Near-horizon structure of escape zones of electrically charged particles around weakly magnetized rotating black hole. II. Acceleration and escape in the oblique magnetosphere

TL;DR

This paper explores how inclined magnetic fields around rotating black holes influence the acceleration and escape of charged particles, revealing that nonaxisymmetric fields significantly enhance escape probabilities and velocities.

Contribution

It extends previous axisymmetric models by analyzing nonaxisymmetric magnetic fields, showing increased particle escape and ultrarelativistic acceleration due to broken symmetry.

Findings

Inclined magnetic fields increase escape zones.

Breaking symmetry allows ultrarelativistic particle velocities.

Transient chaos influences particle trajectories.

Abstract

Strong gravity and magnetic fields are key ingredients that power processes of accretion and ejection near compact objects. While the particular mechanisms that operate here are still discussed, it seems that the presence of an ordered magnetic field is crucial for the acceleration and collimation of relativistic jets of electrically charged particles on superhorizon length scales. In this context, we further study the effect of a large-scale magnetic field on the dynamics of charged particles near a rotating black hole. We consider a scenario in which the initially neutral particles on regular geodesic orbits in the equatorial plane are destabilized by a charging process (e.g., by photoionization). Some charged particles are accelerated out of the equatorial plane, and they follow jetlike trajectories with relativistic velocities. In our previous paper, we investigated this scenario for the case of perfect alignment of the magnetic field with the axis of rotation; i.e., the system was considered axisymmetric. Here we relax this assumption and investigate nonaxisymmetric systems in which the magnetic field is arbitrarily inclined with respect to the black hole spin. We study the system numerically in order to locate the zones of escaping trajectories and compute the maximum (terminal) escape velocity. It appears that breaking the axial symmetry (even by small inclination angles) substantially increases the fraction of escaping orbits and allows the acceleration to ultrarelativistic velocities that were excluded in the axisymmetric setup. The presence of transient chaotic dynamics in the launching region of the relativistic outflow is confirmed with chaotic indicators.