THE SHAKURA-SUNYAEV DISK CAN SMOOTHLY MATCH AN ADVECTION-DOMINATED ACCRETION FLOW

摘要

We use the standard Runge-Kutta method to solve a set of basic equations describing black hole accretion flows composed of two-temperature plasma. We do not invoke any extra energy transport mechanism, such as thermal conduction, and we do not specify any ad hoc outer boundary condition for the advection-dominated accretion flow (ADAF) solution. We find that in the case of high viscosity and nonzero radiative cooling, the ADAF solution can have an asymptotic approach to the Shakura-Sunyaev disk (SSD) solution and that the SSD-ADAF transition radius is close to the central black hole. Our results further prove the mechanism of thermal instability-triggered SSD-ADAF transition suggested previously by Takeuchi & Mineshige and Gu & Lu.