General Relativistic Magnetohydrodynamic Simulations of Black Hole Accretion Disks

Observations are providing increasingly detailed quantitative informationabout the accretion flows that power such high energy systems as X-ray binariesand active galactic nuclei. Analytic models of such systems must rely onassumptions such as regular flow geometry and a simple, parameterized stress.Global numerical simulations offer a way to investigate the basic physicaldynamics of accretion flows without these assumptions. For black hole accretionstudies one solves the equations of general relativistic magnetohydrodynamics.Magnetic fields are of fundamental importance to the structure and evolution ofaccretion disks because magnetic turbulence is the source of the anomalousstress that drives accretion. We have developed a three-dimensional generalrelativistic magnetohydrodynamic simulation code to evolve time-dependentaccretion systems self-consistently. Recent global simulations of black holeaccretion disks suggest that the generic structure of the accretion flow isusefully divided into five regimes: the main disk, the inner disk, the corona,the evacuated funnel, and the funnel wall jet. The properties of each of theseregions are summarized.Comment: invited review at the conference "Stellar-mass, Intermediate-mass, and Supermassive Black Holes", held in Kyoto, Japan, Octorber 28-31, 2003, to be published in Progress of Theoretical Physics Supplemen