General Relativistic Magnetohydrodynamic Accretion Disks: Simulations and Theory

Robert Penna

November 26, 2012

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Abstract: Standard accretion disk models fold the physics of magnetic fields and turbulence into a constant viscosity parameter, alpha. Applications such as black hole spin measurements can be sensitive to the details of magnetic fields and turbulence, so more realistic disk models are needed. I will present simulations of three-dimensional, magnetohydrodynamic accretion disks in the Kerr metric for a range of black hole spins and disk thicknesses. I will discuss models extending standard disk theory based on insights from the simulations. I will emphasize recent results for the dependence of the alpha-viscosity parameter on radius and a one-dimensional model that captures the shape of alpha(r). I will discuss the impact of these developments on black hole spin measurements.