Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Solar Cycle Variability and Surface Differential Rotation from Ca II
  K-Line Time Series Data   Analysis of over 36 years of time series data from the NSO/AFRL/Sac Peak
K-line monitoring program elucidates five components of the variation of the
seven measured chromospheric parameters: (a) the solar cycle (period ~ 11
years), (b) quasi-periodic variations (periods ~100 days), (c) a broad band
stochastic process (wide range of periods), (d) rotational modulation, and (e)
random observational errors, independent of (a)-(d). Correlation and power
spectrum analyses elucidate periodic and aperiodic variation of these
parameters. Time-frequency analysis illuminates periodic and quasi periodic
signals, details of frequency modulation due to differential rotation, and in
particular elucidates the rather complex harmonic structure (a) and (b) at time
scales in the range ~0.1 - 10 years. These results using only full-disk data
suggest that similar analyses will be useful at detecting and characterizing
differential rotation in stars from stellar light-curves such as thosebeing
produced by NASA's Kepler observatory. Component (c) consists of variations
over a range of timescales, in the manner of a 1/f random process with a
power-law slope index that varies in a systematic way. A time-dependent
Wilson-Bappu effect appears to be present in the solar cycle variations (a),
but not in the more rapid variations of the stochastic process (c). Component
(d) characterizes differential rotation of the active regions. Component (e) is
of course not characteristic of solar variability, but the fact that the
observational errors are quite small greatly facilitates the analysis of the
other components. The data analyzed in this paper can be found at the National
Solar Observatory web site http://nsosp.nso.edu/cak_mon/, or by file transfer
protocol at ftp://ftp.nso.edu/idl/cak.parameters

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The categories of this paper are: hep-lat
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The categories of this paper are: quant-ph
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The categories of this paper are: alg-geom
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The categories of this paper are: supr-con
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The categories of this paper are: hep-ph
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The categories of this paper are: hep-th
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The categories of this paper are: q-fin
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The categories of this paper are: bayes-an
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The categories of this paper are: plasm-ph
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The categories of this paper are: hep-ex
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The categories of this paper are: cs
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The categories of this paper are: mtrl-th
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The categories of this paper are: atom-ph
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The categories of this paper are: math
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The categories of this paper are: eess
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The categories of this paper are: funct-an