**Speaker:**
John Hawley (U. Virginia)

**Title:**
3D Simulations of Magnetic Accretion Disks: Local to Global

**Abstract:**
Observations are providing increasingly detailed quantitative
information about the accretion flows that power such high energy
systems as X-ray binaries and Active Galactic Nuclei. These
observations have been modeled in some detail by a variety of accretion
scenarios, but such models must rely on assumptions such as regular
flow geometry and a simple, parameterized stress. It is now known that
magnetic fields are of fundamental importance for the structure and
evolution of accretion disks. Magnetic turbulence is almost certainly
the source of anomalous stress in accretion disks. Numerical MHD
simulations offer a way to investigate the basic physical dynamics of
accretion flows self-consistently. In this talk I will review the
development of these simulations, from local to global models. I will
focus on two recent applications: (1) underluminous
(``non-radiating'') accretion flows, of which the Galactic Center is
the best known example, and (2) the structure and dynamics of the inner
edge of accretion disks around black holes.

**Reference for students:**

Balbus and Hawley, 2002, astro-ph/203353