Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: First nonlinear force-free field extrapolations of SOLIS/VSM data   We study the coronal magnetic field structure inside active regions and its
temporal evolution. We attempt to compare the magnetic configuration of an
active region in a very quiet period with that for the same region during a
flare. Probably for the first time, we use vector magnetograph data from the
Synoptic Optical Long-term Investigations of the Sun survey (SOLIS) to model
the coronal magnetic field as a sequence of nonlinear force-free equilibria. We
study the active region NOAA 10960 observed on 2007 June 7 with three snapshots
taken during a small C1.0 flare of time cadence 10 minutes and six snapshots
during a quiet period. The total magnetic energy in the active region was
approximately $3 \times 10^{25}$ J. Before the flare the free magnetic energy
was about 5% of the potential field energy. A part of this excess energy was
released during the flare, producing almost a potential configuration at the
beginning of the quiet period. During the investigated period, the coronal
magnetic energy was only a few percent higher than that of the potential field
and consequently only a small C1.0 flare occurred. This was compared with an
earlier investigated active region 10540, where the free magnetic energy was
about 60% higher than that of the potential field producing two M-class flares.
However, the free magnetic energy accumulates before and is released during the
flare which appears to be the case for both large and small flares.

4
The categories of this paper are: cond-mat
20
The categories of this paper are: acc-phys
26
The categories of this paper are: bayes-an
27
The categories of this paper are: comp-gas
11
The categories of this paper are: hep-lat
17
The categories of this paper are: q-fin
8
The categories of this paper are: hep-ex
34
The categories of this paper are: chem-ph
33
The categories of this paper are: plasm-ph
28
The categories of this paper are: alg-geom
25
The categories of this paper are: patt-sol
31
The categories of this paper are: ao-sci
9
The categories of this paper are: nlin
1
The categories of this paper are: cs
37
The categories of this paper are: supr-con
23
The categories of this paper are: solv-int