THE FATE OF NONRADIATIVE MAGNETIZED ACCRETION FLOWS: MAGNETICALLY FRUSTRATED CONVECTION

摘要

We present a scenario for nonradiative accretion onto the supermassive black hole at the Galactic center. Conducting MHD simulations with 1400~3 grid zones that break the axial and reflection symmetries of earlier investigations and extend inward from the Bondi radius, we find a quasi-hydrostatic radia! density profile ρ∝ r~(-0.72) with a superadiabatic gradient corresponding to an n ～ 0.72 polytrope. Buoyancy generated by magnetic dissipation is resisted by the same fields so effectively that energy is advected inward: a state of magnetically frustrated convection. This scenario is consistent with observational constraints on energetics and outer boundary conditions.