Inductive acceleration of UHECRs in sheared relativistic jets

TL;DR

This paper proposes a new mechanism for accelerating ultra-high energy cosmic rays in sheared relativistic jets of active galaxies, emphasizing drift-induced energy gain that favors light nuclei like protons.

Contribution

It introduces a novel acceleration scheme based on drift in sheared jets, highlighting its efficiency and preference for light nuclei at high energies.

Findings

Drift in sheared jets can accelerate protons to ultra-high energies.

The mechanism favors acceleration of light nuclei over heavier elements.

Proposes a new explanation for the composition of UHECRs above the ankle.

Abstract

Relativistic outflows carrying large scale magnetic fields have large inductive potential and may accelerate protons to ultra high energies. We discuss a novel scheme of Ultra-High Energy Cosmic Ray (UHECR) acceleration due to drifts in magnetized, cylindrically collimated, sheared jets of powerful active galaxies (with jet luminosity $\geq 10^{46}$ erg s$^{-1}$). A positively charged particle carried by such a plasma is in an unstable equilibrium if ${\bf B} \cdot \nabla \times {\bf v}< 0$, so that kinetic drift along the velocity shear would lead to fast, regular energy gain. The highest rigidity particles are accelerated most efficiently implying the dominance of light nuclei for energies above the ankle in our model: from a mixed population of pre-accelerated particle the drift mechanism picks up and boosts protons preferably.