Vortices in a gas-discharge plasma
Processes of vortex generation in a weakly ionized gas are reviewed in circumstances where a high-speed flow propagates along the gas discharge and acoustic waves interact with a positive column. Results on the effect of longitudinal gas flow on the positive-column properties are presented. It is shown that in certain conditions the gas flow in the positive column gives rise to vortices that cause the plasma to mix radially, producing a uniformly excited gas at high pressures. Results concerning the interaction of acoustic waves with low-temperature plasma are reviewed, and the acoustic-stimulated formation of vortex motion leading to an uncontracted discharge at elevated pressures is discussed. Also examined are flashes of superluminescence in an argon discharge caused by an abrupt transition of a positive column containing acoustic vortices from the uncontracted state to the contracted one at heightened pressures; this transition is understood to occur because of the turbulent-to-laminar transition in the acoustic flow. Finally, a gas-discharge acoustically induced laser is described.