High-energy cosmic ray production by a neutron star falling into a black hole

TL;DR

This paper proposes a novel one-shot mechanism where a neutron star falling into a black hole accelerates surrounding plasma to produce ultra-high-energy cosmic rays, potentially explaining their rarity.

Contribution

It introduces a new process involving black hole-induced acceleration of neutron stars to generate cosmic rays with energies around 10^19 eV.

Findings

Energy estimates for iron nuclei reach 10^19 eV.

Mechanism operates via electric fields induced near the black hole horizon.

Potential explanation for the rarity of high-energy cosmic ray events.

Abstract

We propose a one-shot mechanism for high-energy cosmic ray generation by a neutron star falling into a black hole surrounded by low density plasma. The function of the black hole in this scenario is to accelerate the star to a speed arbitrarily close to that of light. When the star - essentially, a magnetized sphere - approaches the horizon it imparts energy to the ambient plasma charges via the induced electric field. Disregarding radiation losses, for iron nucleus, a simple estimate gives energies on the order of 10^19 eV for stars with magnetic fields as weak as 10^6 teslas. The proposed mechanism should also work in chance encounters between rapidly moving neutron stars and molecular clouds. The rarity of such encounters may explain the apparent randomness and rarity of the high-energy cosmic ray events.