THERMAL-INSTABILITY OF ADVECTION-DOMINATED DISKS AGAINST REVISED LOCAL PERTURBATIONS

The thermal stability of advection-dominated accretion disks against l ocal perturbations is re-examined in order to correct some errors in o ur previous paper. Thermal perturbations which are local in the radial direction are found to also be local in the vertical direction. Becau se of this, the using of vertically integrated quantities was irreleva nt in analyzing the stability of local thermal perturbations when the disks are geometrically thick. Our new results, obtained by correcting the error, show that if the turbulence acts as a diffusion process in thermal energy transport, it strongly dampens the thermal perturbatio ns. In these cases when the diffusion process is weak, however, pertur bations grow due to a variation of the viscous heating associated with the perturbations. One such example of growth is in the case where ra diation pressure greatly dominates the gas pressure.