Experiments with Plasma Moving through Neutral Gas

Abstract

The behavior of a rotating plasma machine has been investigated. It is found that when the gas pressure and the current are varied within very wide limits the burning voltage remains constant. The voltage is proportional to the magnetic field. The reason for this behavior seems to be the existence of a critical velocity, above which a strong interaction between a plasma and a neutral gas takes place.

Alfvén ionization in an MHD-gas interactions code

“…Now critical velocities are very large, of the order of several km/s, 16 but these are velocities frequently reached in laboratory experiments, 18 theoretically expected in Brown dwarf atmospheres 17 or observationally detected in the solar atmosphere. For example, Rubio 43 and Vitas et al 44 show supersonic flows in the solar photosphere that are easily in the velocity range required.…”

“…Since the experimental results of Fahleson, 18 Danielsson and Brenning, 42 and others show a limit, at the critical velocity v c , are unable to drive further relative velocity between the two fluids then their experiments were consistent with f being close to unity when f 1 is calculated using the entire size of their apparatus. However, we do point out that the fluid dynamics are unresolved in these experiments, they only measured the mean velocity across of the entire device.…”

“…Experimental evidence for such a mechanism is abundant; Fahleson 18 used a "Rotating plasma device" which exploits an E Â B drift to drive ions through a background of neutral gas. Their results show a limit near the theoretical critical ionization velocity (CIV) which indicates that, in their experimental conditions, the plasma could not be driven through the neutral gas at velocities greater than the CIV.…”

Ionization fronts in coupled MHD-gas simulations

“…(10). 28,29 Each time an ionizing reaction occurs, then the kinetic energy of the free electron is reduced by E I , with the remaining kinetic energy shared between it and the newly created free electron, and an atom that was once part of the neutral species has become a plasma ion. Energy balance is maintained by tapping an internal energy state that is not represented in the model equations.…”

Simulation study of the ionizing front in the critical ionization velocity phenomenon.

“…2. Whereas the waves and electron heating inside the neutral cloud has been studied extensively before (RAADU, 1978;GALEEV, 1981;MACHIDA et al, 1984;ABE and MACHIDA, 1985;MACHIDA and GOERTZ, 1986) very little theoretical work has been done on the structure and dynamics of the ionizing front. In this paper we report the results of a 2-1/2 D electrostatic code linked with our Plasma and Neutral Interaction Code (PANIC, see MACHIDA and GOERTZ, 1987) which focuses on the understanding of the ionizing front.…”