Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Shape Parameters of 1991 to 2016 Solar Corona   The global structure of solar corona observed in optical window is governed
by the global magnetic field with different characteristics over solar activity
cycle. Ludendorff flattening index becomes a popular measure of the global
structure of solar corona as observed during eclipse. In this study, 15 digital
images of solar corona from 1991 to 2016 were analyzed in order to construct
the coronal flattening profiles as a function of radius. In most of the cases,
the profile can be modeled with 2nd order polynomial function so that the
radius with maximum flattening index ($R_{\text{max}}$) can be determined.
Along with this value, Ludendorff index ($a+b$) was also calculated. Both
Ludendorff index and $R_{\text{max}}$ show anti-correlation with monthly
sunspot number, though the $R_{\text{max}}$ values are more scattered. The
variation of $R_{\text{max}}$ can be regarded as the impact of changing coronal
brightness profile over equator.

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The categories of this paper are: q-bio
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The categories of this paper are: cond-mat
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The categories of this paper are: atom-ph
34
The categories of this paper are: chem-ph
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The categories of this paper are: dg-ga
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The categories of this paper are: supr-con
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The categories of this paper are: bayes-an
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The categories of this paper are: mtrl-th
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The categories of this paper are: math-ph
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The categories of this paper are: plasm-ph
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The categories of this paper are: alg-geom
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The categories of this paper are: patt-sol
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The categories of this paper are: hep-th
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The categories of this paper are: nucl-ex
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The categories of this paper are: ao-sci
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The categories of this paper are: hep-ex