Static Spiral Patterns in a Dielectric Barrier Discharge

Static spiral patterns are observed in a dielectric barrier discharge system. It bifurcates from the concentric-ring pattern with the increase of the applied voltage. The formation of the static spiral patterns is investigated using an intensified-charge coupled device camera. It is found that the discharge filaments are the basic unit of the spiral patterns and they do not occur at the same location during successive half cycles. The uniform spiral arms, as seen with the naked eyes, are formed by the numerous discharge filaments located in different positions during successive acquisition intervals. The correlation coefficient between the discharges of successive half cycles is relatively low and is independent of the delay time between images.