The Jet–disk Boundary Layer in Black Hole Accretion

Magnetic fields lines are trapped in black hole event horizons by accreting plasma. If the field lightly loaded with plasma, then their motion is controlled footpoints on horizon and thus spin of hole. In this paper, we investigate boundary layer between polar a dense, equatorial accretion flow. We present an analytic model for aligned prograde retrograde systems argue that there significant shear across "jet-disk boundary" at most radii all spins. Specializing to accretion, where predicts strongest shear, show numerically jet-disk unstable. The resulting mixing episodically loads plasma onto it heated, forced rotate hole, permitted escape outward into jet. one case follow mass loading detail using Lagrangian tracer particles find time-averaged mass-loading rate ~ 0.01 Mdot.