Turbulence and Particle Acceleration in Shearing Flows

TL;DR

This paper investigates how shear-driven instabilities influence particle acceleration in relativistic shearing flows, showing that large-scale AGN jets can accelerate electrons and protons to very high energies under certain conditions.

Contribution

It provides new insights into the constraints on particle acceleration in shearing flows, emphasizing the role of jet stability and seed injection requirements.

Findings

Shearing layers in AGN jets likely extend over a significant fraction of the jet radius.

Seed injection of GeV electrons is necessary for efficient acceleration.

Acceleration to PeV energies for electrons and EeV for protons is feasible within stability constraints.

Abstract

We explore constraints imposed by shear-driven instabilities on the acceleration of energetic particles in relativistic shearing flows. We show that shearing layers in large-scale AGN jets are likely to encompass a sizeable fraction ($\geq 0.1$) of the jet radius, requiring seed injection of GeV electrons for efficient acceleration. While the diffusion process may depend on pre-developed turbulence if injection occurs at higher energies, electron acceleration to PeV and proton acceleration to EeV energies appears possible within the constraints imposed by jet stability.