Two-stage acceleration of interstellar ions due to the interaction of high-energy lepton plasma flow

TL;DR

This paper uses particle-in-cell simulations to reveal a two-stage process for accelerating interstellar ions via high-energy lepton plasma flows, involving magnetic turbulence and shock reflection, leading to high-energy proton spectra.

Contribution

It introduces a novel two-stage acceleration mechanism for protons in lepton plasma interactions, combining magnetic turbulence and shock reflection effects.

Findings

Protons are first accelerated transversely by magnetic islands.

Protons develop an inverse-power energy spectrum.

A shockwave forms, reflecting protons at twice the shock speed, creating a monoenergetic peak.

Abstract

We present the particle-in-cell (PIC) simulation results of the interaction of a high-energy lepton plasma flow with background electron-proton plasma and focus on the acceleration processes of the protons. It is found that the acceleration follows a two-stage processes. In the first stage, protons are accelerated transversely (perpendicular to the lepton flow) by the turbulent magnetic field "islands" generated via the strong Weibel-type instabilities. The accelerated protons shows a perfect inverse-power energy spectrum. As the interaction continues, a shockwave structure forms and the protons in front of the shockwave are reflected at twice of the shock speed, resulting in a quasi-monoenergetic peak located near 200MeV under the simulation parameters.