Magnetosphere Dynamics of Single and Binary Black Holes*

Collisions of black holes immersed in external magnetic fields are prime candidates for coincident detection in both gravitational and electromagnetic radiation. We present work in progress to model the magnetospheres surrounding such systems, in order (1) to characterize the nonlinear interaction between the source and its surrounding magnetosphere, and (2) to evaluate the electromagnetic counterparts of gravitational waves, including the production of collimated jets. We apply our recently-released General Relativistic Force-Free Electrodynamics open-source code GiRaFFE to single and binary black holes immersed in an external magnetic field, to test our implementation and study the dynamics of the magnetosphere and its role in producing electromagnetic counterparts, a mechanism not entirely elucidated. We analyze the emission of light in terms of the Poynting luminosity, to reveal the effects of (1) strong gravitational fields, (2) rotation, and (3) tilt between the magnetic field lines and rotation axis, all on the amplification and collimation of Poynting jets. We find that the geometry brings the magnetosphere to stability, and that the spin and the tilt affect the amplitude of the flux, with no indication of high spin threshold for jet formation.