Studying asphericity in the solar sound speed from MDI and GONG data

Abstract

We study the variation of the frequency splitting coefficients describing the solar asphericity in both GONG and MDI data, and use these data to investigate temporal sound-speed variations as a function of both depth and latitude during the period 1995-2000. The temporal variations in even splitting coefficients are found to be correlated with the corresponding component of magnetic flux at the solar surface. The sound-speed variations associated with the surface magnetic field appear to be superficial. Temporally averaged results show a significant excess in sound speed around r=0.92 R_⊙ and latitude of 60°.