Wave-driven non-classical electron transport in a low temperature magnetically expanding plasma

Abstract

The presence of instabilities in a low density, low temperature plasma expanding through an axially symmetric magnetic nozzle is investigated in the context of non-classical electron cross field transport. Electrostatic probes are used to characterize the background plasma properties and instabilities. The measurements show a primarily azimuthally propagating mode with a broad, incoherent power spectrum that appears linear at low frequencies. It is demonstrated that the observed dispersion is consistent with the lower hybrid drift instability. The energy and linear growth rate of this wave are related through quasilinear theory to an effective electron collision frequency that is shown to be dominant over classical collisions.