Extragalactic cosmic ray self-confinement around sources

TL;DR

This paper investigates how plasma instabilities caused by cosmic ray currents near extragalactic sources can lead to self-confinement of cosmic rays, affecting their escape and propagation at ultra-high energies.

Contribution

It introduces a model for cosmic ray self-confinement due to plasma instabilities, quantifying energy thresholds based on magnetic field strength and source luminosity.

Findings

Cosmic rays are confined near sources for energies below certain thresholds.

Self-generated magnetic perturbations can hinder cosmic ray escape.

Confinement depends on magnetic field strength, coherence length, and source luminosity.

Abstract

Most models of the origin of ultra high energy cosmic rays rely on the existence of luminous extragalactic sources. Cosmic rays escaping the galaxy where the source is located produce a sufficiently large electric current to justify the investigation of plasma instabilities induced by such current. Most interesting is the excitation of modes that lead to production of magnetic perturbations that may scatter particles thereby hindering their escape, or at least changing the propagation mode of escaping cosmic rays. We argue that self-generation of waves may force cosmic rays to be confined in the source proximity for energies $E\lesssim 10^{7} L_{44}^{2/3}$ GeV for low background magnetic fields ($B_{0}\ll nG$). For larger values of $B_{0}$, cosmic rays are confined close to their sources for energies $E\lesssim 2\times 10^{8} \lambda_{10} L_{44}^{1/4} B_{-10}^{1/2}$ GeV, where $B_{-10}$ is the field in units of $0.1$ nG, $\lambda_{10}$ is its coherence length in units of 10 Mpc and $L_{44}$ is the source luminosity in units of $10^{44}$ erg/s.