Motion of a charged test particle around a static black hole in a monopole magnetic field

TL;DR

This paper investigates the motion of charged particles around a black hole in a monopole magnetic field, revealing that radial motion is unaffected by the magnetic field while tangential motion is confined, affecting plasma behavior.

Contribution

It demonstrates that radial motion remains unchanged by magnetic fields and shows how magnetic confinement influences particle trajectories near black holes.

Findings

Radial motion of charged particles is unaffected by magnetic fields.

Charged particles are confined to a thin cone in tangential motion.

Plasma can hover over the black hole and become very hot.

Abstract

We study the motion of a charged test particle in the spacetime with a spherically symmetric black hole which is immersed in a monopole magnetic field. We show that the radial motion of the charged test particle is governed by completely the same equation as that in the case of no magnetic field. This result implies that the black hole will acquire the electric charge if it is surrounded by the collisionless plasma composed of protons and electrons which obey the Maxwell velocity distribution. The drastically different situation appears in the tangential motions of charged test particles due to the magnetic field. The trajectory of a charged test particle in the black hole with the magnetic field of the order of 10 Gauss near the black hole, is confined on a very thin cone as long as the specific angular momentum of the particle is not much larger than the gravitational radius of the black hole times the speed of light. This result leads to a possibility that a plasma lump can hover over the black hole and is very hot, in the monopole magnetic field.