Instability of high-frequency acoustic waves in accretion disks with turbulent viscosity

Abstract

Dynamics of linear perturbations in a differentially rotating accretion disk with non-homogeneous vertical structure is investigated. It has been found that turbulent viscosity results in instability of both pinching oscillations, and bending modes. Not only the low-frequency fundamental modes, but also the high-frequency reflective harmonics appear to be unstable. The question of the limits of applicability of the thin disk model (MTD) is also investigated. The insignificant distinctions in the dispersion properties of MTD and three-dimensional model appear for wave numbers k<(1-3)/h (h is the half-thickness of a disk). In the long-wavelenght limit, the relative difference between eigenfrequencies of the unstable acoustic mode in the 3D-model and the MTD is smaller than 5%.