Cold Accretion Disks with Coronae and Advection

Cold optically thick accretion disks with hot coronae and radial advection have been investigated. Within the framework of -viscosity models, we assume that all the mass accretion and angular momentum transport take place in the cold disk, but that a fraction of the gravitational energy released is dissipated in the corona. Both the coronal energy dissipation and the advection heat transport have a stabilization e ect on the thermal and viscous instabilities of the disk. If that more than 95 percent of the total power is dissipated in the corona, then the locally unstable behavior of the disk is restricted to a relatively narrow spatial region and is found to lie in a small range of mass accretion rates. The global temporal variability of the disk can be very mild or may disappear, and which may be applicable to the low-frequency ( 0:04 Hz) quasi-periodic oscillations observed in black hole candidates Cyg X{1 and GRO J0422+32. Subject headings: accretion, accretion disks | black hole physics | instabilities