Stability of a hot two-temperature accretion disc with advection

Abstract

The effects of radial advection and thermal diffusion were considered in investigating the linear stability of an optically thin, two-temperature accretion disc. If the disc has only very little advection, we proved that the thermal instability exists when the disc is geometrically thin. But it dispears in a geometrically slim disc if the thermal diffusion was considered. Moreover, if the disc is advection dominated, the thermal instability does not exist. In addition, we found that the instabilities of inertial-acoustic modes exist only in a geometrically thin disc or an advection-dominated disc with low Mach number, whereas the Lightman & Eardley viscous instability always dispears in a two-temperature disc. A simple comparison also showed that an optically thin, bremsstrahlung cooling dominated disc is generally more thermally unstable than a two-temperature disc if it is not advection-dominated.