Femtosecond Laser Triggered Breakdown Discharge Patterns in Long Air Gap

Lightning control has long been a dream for scientists. Femtosecond laser-triggered discharge in long air gap is the main research measure for providing perspectives on fundamental lightning understanding and technical routes. A record of laser-triggered negative discharge images in a long air gap on full track is presented in this letter in the study of laser-triggered discharges in a 2 m rod-rod gap under negative switching impulse. Laser-triggered breakdown in a long air gap was shown to have two patterns distinguished from the elongation length of a guided negative leader. For the pattern based on leader reillumination, plasma lifetime was shown to be more than tens of microseconds in guiding a negative leader after a dark period. The laser filament fixed the position of discharge initiation, determined leader propagation direction, and increased breakdown probability. This pattern can provide downward-leader prediction for an expected space position for more than tens of microseconds, which creates more advantages in triggering lightning strokes.