2018/05/23 by А. Г. Косовичев, Alexander Kosovichev, J. P. Rozelot +1 · 23 citations
Biochemistry, Genetics and Molecular Biology · Physics and Astronomy · #Astrophysics #Coronal mass ejection #Geodesy #Geology #Geomagnetism and Paleomagnetism Studies #Geophysics #Helioseismology #Magnetic field #Maxima #Observatory #Oscillation (cell signaling) #Physics #RADIUS #Solar and Space Plasma Dynamics #Solar observatory #Solar physics #Solar radius #Solar wind #Stellar, planetary, and galactic studies #astro-ph.SR
paper · pdf · doi:10.3847/1538-4357/aac81d
published in The Astrophysical Journal 861(2), 90 (IOP Publishing) · 9 pages, 5 figures, to appear in ApJ
arxiv created 2018/05/23 · openalex publication_date 2018/07/09 · arxiv updated 2018/07/25 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/06
Abstract The questions asking whether the Sun shrinks with the solar activity and what causes this have been a subject of debate. Helioseismology provides a means to measure with high precision the radial displacement of subsurface layers, the so-called “seismic radius,” through the analysis of oscillation frequencies of surface gravity ( f ) modes. Here, we present results of a new analysis of 21 years of helioseismology data from two space missions, the Solar and Heliospheric Observatory and the Solar Dynamics Observatory , 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 a depth of about 5 ± 2 Mm, where the radius is reduced by 5–8 km. These variations can be interpreted as changes in the solar subsurface structure caused by the predominately vertical ∼10 kG magnetic field.