Optically thin, advection-dominated two-temperature disks

We present global models of optically thin, advection-dominated two-temperature accretion flows onto black holes, paying careful attention to transonic properties of the flows. We treat the physical quantities integrated over the vertical direction, and adopt the standard alpha-viscosity and the pseudo-Newtonian potential. Bremsstrahlung and synchrotron cooling amplified by Comptonization is considered as to be cooling processes of electrons. It is found that when moderate synchrotron cooling is included, the electron temperature distribution in the inner part of the disk is roughly hat with temperatures slightly lower than the electron rest mass energy. This high electron temperature is appropriate to explain the hard X-rays from X-ray sources and AGNs. It is also found that in the inner part of the disks the energy input to electrons from ions by the ion-electron Coulomb collision is negligible as the electron heating, i.e., the electron temperature is determined by the balance between advective heating and synchrotron cooling.