Formation of side discharges in dielectric barrier discharge.

Pattern formation and self-organization are fascinating phenomena found widely in nature and in laboratory environment such as dielectric barrier discharge (DBD). Significant efforts have been made to explain the dynamic pattern formation. In DBD, the formation of side discharges is generally supposed to be a key factor responsible for diversity and spatial-temporal symmetry breaking of pattern formation. However, it is still not clear how such discharges are induced. Here, we present the observations of side discharges in a filamentary dielectric barrier discharge from both numerical simulations and experiments. Two-dimensional particle-in-cell simulations with Monte Carlo collisions included have revealed formation dynamics of side discharges, suggesting that transverse plasma diffusion and ion induced secondary electron emission play critical roles. Moreover, a novel honeycomb superlattice pattern is observed in experiment, where the side discharges associated with honeycomb superlattice are verified by utilizing a high speed camera. Experimental observations and numerical simulation are in good agreement.