Near-horizon structure of escape zones of electrically charged particles around weakly magnetized rotating black hole

TL;DR

This paper investigates how large-scale magnetic fields influence the escape of charged particles from near a rotating black hole, revealing chaotic dynamics and the formation of escape zones that depend on black hole spin and magnetic field strength.

Contribution

It introduces a novel analysis of escape zones of charged particles near Kerr black holes using recurrence plots and basin-boundary plots, highlighting the role of chaos and magnetic fields.

Findings

Chaotic dynamics support the formation of near-horizon escape zones.

Black hole spin and magnetic field strength affect escape zone location.

Maximum escape velocities are computed for different conditions.

Abstract

An interplay of magnetic fields and gravitation drives accretion and outflows near black holes. However, a specific mechanism is still a matter of debate; it is very likely that different processes dominate under various conditions. In particular, for the acceleration of particles and their collimation in jets, an ordered component of the magnetic field seems to be essential. Here we discuss the role of large-scale magnetic fields in transporting the charged particles and dust grains from the bound orbits in the equatorial plane of a rotating (Kerr) black hole and the resulting acceleration along trajectories escaping the system in a direction parallel to the symmetry axis (perpendicular to the accretion disk). We consider a specific scenario of destabilization of circular geodesics of initially neutral matter by charging (e.g., due to photoionization). Some particles may be set on escaping trajectories and attain relativistic velocity. The case of charged particles differs from charged dust grains by their charge-to-mass ratio, but the acceleration mechanism operates in a similar manner. It appears that the chaotic dynamics controls the outflow and supports the formation of near-horizon escape zones. We employ the technique of recurrence plots to characterize the onset of chaos in the outflowing medium. We investigate the system numerically and construct the basin-boundary plots, which show the location and the extent of the escape zones. The effects of black hole spin and magnetic field strength on the formation and location of escape zones are discussed, and the maximal escape velocity is computed.