Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Self-absorption in the solar transition region   Transient brightenings in the transition region of the Sun have been studied
for decades and are usually related to magnetic reconnection. Recently,
absorption features due to chromospheric lines have been identified in
transition region emission lines raising the question of the thermal
stratification during such reconnection events. We analyse data from the
Interface Region Imaging Spectrograph (IRIS) in an emerging active region. Here
the spectral profiles show clear self-absorption features in the transition
region lines of Si\,{\sc{iv}}. While some indications existed that opacity
effects might play some role in strong transition region lines, self-absorption
has not been observed before. We show why previous instruments could not
observe such self-absorption features, and discuss some implications of this
observation for the corresponding structure of reconnection events in the
atmosphere. Based on this we speculate that a range of phenomena, such as
explosive events, blinkers or Ellerman bombs, are just different aspects of the
same reconnection event occurring at different heights in the atmosphere.

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The categories of this paper are: q-alg
31
The categories of this paper are: ao-sci
22
The categories of this paper are: chao-dyn
14
The categories of this paper are: math-ph
29
The categories of this paper are: funct-an
9
The categories of this paper are: nlin
16
The categories of this paper are: stat
4
The categories of this paper are: cond-mat
17
The categories of this paper are: q-fin
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The categories of this paper are: alg-geom
11
The categories of this paper are: hep-lat
3
The categories of this paper are: physics
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The categories of this paper are: patt-sol
5
The categories of this paper are: gr-qc
13
The categories of this paper are: quant-ph
33
The categories of this paper are: plasm-ph