Electric Penrose process: high-energy acceleration of ionized particles by non-rotating weakly charged black hole

TL;DR

This paper explores how a small electric charge on a non-rotating black hole can accelerate ionized particles to ultra-high energies, potentially explaining cosmic rays like PeV protons from the Galactic center.

Contribution

It introduces a novel mechanism called the Electric Penrose process, showing how weakly charged black holes can serve as particle accelerators for cosmic rays.

Findings

Ionized particles can reach ultra-high energies near weakly charged black holes.

The Galactic center black hole could act as a PeVatron for protons.

The mechanism offers an alternative explanation for cosmic ray acceleration.

Abstract

In many astrophysical scenarios the charge of the black hole is often neglected due to unrealistically large values of the charge required for the Reissner-Nordstr\"om spacetime metric. However, black holes may possess small electric charge due to various selective accretion mechanisms. In this paper we investigate the effect of a small hypothetical electric charge of a Schwarzschild black hole on the ionization of a freely falling neutral particle and subsequent escape of the ionized particle from the black hole. We show that the energy of ionized particle can grow ultra-high and discuss distinguishing signatures of particle acceleration by weakly charged black holes. We also discuss a possible application of the proposed mechanism as an alternative cosmic ray acceleration scenario. In particular we show that the Galactic centre supermassive black hole is capable to act as a PeVatron of protons. The presented mechanism can serve as a simple toy model of a non-rotating compact object acting as a particle accelerator with a potential astrophysical implementations related to the cosmic ray physics and beyond.