Acceleration of the charged particles due to chaotic scattering in the combined black hole gravitational field and asymptotically uniform magnetic field

Abstract

To test the role of large-scale magnetic fields in accretion processes, we study the dynamics of the charged test particles in the vicinity of a black hole immersed into an asymptotically uniform magnetic field. Using the Hamiltonian formalism of the charged particle dynamics, we examine chaotic scattering in the effective potential related to the black hole gravitational field combined with the uniform magnetic field. Energy interchange between the translational and oscillatory modes of the charged particle dynamics provides a mechanism for charged particle acceleration along the magnetic field lines. This energy transmutation is an attribute of the chaotic charged particle dynamics in the combined gravitational and magnetic fields only, the black hole rotation is not necessary for such charged particle acceleration. The chaotic scatter can cause a transition to the motion along the magnetic field lines with small radius of the Larmor motion or vanishing Larmor radius, when the speed of the particle translational motion is largest and it can be ultra-relativistic. We discuss the consequences of the model of ionization of test particles forming a neutral accretion disc, or heavy ions following off-equatorial circular orbits, and we explore the fate of heavy charged test particles after ionization where no kick of heavy ions is assumed and only the switch-on effect of the magnetic field is relevant. We demonstrate that acceleration and escape of the ionized particles can be efficient along the Kerr black hole symmetry axis parallel to the magnetic field lines. We show that a strong acceleration of the ionized particles to ultra-relativistic velocities is preferred in the direction close to the magnetic field lines. Therefore, the process of ionization of Keplerian discs around the Kerr black holes can serve as a model of relativistic jets. a

Fifty Years of Energy Extraction from Rotating Black Hole: Revisiting Magnetic Penrose Process

“…Ejection of ionized particles to infinity takes place along magnetic field lines, which can be open to infinity at the polar caps of black holes. Then, charged particles escape to infinity due to chaotic scattering effect caused by the interchange between the oscillatory and translational modes of the total energy of escaping particles E 0 → E z [96]. Thus, the combination of MPP with chaotic scattering effect leads to the high Lorentz factors and alignment of trajectories of escaping particles along the rotation axis of a black hole.…”

“…Comparison of trajectories in two cases with negative (left) and positive (rights) magnetic parameter B is represented in Figure 3, which is reproduced from [96]. The trajectories are found in [96] by numerical integration of the full set of equations of motion. Acceleration is larger in case of positive B.…”

Orbital widening due to radiation reaction around a magnetized black hole

“…The dynamics and the corresponding oscillatory motion of the charged particles in the absence of radiation reaction force in the magnetized Schwarzschild spacetime can be found in Kološ et al () and in the magnetized Kerr spacetime in Kološ et al () and Stuchlík & Kološ (). Let us introduce two dimensionless parameters characterizing the influences of the magnetic field and radiation reaction force in the BH's vicinity as follows: where q and m are charge and mass of a test particle, and M is the BH mass.…”

Particle motion around generic black holes coupled to non-linear electrodynamics

“…The main purpose of the studying the particle motion around compact objects is to test the model or solution of gravity theories. Particularly, the accretion disc around the astrophysical black holes is considered as a relevant model of some X-ray sources and the observation of inner edge radii of accretion disc can give constraints on parameters of alternative and modified theories of gravity [20][21][22][23][24][25][26][27][28][29][30][31][32][33][34][35][36][37][38][39]. Above presented facts are good motivation for study test particle's motion around black hole described by the general relativistic solution coupled with non-linear electrodynamics.…”