Submicrosecond laser-filament-assisted corona bursts near a high-voltage electrode

Long, about a half of microsecond, nonuniform corona UV burst is observed after a femtosecond-laser-filament plasma appears nearby an electrode biased (positively or negatively) slightly higher than the corona discharge threshold and well-isolated from the natural streamer discharge. A bright UV emission area moving outwards, over a 20 cm distance, with the velocity of 0.6% of the speed of light and tearing from the filament plasma in the case of the negative voltage is observed. In the case of positive voltage, a bright, bouncing UV cone is formed at around 4 cm far from the filaments exposing the appearance of a leader. Both phenomena could be explained upon supposing the formation of runaway electrons in the vicinity of the filament plasma and electrode.