Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Rapid Changes of Photospheric Magnetic Field after Tether-Cutting
  Reconnection and Magnetic Implosion   The rapid, irreversible change of the photospheric magnetic field has been
recognized as an important element of the solar flare process. This Letter
reports such a rapid change of magnetic fields during the 2011 February 13 M6.6
flare in NOAA AR 11158 that we found from the vector magnetograms of the
Helioseismic and Magnetic Imager with 12-min cadence. High-resolution
magnetograms of Hinode that are available at ~-5.5, -1.5, 1.5, and 4 hrs
relative to the flare maximum are used to reconstruct three-dimensional coronal
magnetic field under the nonlinear force-free field (NLFFF) assumption. UV and
hard X-ray images are also used to illuminate the magnetic field evolution and
energy release. The rapid change is mainly detected by HMI in a compact region
lying in the center of the magnetic sigmoid, where the mean horizontal field
strength exhibited a significant increase by 28%. The region lies between the
initial strong UV and hard X-ray sources in the chromosphere, which are
cospatial with the central feet of the sigmoid according to the NLFFF model.
The NLFFF model further shows that strong coronal currents are concentrated
immediately above the region, and that more intriguingly, the coronal current
system underwent an apparent downward collapse after the sigmoid eruption.
These results are discussed in favor of both the tether-cutting reconnection
producing the flare and the ensuing implosion of the coronal field resulting
from the energy release.

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The categories of this paper are: math
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The categories of this paper are: cond-mat
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The categories of this paper are: chem-ph
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The categories of this paper are: quant-ph
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The categories of this paper are: acc-phys
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The categories of this paper are: bayes-an
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The categories of this paper are: hep-th
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The categories of this paper are: eess
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The categories of this paper are: nlin
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The categories of this paper are: q-fin
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The categories of this paper are: atom-ph
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The categories of this paper are: patt-sol
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The categories of this paper are: cs
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The categories of this paper are: stat
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The categories of this paper are: mtrl-th
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The categories of this paper are: hep-lat