http://arxiv.org/abs/1403.0938
Spinning black holes tend to expel magnetic fields. In this way they are similar to superconductors. It has been a persistent concern that this black hole “Meissner effect” could quench jet power at high spins. We show that split monopole fields are not expelled by the Meissner effect and may continue to power jets up to the extremal limit. This provides a natural way for the rapidly rotating black holes in Cyg X-1 and GRS 1915+105 to power jets. We consider two earlier proposals for evading the Meissner effect: the claim that hoop stresses in a conductive magnetosphere can drag fields onto the horizon despite the Meissner effect and the claim that spin-powered jets can exist even if field lines do not thread the horizon. We show that both of these proposals are impossible. Finally, we note that in our general relativistic magnetohydrodynamic simulations of black hole jets, there is no evidence that jets are quenched by the Meissner effect. The simulated jets develop a large split monopole component spontaneously which supports our proposal for how the Meissner effect is evaded and jets from rapidly rotating black holes are powered in nature.
R. Penna
Thu, 6 Mar 14
16/53