2024/09/25 by João S. Santos, Vítor Cardoso, Santos, João S. +3
Engineering · Physics and Astronomy · #Astrophysical Phenomena and Observations #FOS: Physical sciences #General Relativity and Quantum Cosmology (gr-qc) #High Energy Astrophysical Phenomena (astro-ph.HE) #High Energy Physics - Theory (hep-th) #Particle Accelerators and Free-Electron Lasers #Pulsars and Gravitational Waves Research
paper · pdf · doi:10.48550/arxiv.2409.17225
openalex publication_date 2024/09/25 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/30
We study electromagnetic radiation reaction on a charged particle around a weakly magnetized Kerr black hole. We solve numerically the Teukolsky equation to find energy fluxes in electromagnetic radiation at the horizon and at spatial infinity. We also employ analytical methods in the low-frequency limit, finding excellent agreement with the numerical results. For a wide range of parameters, energy fluxes on the horizon are negative for all orbital radii: the modes are amplified through superradiance. More interestingly, the flux on the horizon is larger (in absolute value) than the flux at infinity for orbits with orbital radius r0 \gtrsim 9M -- floating orbits are a generic outcome of having magnetic fields around black holes. Particles on these orbits extract energy from the BH through their radiation field; the net effect is an increase in the particles' kinetic energy, so that they outspiral to infinity. Although in realistic accretion disks viscous forces are expected to dominate, floating orbits remain an interesting feature of the existence of ergoregions in black hole spacetimes.