Vertical structure of thin Keplerian disks

Models for the vertical structure of gas-pressure dominated accretion disks with the turbulent heat transport involved are established. Given an explicit law for the opacity and also the turbulent Prandtl number Pr, the equations can be so formulated that the only free parameter, Χs, is the surface value of the ratio of radiative and turbulent temperature diffusivity. It simultaneously involves the surface temperature and the well-known free parameter α, taken here for heat diffusivity rather than eddy viscosity. We find negative eddy heat fluxes as well as density inversions. The disk structure is generally determined by the surface value of radiative diffusivity and eddy viscosity, Χs/Pr. By approximate analytical methods we find the models with opacity for hot gases (T>104 K) to be stable against break-up into rings. Cooler disks, however, prove to be unstable but for the lowest temperatures they become stable again. These results, therefore, are in accordance to the widely accepted S-curve concept of the dwarf-nova outburst behaviour. 18 refs., 4 figs., 3 tabs. (author)