Synchrotron-limited Particle Acceleration in Relativistic Shearing Flows

TL;DR

This paper investigates how electrons can be accelerated to ultra-relativistic energies in AGN jets through shear flows, revealing that mildly relativistic jets can sustain electrons with Lorentz factors exceeding 10^8.

Contribution

It provides numerical solutions and analytical comparisons for synchrotron-limited electron acceleration in mildly relativistic shearing flows, advancing understanding of particle acceleration in large-scale jets.

Findings

Electrons can reach Lorentz factors of ~10^8 in mildly relativistic jets.

Numerical solutions align with analytical estimates of electron cutoff energies.

Large-scale jets are suitable environments for distributed ultra-relativistic electron acceleration.

Abstract

Fermi-type shear particle acceleration is a promising mechanism for sustaining ultra-relativistic particles along the kilo-parsec scale jets in Active Galactic Nuclei (AGNs). We explore the possibility of synchrotron-limited electron acceleration in mildly relativistic shearing flows and present numerical solutions to the corresponding particle transport equation. We compare our findings with analytical calculations to infer an effective electron cutoff energy, and discuss the relationship to a simplified box model treatment. The results show that mildly relativistic large-scale jets offer a suitable environment for distributed electron acceleration beyond Lorentz factors of $\gamma_e \sim 10^8$.