Overview of plasma wave studies using the Basic Plasma Science Facility

Abstract

The Basic Plasma Science Facility (BaPSF) at UCLA is a US national user facility for studies of fundamental processes in magnetized plasmas. The centerpiece of the facility is the Large Plasma Device (LAPD), a 20m long, magnetized linear plasma device1. This LAPD has been utilized to study a number of fundamental processes, including: collisionless shocks2, dispersion and damping of kinetic and inertial Alfvén waves3, compressional Alfvén waves for ion-cyclotron range of frequencies heating4, flux ropes and magnetic rcconnection5, three-wave interactions and parametric instabilities of Alfvén waves6, turbulence and transport7 and interactions of energetic ions and electrons with plasma waves8. A brief overview of research using the facility will be given, followed by a more detailed discussion of two recent studies of the physics of Alfvén waves. Recent experiments have resulted in the first laboratory observation of the parametric instability of shear Alfvén waves9. Shear waves with sufficiently high $\omega/\Omega_{\mathrm{i}}(> 0.6)$ and above a threshold wave amplitude are observed to decay into co-propagating daughter waves; one a shear Alfvén wave and the other a low-frequency quasimode. The observed process is similar to the modulational decay instability.