Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Time Evolution of Coronal Magnetic Helicity in the Flaring Active Region
  NOAA 10930   To study the three-dimensional (3D) magnetic field topology and its long-term
evolution associated with the X3.4 flare of 2006 December 13, we investigate
the coronal relative magnetic helicity in the flaring active region (AR) NOAA
10930 during the time period of December 8-14. The coronal helicity is
calculated based on the 3D nonlinear force-free magnetic fields reconstructed
by the weighted optimization method of Wiegelmann, and is compared with the
amount of helicity injected through the photospheric surface of the AR. The
helicity injection is determined from the magnetic helicity flux density
proposed by Pariat et al. using Solar and Heliospheric Observatory/Michelson
Doppler Imager magnetograms. The major findings of this study are the
following. (1) The time profile of the coronal helicity shows a good
correlation with that of the helicity accumulation by injection through the
surface. (2) The coronal helicity of the AR is estimated to be
-4.3$\times$10$^{43}$ Mx$^{2}$ just before the X3.4 flare. (3) This flare is
preceded not only by a large increase of negative helicity,
-3.2$\times$10$^{43}$ Mx$^{2}$, in the corona over ~1.5 days but also by
noticeable injections of positive helicity though the photospheric surface
around the flaring magnetic polarity inversion line during the time period of
the channel structure development. We conjecture that the occurrence of the
X3.4 flare is involved with the positive helicity injection into an existing
system of negative helicity.

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The categories of this paper are: supr-con
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The categories of this paper are: solv-int
9
The categories of this paper are: nlin
10
The categories of this paper are: q-bio
1
The categories of this paper are: cs
29
The categories of this paper are: funct-an
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The categories of this paper are: comp-gas
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The categories of this paper are: hep-ph
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The categories of this paper are: math-ph
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The categories of this paper are: alg-geom
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The categories of this paper are: stat
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The categories of this paper are: atom-ph
7
The categories of this paper are: hep-th
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The categories of this paper are: nucl-th
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The categories of this paper are: q-alg
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The categories of this paper are: patt-sol