Acoustic self-oscillation in a spherical microwave plasma

Abstract

We present a method of sound amplification and self-oscillation in high pressure partially ionized gas. Continuous microwaves incident on partially ionized gas may sustain and amplify an acoustic field if increased ionization during the sound field's adiabatic compression enhances RF power absorption. Amplifying sound in this way enables the generation of high amplitude sound in a cavity containing partially ionized gas without mechanical driving or precise knowledge of its resonance frequency. This method of amplification may open opportunities within thermoacoustics such as using 3D geometries and volumetric gain mechanisms.

Convective instability in a stratified ideal gas containing an acoustic field

“…2004) and numerically (Hart, Glatzmaier & Toomre 1986 b ; Featherstone & Hindman 2016) for quite a while. Progress on the experimental front will require stabilization of the acoustic field in the plasma experiment, one method of which was studied theoretically by Pree, Putterman & Koulakis (2019). Further theoretical exploration of the differences between acoustic ‘gravity’ and actual gravity, and in particular how well the former models the later, will be required to put such experiments on firmer ground.…”