The Radial-Azimuthal Instability of Gas-Pressure-Dominated Accretion Disk with Advection

The radial-azimuthal instability of gas-pressure-dominated accretion disk with advection is examined in this paper. We find that the including of very little advection has significant effects on two acoustic modes, which are no longer complex conjugates of each other. They increase the instability of the O-mode and damp that of the I-mode. We also find that when the azimuthal perturbations are considered, the stability properties of disk are different from that in pure radial perturbation case. The increase of azimuthal wave number will stabilize the acoustic modes but make the viscous mode more unstable and does not change the thermal mode very much for optically thin disk. The I-mode is more stable. The O-mode, viscous mode and thermal mode tend to become more unstable with the increase of azimuthal perturbation wavenumber for optically thick disk. For a geometrically slim, advection-dominated disk, the increasing of azimuthal perturbations make thermal mode more unstable and acoustic mode more stable.