MAGNETIC FLARES AND THE OBSERVED PI(T)SIMILAR-TO-1 IN SEYFERT-GALAXIES

We here consider the pressure equilibrium during an intense magnetic f lare above the surface of a cold accretion disk. Under the assumption that the heating source for the plasma trapped within the flaring regi on is an influx of energy transported inward with a group velocity clo se to c, e.g., by magnetohydrodynamic waves, this pressure equilibrium can constrain the Thomson optical depth, tau(T), to be of order unity . We suggest that this may be the reason why tau(T) similar to 1 in Se yfert galaxies. We also consider whether current data can distinguish between the spectrum produced by a single X-ray-emitting region with t au(T) similar to 1 and that formed by many different flares spanning a range of tau(T). We find that the current observations do not yet hav e the required energy resolution to permit such a differentiation. Thu s, it is possible that the entire X-ray/gamma-ray spectrum of Seyfert galaxies is produced by many independent magnetic hares with an optica l depth of 0.5 < tau(T) < 2.