Electron Modulational Instability in the Strong Turbulent Regime for an Electron Beam Propagating in Background Plasma

TL;DR

This paper investigates a new electron modulational instability regime in a plasma, revealing rapid local growth of Langmuir wave packets and resulting strong ion density perturbations, with implications for beam-plasma interactions.

Contribution

It identifies and characterizes a novel electron modulational instability regime in turbulent plasma, supported by simulations and analytical theory, highlighting new physical regimes.

Findings

Rapid local growth of Langmuir wave packets.

Formation of strong ion density perturbations.

Observation of periodic burst features in plasma evolution.

Abstract

We study collective processes for an electron beam propagating through a background plasma using simulations and analytical theory. A new regime where the instability of a Langmuir wave packet can grow locally much faster than ion frequency is clearly identified. The key feature of this new regime is an Electron Modulational Instability that rapidly creates a local Langmuir wave packet, which in its turn produces local charge separation and strong ion density perturbations because of the action of the ponderomotive force, such that the beam-plasma wave interaction stops being resonant. Three evolution stages of the process and observed periodic burst features are discussed. Different physical regimes in the plasma and beam parameter space are demonstrated for the first time.