CME)
associated with the X10 flare.
---------------------------------------------------------
Title: An Hα Surge Provoked by Moving Magnetic Features near an
Emerging Flux Region
Authors: Brooks, D. H.; Kurokawa, H.; Berger, T. E.
2007ApJ...656.1197B Altcode:
We present a detailed study of Hα surges from cotemporal
high-resolution multiwavelength images of NOAA AR 8227 obtained by
the 50 cm Swedish Vacuum Solar Telescope (formerly situated on La
Palma, Spain) and TRACE. We find that two kinds of collisions between
opposite polarity magnetic flux produce the surges. First, one edge of
an emerging flux region (EFR) collides with the preexisting magnetic
field and causes continual surge activities, which have already been
named EFR surges by previous authors. Secondly, moving magnetic features
(MMFs), which emerge near the sunspot penumbra, pass through the ambient
plasma and eventually collide with the opposite polarity magnetic
field of the EFR. During their passage from the sunspot penumbra to
the EFR, the MMFs constantly interacted with other magnetic elements
and had a close relationship and showed similar flow patterns to Ca
II K bright points. These brightenings were located at the leading
edges of the MMFs. Cancellation of opposite polarity magnetic flux
at the surge footpoint is observed, accompanied by chromospheric and
coronal brightenings. We explain the evolutionary and morphological
characteristics of the multiwavelength features associated with the Hα
surges in both cases by the extension of previous 2D schematic models of
reconnection in surges. Furthermore, by measuring the expansion velocity
and photospheric magnetic field around the surge footpoint, we estimate
a dimensionless reconnection rate of 0.04 (ratio of inflow velocity to
Alfvén velocity). This is sufficient to produce a significant surge
that heats the chromospheric plasma to coronal temperatures.
---------------------------------------------------------
Title: The in-flight monitoring and validation of the SOHO CDS Normal
Incidence Spectrometer radiometric calibration
Authors: Lang, J.; Brooks, D. H.; Lanzafame, A. C.; Martin, R.; Pike,
C. D.; Thompson, W. T.
2007A&A...463..339L Altcode:
The scientific return from an extreme-ultraviolet spectrometer depends
on the accuracy and precision of its radiometric calibration. For
the Coronal Diagnostic Spectrometer on SOHO, radiometric calibration
started pre-launch in the laboratory and continued after launch
by making comparison measurements of the same area of the Sun with
calibrated sounding rocket payloads and also by intercalibration with
the SUMER instrument on SOHO. The present work uses the measurement
of line ratios to monitor and validate the calibration over the
first six years of observation. As well as using branching ratios
and line ratios independent of the electron temperature and density,
line ratios dependent on electron temperature or density have also been
used successfully to validate and monitor the calibration. The results
indicate that, within the uncertainties, the radiometric calibration has
been validated and maintained over the first six years of observations
apart from three specific wavelengths, 338.98 Å, 315.0 Å, and 311.8
Å. Problems with lines at 608.4 Å, 303.4 Å (seen in second order),
335.4 Å, and 360.7 Å are attributed to difficulties with the burn-in
correction.
---------------------------------------------------------
Title: The Intercalibration of SOHO EIT, CDS-NIS, and TRACE
Authors: Brooks, David H.; Warren, Harry P.
2006ApJS..164..202B Altcode:
Using coordinated observations of a quiet coronal region, we study the
intercalibration of the CDS and EIT instruments on board the Solar and
Heliospheric Observatory (SOHO) and the Transition Region and Coronal
Explorer (TRACE). We derive the differential emission measure (DEM)
distribution from CDS spectral line intensities and convolve it with
EIT and TRACE temperature response functions, calculated with the
latest atomic data from the CHIANTI database, to predict count rates
in their observing channels. We examine different analysis methods and
briefly discuss some more advanced aspects of atomic modeling such as
the density dependence of the ionization fractions. We investigate the
implications for our study using data from the ADAS database. We find
that our CDS DEM can predict the TRACE and EIT 171 and 195 Å channel
count rates to within 25%. However, the accuracy of the predictions
depends on the ionization fractions and elemental abundances used. The
TRACE 284 Å and EIT 284 and 304 Å filter predictions do not agree
well with the observations, even after taking the contribution from
the optically thick He II 304 Å line to the TRACE 284 Å channel into
account. The different CDS DEM solutions we derive using different
ionization fractions produce fairly similar results: the majority of
the CDS line intensities used are reproduced to within 20% with only
around one-fifth reproduced to worse than 50%. However, the comparison
provides us with further clues with which to explain the discrepancies
found for some lines, and highlights the need for accurate equilibrium
ionization balance calculations even at low density.
