Changes in the subsurface stratification of the Sun with the 11-year activity cycle

Abstract

We report on the changes of the Sun's subsurface stratification inferred from helioseismology data. Using SOHO/MDI (SOlar and Heliospheric Observatory/Michelson Doppler Imager) data for the last 9 years and, more precisely, the temporal variation of f-mode frequencies, we have computed the variation of the radius of subsurface layers of the Sun by applying helioseismic inversions. We have found a variability of the ``helioseismic'' radius in antiphase with the solar activity, with the strongest variations of the stratification being just below the surface around 0.995$R_{\odot }$. Besides, the radius of the deeper layers of the Sun, between 0.975$R_{\odot }$ and 0.99$R_{\odot }$ changes in phase with the 11-year cycle.

arXiv comment14 pages, 7 figures, accepted in ApJL

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• Helioseismic Probing of Solar Variability: The Formalism and Simple Asses sments

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