A Magnetohydrodynamic Nonradiative Accretion Flow in Three Dimensions

John F. Hawley, Steven A. Balbus

Virginia Institute of Theoretical Astronomy,

Department of Astronomy, University of Virginia,

Charlottesville, VA 22903; jh8h@virginia.edu; sb@virginia.edu

James M. Stone

Department of Astronomy, University of Maryland

College Park, MD 20742; jstone@astro.umd.edu

Submitted to Astrophysical Journal Letters

Abstract:

We present a global magnetohydrodynamic (MHD) three dimensional simulation of a nonradiative accretion flow originating in a pressure supported torus. The evolution is controlled by the magnetorotational instability which produces turbulence. The flow forms a nearly Keplerian disk. The total pressure scale height in this disk is comparable to the vertical size of the initial torus. Gas pressure dominates only near the equator; magnetic pressure is more important in the surrounding atmosphere. A magnetically dominated bound outflow is driven from the disk. The accretion rate through the disk exceeds the final rate into the hole, and a hot torus forms inside 10 rg. Hot gas, pushed up against the centrifugal barrier and confined by magnetic pressure, is ejected in a narrow, unbound, conical outflow. The dynamics are controlled by magnetic turbulence, not thermal convection, and a hydrodynamic alpha model is inadequate to describe the flow. The limitations of two dimensional MHD simulations are also discussed.

Subject headings: accretion -- accretion disks -- instabilities -- MHD -- black hole physics -- X-ray: stars - binaries:


Table of Contents

Movies, Images

Movie 1 is 3D volumetric rendering of entire simulation domain.

Movie 2 is 3D volumetric rendering of the inner region of the simulation.

This image shows the end time of the simulation in log density, from R= 0 to 100 and -50 < Z < 50. Watch the disk evolve to this state in a 2.8 MByte MPEG movie of azimuthally averaged density.

This image shows the end time of the simulation in log density, from R= 0 to 100 and -50 < Z < 50. Watch the disk evolve to this state in a 2.8 MByte MPEG movie of density at a specific phi slice. In addition the color scale is adjusted to reveal lower density material.