Near-Horizon Extreme Kerr Magnetospheres

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Written by Roberto Oliveri

Black holes surrounded by an accreting plasma admit a very rich dynamics. Under the assumption of vanishing Lorentz force density and negligible matter backreaction, the dynamics of the black hole magnetosphere is governed by Force-Free Electrodynamics (FFE) in the fixed background geometry. The FFE equations are highly nonlinear and typically can only be solved numerically. In this talk, I consider FFE in the Near-Horizon geometry of an Extreme Kerr black hole (NHEK). First, I show how several classes of exact analytical solutions can be found thanks to the enhanced isometry group of NHEK spacetime. Second, I characterize those potentially physical solutions with finite energy and angular momentum fluxes with respect to the asymptotically flat observer.