Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Solar Magnetic Field Studies Using the 12-Micron Emission Lines. IV.
  Observations of a Delta-Region Solar Flare   We have recently developed the capability to make solar vector (Stokes IQUV)
magnetograms using the infrared line of MgI at 12.32 microns. On 24 April 2001,
we obtained a vector magnetic map of solar active region NOAA 9433,
fortuitously just prior to the occurrence of an M2 flare. Examination of a
sequence of SOHO/MDI magnetograms, and comparison with ground-based H-alpha
images, shows that the flare was produced by the cancellation of newly emergent
magnetic flux outside of the main sunspot. The very high Zeeman-sensitivity of
the 12-micron data allowed us to measure field strengths on a spatial scale
which was not directly resolvable. At the flare trigger site, opposite polarity
fields of 2700 and 1000 Gauss occurred within a single 2 arc-sec resolution
element, as revealed by two resolved Zeeman splittings in a single spectrum.
Our results imply an extremely high horizontal field strength gradient (5 G/km)
prior to the flare, significantly greater than seen in previous studies. We
also find that the magnetic energy of the cancelling fields was more than
sufficient to account for the flare's X-ray luminosity.

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The categories of this paper are: cs
36
The categories of this paper are: cmp-lg
14
The categories of this paper are: math-ph
29
The categories of this paper are: funct-an
22
The categories of this paper are: chao-dyn
8
The categories of this paper are: hep-ex
18
The categories of this paper are: econ
3
The categories of this paper are: physics
10
The categories of this paper are: q-bio
37
The categories of this paper are: supr-con
35
The categories of this paper are: mtrl-th
33
The categories of this paper are: plasm-ph
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The categories of this paper are: dg-ga
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The categories of this paper are: hep-ph
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The categories of this paper are: eess
28
The categories of this paper are: alg-geom