KEPLERIAN COMPLEXITY - NUMERICAL SIMULATIONS OF ACCRETION DISK TRANSPORT

Supercomputer simulations have been used in conjunction with analytic studies to investigate the central issue of astrophysical accretion-di sk dynamics: the nature of the angular momentum transport. Simulations provide the means to investigate and experiment with candidate mechan isms, including global hydrodynamic instabilities, spiral shock waves, and local magnetohydrodynamic (MHD) instabilities. Simulations have d emonstrated that accretion disks are generally MHD turbulent. These re sults suggest that the fundamental physical mechanism for angular mome ntum transport in accretion disks has now been identified.