A Multimode Investigation of Granular and Supergranular Motions I: Boussinesq Model

Abstract

Two types of large-scale convective motions, granulation and supergranulation, are observed in the outer layers of the sun and their observed characteristics can be summarized as follows:

These convective motions take place in a highly turbulent medium, and in the outermost layers of the sun the eddy thermal diffusivity and eddy kinematic viscosity are well in excess of their radiative and molecular values. The therma1 diffusivity is evaluated usually by the mixing-length theory or its extensions, whereas there does not seem to exist an adequate theory to determine, a priori, the variations with depth of the eddy viscosity.