Current subsidiary peak in triggered lightning strokes

Mainly based on the channel base current of the 0803 and 0902 flashes detected in the Shandong Artificial Triggering Lightning Experiment (SHATLE) from 2005 to 2010, the current waveforms of six return strokes and an RM process (a process characterized by both a return stroke and an M‐component) containing subsidiary peaks were analyzed. The percentage of strokes with subsidiary peak is approximately 17%. The amplitudes of the stroke primary and subsidiary peaks varied from 8.53 to 16.34 kA and 5.40 to 15.86 kA, respectively. The time intervals between the primary and the secondary peak varied from 6.3 to 12.0  μ s. The strokes of the 0803 and 0902 flashes have different current waveform characteristics, indicating that the mechanisms generating the subsidiary peaks in the two lightning may be different. To learn more about the causes of forming the subsidiary peaks based on the assumption that channel branches and every peak corresponds to a physical process, a Heidler function model was used to simulate the current waveforms of four strokes and an RM in flash 0902. The simulated results indicated that the Heidler function component could reflect the physical characteristics of the peaks to some extent. Based on simulated results and comparison of waveforms, four possibilities of forming subsidiary peaks were proposed: channel branching, flashover along a triggering wire from a previous unsuccessful launch, the corona current or reflection of the current. Branching and flashover may be the main causes of generating the subsidiary peaks in 0902 and 0803 flashes, respectively.