Motion of charged particles and quasinormal modes around the magnetically and tidally deformed black hole

TL;DR

This paper investigates how tidal forces and magnetic fields around deformed black holes influence charged particle motion and scalar field decay, revealing energy release enhancements and modifications to quasinormal mode frequencies.

Contribution

It provides analytical and numerical analysis of particle dynamics and scalar field decay in deformed black hole spacetimes, highlighting effects of magnetic fields and tidal forces.

Findings

Magnetic fields and tidal forces enhance energy release during accretion.

Stable anti-Larmor orbits exist near the horizon for strong magnetic fields.

Tidal forces significantly suppress quasinormal mode frequencies.

Abstract

Here we consider two phenomena in the vicinity of a black hole deformed by the tidal gravitational force of surrounding matter and by a strong magnetic field: equatorial motion of charged particles and the decay of a test scalar field. We were able to analyze both phenomena with analytical and simple numerical tools, which was unexpected given the low symmetry of the system. We show that both the tidal gravitational force and the magnetic field strongly enhance the release of the binding energy for the matter spiralling into the black hole. In the presence of the magnetic field, the left and right handed rotations of charged particles are not equivalent and for sufficiently large $|q| B$ there are stable anti-Larmor orbits very close to the event horizon, although Larmor orbits are only stable at some distance from the black hole. The larger the tidal force, the closer the innermost stable orbit to the black hole for both types of rotation. It was also shown that the real oscillation frequencies of the characteristic quasinormal modes are considerably suppressed by the tidal force.