Numerical Simulations of Dissipation in Accretion Disks

We perform general relativistic magneto-hydrodynamic simulations to study the dynamics of and radiation from accretion onto stellar mass black holes. Recent theoretical work suggested magnetic torques exerted at the innermost stable circular orbit can drive significant bulk vertical energy transport in regions close to the black hole, and hence dissipate a larger fraction of accretion power near the photosphere compared to standard models. This additional heating in turn may lead to the non-thermal high-energy (into several hundred keVs) radiation observed in some systems. We analyze time-dependent global simulations to further assess the feasibility of such models and illuminate the underlying physical mechanisms.