  The inward flow of matter through accretion disks is driven by MHD
turbulence. Global general relativistic MHD simulations shed quantitative light
on this process, revealing a number of aspects of accretion previously
unrecognized. Among them are strong stresses in the marginally stable and
plunging regions near the black hole and electromagnetically-dominated conical
relativistic jets that can form spontaneously from the accretion flow. The
energy release associated with both of these effects can significantly augment
the classical energy-release estimates based on purely hydrodynamic models.
