Transition from Standard Disk to Advection‐dominated Accretion Flow

We studied a global accretion flow model with a radial transition from outer standard disks to inner advection-dominated accretion flows. The height-integrated viscous hydrodynamic equations were solved numerically using radiative transfer equations. We found two kinds of solutions: (1) standard-disk solutions and (2) solutions with transitions from inner advection-dominated accretion flows to outer standard disks, thus confirming the recent results of Honma. We investigated in detail the thermal structure of the transition region, finding a series of transition solutions with a different transition radius for a given set of physical parameters. The transitions occur only when the efficiency of the energy transport by the turbulence is above a minimum value. The physical mechanism of the transition is also discussed.