Differential Rotation and Global-Scale Velocity Fields

Abstract

A review is given of the observational and theoretical background of global-scale velocity fields on the solar surface. A newly-developed method of reduction of the Mount Wilson velocity data is described, and the results from this new method are compared with the results of the old method. A preliminary analysis is made of the new results over a short time interval. Small-scale latitude irregularities in the differential rotation are shown to exist. Variations in time which occur in the rotation rate are broadly distributed in latitude and longitude. Although a non-solar (instrumental) cause cannot be found for these variations, such a cause cannot be ruled out at this time. Global-scale non-axisymmetric velocity field patterns intermediate between solar diameter and super-granular scale are shown to exist on the solar surface as predicted by theory.