A MODEL FOR VARIABILITY OF AGN

The theory of AGN accretion disks is reviewed to determine a methodology for constructing time-dependent models of the disks which can be compared to observed continuum variations. Angular-momentum transport is identified as a problematic constituent of existing models, and internal waves are proposed as the mechanisms which can drive a dynamo and thereby transport angular momentum in thin, nongravitating Keplerian disks. The model developed predicts that the disks will show limited instabilities over large annuli with frequencies similar to the dynamo-growth rate and the wave-propagation rate.