---------------------------------------------------------
Title: On Deriving Plasma Velocity Information from CDS/NIS
Observations: Application to the Dynamics of Blinkers
Authors: Brooks, David Hamilton; Bewsher, Danielle
2006SoPh..234..257B Altcode:
Using standard instrument software and two independently developed
data reduction and analysis procedures, we re-examine the accuracy of
plasma velocity information derived from data obtained by the Solar
and Heliospheric Observatory (SOHO)-Coronal Diagnostic Spectrometer
(CDS). We discuss only the Ov 629 Å line data obtained by the Normal
Incidence Spectrometer (NIS) and analyse a quiet Sun (QS) and active
region (AR) dataset. Using the QS data, we demonstrate that the
well-known North-South tilt in wavelength along the NIS slit varies
significantly with time, which is not accounted for in the standard CDS
correction procedures. In addition, when residual N - S trends exist in
the data after processing, they may not be detected, nor removed, using
the standard analysis software. This underscores the need for careful
analysis of velocity results for individual datasets when using standard
correction procedures. Furthermore, even when the results obtained by
the two independent methods are well correlated (coefficients greater
than 0.9), discrepancies in the values of the derived Doppler velocities
can remain (95% within ±5 km s<SUP>−1</SUP>). Therefore, we apply the
results to examine the velocities obtained for EUV blinkers by previous
authors. It is found that a strong correlation exists in the patterns
of variation of the blinker velocities (> 0.98), even though there
may be differences in their magnitudes. That is, in a clear majority of
cases, the methods agree that a blinker is red-shifted or blue-shifted,
although the uncertainty in the absolute velocity may be large.
---------------------------------------------------------
Title: Horizontal and Vertical Flow Structure in Emerging Flux Regions
Authors: Kozu, Hiromichi; Kitai, Reizaburo; Brooks, David H.; Kurokawa,
Hiroki; Yoshimura, Keiji; Berger, Thomas E.
2006PASJ...58..407K Altcode:
In order to obtain an overall view of the flow structure of convective
gas in emerging flux regions (EFRs), we studied three EFRs in two
solar active regions, NOAA 8218 and NOAA 10774. Using the Local
Correlation Tracking method, we found several horizontally divergent
flow structures, which were stable over a period of 1 hour, in 2
EFRs in NOAA 8218. The horizontal flow velocities and the sizes
of the structures were around 500m s<SUP>-1</SUP> and about 4Mm
in radius, respectively. We analyzed another dataset of NOAA 10774
using spectroscopic methods and found temporarily stable up-ward gas
flows in the central part of the EFR. The line-of-sight velocities
were around 150m s<SUP>-1</SUP> and the size of the flow patch was
2 to 5Mm in radius. These results support our previous findings that
convective-cell-like flow appears in the central part of an EFR. We
estimated from these results that the depth of the flow cell in EFRs
is about 600km, and the turn-over time of the cell is about 2 hours.
---------------------------------------------------------
Title: Ionization state, excited populations and emission of
impurities in dynamic finite density plasmas: I. The generalized
collisional radiative model for light elements
Authors: Summers, H. P.; Dickson, W. J.; O'Mullane, M. G.; Badnell,
N. R.; Whiteford, A. D.; Brooks, D. H.; Lang, J.; Loch, S. D.; Griffin,
D. C.
2006PPCF...48..263S Altcode: 2005astro.ph.11561S
The paper presents an integrated view of the population structure and
its role in establishing the ionization state of light elements in
dynamic, finite density, laboratory and astrophysical plasmas. There
are four main issues, the generalized collisional-radiative picture
for metastables in dynamic plasmas with Maxwellian free electrons and
its particularizing to light elements, the methods of bundling and
projection for manipulating the population equations, the systematic
production/use of state selective fundamental collision data in the
metastable resolved picture to all levels for collisonal-radiative
modelling and the delivery of appropriate derived coefficients for
experiment analysis. The ions of carbon, oxygen and neon are used in
illustration. The practical implementation of the methods described
here is part of the ADAS Project.
