Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: A Hot Downflowing Model Atmosphere For Umbral Flashes And The Physical
  Properties Of Their Dark Fibrils   We perform NLTE inversions in a large set of umbral flashes, including the
dark fibrils visible within them, and in the quiescent umbra by using the
inversion code NICOLE on a set of full Stokes high-resolution Ca II 8542 A
observations of a sunspot at disk center. We find that the dark structures have
Stokes profiles that are distinct from those of the quiescent and flashed
regions. They are best reproduced by atmospheres that are more similar to the
flashed atmosphere in terms of velocities, even if with reduced amplitudes. We
also find two sets of solutions that finely fit the flashed profiles: a set
that is upflowing, featuring a transition region that is deeper than in the
quiescent case and preceded by a slight dip in temperature, and a second
solution with a hotter atmosphere in the chromosphere but featuring downflows
close to the speed of sound at such heights. Such downflows may be related, or
even dependent, on the presence of coronal loops, rooted in the umbra of
sunspots, as is the case in the region analyzed. Similar loops have been
recently observed to have supersonic downflows in the transition region and are
consistent with the earlier "sunspot plumes" which were invariably found to
display strong downflows in sunspots. Finally we find, on average, a magnetic
field reduction in the flashed areas, suggesting that the shock pressure is
moving field lines in the upper layers.

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The categories of this paper are: acc-phys
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The categories of this paper are: hep-ex
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The categories of this paper are: adap-org
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The categories of this paper are: bayes-an
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The categories of this paper are: ao-sci
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The categories of this paper are: comp-gas
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The categories of this paper are: atom-ph
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The categories of this paper are: nucl-ex
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The categories of this paper are: gr-qc
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The categories of this paper are: stat
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The categories of this paper are: econ
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The categories of this paper are: cond-mat
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The categories of this paper are: hep-lat
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The categories of this paper are: hep-th
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The categories of this paper are: dg-ga
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The categories of this paper are: nucl-th