Mechanism of mass loss in thermal equilibrium of advection-dominated accretion flows

Abstract Based on the analytical works, hydrodynamical numerical simulations, and observations, outflows play a crucial role in accretion systems. These simulations suggest that the mass accretion rate decreases inward as the radius decreases. In this paper, we consider a power-law function for the mass inflow rate, represented as $\dot{M} \propto r^{s}$, where the power index s is proportional to the dimensionless thickness $(H/R)$ of the disc. By using self-similar solutions, we examine the effects of outflows on steady-state, axisymmetric, optically thin advection-dominated accretion flows in cylindrical coordinates. Our results indicate that for solutions with a non-free s, the flow geometry becomes quasi-spherical, with $H/R_{\rm out}$ approximately equal to 0.8 in the outer regions. This is in good agreement with global solutions. Furthermore, our findings demonstrate that the viscous heating rate will surpass the advective cooling rate. Consequently, in the presence of outflows, thermal energy can be removed, and outflows can carry away the thermal energy generated by viscous dissipation. Thermal equilibrium occurs in this model in the presence of outflows.