Magnetospheres of Black Hole Systems in Force-Free Plasma

TL;DR

This paper investigates the electromagnetic energy output from black hole systems in dynamic, force-free plasma environments, extending previous stationary models to asymmetric and binary configurations, revealing Poynting flux generation under various conditions.

Contribution

It extends force-free black hole magnetosphere models to include asymmetric and dynamical systems, analyzing Poynting flux in misaligned single and binary black hole scenarios.

Findings

Misaligned single black holes produce Poynting flux with variable luminosity.

Binary black holes generate Poynting flux during both head-on and orbital motions.

Poynting flux depends on black hole spin, misalignment, and system dynamics.

Abstract

The interaction of black holes with ambient magnetic fields is important for a variety of highly energetic astrophysical phenomena. We study this interaction within the force-free approximation in which a tenuous plasma is assumed to have zero inertia. Blandford and Znajek (BZ) used this approach to demonstrate the conversion of some of the black hole's energy into electromagnetic Poynting flux in stationary and axisymmetric single black hole systems. We adopt this approach and extend it to examine asymmetric and, most importantly, dynamical systems by implementing the fully nonlinear field equations of general relativity coupled to Maxwell's equations. For single black holes, we study in particular the dependence of the Poynting flux and show that, even for misalignments between the black hole spin and the direction of the asymptotic magnetic field, a Poynting flux is generated with a luminosity dependent on such misalignment. For binary black hole systems, we show both in the head-on and orbiting cases that the moving black holes generate a Poynting flux.