Response of a Weakly Ionized Plasma to Turbulent Gas Flow

An arc discharge struck in a stream of flowing argon gas is studied as the flow is increased from the laminar regime to the regime of fully developed pipe turbulence, with Reynolds numbers (Re) ranging from zero to 6300. The properties of the discharge such as the density and density fluctuations, temperature, and electric field are measured with Langmuir-type probes. The discharge is found to respond strongly to the turbulent fluctuations of the un-ionized background gas. With increasing Reynolds number, plasma density fluctuations go up, the plasma column expands, and certain transport coefficients of the discharge rise well above their classical values. In particular, at Re = 6300, the plasma loss rate exceeds the expected classical value by about an order of magnitude. The observed phenomena can be understood in terms of relatively basic physical models.