Electromagnetic Energy Extraction from Kerr Black Holes: Ab Initio Calculations

The possibility of extracting energy from a rotating black hole via the Blandford–Znajek mechanism represents a cornerstone of relativistic astrophysics. We present general-relativistic collisionless kinetic simulations of Kerr black hole magnetospheres covering a wide range of black hole spin rates. Considering a classical split-monopole magnetic field, we can reproduce with these ab initio calculations the force-free electrodynamics of rotating black holes and measure the power of the jet launched as a function of the spin. The Blandford–Znajek luminosity we find is in very good agreement with analytic calculations and compatible with general-relativistic magnetohydrodynamic simulations via a simple rescaling. These results provide strong evidence of the robustness of the Blandford–Znajek mechanism and accurate estimates of the electromagnetic luminosity to be expected in those scenarios involving rotating black holes across the mass scale.