Measuring the Sun’s Internal Rotation Using Solar p-Mode Oscillations

Abstract

2-dimensional velocity images of the Sun were obtained for 5 days in June, 1984. This time series of images has been analyzed to obtain frequencies of solar p-mode oscillations with degrees between 8 and 50, with all azimuthal orders for each degree. I describe the analysis of these observations in some detail. The principal results of the analysis are measurements of the frequency splitting between modes with the same degree and radial order; these are related to the latitudinal variation of solar rotation, averaged over a depth range that depends on the degree. The observed spittings suggest that for 0.3R⊙ ≤ r ≤ 0.7R⊙, the solar latitudinal differential rotation is much smaller than at the surface (i.e., the rotation is roughly constant on spheres), and moreover than the rotation rate is close to the surface equatorial value. A preliminary analysis of the data shows no significant variation in the average mode amplitude with azimuthal order, for all degrees less than 50.