Physical Constraints on, and a Model for, the Active Regions in Seyfert Galaxies

Abstract

We discuss several physical constraints on the nature of the Active Regions (AR) in Seyfert 1 Galaxies, and show that a plausible model consistent with these constraints is one in which the ARs are magnetically confined and ``fed''. The unique X-ray index of these sources points to a large compactness parameter ($l\gg 1$). This, together with the conditions required to account for the observed optical depth being close to unity, suggests that the magnetic energy density in the AR should be comparable to the equipartition value in the accretion disk, and that it should be released in a flare-like event above the surface of the cold accretion disk. We consider the various issues pertaining to magnetic flares and attempt to construct a coherent picture, including a reason for the optical depth in the AR being $\sim 1$, and an understanding of the characteristics of the X-ray reflection component and the power density spectra associated with this high-energy emission.