Magnetocentrifugal launching of jets from disks around Kerr black holes

Strong magnetic fields modify particle motion in the curved space-time of spinning black holes and change the stability conditions of circular orbits. We study conditions for magnetocentrifugal jet launching from accretion disks around black holes, whereby large scale black hole lines anchored in the disk may fling tenuous coronal gas outward. For a Schwarzschild black hole, magnetocentrifugal launching requires that the poloidal component of magnetic fields makes an angle less than $60^\circ$ to the outward direction at the disk surface, similar to the Newtonian case. For prograde rotating disks around Kerr black holes, this angle increases and becomes $90^\circ$ for footpoints anchored to the disk near the horizon of a critically spinning $a=M$ black hole. Thus, a disk around a critically spinning black hole may centrifugally launch a jet even along the rotation axis.