The Solar Oblateness and the Gravitational Quadrupole Moment

Abstract

The connection between the oblateness and the gravitational quadrupole moment of the Sun is developed under the assumption of the absence of magnetic and velocity fields in the surface layers. This discussion is generalized to include also the effects of surface rotation for rotation on cylinders. The theory of the generation by surface fields of oblateness and equatorial temperature excess is developed and used to discuss the various attempts by Roxburgh, Cocke, Sturrock, and Gilvarry to account for the observed oblateness as an effect of surface fields only. The severe constraint on allowed surface fields introduced by the observed latitude independence of solar brightness is analyzed. It is concluded that an acceptable explanation of the solar oblateness, other than the effects of a gravitational quadrupole and surface rotation, has yet to be found.