Anode pattern formation in atmospheric pressure air glow discharges with water anode

Pattern formation in the anode layer at a water electrode in atmospheric pressure glow discharges in air is studied. With increasing current a sequence of different anode spot structures occurs from a constricted homogeneous spot in the case of small currents to a pattern consisting of small distinct spots for larger currents. The dependence of the number of spots on the current is (18.5+0.4N) mA with N the number of spots. The spots group together and form stripe patterns. Disappearance of the spots with increasing conductivity of the electrode seems to indicate that mechanisms of electrical nature govern the phenomenon. Similarities and differences with other experiments and models revealing pattern formation in glow discharges are discussed.