Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Does the Sun Shrink with Increasing Magnetic Activity?   We have analyzed the full set of SOHO/MDI f- and p-mode oscillation
frequencies from 1996 to date in a search for evidence of solar radius
evolution during the rising phase of the current activity cycle. Like Antia et
al. (2000), we find that a significant fraction of the f-mode frequency changes
scale with frequency; and that if these are interpreted in terms of a radius
change, it implies a shrinking sun. Our inferred rate of shrinkage is about 1.5
km/y, which is somewhat smaller than found by Antia et al. We argue that this
rate does not refer to the surface, but rather to a layer extending roughly
from 4 to 8 Mm beneath the visible surface. The rate of shrinking may be
accounted for by an increasing radial component of the rms random magnetic
field at a rate that depends on its radial distribution. If it were uniform,
the required field would be ~7 kG. However, if it were inwardly increasing,
then a 1 kG field at 8 Mm would suffice.
  To assess contribution to the solar radius change arising above 4Mm, we
analyzed the p-mode data. The evolution of the p-mode frequencies may be
explained by a magnetic^M field growing with activity. The implications of the
near-surface magnetic field changes depend on the anisotropy of the random
magnetic field. If the field change is predominantly radial, then we infer an
additional shrinking at a rate between 1.1-1.3 km/y at the photosphere. If on
the other hand the increase is isotropic, we find a competing expansion at a
rate of 2.3 km/y. In any case, variations in the sun's radius in the activity
cycle are at the level of 10^{-5} or less, hence have a negligible contribution
to the irradiance variations.

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The categories of this paper are: dg-ga
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The categories of this paper are: chao-dyn
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The categories of this paper are: hep-ph
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The categories of this paper are: eess
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The categories of this paper are: nlin
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The categories of this paper are: patt-sol
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The categories of this paper are: solv-int
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The categories of this paper are: atom-ph
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The categories of this paper are: gr-qc
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The categories of this paper are: funct-an
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The categories of this paper are: hep-th
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The categories of this paper are: quant-ph
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The categories of this paper are: cs
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The categories of this paper are: econ
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The categories of this paper are: chem-ph
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The categories of this paper are: q-bio