Orbital widening due to radiation reaction around a magnetized black hole

Abstract

Radiation reaction acting on a charged particle moving at a stable circular orbit of a magnetized black hole (BH) can lead to the shift of the orbital radius outward from the BH. The effect causes an increase of the energy and angular momentum of the particle measured by an observer at rest at infinity. In this paper, we show that “widening” of such orbits is independent of the field configuration, but it appears only in the cases with the external Lorentz force acting outward from the BH. This condition corresponds to qLB > 0, where q and L are the charge and angular momentum of the particle, and B is intensity of the external magnetic field. As examples of the orbital widening, we consider two scenarios with an external homogeneous magnetic field and a magnetic dipole field generated by a current loop around a Schwarzschild BH. We show that the orbital widening is accompanied by quasi‐harmonic oscillations of the particle, which are considerably large in the magnetic dipole fields. We also estimate the timescales of orbital widening, from which it follows that the effect can be relevant in the vicinity of stellar‐mass BHs.

Influence of Cosmic Repulsion and Magnetic Fields on Accretion Disks Rotating around Kerr Black Holes

“…Equations (169) and (173) represent the covariant form of the Landau-Lifshitz equations. Detailed analysis of the particular case of the motion of charged particles around a Schwarzschild black hole immersed into an external asymptotically uniform magnetic field was presented in [36], where the equations of motion are given in separated form and the results of their numerical integration are obtained in typical situations; the special case of the widening of circular orbits was discussed in [37]. Effect of radiation reaction on charged particle dynamic around rotating Kerr black hole can be seen in Figure 20.…”

“…We study the influence of the dimensionless black hole spin a on the fate of the ionized Keplerian disks for given magnetic intensity parameter characterizing the ratio of the electromagnetic and gravitational forces acting on charged test particles. The special case of ionized Keplerian disks orbiting a Schwarzschild black hole (a = 0) was studied in detail in [35], back-reaction effect due to radiation of the charge particles on their motion was studied in [36,37].…”

Rotating normal and phantom Einstein–Maxwell–dilaton black holes: Geodesic analysis

“…The presence of a phantom electromagnetic field (η 2 = −1) and/or phantom scalar field [η 1 = −1 ⇔ γ ∈ (−∞, −1) ∪ [1, ∞)] affects greatly the motion of photons and massive particles. Circular motion and the determination of isco and lsco are among the first tasks workers perform for purposes of astrophysical applications to accretion disks (see [23,43,[48][49][50][51][52][53][54][55] and references terein). From this point of view we noticded that the presence of phantom fields may widen, in the ra-plane, the set of existence of stable circular orbits; in some other cases this same set is much restricted.…”

Equatorial and Polar Quasinormal Modes and Quasiperiodic Oscillations of Quantum Deformed Kerr Black Hole

“…In some phenomenological models of QPOs, the oscillations of the disk have the same frequencies as the oscillations of a particle moving around the BH, so we can simplify the calculations and directly calculate the epicyclic frequencies of oscillating particles. From the analytical and numerical perspective, the QPOs are investigated via the epicyclic (or quasi-cyclic) motion of charged particles around spinning BHs in the presence of magnetic fields [16,17] and sometimes using only neutral particles in a curved background without the use of magnetic field. The latter is assumed to be weak such that the spacetime curvature is undisturbed due to the magnetic fields.…”