Radial Variations of Sound Speed

Radial Variations of  Sound Speed

. Red and blue correspond to faster and slower sound speeds, respectively, relative to a Standard Solar Model (yellow). When the sound travels faster than predicted by theory, the temperature is higher than expected; slow sound waves imply temperatures that are colder than expected. The conspicuous red layer, about a third of the way down, shows unexpected high temperatures at the boundary between the turbulent outer region (convective zone) and the more stable region inside it (radiative zone). Latitudinal variations in temperature are seen near the photosphere (center). These speed of sound measurements were made by the MDI/SOI and VIRGO instruments aboard the SOHO spacecraft. (Courtesy of Alexander G. Kosovichev, the SOHO MDI/SOI consortium, and the SOHO VIRGO consortium. SOHO is a project of international cooperation between ESA and NASA.)

Copyright 2010, Professor Kenneth R. Lang, Tufts University