---------------------------------------------------------
Title: Transition Region Downflows in the Impulsive Phase of Solar
Flares
Authors: Kamio, S.; Kurokawa, H.; Brooks, D. H.; Kitai, R.; UeNo, S.
2005ApJ...625.1027K Altcode:
We present observations of four flares that occurred during
coordinated observations between the Coronal Diagnostic Spectrometer
(CDS) on board SOHO and the Domeless Solar Telescope (DST) at Hida
Observatory. We studied the evolution of relative Doppler velocities
in the flare kernels by using He I (3.5×10<SUP>4</SUP> K), O V
(2.2×10<SUP>5</SUP> K), and Mg IX (1.0×10<SUP>6</SUP> K) spectra
obtained with high time cadence (42 s) SOHO CDS observations and the
Hα monochromatic images obtained with the DST. We found that the
transition region plasma of O V showed strong downward velocities
up to 87 km s<SUP>-1</SUP> simultaneously with the downflows in the
lower temperature chromospheric emissions in He I and Hα during the
impulsive phase of all four flares. From these results we suggest
that the downflows in the transition region and the chromosphere are a
common feature in the impulsive phase of flares. For the Mg IX line we
did not detect any significant change in velocity, which suggests that
the 10<SUP>6</SUP> K plasma was close to the intermediate temperature
between the upflowing plasma (10<SUP>7</SUP> K) and the downflowing
plasma (10<SUP>4</SUP>-10<SUP>5</SUP> K). These are important for
understanding the dynamics of the solar atmosphere in response to the
sudden energy deposition of a flare.
---------------------------------------------------------
Title: ADAS analysis of the differential emission measure structure
of the inner solar corona. II. A study of the "quiet Sun"
inhomogeneities from SOHO CDS-NIS spectra
Authors: Lanzafame, A. C.; Brooks, D. H.; Lang, J.
2005A&A...432.1063L Altcode: 2004astro.ph.12118L
We present a study of the differential emission measure (DEM)
of a “quiet Sun” area observed in the extreme ultraviolet
at normal incidence by the Coronal Diagnostic Spectrometer (CDS)
on the SOHO spacecraft. The data used for this work were taken
using the NISAT<SUB>S</SUB> observing sequence. This takes the full
wavelength ranges from both the NIS channels (308 381 Å and 513 633
Å) with the 2 arcsec by 240 arcsec slit, which is the narrowest slit
available, yielding the best spectral resolution. In this work we
contrast the DEM from subregions of 2 × 80 arcsec<SUP>2</SUP> with
that obtained from the mean spectrum of the whole raster (20 × 240
arcsec<SUP>2</SUP>). We find that the DEM maintains essentially the
same shape in the subregions, differing by a constant factor between
0.5 and 2 from the mean DEM, except in areas were the electron density
is below 2 × 10<SUP>7</SUP> cm<SUP>-3</SUP> and downflow velocities
of 50 km s<SUP>-1</SUP> are found in the transition region. Such areas
are likely to contain plasma departing from ionisation equilibrium,
violating the basic assumptions underlying the DEM method. The
comparison between lines of Li-like and Be-like ions may provide
further evidence of departure from ionisation equilibrium. We find
also that line intensities tend to be lower where velocities of the
order of 30 km s<SUP>-1</SUP> or higher are measured in transition
region lines. The DEM analysis is also exploited to improve the
line identification performed by [CITE] and to investigate possible
elemental abundance variations from region to region. We find that the
plasma has composition close to photospheric in all the subregions
examined. <P />Table 5 is only available in electronic form at the
CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via
http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/432/1063
---------------------------------------------------------
Title: A Study of a Tiny Two-Ribbon Flare Driven by Emerging Flux
Authors: Sakajiri, Takuma; Brooks, David H.; Yamamoto, Tetsuya;
Shiota, Daikou; Isobe, Hiroaki; Akiyama, Sachiko; Ueno, Satoru; Kitai,
Reizaburo; Shibata, Kazunari
2004ApJ...616..578S Altcode:
We present observations of the eruption of a miniature filament that
occurred near NOAA Active Region 9537 on 2001 July 14. The eruption was
observed by the Hida Observatory Domeless Solar Telescope, in the Hα
line center and +/-0.4 Å wings, the Solar and Heliospheric Observatory
EUV Imaging Telescope (EIT) and Michelson Doppler Imager, and the Yohkoh
Soft X-Ray Telescope (SXT). The miniature filament began to form and
was clearly visible in Hα images by around 06:50 UT. It erupted about
25 minutes later, accompanied by a small two-ribbon subflare (with
an area of 61 arcsec<SUP>2</SUP>). The two ribbons were also found to
approach each other at a speed of 3.33 km s<SUP>-1</SUP>. We found that
this event was caused by the emergence of new magnetic flux in a quiet
region. The emerging flux appeared as a bright region in the EIT and
SXT images taken on the previous day. It moved southward into an area
of preexisting opposite-polarity flux, where a cancelling magnetic
flux region was formed. The miniature filament then appeared, and we
suggest that it played some role in inhibiting the release of energy
by delaying reconnection between the emerging and preexisting flux, as
evidenced by the disappearance of the bright region between opposite
polarities in the EUV and soft X-ray images. Consequently, magnetic
energy was stored as a result of the slow converging motion of the two
opposite-polarity flux regions (0.17 km s<SUP>-1</SUP>). Reconnection
below the filament provoked the filament eruption, and the two-ribbon
flare occurred. Miniature filaments are thought to be small-scale
analogs of large-scale filaments. Our observations also suggest some
common properties between small-scale and large-scale flares. These
results support the view that a unified magnetic reconnection model
may be able to explain all scales of flares.
