2025ApJ...995..138W

In our previous work, we constructed a black hole accretion model incorporating magnetic fields and disk winds. However, this model was derived under conditions of a small viscosity parameter α (α < α_crit, where α_crit is the critical viscosity parameter) and for accretion systems around stellar-mass black holes. In the present study, we extend this model to regimes with α > α_crit and to supermassive black hole accretion systems. Our study reveals that under the condition of α > α_crit, the topological structure of thermal equilibrium solutions in black hole accretion disks undergoes significant changes. In the saturated state, the region dominated by advective cooling is confined to the inner disk, yet it expands radially as α increases. This may provide a theoretical explanation for the strong advection-dominated accretion flow (ADAF) principle, specifically addressing the connection problem between the standard thin disk (SSD) and ADAF. Furthermore, we find that the properties of the accretion disk depend on the mass of the central black hole. For stellar-mass black hole accretion systems, the optically thick radiative cooling solutions (similar to the SSD) remain stable, whereas for black holes with M ≥ 10⁵M_⊙, the optically thick radiative cooling solutions exhibit unstable behavior. These differences may help explain the distinct variability behaviors observed between X-ray binaries and active galactic nuclei.