Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Observation of Magnetic reconnection at a 3D null point associated with
  a solar eruption   Magnetic null has long been recognized as a special structure serving as a
preferential site for magnetic reconnection (MR). However, the direct
observational study of MR at null-points is largely lacking. Here, we show the
observations of MR around a magnetic null associated with an eruption that
resulted in an M1.7 flare and a coronal mass ejection. The GOES X- ray profile
of the flare exhibited two peaks at 02:23 UT and 02:40 UT on 2012 November 8,
respectively. Based on the imaging observations, we find that the first and
also primary X- ray peak was originated from MR in the current sheet underneath
the erupting magnetic flux rope (MFR). On the other hand, the second and also
weaker X-ray peak was caused by MR around a null-point located above the
pre-eruption MFR. The interaction of the null-point and the erupting MFR can be
described as a two-step process. During the first step, the erupting and fast
expanding MFR passed through the null-point, resulting in a significant
displacement of the magnetic field surrounding the null. During the second
step, the displaced magnetic field started to move back, resulting in a
converging inflow and subsequently the MR around the null. The null-point
reconnection is a different process from the current sheet reconnection in this
flare; the latter is the cause of the main peak of the flare, while the former
is the cause of the secondary peak of the flare and the conspicuous high-lying
cusp structure.

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The categories of this paper are: supr-con
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The categories of this paper are: cmp-lg
3
The categories of this paper are: physics
13
The categories of this paper are: quant-ph
7
The categories of this paper are: hep-th
24
The categories of this paper are: dg-ga
19
The categories of this paper are: eess
21
The categories of this paper are: adap-org
35
The categories of this paper are: mtrl-th
31
The categories of this paper are: ao-sci
9
The categories of this paper are: nlin
20
The categories of this paper are: acc-phys
15
The categories of this paper are: nucl-ex
12
The categories of this paper are: nucl-th
8
The categories of this paper are: hep-ex
17
The categories of this paper are: q-fin