High‐speed video observations of a natural negative stepped leader and subsequent dart‐stepped leader

Abstract

AbstractWe present new high‐speed video observations of a natural negative stepped leader and a subsequent negative dart‐stepped leader. Observations were made at a distance of 770 m using a high‐speed video camera at 10,000 frames per second, a microwave‐frequency radio receiver, a broadband electric field antenna, and an avalanche photodiode array. Lightning leader breakdown was observed in detail for both the negative stepped leader and the subsequent dart‐stepped leader. During the negative stepped leader breakdown, detailed images were captured of the discharge structures near the leader tips. These structures bear a remarkable resemblance to the corona streamer zone and space leader discharges that have been observed in laboratory‐generated negative stepped leaders. During the dart‐stepped leader breakdown, no corona streamer zone was observed outside of the decaying return stroke channel, but small luminous structures that are suggestive of space leaders were observed just ahead of the main dart leader tip. Two distinct low‐luminosity zones were observed just ahead of the dart leader tip, suggestive of two distinct breakdown regimes. A multipath junction was observed in the main channel to ground following the first return stroke but was not observed following the second return stroke. Finally, microwave‐frequency radio emissions for both leader types and their return strokes were recorded, and their time domain behavior is compared and discussed.