AGN Accretion Disks with Finite Turbulent Prandtl Number

Extract

The present paper reports results of a study of turbulent energy transport in AGN accretion disks. We follow the spirit of the papers by Shakura et al. and Rüdiger et. al in which the concept of an eddy heat conductivity was introduced and developed. For the viscosity we use a standard α− description with the main component of the stress tensor t_rø proportional to the gas pressure. The dimensionless Prandtl number Pr given as the ratio of turbulent kinematic viscosity and turbulent heat conductivity enters the model as a free parameter. The disk structure depends sensitively on material properties such as opacities and specific heats. In our calculations we have used an equation of state and mean opacities taking into account a list of the most important ionization processes as well as the radiation contributions to thermodynamic quantities.