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

Abstract

[1] We 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.Citation: Petersen, D. A., and W. H. Beasley (2013), High-speed video observations of a natural negative stepped leader and subsequent dart-stepped leader,

The physical concept of recoil leader formation

“…The high-speed camera, a Photron SA1.1, was operated at a frame rate of 10,000 fps. The lack of any observable luminous channel in the frame immediately prior this sequence indicates the absence of residual luminosity from the prior return stroke[19].…”

Upward negative leaders in positive triggered lightning: Stepping and branching in the initial stage

“…For the ordinary-observed downward negative leader, the properties are generally obtained in the later stage of the leader propagation when it extends out of the cloud or even gets close to the ground [e.g., Jiang et al, 2017;Qi et al, 2016;Stolzenburg et al, 2015;Petersen and Beasley, 2013]. This fundamental issue is always studied through optical means such as high-speed video cameras and remote sensing of electromagnetic field with fine time resolution, which have provided lots of new insights into the associated physical mechanism while insufficiency still exist in acquiring the important parameters of the natural negative leaders in atmosphere, such as the current waveform, the precise charge associated with an individual step, or even the line charge density of the step.…”

Using High-Speed Photography to Study Undercatch in Tipping-Bucket Rain Gauges*

“…The camera we used was a Photron FASTCAM SA1.1. 1 This is a type of camera used to investigate the structure of lightning strokes (Petersen and Beasley 2013;Hill et al 2011). For our needs, we set the frame rate at a comparatively low rate of 500 frames per second (fps), yielding a resolution of 0.002 s. The rain gauge we used was a Met One model 380 12-in.…”