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Cyclic Changes of the Sun's Seismic Radius View all abstracts by submitter

Alexander Kosovichev   Submitted: 2018-05-25 12:01

The questions whether the Sun shrinks with the solar activity and what causes this have been a subject of debate. Helioseismology provides means to measure with high precision the radial displacement of subsurface layers, co-called "seismic radius", through analysis of oscillation frequencies of surface gravity (f) modes. Here, we present results of a new analysis of twenty one years of helioseismology data from two space missions, Solar and Heliospheric Observatory (SoHO) and Solar Dynamics Observatory (SDO), which allow us to resolve previous uncertainties and compare variations of the seismic radius in two solar cycles. After removing the f-mode frequency changes associated with the surface activity we find that the mean seismic radius is reduced by 1-2 km during the solar maxima, and that most significant variations of the solar radius occur beneath the visible surface of the Sun at the depth of about 5 Mm, where the radius is reduced by 5-8 km. These variations can be interpreted as changes in the solar subsurface structure caused by predominately vertical ~10 kG magnetic field.

Authors: Alexander Kosovichev, Jean-Pierre Rozelot
Projects: None

Publication Status: to appear in ApJ
Last Modified: 2018-05-26 17:24
Go to main E-Print page  Does Nearby Open Flux Affect the Eruptivity of Solar Active Regions?  Onset of Photospheric Impacts and Helioseismic Waves in X9.3 Solar Flare of September 6, 2017   Edit Entry  Download Preprint  Submitter's Homepage Delete Entry 

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