Exact relativistic kinetic theory of an electron beam-plasma system: hierarchy of the competing modes in the system parameter space

TL;DR

This paper provides a comprehensive relativistic kinetic analysis of electron beam-plasma stability, revealing the competition among three mode types across parameter space, supported by simulations.

Contribution

It introduces an exact linear relativistic kinetic model to map the multidimensional unstable spectrum of beam-plasma systems, extending beyond previous simplistic approaches.

Findings

Identification of three competing mode types based on wavenumber direction

Mapping of mode dominance regions in three-dimensional parameter space

Validation of theoretical results with multidimensional particle-in-cell simulations

Abstract

Besides being one of the most fundamental basic issues of plasma physics, the stability analysis of an electron beam-plasma system is of critical relevance in many areas of physics. Surprisingly, decades of extensive investigation had not yet resulted in a realistic unified picture of the multidimensional unstable spectrum within a fully relativistic and kinetic framework. All attempts made so far in this direction were indeed restricted to simplistic distribution functions and/or did not aim at a complete mapping of the beam-plasma parameter space. The present paper comprehensively tackles this problem by implementing an exact linear model. We show that three kinds of modes compete in the linear phase, which can be classified according to the direction of their wavenumber with respect to the beam. We then determine their respective domain of preponderance in a three-dimensional parameter space. All these results are supported by multidimensional particle-in-cell simulations.