---------------------------------------------------------
Title: Hida Domeless Solar Telescope and SOHO Coronal Diagnostic
Spectrometer Observations of Short-Duration Active Region
Blinkers. II. Extreme-Ultraviolet Properties
Authors: Brooks, D. H.; Kurokawa, H.
2004ApJ...611.1125B Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Short-Duration Active Region Brightenings Observed in the
Extreme Ultraviolet and Hα by the Solar and Heliospheric Observatory
Coronal Diagnostic Spectrometer and Hida Domeless Solar Telescope
Authors: Brooks, D. H.; Kurokawa, H.; Kamio, S.; Fludra, A.; Ishii,
T. T.; Kitai, R.; Kozu, H.; Ueno, S.; Yoshimura, K.
2004ApJ...602.1051B Altcode:
We present the first detection of an Hα counterpart to the EUV
blinker. The observations come from a coordinated campaign between
the Hida Observatory Domeless Solar Telescope (DST) and the Solar
and Heliospheric Observatory Coronal Diagnostic Spectrometer (CDS)
conducted in 2002 July and August. Utilizing studies designed for
high-cadence observations, many short-duration brightenings (<3
minutes) were identified in the He I λ584.334 and O V λ629.732
spectral lines in CDS data of active region NOAA 10039/10044. These
brightenings show similar characteristics (increases in intensity,
size) to longer duration EUV blinkers previously reported in active
regions and the quiet Sun. Focusing on two events that show pronounced
emission in the upper chromosphere (He I), we have been able to identify
cospatial bright points in the lower chromosphere (Hα center, +/-0.5
Å) that show enhanced emission during the EUV blinker. These bright
features have lifetimes similar to those of their EUV counterparts,
and their peak intensities occur nearly simultaneously with the peak
blinker intensities in the He I and O V lines. In both cases the He
I and O V lines show excess line broadening at the peak of the event
(>15 km s<SUP>-1</SUP>). Our high-cadence observations also enabled
us to examine the dimensions and lifetimes of short-duration active
region blinkers in detail. We find that the instrumental spatial and
temporal resolution can combine to distort their characteristics:
even short-duration blinkers appear to be composed of elementary
brightening events. The optical brightenings also appear to closely
follow the behavior of the elementary brightenings. The spatial and
temporal relationships between the brightenings indicate a causal link
between the EUV and Hα blinkers.
---------------------------------------------------------
Title: A Reexamination of the Evidence for Reconnection Inflow
Authors: Chen, P. F.; Shibata, K.; Brooks, D. H.; Isobe, H.
2004ApJ...602L..61C Altcode:
In the flare event of 1999 March 18, a threadlike structure observed
in EUV Imaging Telescope images was found to move inward and collapse
to an X-shaped configuration below the ejecta, strongly suggestive
of the occurrence of magnetic reconnection. On the basis of the
numerical results of a coronal mass ejection (CME) flare model, a
similar threadlike structure in the Fe XII 195 Å image is reproduced
in this Letter. It is found that, as in the observations, the thread
experiences an outward motion in the preflare phase, which is followed
by an inward motion. Our simulation suggests that its formation and
outward motion in the preflare phase result from the CME expansion;
after the onset of the flare, the threadlike structure is always
located on the upstream side of the interface between the reconnection
inflow and outflow. Its apparent inward motion, which is several times
slower than the in situ reconnection inflow, is mainly attributed to
the rising motion of the reconnection X-point.
