Leader-chasing behavior in negative artificial triggered lightning flashes

Fukun Wang,Jianguo Wang,Wenhan Ding,Li Cai,Rui Su,Zhiling Xu

doi:10.1038/s41598-021-90940-x

Abstract

Two special cases of dart leader propagation were observed by the high-speed camera in the leader/return stroke sequences of a classical triggered lightning flash and an altitude-triggered lightning flash, respectively. Different from most of the subsequent return strokes preceded by only one leader, the return stroke in each case was preceded by two leaders occurring successively and competing in the same channel, which herein is named leader-chasing behavior. In one case, the polarity of the latter leader was opposite to that of the former leader and these two combined together to form a new leader, which shared the same polarity with the former leader. In the other case, the latter leader shared the same polarity with the former leader and disappeared after catching up with the former leader. The propagation of the former leader in this case seems not to be significantly influenced by the existence of the latter leader.

Highlights

Two special cases of dart leader propagation were observed by the high-speed camera in the leader/ return stroke sequences of a classical triggered lightning flash and an altitude-triggered lightning flash, respectively
The subtypes β1 and β2 were made by Schonland[14]; Type β2 leader is a relatively rare variant of type β leader whose propagation is associated with the occurrence of dart streamers
We reported two cases of leader-chasing behavior, which are observed for the first time, during the propagation of dart leaders in two artificial triggered lightning flashes

Summary

Introduction

Two special cases of dart leader propagation were observed by the high-speed camera in the leader/ return stroke sequences of a classical triggered lightning flash and an altitude-triggered lightning flash, respectively. Campos et al.[15] made detailed research on seven cases of type β2 stepped leaders and proposed that dart streamer is the visible manifestation of one or more recoil leaders These recoil leaders begin inside the cloud and connect to the in-cloud, positive portion of the bipolar, bidirectional leader, and travel downward to the lower end of the negative stepped leader path. Different from type β2 stepped leaders, the leaders reported here are dart leaders descending continuously with a higher speed in the residual channel left by preceding return strokes instead of the virgin air, whose optical characteristics have been well studied[16,17,18,19,20]

Methods

Conclusion