Multi-layer accretion disks around black holes and formation of a hot ion-torus

We present the first 2D steady-state numerical radiative hydrodynamical cal culations showing the formation of a low-density hot torus in the Very inne r region of accretion disks around a black hole. The inner part of the disk is found to be thermally unstable when Bremsstrahlung is the dominant cool ing mechanism. Within the parameter regime used and in the absence of magne tic fields, the torus-plasma is highly time-dependent with supersonic oscil lating motion with respect to the electron temperature. When the soft photons from the disk comptonize the electrons efficiently, t he ion-pressure supported torus shrinks in volume, but decelerates further the inward motion into the hole. We speculate that magnetic fields would st abilize the tori by lowering its energy package through initiating jets and /or outflows. In the outer region, we find that the scale height of the angular velocity H-Omega largely exceeds the scale height of the density H-rho. This yields a multi-layer flow-structure in the vertical direction which slows the inwa rds motion into the BH significantly, enhancing further the formation of th e hot torus.