---------------------------------------------------------
Title: A study of the causal relationship between the emergence of
a twisted magnetic flux rope and a small Hα two-ribbon flare
Authors: Brooks, D. H.; Kurokawa, H.; Yoshimura, K.; Kozu, H.; Berger,
T. E.
2003A&A...411..273B Altcode:
We present results from an analysis of a small two-ribbon flare which
occurred above emerging flux in solar active region NOAA 8218 on 1998,
May 13th and which was observed by the Swedish Vacuum Solar Telescope
(SVST) on the island of La Palma, Spain. The relatively simple magnetic
morphology and small size of the flare together with the high quality
of the SVST observations allow us to examine the essential properties
of flares in emerging flux regions in greater detail than before. <P
/>In this paper we compare and contrast the flaring emerging flux region
simultaneously with a non-flaring emerging flux region within the same
field of view. Unusual magnetic footpoint motions are observed in the
flaring region, coincident with the Hα kernels, which result in a
high level of shearing of the magnetic neutral line between opposite
polarities. The Hα images show dark filament structures which form an
inverted S-like shape immediately prior to the flare and then separate
after the energy release disrupts the magnetic field. We interpret
the motions and structures as strong evidence for the emergence of a
twisted magnetic flux rope which developed a sheared configuration with
the overlying magnetic field. In contrast the companion region shows
separating footpoints, with apparent arch-like filament connections in
the Hα images, consistent with the expected appearance of emerging
flux. The observations imply that the attachment of the inverted
S-shaped structure may be an observational consequence of the magnetic
reconnection or untwisting of the field which triggered the flare. We
also find some evidence that the increase in magnetic flux is faster
in the flaring region. <P />Finally, we propose a simple schematic
model of the emergence of a twisted magnetic flux rope and attached
branch which can account for the observed footpoint motions and Hα
structures of the flaring region. Such a model can, in principle,
induce partial magnetic reconnection in the overlying coronal field
and we found some evidence of coronal loop footpoint brightenings
which support our conclusions. Our high resolution study supports the
results of previous authors that even a small twisted structure in an
emerging flux tube can be important for flare production.
---------------------------------------------------------
Title: Spectroscopic diagnostics of UV power and accretion in T
Tauri stars
Authors: Brooks, D. H.; Costa, V. M.
2003MNRAS.339..467B Altcode:
It is known that in the upper atmospheres of the Sun and some late-type
stars there is a systematic relationship between the optically
thin total radiated power and the power emitted by single spectral
lines. Using recently derived emission-measure distributions from IUE
spectra for BP Tau, CV Cha, RY Tau, RU Lupi and GW Ori, we demonstrate
that this is also true for classical T Tauri stars (CTTSs). As in
the solar case it is found that the CIV resonance doublet at 1548 Å
is also the most accurate indicator of the total radiated power from
the atmospheres of CTTSs. Since the total radiated-power density in
CTTSs exceeds that of the Sun by over three orders of magnitude we
derive new analytic expressions that can be used to estimate the
values for these stars. We also discuss the implications of these
results with regard to the influence or absence of accretion in this
sample of stars and suggest that the method can be used to infer
properties of the geometrical structure of the emission regions. As a
demonstration case we also use archived HST-GHRS data to estimate the
total radiative losses in the UV emitting region of BP Tau. We find
values of 4.57 × 10<SUP>9</SUP> erg cm<SUP>-2</SUP> s<SUP>-1</SUP>
and 5.11 × 10<SUP>32</SUP> erg s<SUP>-1</SUP> dependent on the
geometry of the emission region. These results are several orders
of magnitude larger than would be expected if the UV emission came
primarily from an atmosphere covered in solar-like active regions
and are closer to values associated with solar flares. They lead to
luminosity estimates of 0.07 and 0.13 L<SUB>solar</SUB>, respectively,
which are in broad agreement with results obtained from theoretical
accretion shock models. Taken together they suggest that accretion
may well be the dominant contributor to the UV emission in BP Tau.
