The Physics of Accretion Disks with Magnetic Flares

Abstract

Rapid progress in multi-wavelength observations of Seyfert Galaxies in recent years is providing evidence that X-ray emission in these objects may be produced by magnetic flares occurring above a cold accretion disk. Here we attempt to develop a physically consistent model of accretion disks producing radiation via magnetic flares as well as the optically thick intrinsic disk emission. We place a special emphasis on comparison of the theory and the observations of Active Galactic Nuclei (AGN) and Galactic Black Hole Candidates (GBHCs). In particular, theoretical issues considered in this work provide tentative explanations for: (1) the origin of the Big Blue Bump of Seyfert 1 Galaxies. (2) the recently discovered X-ray Baldwin effect and the controversy over the existence of BBBs in quasars more luminous than typical Seyferts. (3) The differences and similarities in X-ray spectra of Galactic Black Hole Candidates and Seyfert 1s. (4) The hard/soft state transitions of GBHCs and AGN. Our conclusion is that the agreement between the theory and observations is very encouraging and we thus suggest that the physics of magnetic flares is the physics that should be added to the standard accretion disk theory in order to produce a more realistic description of radiation from accretion flows with a large angular momentum.