Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Very Long-period Pulsations before the Onset of Solar Flares   Solar flares are the most powerful explosions occurring in the solar system,
which may lead to disastrous space weather events and impact various aspects of
our Earth. So far, it is still a big challenge in modern astrophysics to
understand the origin of solar flares and predict their onset. Based on the
analysis of soft X-ray emission observed by the Geostationary Operational
Environmental Satellite (GOES), this work reported a new discovery of very
long-periodic pulsations occurred in the preflare phase before the onset of
solar flares (preflare-VLPs). These pulsations are typically with period of 8 -
30 min and last for about 1 - 2 hours. They are possibly generated from LRC
oscillations of plasma loops where electric current dominates the physical
process during magnetic energy accumulation in the source region. The
preflare-VLP provides an essential information for understanding the triggering
mechanism and origin of solar flares, and may help us to response to solar
explosions and the corresponding disastrous space weather events as a
convenient precursory indicator.

27
The categories of this paper are: comp-gas
14
The categories of this paper are: math-ph
4
The categories of this paper are: cond-mat
13
The categories of this paper are: quant-ph
0
The categories of this paper are: hep-ph
22
The categories of this paper are: chao-dyn
3
The categories of this paper are: physics
28
The categories of this paper are: alg-geom
18
The categories of this paper are: econ
10
The categories of this paper are: q-bio
12
The categories of this paper are: nucl-th
30
The categories of this paper are: q-alg
23
The categories of this paper are: solv-int
37
The categories of this paper are: supr-con
36
The categories of this paper are: cmp-lg
32
The categories of this paper are: atom-ph