Schematic depiction of the physical mechanism through which magnetic flux is expelled from the black hole. Magnetic field lines threading the horizon are shown as thin black lines. The bundle of magnetic field lines of interest is depicted as a thick red line. The temporal evolution of the mechanism is shown from left to right: (a) Magnetic flux is advected by the accreting matter toward the black hole. Close to the black hole the magnetic field is mostly equatorial. (b) The equatorial magnetic field slightly above and below the midplane reconnect. (c) Two structures form during the magnetic reconnection of the equatorial magnetic field, a magnetic field loop close to the black hole’s event horizon, and a tube of vertical magnetic field lines. (d) The vertical flux tube, filled with plasma of lower density than its environment, is buoyantly carried away from the black hole.