Pulsed and streamer discharges in air above breakdown electric field

A 3D particle model is developed to investigate the streamer formation in electric fields above the breakdown threshold, in atmospheric air (1bar, 300 Kelvin). Adaptive particle management, adaptive mesh refinement and parallel computing techniques are used in the code. Photoionization and electron detachment from natural background ionization in the form of O2- are included in the simulation. Many discharges grow up from different locations, instead of double-headed streamers present in previous fluid models. Our findings are in agreement with the experimental observation. We also estimate the ‘ionization screening time’ when the electric field drops below breakdown, due to the effect of space charge separation. We conclude that single isolated streamers hardly exist in air in the electric fields well above the breakdown value.