Accretion Disc Electrodynamics -- A Model for Double Radio Sources

Abstract

The creation of a magnetosphere above and below a magnetized accretion disk in which electromagnetic momentum is focused continuously towards the axis of rotation is proposed as a mechanism for establishing and maintaining linear structure on length scales from parsecs to megaparsecs in strong extragalactic double radio sources. An exact formal force-free magnetospheric solution is presented for a Newtonian disk in which the distribution of toroidal surface current is approximately inversely proportional to one of the cylindrical polar coordinates; this analysis also considers a rotating magnetosphere, an electromagnetic wind, electromagnetic torque, and inertial effects. Electromagnetic braking of the disk is examined along with the validity of the approximations implicit in the Newtonian treatment. Application of the proposed mechanism to models of extragalactic double radio sources and the X-ray source Sco X-1 is discussed.