Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Negative flare in the He I 10830 \AA\ line in facula   A small-scale flare SOL2012-09-21T02:19 (B2) occurred in a spotless active
region that we observed at a ground-based telescope equipped with a
spectrograph. During the flare, we registered an increase in absorption in the
He I 10830 \AA\ line by 25%, while other chromospheric and coronal spectral
lines demonstrated increase in brightness at the same location. This phenomenon
called negative flare had rarely been observed at the Sun before. In this
paper, we describe the morphology of this flare and investigate its dynamics
based on our spectral observations and space imaging data. The H$\alpha$ and He
I 10830 \AA\ lines reach their extreme intensities 5 and 6 minutes after the
171 \AA\ line. The brightening first occurred in the 171 \AA\ and 193 \AA\
Solar Dynamics Observatory (SDO) channels followed by the 94 \AA, 304 \AA, and
1600 \AA\ signals $\sim$2 minutes after (for the maximum phases). However, the
abrupt changes in line-of-sight (LOS) velocities in the chromospheric lines
occur simultaneously with the intensity changes in the 304 \AA\ and 1600 \AA\
lines: we observed a downward motion that was followed by two upward motions.
The measured horizontal speed of the perturbation propagation was close to 70
km s$^{-1}$ both in the chromospheric and coronal lines. We assume that we
observed the photoionization-recombination process caused by UV radiation from
the transition region during the coronal flare. With this, we point out the
difficulties in interpreting the time lag between the emission maximum in the
SDO UV channels and the second absorption maximum in the He I 10830 \AA\ line.

31
The categories of this paper are: ao-sci
37
The categories of this paper are: supr-con
22
The categories of this paper are: chao-dyn
36
The categories of this paper are: cmp-lg
10
The categories of this paper are: q-bio
25
The categories of this paper are: patt-sol
13
The categories of this paper are: quant-ph
18
The categories of this paper are: econ
3
The categories of this paper are: physics
35
The categories of this paper are: mtrl-th
20
The categories of this paper are: acc-phys
5
The categories of this paper are: gr-qc
26
The categories of this paper are: bayes-an
14
The categories of this paper are: math-ph
4
The categories of this paper are: cond-mat
11
The categories of this paper are: hep-lat