Magnetic Hair and Reconnection in Black Hole Magnetospheres

TL;DR

This paper investigates the magnetic structure and reconnection processes in black hole magnetospheres using advanced simulations, confirming the no-hair theorem and exploring potential high-energy emissions.

Contribution

It introduces detailed relativistic plasma simulations of black hole magnetospheres, demonstrating magnetic reconnection and flux decay consistent with the no-hair theorem.

Findings

Magnetic flux on the horizon decays exponentially over time.

Reconnection occurs via plasmoid-unstable current sheets.

Magnetospheres could produce strong X-ray emissions.

Abstract

The no-hair theorem of general relativity states that isolated black holes are characterized by three parameters: mass, spin, and charge. In this Letter we consider Kerr black holes endowed with highly magnetized plasma-filled magnetospheres. Using general relativistic kinetic plasma and resistive magnetohydrodynamics simulations, we show that a dipole magnetic field on the event horizon opens into a split-monopole and reconnects in a plasmoid-unstable current-sheet. The no-hair theorem is satisfied, in the sense that all components of the stress-energy tensor decay exponentially in time. We measure the decay time of magnetic flux on the event horizon for plasmoid-dominated reconnection in collisionless and collisional plasma. The reconnecting magnetosphere should be a powerful source of hard X-ray emission when the magnetic field is strong.