Magnetic Activity in Thick Accretion Disks and Associated Observable Phenomena I. Flux Expulsion

Abstract

We study the dynamics of toroidal magnetic flux tubes, symmetric about the rotation axis, inside non-magnetic thick accretion disks around black holes. We present model equations which include effects of gravity, centrifugal force, pressure gradient force, Coriolis force, drag, magnetic tension and magnetic buoyancy. We solve them assuming the disk to be adiabatic. We show that under a wide range of parameters describing the size and the field strength, as well as angular momentum distribution inside the disk, buoyant flux tubes, either released on the equatorial plane or at the outer edge of the disk, can gather in the chimney-like openings near the axis. This behavior makes the chimneys magnetically most active and could shed light on the origin and acceleration of cosmic jets, as well as the variabilities observed in Blazars.