Temporal properties of flares in accretion disk coronae

Using a non-linear Monte-Carlo code we investigate the radiative response o f an accretion disk corona system to static homogeneous flares. We model a flare by a rapid (comparable to the light crossing time) energy dissipation in the corona ol the disk. If the Hares originate from the disk, the coronal response to the soft phot on shots produces a strongly non-linear Comptonised radiation output, with complex correlation/anti-correlations between energy bands. This behavior s trongly differs from those found with usual linear calculations. Thus any m odel for the rapid aperiodic variability of X-ray binaries invoking a varyi ng soft photon input as a source for the hard X-ray variability has to take into account the coronal temperature response. On the other hand, if the flare is due to a violent heating of the corona, when the perturbation time scale is of the order of a few corona light cros sing times, the shot spectrum evolves from hard to soft. This general trend is independent of the shot profile and geometry. We show that for short di ssipation time, the time averaged spectra are generally harder than in stea dy state situation. In addition, annihilation line and high energy tails ca n be produced without need for non-thermal processes.