Publication date: Jul 2010
Abstract:
Off-equatorial circular orbits with constant latitudes (halo orbits) of
electrically charged particles exist near compact objects. In the
previous paper, we discussed this kind of motion and demonstrated the
existence of minima of the two-dimensional effective potential which
correspond to the stable halo orbits. Here, we relax previous
assumptions of the pseudo-Newtonian approach for the gravitational field
of the central body and study properties of the halo orbits in detail.
Within the general relativistic approach, we carry out our calculations
in two cases. Firstly, we examine the case of a rotating magnetic
compact star. Assuming that the magnetic field axis and the rotation
axis are aligned with each other, we study the orientation of motion
along the stable halo orbits. In the poloidal plane, we also discuss
shapes of the related effective potential halo lobes where the general
off-equatorial motion can be bound. Then we focus on the halo orbits
near a Kerr black hole immersed in an asymptotically uniform magnetic
field of external origin. We demonstrate that, in both the cases
considered, the lobes exhibit two different regimes, namely one where
completely disjoint lobes occur symmetrically above and below the
equatorial plane, and another where the lobes are joined across the
plane. A possible application of the model concerns the structure of
putative circumpulsar discs consisting of dust particles. We suggest
that the particles can acquire a small (but non-zero) net electric
charge, and this drives them to form the halo lobes.
Authors:
Kovář, J.; Kopáček, O.; Karas, V.; Stuchlík, Z.;