Towards a New Standard Theory for Astrophysical Disk Accretion

Abstract

We briefly review recent developments in black hole accretion disk theory, placing new emphasis on the vital role played by magnetohydrodynamic (MHD) stresses in transporting angular momentum. The apparent universality of accretion-related outflow phenomena is a strong indicator that vertical transport of angular momentum by large-scale MHD torques is important and may even dominate radial transport by small-scale MHD turbulence. This leads to an enhanced overall rate of angular momentum transport and allows accretion of matter to proceed at an interesting rate. Furthermore, we argue that when vertical transport is important, the radial structure of the accretion disk is modified and this affects the disk emission spectrum. We present a simple model demonstrating that energetic, magnetically-driven outflows give rise to a disk spectrum that is dimmer and redder than a standard accretion disk accreting at the same rate. We briefly discuss the implications of this key result for accreting black holes in different astrophysical systems.

Accepted for publication as brief review in Mod. Phys. Let. A

References in corpus (3)

• Angular momentum transport in protostellar discs
• The UV Properties of SDSS Selected Quasars
• Radio and X-ray Properties of Relativistic Beaming Models for Ultra-Luminous X-ray Sources

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• New Global 3D MHD Simulations of Black Hole Disk Accretion and Outflows
• A Simplified Model of ADAF with the Jet Driven by the Large-Scale Magnetic Field