---------------------------------------------------------
Title: ADAS analysis of the differential emission measure structure
of the inner solar corona . Application of the data adaptive smoothing
approach to the SERTS-89 active region spectrum
Authors: Lanzafame, A. C.; Brooks, D. H.; Lang, J.; Summers, H. P.;
Thomas, R. J.; Thompson, A. M.
2002A&A...384..242L Altcode:
The differential emission measure (DEM) of a solar active region is
derived from SERTS-89 rocket data between 170 and 450 Å (Thomas &
Neupert \cite{Thomas_Neupert:94}). The integral inversion to infer
the DEM distribution from spectral line intensities is performed by
the data adaptive smoothing approach (Thompson \cite{Thompson:90},
\cite{Thompson:91}). Our analysis takes into account the density
dependence of both ionisation fractions and excitation coefficients
according to the collisional-radiative theory as implemented in
ADAS, the Atomic Data and Analysis Structure (McWhirter &
Summers \cite{McWhirter_Summers:84}; Summers \cite{Summers:94};
Summers \cite{Summers:01}). Our strategy aims at checking, using
observational data, the validity and limitations of the DEM method
used for analysing solar EUV spectra. We investigate what information
it is possible to extract, within defined limitations, and how the
method can assist in a number of cases, e.g. abundance determination,
spectral line identification, intensity predictions, and validation
of atomic cross-sections. Using the above data and theory, it is
shown that a spurious multiple peak in the DEM distribution between
log (T<SUB>e</SUB>)=6.1 and 6.7, where T<SUB>e</SUB> is the electron
temperature, may derive from an inaccurate treatment of the population
densities of the excited levels and ionisation fractions or from using
an integral inversion technique with arbitrary smoothing. Therefore,
complex DEM structures, like those proposed for solar and stellar
coronae by several authors, must be considered with caution. We address
also the issue of systematic differences between iso-electronic
sequences and show that these cannot be unambiguously detected in
the coronal lines observed by SERTS. Our results indicate that a
substantial improvement is required in the atomic modelling of the
complex element Fe. The elemental abundance ratio Si/Ne is found to
be close to its photospheric value. The same result may be true for
the Fe/Ne abundance, but this latter result is uncertain because of
the problems found with Fe.
---------------------------------------------------------
Title: Solar Si XI Line Ratios Observed by the Normal Incidence
Spectrometer on SOHO CDS
Authors: Lang, J.; Brooks, D. H.; O'Mullane, M. G.; Pike, C. D.;
Summers, H. P.; Thompson, W. T.
2001SoPh..201...37L Altcode:
New measurements of line intensity ratios in the Be-like ion Si xi are
presented for observations of the quiet Sun, active regions, coronal
holes and above-limb regions obtained using the Coronal Diagnostic
Spectrometer on the Solar and Heliospheric Observatory. A model ion,
constructed using the best available atomic data, is used to predict
the line intensity ratios for a wide range of electron temperatures
and densities. Comparisons of the theoretical ratios with the new
intensity ratios as well as with those from previous solar observations
and laboratory measurements are given. The usefulness of the ratios
for electron temperature and density diagnostics, as well as for
spectrometer calibration, is discussed.
---------------------------------------------------------
Title: An Optical/ultraviolet Study of RW Aur
Authors: Gameiro, J. F.; Costa, V. M.; Brooks, D. H.
2001AGM....18S0707G Altcode: 2001AGAb...18R..78G
RW Aur is a classical T Tauri star showing unusually high activity and
complex patterns of variability in all optical emission and absorption
lines. Periodic variations in the photospheric absorption features
were also found by Petrov et al. (2001). These authors suggest that
axi-symmetric magnetospheric accretion can account for the periodic
phenomena and most of the variations observed in the optical data. They
also made estimates of physical parameters (such as electron density)
in different regions of the accretion stream. It seems clear that most
of the excess emission is related to a strong magnetic field. Here
we extend their analysis into the ultraviolet region of the spectrum
using data from the IUE satellite. We use emission measure analysis
and diagnostic line ratios to estimate the electron density in the
UV emission zone. We also assess the variability in the ultraviolet
spectrum. The results are compared to those obtained from the optical
observations and provide a further quantitative test of the proposed
accretion models.
