Motions in the Sun at the Photospheric Level VIII. Solar Rotation and Photospheric Circulation

Abstract

From spectra exposed 1953 April 21–23, sight-line velocities have been measured at 332 points over the visible surface of the Sun. For any point the sight-line velocity can be expressed as a linear function of velocity components directed to the west and the north. Least-squares solutions of such observation equations for various latitudes reveal an asymmetry of rotational velocities in the equatorial zone and the presence of meridional currents. These motions suggest the existence of a circulation in the photosphere similar to that shown in the upper atmosphere of the Earth. This hypothesis is examined in the light of an investigation by M. J. Lighthill, and an observational test is proposed.