Magnetized Accretion Flows with Low Angular Momentum Around Supermassive Black Holes

Abstract

We investigate the global structure of slowly rotating accretion flows around black holes in the presence of large-scale magnetic fields. Using a steady, height-integrated transonic model with radial mass loss, we examine how magnetic pressure, tension, and torque modify the dynamics of Bondi-like and disk-like accretion. Adopting a radial magnetic-field prescription based on results from previous numerical simulations, we compare hydrodynamical and magnetized solutions across a range of plasma-$\rm β$ values, from weak to strong field regimes. We find that magnetic stresses substantially alter the sonic radius and change the angular momentum and mass accretion rate reaching the black hole. For sufficiently strong fields, the inner flow becomes highly sub-Keplerian and magnetically dominated ($ β= P_{\mathrm{gas}}/ P_{\mathrm{mag}}<1$), and magnetic stresses can drive transitions to lower angular momentum. We also show that outflows in this magnetized accretion flow can significantly alter the structure of disk-like accretion. We further perform 2D simulations of magnetized Bondi accretion and torus accretion and find that the radial structure and magnetically dominated, sub-Keplerian character of our semi-analytical solutions are qualitatively reproduced.