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 is also shown that the real oscillation frequencies of the characteristic quasinormal modes are considerably suppressed by the tidal force.

• Received 8 August 2012

DOI:https://doi.org/10.1103/PhysRevD.86.084007