Exact kinetic theory for the instability of an electron beam in a hot magnetized plasma

TL;DR

This paper presents an exact relativistic kinetic theory calculation of beam-plasma instabilities in hot, magnetized plasmas, revealing how thermal spreads and non-Maxwellian tails influence instability growth rates and plasma heating efficiency.

Contribution

It provides the first exact calculation of the unstable spectrum for arbitrary magnetic fields and particle distributions in relativistic beam-plasma systems.

Findings

Nonrelativistic plasma temperatures stabilize oblique instabilities.

Non-Maxwellian tails reduce growth rates of longitudinal modes.

Thermal spreads influence the efficiency of turbulent plasma heating.

Abstract

Efficiency of collective beam-plasma interaction strongly depends on the growth rates of dominant instabilities excited in the system. Nevertheless, exact calculations of the full unstable spectrum in the framework of relativistic kinetic theory for arbitrary magnetic fields and particle distributions were unknown until now. In this paper we give an example of such a calculation answering the question whether the finite thermal spreads of plasma electrons are able to suppress the fastest growing modes in the beam-plasma system. It is shown that nonrelativistic temperatures of Maxwellian plasmas can stabilize only the oblique instabilities of relativistic beam. On the contrary, non-Maxwellian tails typically found in laboratory beam-plasma experiments are able to substantially reduce the growth rate of the dominant longitudinal modes affecting the efficiency of turbulent plasma heating.