  Black hole and neutron star accretion flows display unusually high levels of
hard coronal emission in comparison to all other optically thick,
gravitationally bound, turbulent astrophysical systems. Since these flows sit
in deep relativistic gravitational potentials, their random bulk motions
approach the speed of light, therefore allowing turbulent Comptonization to be
an important effect. We show that the inevitable production of hard X-ray
photons results from turbulent Comptonization in the limit where the turbulence
is trans-sonic and the accretion power approaches the Eddington Limit. In this
regime, the turbulent Compton y-parameter approaches unity and the turbulent
Compton temperature is a significant fraction of the electron rest mass energy,
in agreement with the observed phenomena.