---------------------------------------------------------
Title: A study of opacity in SOHO-SUMER and SOHO-CDS spectral
observations. I. Opacity deduction at the limb
Authors: Brooks, D. H.; Fischbacher, G. A.; Fludra, A.; Harrison,
R. A.; Innes, D. E.; Landi, E.; Landini, M.; Lang, J.; Lanzafame,
A. C.; Loch, S. D.; McWhirter, R. W. P.; Summers, H. P.
2000A&A...357..697B Altcode:
A study is presented of the optical thickness of spectral lines of
carbon, nitrogen and oxygen ions in the quiet sun. The observations
consist of cross limb scans by the SUMER and CDS spectrometers on
the SOHO spacecraft. A maximum likelihood spectral line fitting code
has been adapted to analyse the multiplet profiles and to provide an
assessment of errors in the count rates, especially of close lying
components. Branching multiplet component ratios are presented as a
function of position across the limb and contrasted with theoretical
ratios in the optically thin case. The emergent fluxes are analysed
in an escape probability model to deduce the optical thicknesses in
the various spectral lines. Different specifications of the escape
probability are examined. These are used to compare the observations
with a geometric model of the emitting layer thickness across the limb
and the thinning of the emitting layer above the limb. Classification
of the deviations of quiet sun spectral line intensities from the
optically thin case is given to assist in the critical selection of
lines for differential emission measure analysis. This is linked to
a general purpose code for the calculation of the influence of the
line radiation fields on the local excited state population structure
of the selected ions so that the fluxes in any spectral lines can be
predicted. The Atomic Data and Analysis Structure (ADAS) was used for
the atomic calculations and data of the paper.
---------------------------------------------------------
Title: The quiet Sun extreme ultraviolet spectrum observed in normal
incidence by the SOHO coronal diagnostic spectrometer
Authors: Brooks, D. H.; Fischbacher, G. A.; Fludra, A.; Harrison,
R. A.; Innes, D. E.; Landi, E.; Landini, M.; Lang, J.; Lanzafame,
A. C.; Loch, S. D.; McWhirter, R. W. P.; Summers, H. P.; Thompson,
W. T.
1999A&A...347..277B Altcode:
The extreme ultraviolet quiet Sun spectrum, observed at normal incidence
by the Coronal Diagnostic Spectrometer on the SOHO spacecraft, is
presented. The spectrum covers the wavelength ranges 308-381 Ä and
513-633 Ä and is based on data recorded at various positions on the
solar disk between October 1996 and February 1997. Datasets at twelve
of these `positions' were judged to be free from active regions and
data faults and selected for detailed study. A constrained maximum
likelihood spectral line fitting code was used to analyse the spectral
features. In all over 200 spectrum lines have been measured and about
50% identified. The line identification process consisted of a number
of steps. Firstly assignment of well known lines was made and used to
obtain the primary wavelength calibration. Variations of wavelengths
with position were used to assess the precision of calibration
achievable. Then, an analysis method first used in studies with the
CHASE experiment, was applied to the new observations. The behaviour
of the intensities of lines from like ions over the twelve positions,
called `position patterns', were used to distinguish probable emitters
of weaker lines and extend the identifications. Spectral line widths
and expected multiplet intensities were examined to identify lines and
probable blends. The product of the study is a table which includes all
clearly observed emission lines, their measured wavelengths, widths
and count rates. Adopted laboratory wavelengths, ion and transition
designations are also presented for identified lines. The table has an
estimate of the uncertainty of the count rates based on a statistical
analysis of the variability of each line. A marked spectrum is also
provided.
---------------------------------------------------------
Title: EUV Spectral Variability and Non-Equilibrium Ionisation in the
'Quiet' Sun
Authors: Brooks, D. H.; Summers, H. P.; Harrison, R. A.; Lang, J.;
Lanzafame, A. C.
1998Ap&SS.261...91B Altcode: 1999Ap&SS.261...91B
Recent spectroscopic observations by the Solar and Heliospheric
Observatory (SOHO) have revealed the dynamic nature of even the
'quiet' Sun. Spectral variability data clearly show that dynamics in
the solar upper atmosphere take place on timescales shorter than those
of ionisation relaxation. Accuracy in the interpretation of diagnostic
spectral data can only be maintained through detailed quantitative
modelling of the relevant atomic physics. In particular, dynamical
plasma models of the solar plasma require matching dynamic atomic
models to underpin conclusions drawn from the spectral reduction. The
inclusion of important effects such as finite plasma electron density
and the influence of metastable levels is essential to reduce the
uncertainties associated with equilibrium assumptions.
