Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: On the 2012 October 23 circular ribbon flare: emission features and
  magnetic topology   Circular ribbon flares are usually related to spine-fan type magnetic
topology containing null-points. In this paper, we investigate an X-class
circular ribbon flare on 2012 October 23, using the multi-wavelength data from
the \textit{Solar Dynamics Observatory}, \textit{Hinode}, and the
\textit{Ramaty High Energy Solar Spectroscopic Imager}. In \ion{Ca}{2} H
emission, the flare showed three ribbons with two highly elongated ones inside
and outside a quasi-circular one, respectively. A hot channel was displayed in
the extreme ultraviolet (EUV) emissions that infers the existence of a magnetic
flux rope. Two hard X-ray (HXR) sources in the 12--25 keV energy band were
located at the footpoints of this hot channel. Using a nonlinear force-free
magnetic field extrapolation, we identify three topological structures: (1) a
3D null-point, (2) a flux rope below the fan of the null-point, and (3) a
large-scale quasi-separatrix layers (QSL) induced by the quadrupolar-like
magnetic field of the active region. We find that the null-point is embedded
within the large-scale QSL. In our case, all three identified topological
structures must be considered to explain all the emission features associated
with the observed flare. Besides, the HXR sources are regarded as the
consequence of the reconnection within or near the border of the flux rope.

35
The categories of this paper are: mtrl-th
28
The categories of this paper are: alg-geom
20
The categories of this paper are: acc-phys
14
The categories of this paper are: math-ph
1
The categories of this paper are: cs
22
The categories of this paper are: chao-dyn
24
The categories of this paper are: dg-ga
32
The categories of this paper are: atom-ph
10
The categories of this paper are: q-bio
13
The categories of this paper are: quant-ph
12
The categories of this paper are: nucl-th
33
The categories of this paper are: plasm-ph
3
The categories of this paper are: physics
5
The categories of this paper are: gr-qc
11
The categories of this paper are: hep-lat
7
The categories of this paper are: hep-th