High-Frequency Behavior of the Surface-Wave Helicon Instability

Abstract

The surface-wave instability in helicon wave propagation analyzed by Baraff and Buchsbaum is reinvestigated here for the purpose of extending the analysis to values of ωτ greater than unity. We find that although collisions are essential for the mechanism of instability, the formulas and analysis of Baraff and Buchsbaum, derived for ωτ«1, are unchanged until ωτ exceeds some large value ω0τ. This value ω0τ is typically much greater than unity. At higher frequencies the surface wave penetrates from one boundary to the next and some of the Baraff-Buchsbaum approximations start to lose validity.