Electromagnetic emission from plasma with counter-streaming electron beams in the regime of oblique instability dominance

TL;DR

This paper investigates electromagnetic emission from counter-streaming electron beams in plasma, demonstrating high efficiency radiation generation near the second harmonic of plasma frequency through oblique instability dominance, using simulations and linear theory.

Contribution

It introduces a new understanding of efficient electromagnetic emission in plasma with counter-streaming beams driven by oblique instability, supported by simulations and theoretical analysis.

Findings

High beam-to-radiation conversion efficiency achieved

Radiation generated near the second harmonic of plasma frequency

Efficiency and spectrum independent of beam thickness

Abstract

The problem of electromagnetic emission generation in plasma with electron beams is relevant both for practical applications and for interpretation of radio emission processes in astrophysical systems. In this work, we consider the case of counter-propagating electron beams injection into plasma. Such systems may occur in cosmic plasma in the case of closely spaced particle acceleration regions, and they can also be implemented in laboratory facilities. Using particle-in-cell numerical simulations, we have shown that high beam-to-radiation conversion efficiency can be achieved in the case when beams excite small scale oblique plasma oscillations. In this case, the radiation is generated in the vicinity of the second harmonic of the plasma frequency. For such waves the surrounding plasma is transparent. It has been found that the efficiency and spectrum of the radiation are not dependent on the thickness of the beams. It has been also shown that parameters of the system necessary for efficient radiation generation by the discussed mechanism can be found using the exact linear theory of beam-plasma instability.