Asphericity and time variation of the near-surface layers of the sun

Abstract

We present results on the structure of the near-surface layers of the Sun obtained by inverting frequencies of highdegree solar modes from "ring diagrams". We find that there is a substantial latitudinal variation of both sound speed and the adiabatic index Γ₁ in the outer 2% of the Sun. We find that both the sound-speed and Γ₁ profiles change with changes in the level of solar activity.