Magnetohydrodynamical Non-radiative Accretion Flows in Two-Dimensions
  We present the results of axisymmetric, time-dependent magnetohydrodynamic simulations of accretion flows around black holes. The calculations begin from a rotationally supported thick torus which contains a weak poloidal field. Accretion is produced by growth and saturation of the magnetorotational instability (MRI) provided the wavelength of the fastest growing mode is less than the thickness of the torus. Using a computational grid that spans more than two decades in radius, we compare the time-averaged properties of the flow to previous hydrodynamical simulations. The net mass accretion rate is small compared to the mass inflow and outflow rates at large radii associated with turbulent eddies. Turbulence is driven by the MRI rather than convection. The two-dimensional structure of the time-averaged flow is significantly different compared to the hydrodynamical case. We discuss the limitations imposed on our results by the assumption of axisymmetry and the relatively small radial domain. 
James M. Stone (University of Maryland), James E. Pringle (Cambridge   University)