Abstract

We consider a model that takes into account the mass and spin accreted by the hole and the angular momentum torque due to an electrodynamical jet. The spin evolution is calculated with and without accretion; if the accretion stops the jet power indicates an increase before a gradual decline if the initial spin, j > √ 3 /2, as a result of the hole’s increasing size. This naturally has implications for the evolution of the jet. Specific analytic forms have also been calculated for the case of Bondi accretion, thin disk and an MHD disk. The results indicate that the black hole achieves the maximum spin value when there is no jet. It is planned to compare this with fully relativistic MHD simulations.