Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Comparison of Two Coronal Magnetic Field Models for Reconstructing a
  Sigmoidal Solar Active Region With Coronal Loops   Magnetic field extrapolation is an important tool to study the
three-dimensional (3D) solar coronal magnetic field which is difficult to
directly measure. Various analytic models and numerical codes exist but their
results often drastically differ. Thus a critical comparison of the modeled
magnetic field lines with the observed coronal loops is strongly required to
establish the credibility of the model. Here we compare two different
non-potential extrapolation codes, a non-linear force-free field code
(CESE-MHD-NLFFF) and a non-force-free field (NFFF) code in modeling a solar
active region (AR) that has a sigmoidal configuration just before a major flare
erupted from the region. A 2D coronal-loop tracing and fitting method is
employed to study the 3D misalignment angles between the extrapolated magnetic
field lines and the EUV loops as imaged by SDO/AIA. It is found that the
CESE-MHD-NLFFF code with preprocessed magnetogram performs the best, outputting
a field which matches the coronal loops in the AR core imaged in AIA 94 {\AA}
with a misalignment angle of ~10 degree. This suggests that the CESE-MHD-NLFFF
code, even without using the information of coronal loops in constraining the
magnetic field, performs as good as some coronal-loop forward-fitting models.
For the loops as imaged by AIA 171 {\AA} in the outskirts of the AR, all the
codes including the potential-field give comparable results of mean
misalignment angle (~30 degree). Thus further improvement of the codes is
needed for a better reconstruction of the long loops enveloping the core
region.

32
The categories of this paper are: atom-ph
10
The categories of this paper are: q-bio
1
The categories of this paper are: cs
37
The categories of this paper are: supr-con
30
The categories of this paper are: q-alg
0
The categories of this paper are: hep-ph
26
The categories of this paper are: bayes-an
23
The categories of this paper are: solv-int
24
The categories of this paper are: dg-ga
31
The categories of this paper are: ao-sci
20
The categories of this paper are: acc-phys
8
The categories of this paper are: hep-ex
14
The categories of this paper are: math-ph
2
The categories of this paper are: math
13
The categories of this paper are: quant-ph
5
The categories of this paper are: gr-qc