Off-equatorial orbits in strong gravitational fields near compact objects - AstrophysicsReport as inadecuate

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Abstract: Near a black hole or an ultracompact star, motion of particles is governed bystrong gravitational field. Electrically charged particles feel alsoelectromagnetic force arising due to currents inside the star or plasmacircling around. We study a possibility that the interplay betweengravitational and electromagnetic action may allow for stable, energeticallybound off-equatorial motion of charged particles. This would representwell-known generalized Stormer-s -halo- orbits, which have been discussed inconnection with the motion of dust grains in planetary magnetospheres. Wedemonstrate that such orbits exist and can be astrophysically relevant when acompact star or a black hole is endowed with a dipole-type magnetic field. Inthe case of Kerr-Newman solution, numerical analysis shows that the mutuallyconnected gravitational and electromagnetic fields do not allow existence ofstable halo orbits above the outer horizon of black holes. Such orbits areeither hidden under the inner black-hole horizon, or they require the presenceof a naked singularity.

Author: Jiri Kovar, Zdenek Stuchlik, Vladimir Karas



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