Analogue of bead lightning in a pulse discharge initiated by runaway electrons in atmospheric pressure air

A breakdown initiated by runaway electrons in an inhomogeneous electric field in atmospheric pressure air was studied. Bright plasma channels (spark filaments) in the center of the discharge gap were observed on the background of a diffuse discharge by applying high-voltage pulses with an amplitude of about 200 kV across the discharge gap with an interelectrode distance of 18 mm. Their occurrence probability is no more than 10%. The glow of the bright plasma channels is similar to that of a spark channel. It was found that the bright plasma channels appear with a decrease in the discharge current. Its radiation intensity is an order of magnitude lower than that of the diffuse discharge. Such bright plasma channels were observed in pulseperiodic discharges, where nanosecond voltage pulses with amplitudes of 10–15 kV were applied across the discharge gap with an interelectrode distance of 6 mm. The pulse repetition rate was about 400 Hz. Occurrence of the bright plasma channels on the background of diffuse discharge is caused by generation of runaway electrons and the discharge current redistribution over the discharge plasma cross-section during a decrease in the discharge current. It is assumed that the discharge recorded is an analogue of bead lightning observed in the Earth’s atmosphere. © 2015, Pleiades Publishing, Ltd.