High-energy acceleration phenomena in extreme radiation-plasma interactions

TL;DR

This paper uses particle-in-cell simulations to explore how intense gamma-ray flux interacts with plasma, leading to complex acceleration processes for electrons and ions driven by radiation and plasma instabilities.

Contribution

It provides a detailed simulation study of multi-stage acceleration mechanisms in extreme radiation-plasma interactions, including analytical insights and sensitivity analysis.

Findings

Electrons are accelerated to energies exceeding photon energies.

Ions are driven to near-relativistic speeds by charge-separation fields.

A forward-directed suprathermal electron tail is generated by Weibel instability.

Abstract

We simulate, using a particle-in-cell code, the chain of acceleration processes at work during the Compton-based interaction of a dilute electron-ion plasma with an extreme-intensity, incoherent gamma-ray flux with a photon density several orders of magnitude above the particle density. The plasma electrons are initially accelerated in the radiative flux direction through Compton scattering. In turn, the charge-separation field from the induced current drives forward the plasma ions to near-relativistic speed and accelerates backwards the non-scattered electrons to energies easily exceeding those of the driving photons. The dynamics of those energized electrons is determined by the interplay of electrostatic acceleration, bulk plasma motion, inverse Compton scattering and deflections off the mobile magnetic fluctuations generated by a Weibel-type instability. The latter Fermi-like effect notably gives rise to a forward-directed suprathermal electron tail. We provide simple analytical descriptions for most of those phenomena and examine numerically their sensitivity to the parameters of the problem.