2004ApJ...601..405S

In the innermost regions of radiation pressure-supported accretion disks, the turbulent magnetic pressure may greatly exceed that of the gas. If this is the case, it is possible for bulk Alfvénic motions driven by the magnetorotational instability (MRI) to surpass the electron thermal velocity. Bulk, rather than thermal, Comptonization may then be the dominant radiative process that mediates gravitational energy release. For sufficiently large turbulent stresses, we show that turbulent Comptonization produces a significant contribution to the far-UV and X-ray emission of black hole accretion disks. The existence of this spectral component provides a means of obtaining direct observational constraints on the nature of the turbulence itself. We describe how this component may affect the spectral energy distributions and variability properties of X-ray binaries and active galactic nuclei (AGN).