Solar and Stellar Convection

Abstract

The flow field in stellar convection zones, characterised by high Rayleigh number, low Prandtl number and large Reynolds number, is time dependent and turbulent, consisting of eddies having a range of scale-lengths upto the size of the convection zone. The mixing lengths approximation has been the most widely used formalism to model such a flow, in spite of all its shortcomings. It is possible to test the consistency of this approach as well as to get a good estimate of the mixing-length in the framework of linear stability analysis. The salient features of stellar convection distinguishing it from the laboratory flows are discussed. The underlying physical ideas behind the local and non-local mixing-lenght theories and tests of the resultant models are outlined. Some of the results from other attempts to treat stellar convection using truncated modal analysis and finite difference schemes are briefly summarised.