Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Asteroseismology and Magnetic Cycles   Small cyclic variations in the frequencies of acoustic modes are expected to
be a common phenomenon in solar-like pulsators, as a result of stellar magnetic
activity cycles. The frequency variations observed throughout the solar and
stellar cycles contain information about structural changes that take place
inside the stars as well as about variations in magnetic field structure and
intensity. The task of inferring and disentangling that information is,
however, not a trivial one. In the sun and solar-like pulsators, the direct
effect of the magnetic field on the oscillations might be significantly
important in regions of strong magnetic field (such as solar- / stellar-spots),
where the Lorentz force can be comparable to the gas-pressure gradient. Our aim
is to determine the sun- / stellar-spots effect on the oscillation frequencies
and attempt to understand if this effect contributes strongly to the frequency
changes observed along the magnetic cycle. The total contribution of the spots
to the frequency shifts results from a combination of direct and indirect
effects of the magnetic field on the oscillations. In this first work we
considered only the indirect effect associated with changes in the
stratification within the starspot. Based on the solution of the wave equation
and the variational principle we estimated the impact of these stratification
changes on the oscillation frequencies of global modes in the sun and found
that the induced frequency shifts are about two orders of magnitude smaller
than the frequency shifts observed over the solar cycle.

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The categories of this paper are: plasm-ph
16
The categories of this paper are: stat
20
The categories of this paper are: acc-phys
32
The categories of this paper are: atom-ph
15
The categories of this paper are: nucl-ex
30
The categories of this paper are: q-alg
11
The categories of this paper are: hep-lat
8
The categories of this paper are: hep-ex
27
The categories of this paper are: comp-gas
5
The categories of this paper are: gr-qc
28
The categories of this paper are: alg-geom
12
The categories of this paper are: nucl-th
31
The categories of this paper are: ao-sci
0
The categories of this paper are: hep-ph
25
The categories of this paper are: patt-sol
22
The categories of this paper are: chao-dyn