Magnetic viscosity in relativistic accretion disks

Abstract

We formulate a detailed, self-consistent model of magnetic viscosity in an accretion disk around a rotating, Kerr black hole, in order to help clarify the nature of viscosity in the theory of accretion disks. The magnetic field is amplified by shear and dissipated by reconnection; in steady state a stable balance occurs, leading to a chaotic field configuration consisting of magnetic cells that reconnect with each other about once per orbit. We give detailed models of stationary disks based on the viscosity of this field. The observable properties of these models are similar to those of previous models based on less detailed models of viscosity. We include the relativistic equations governing the time-evolution of an accretion disk around a Kerr black hole, and some criteria for the existence of a radiation-pressure-dominated region or an optically thin region in a stationary disk.