High-Speed Video Observations of Natural Lightning Attachment Process With Framing Rates up to Half a Million Frames per Second

Abstract

Using high-speed video cameras operating with framing rates of 20 and 525 kfps, we imaged the attachment process of a natural negative cloud-to-ground flash, occurring at a distance of 490 m. Nine upward leaders were observed. A total of 12 space stems/leaders in 47 steps of the downward negative stepped leader were captured. The two-dimensional length of them was between 2.0 and 5.9 m, with an average of 3.0 m. The average interstep interval, step length, and two-dimensional speed of the downward negative leader and that of upward positive leader were statistically analyzed. The last step of the downward negative leader making contact with the upward connecting leader was recorded. The two-dimensional length of the final imaged gap between the tips of opposite-polarity leaders was estimated to be about 13 m.