Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Solar prominences with Na and Mg emissions and centrally reversed Balmer
  line   We study spectral lines in exceptionally bright solar limb prominences with
pronounced sodium and magnesium emission. We find that most prominences with
significant NaD2 and Mgb2 emission show centrally reversed profiles of H-alpha
and occasionally even of H-beta, which are are well reproduced by semi-infinite
models. The maximum H-alpha source function corresponds to an excitation
temperature of 3950 K, for pronounced central reversions 4000 K; the related
optical thickness exceeds 10.0. The narrow widths of the NaD2 and Mgb2 profiles
yield a non-thermal broadening of 5 km/s.

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The categories of this paper are: cmp-lg
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The categories of this paper are: comp-gas
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The categories of this paper are: q-fin
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The categories of this paper are: acc-phys
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The categories of this paper are: econ
3
The categories of this paper are: physics
16
The categories of this paper are: stat
5
The categories of this paper are: gr-qc
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The categories of this paper are: hep-ex
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The categories of this paper are: atom-ph
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The categories of this paper are: alg-geom
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The categories of this paper are: chao-dyn
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The categories of this paper are: cs
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The categories of this paper are: plasm-ph
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The categories of this paper are: nlin
24
The categories of this paper are: dg-ga