Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Midterm Periodicity Analysis of the Mount Wilson Magnetic Indices Using
  the Synchrosqueezing Transform   A novel time--frequency technique, called the synchrosqueezing transform
(SST), is used to investigate the midterm periodic variations of magnetic
fields on the solar surface. The Magnetic Plage Strength Index (MPSI) and the
Mount Wilson Sunspot Index (MWSI), measured daily by the Mount Wilson
Observatory between 1970 January 19 and 2012 January 22, are selected. The
short-, mid, and longer-term periodicities are represented and decomposed by
the SST with hardly any mode mixing. This demonstrates that the SST is a useful
time--frequency analysis technique to characterize the periodic modes of
helioseismic data. Apart from the fundamental modes of the annual periodicity,
$\sim$27 day rotational cycle and $\sim$11 year solar cycle, the SST reveals
several midterm periodicities in the two magnetic activity indices,
specifically, $\sim$157 day (i.e., Rieger-type periodicity), and $\sim$1.3 and
1.7 years. The periodic modes, with 116.4 and 276.2 day periodicity in the
MPSI, with 108.5 and 251.6 day periodicity in the MWSI, and the 157.7 day
periodicity in the two indices, are in better accord with those significant
periodicities derived from the Rossby waves theoretical model. This study
suggests that the modes are caused by the Rossby waves. For the 1.30 and 1.71
year periodicity of the MPSI, and the 1.33 and 1.67 year periodicity of the
MWSI, our analysis infers that they are related to those periodicity with the
same timescale in the interior of the Sun and in the high atmospheric layers.

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The categories of this paper are: plasm-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: acc-phys
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The categories of this paper are: patt-sol
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The categories of this paper are: q-fin
10
The categories of this paper are: q-bio
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The categories of this paper are: nucl-th
7
The categories of this paper are: hep-th
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The categories of this paper are: cmp-lg
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The categories of this paper are: nucl-ex
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The categories of this paper are: chem-ph
1
The categories of this paper are: cs
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The categories of this paper are: stat
2
The categories of this paper are: math
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The categories of this paper are: eess