Electrostatic ion perturbations in kinematically complex shear flows

TL;DR

This paper investigates how ion electrostatic wave perturbations behave in plasma flows with complex shear, revealing different instability types and beat wave phenomena through numerical analysis.

Contribution

It introduces a numerical study of ion electrostatic perturbations in complex shear flows, identifying new instability mechanisms and wave behaviors.

Findings

Identification of shear flow instabilities with exponential wave vector evolution.

Discovery of parametric instability in periodic wave vector regimes.

Observation of beat wave phenomena with quasi-periodic behavior.

Abstract

The scope of the present paper is to determine how ion electrostatic wave perturbations in plasma flows are influenced by the presence of a kinematically complex velocity shear. For this purpose we consider a model based on the following set of physical equations: the equation of motion, the continuity equation and the Poisson equation for the electric potential governing the evolution of the system. After linearizing the equations, we solve them numerically. We find out that for a variety of specific values of parameters the system may exhibit quite interesting dynamic behaviour. In particular, we demonstrate that the system exhibits two different kinds of shear flow instabilities: (a)~when the wave vectors evolve exponentially, the ion sound modes become unstable as well; while, (b)~on the other hand, one can find areas in a parametric space where, when the wave vectors vary periodically, the physical system is subject to a strongly pronounced parametric instability. We also show the possibility of the generation of beat wave phenomena, characterized by a noteworthy quasi-periodic temporal behaviour. In the conclusion, we discuss the possible areas of applications and further directions of generalization of the presented work.