B. The Solar Atmospheric Convection Zone

Abstract

Observational progress has, in the last decade, greatly surpassed theoretical progress in our study of the non-thermal velocity fields in the solar photosphere and chromosphere. This differential progress has not been simply a matter of filling in details. Attempted formulation of the theoretical problem of the velocity fields arising from convective instability in stellar atmospheres has resulted in no really new conceptual developments, nor large clarifications in approach, to match the observational ones just summarized by Noyes. Discussion of the problem at Varenna consisted mainly in the expression by aerodynamicists of severe reservations on the likelihood of gaining deep physical insight, or reliable numerical results, from the mixing-length approach generally used in astrophysics, with essentially no suggestions of a better approach. What progress that has been made in the general area of convective problems similar to those of interest in stellar atmospheres lies in the exploration of the physical structure of simplified convective configurations, often by exploration of various intuitive approaches.