Control of gradient-driven instabilities using shear Alfv\'en beat waves

TL;DR

This paper introduces a novel method to control gradient-driven plasma instabilities by using nonlinear interactions with shear Alfvén beat waves, demonstrating suppression of instabilities in a laboratory setting.

Contribution

It presents a new technique employing nonlinear Alfvén wave interactions to manipulate and suppress plasma instabilities, advancing plasma control methods.

Findings

Successful suppression of unstable fluctuations in LAPD

Demonstration of beat-wave response at different frequencies

Potential for active plasma instability control

Abstract

A new technique for manipulation and control of gradient-driven instabilities through nonlinear interaction with Alfv\'en waves in a laboratory plasma is presented. A narrow field-aligned density depletion is created in the Large Plasma Device (LAPD), resulting in coherent unstable fluctuations on the periphery of the depletion. Two independent kinetic Alfv\'en waves are launched along the depletion at separate frequencies, creating a nonlinear beat-wave response at or near the frequency of the original instability. When the beat-wave has sufficient amplitude, the original unstable mode is suppressed, leaving only the beat-wave response at a different frequency, generally at lower amplitude.