Helioseismic test of non-homologous solar radius changes with the 11-year activity cycle

Abstract

Recent models of variations of the Sun's structure with the 11-year activity cycle by Sofia et al (2005) predict strong non-homologous changes of the radius of subsurface layers, due to subsurface magnetic fields and field-modulated turbulence. According to their best model the changes of the surface radius may be 1000 times larger than those at the depth of 5 Mm. We use f-mode oscillation frequency data from the MDI instrument of Solar and Heliospheric Observatory (SOHO) and measurements of the solar surface radius variations from SOHO and ground-based observatories during solar cycle 23 (1996-2005) to put constraints on the radius changes. The results show that the above model overestimates the change of the radius at the surface relative to the change at 5Mm.

arXiv comment9 pages, 2 figures, ApJ Lett in press

References in corpus (5)

• Sources of oscillation frequency increase with rising solar activity
• Changes in the subsurface stratification of the Sun with the 11-year activity cycle
• Seismic Test of Solar Models, Solar Neutrinos and Implications for Metal-Rich Accretion
• Helioseismic Probing of Solar Variability: The Formalism and Simple Asses sments
• The Non-Homologous Nature of Solar Diameter Variations

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• What have we learned from helioseismology, what have we really learned, and what do we aspire to learn?
• Impact of a radius and composition variation on the solar subsurface layers stratification
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