Charged Particle Motion Near a Magnetized Black Hole: A Near-Horizon Approximation

Abstract

In this paper, the orbits of a charged particle near the event horizon of a magnetized black hole are investigated. For a static black hole of mass $M$ immersed in a homogeneous magnetic field $B$, the dimensionless parameter $b=eBGM/(m{c}^4)$ controls the radius of the circular orbits and determines the position of the innermost stable circular orbit (ISCO), where $m$ and $e$ are the mass and charge of the particle. For large values of the parameter $b$, the ISCO radius can be very close to the gravitational radius. We demonstrate that the properties of such orbits can be effectively and easily found by using a properly constructed ``near-horizon approximation''. In particular, we show that the effective potential (which determines the position of the orbit) can be written in a form which is invariant under rescaling of the magnetic field, and as a result is universal in this sense. We also demonstrate that in the near-horizon approximation, the particle orbits are stationary worldlines in Minkowski spacetime. We use this property to solve the equation describing slow changes in the distance of the particle orbit from the horizon, which arise as a result of the electromagnetic field radiated by the particle itself. This allows us to evaluate the life-time of the particle before it reaches the ISCO and ultimately falls into the black hole.

14 pages, 5 figures. New references added. Typos are corrected

References in corpus (8)

• First M87 Event Horizon Telescope Results. VIII. Magnetic Field Structure near The Event Horizon
• Motion of charged particles near weakly magnetized Schwarzschild black hole
• Radiative Penrose process: Energy Gain by a Single Radiating Charged Particle in the Ergosphere of Rotating Black Hole
• Charged Particles Circular Orbits around Weakly Charged and Magnetized Kerr Black Holes
• Particle Dynamics in Weakly Charged Extreme Kerr Throat
• Black holes and magnetic fields
• Circular orbits of Charged Particles around a Weakly Charged and Magnetized Schwarzschild Black Hole
• Magnetized black holes: interplay between charge and rotation

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