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Viscous fingering and spatiotemporal dynamics of micro discharges occurring in an atmospheric plasma discharge

Cormac Corr, Rod Boswell and Cameron Samuell

Space Plasma, Power and Propulsion group
Research School of Physical Sciences and Engineering
The Australian National University
Canberra, ACT, Australia, 0200

Abstract

We have developed a radio frequency powered low temperature, non-equilibrium argon gas discharge consisting of two parallel electrodes, at least one covered with a thin dielectric layer. The discharges that take place in such an experimental device are of different types, depending on the experimental conditions, especially on the product pd of gas pressure p and the gas gap width d. The spatiotemporal pattern formations and micro discharge phenomena occurring in this atmospheric plasma discharge have been studied using high-resolution movies. In particular, we observe moving finger-like structures, occurring as the argon plasma expands radially across the electrodes, which are indicative of fluid-like behaviour. These patterns can be compared with the finger patterns associated with the Saffman-Taylor instability that is observed in the Hele-Shaw cell when a less viscous liquid displaces a more viscous one. In this work we have constructed a Hele-Shaw cell and use dyed water and glycerol to observe this phenomenon. Other spatiotemporal phenomena include travelling localized discharges and star-like discharges. All of the observed phenomena can be controlled by varying the rf input power, gas flow and discharge gap size.