Self-organization, generation, annihilation, and dynamics of filaments in dielectric barrier discharges

The localized objects forming the patterns in Dielectric Barrier Discharges (DBDs) are luminous plasma filaments that exhibit particle-like behaviour, i.e. generation, annihilation, dynamics, scattering, and collective effects leading to self-organized structures (hexagons, stripes, concentric rings, spirals). We use simple experiments and models to study the basic mechanisms behind pattern formation and dynamics in DBDs. Experiments and models show that the formation of filaments can be described in term of activation and inhibition mechanisms, and that the physical quantities playing the role of activators and inhibitors can be clearly identified. We analyze in details the formation of a self-organized pattern after a few cycles of the applied voltage and show how the pattern can evolve on a longer time scale. We also show that the model can reproduce well some aspects of the filament dynamics that are observed in fast imaging experiments, such as division and merging of filaments. The motion of a filament along the dielectric layer can be observed under some conditions and we show that this apparent motion can be the result of an interaction between two filaments, a visible one operating in a glow regime, and a less visible or invisible one operating in a low current, Townsend regime. We discuss how the association of activation-inhibition mechanisms with the important property of bistability of non equilibrium discharges can lead to a large variety of patterns that are very similar to patterns observed in other physical, chemical, or biological systems.