Magnetic activity in thick accretion disks and associated observable phenomena. 2: Flux storage

Abstract

In paper I, we have studied the conditions under which flux tubes are expelled from adiabatic thick accretion disks. In the present paper, we explore a few other models of thick disks, where flux tubes could be stored. We show that flux tubes with sufficiently weak fields are not expelled out if they move adiabatically inside an isothermal disk; they continue to oscillate around mean equipotential surfaces inside the disk. If the field in the flux tube is amplified due to the shear, they are eventually expelled away. We explore a `toy' model also, where the entropy increase outwards from the center of the thick disk and find a similar behavior. Flux storage in the disk, as in the case of the sun, in general, enhances the possibility of sustained magnetic activity formation of coronae in the chimney region. The existence of coronae on the disk surface may explain the short-time variability in the spectra of Blazars and the emission of energetic particles from AGNs and Quasars. It may also supply matter to the cosmic jets through magnetized winds.