Magnetically Driven Accretion Flows in the Kerr Metric. I. Models and Overall Structure

This is the first in a series of papers that investigate the properties of accretion flows in the Kerr metric through three-dimensional general relativistic magnetohydrodynamic simulations of tori with a nearly Keplerian initial angular velocity profile. We study four models with increasing black hole spin, from a / M = 0 to 0.998, for which the structural parameters of the initial tori are maintained nearly constant. The subsequent accretion flows arise self-consistently from stresses and turbulence created by the magnetorotational instability. We investigate the overall evolution and the late-time global structure in the resulting nonradiative accretion flows, including the magnetic fields within the disks, the properties of the flow in the plunging region, and the flux of conserved quantities into the black hole. Independent of black hole spin, the global structure is described in terms of five regions: the main disk body, the coronal envelope, the inner disk (consisting of an inner torus and plunging region), an evacuated axial funnel, and a biconical outflow confined to the corona-funnel boundary. We find evidence for lower accretion rates, stronger funnel-wall outflows, and increased stress in the near-hole region with increasing black hole spin.