The formation mechanism and movement behavior of discrete spots and stripes on a water anode with argon flow regulation

A stable glow discharge in ambient air is sustained between the tungsten rod and the water anode via the introduction of argon flow. With the discharge current and gap width fixed while the argon flow rate is varied, patterns are generated on the water anode, which—as observed via fast photography—are dynamic and consist of spots, stripes, labyrinths, or irregular meshes. It can be concluded that the formation of the coexisting spots-and-stripes pattern, the labyrinth pattern, and the irregular mesh pattern is affected by negative ions. To the authors’ knowledge, these patterns have been first observed on the water anode. The newly formed spots—which keep away from the existing spots and stripes in the center of the coexisting spots-and-stripes pattern—increase in number over time and can develop into short or long stripes. The tentacles of stripes in the dynamic labyrinth pattern extend in the direction in which the Coulomb force from the surrounding stripes encounters the least resistance. Some stripes in the center of the dynamic irregular mesh pattern can continuously thicken and expand into cells due to the uneven distribution of negative ions.