Reynolds Stress Model And Its Helioseismological Testing

How to deal with the turbulent convection motion in stars is a very important problem in the theory of stellar structure and evolution. A Reynolds stress model based on hydrodynamic moment equations was established and applied to the solar model. The convection model and the free parameters involved in the model are tested and determined in the solar interior. The aim is to test the effects of some physical processes on the structure of the solar convection zone, such as the dissipation, diffusion, and anisotropy of turbulence that have been ignored in the classical mixing-length theory (MLT). Free parameters introduced by the Reynolds stress model are also tested with the aid of helioseismology in order to find appropriate values for astrophysical applications.It is found that, the Reynolds stress models usually give larger convective heat fluxes than the MLT does, and the heat transport efficiency is sensitively related to the dissipation parameters used in the Reynolds stress models. The turbulent diffusion is found to have important effects on the structure of the solar convection zone. It leads to significantly lowered and expanded profiles for the Reynolds correlations, and a larger temperature gradient in the central part of the super-adiabatic convection region but a small one near the boundaries of the convection zone. Solar models with our Reynolds stress model give small but meaningful differences in the global structure such as temperature and sound speed compared with the standard solar model using the MLT.The free parameters involved in the Reynolds stress model are determined in the solar interior with the aid of helioseismology. It is found that, with appropriate choices of the turbulent parameters, solar model with both local and non-local...