Surface forward and backward discharges and corresponding residual charge accumulation characteristics under positive impulse

The backward discharge induced by residual charge has attracted considerable attention, but the complex mechanism requires further investigation. This article analyzes the surface discharge and the residual surface charge accumulation characteristics in atmospheric air under a positive impulse. The photographic figure method, the dust figure method, and the electrostatic probe method are employed, allowing the residual charge distribution to be quantitatively determined. One main forward discharge is observed at the impulse front and several subsequent backward discharges are observed at the impulse tail. The propagation length of the forward streamer is closely related to the voltage at the moment of discharge. A model illustrating the evolution process of surface forward and backward discharges as well as the corresponding residual charge accumulation characteristics is established. The residual surface charge plays a significant role in the development of the streamer discharge. The backward discharge is incurred by the positive charge that is deposited by the previous forward discharge.