Correlation Between Speed of the Leader and Peak Current of the Return Stroke in Negative Lightning Flashes

• Published in: Geophysical research letters 2025-01, Vol.52 (2), p.n/a
• Main Authors: Cruz, Ivan T., Saba, Marcelo M. F., Silva, José Claudio O., Abbasi, Rasha U., Hunt, Hugh G. P., Schumann, Carina, Silva, Diego R. R., Silva, Tagianne P., Lauria, Paola B., Kieu, Ny T.
• Format: Article
• Language: English
• Subjects: average speed; Cameras; Correlation; dart leader; Dart leaders; Dimensional analysis; final speed; high‐speed camera; Leader currents; Lightning; Lightning flashes; Lightning location; peak current; Return stroke; Return strokes (lightning); Speed limits; stepped leader; Stepped leaders
• ISSN: 0094-8276; 1944-8007
• DOI: 10.1029/2024GL111594

This study analyzes the two‐dimensional speed profiles of 107 stepped leaders and 93 dart leaders recorded by high‐speed cameras in Utah (USA), together with data from lightning location system. The results shows that the final and average speed of the stepped leader has a very strong (R = 0.82) and strong (R = 0.71) correlation with the peak current of the return stroke. It also shows that 91% of the stepped leaders increased their speed near the ground (average increase of 69%). The same analysis for dart leaders shows weak correlation with the peak current of the prospective return stroke (R = 0.39 to average speed and R = 0.28 to final speed). This paper briefly discusses why peak current is better correlated with final speed than with the average speed, and why stepped leaders exhibit a significant correlation, while dart leaders do not. Plain Language Summary This study looks at how fast stepped leaders and dart leaders of lightning flashes propagate from the cloud base to ground, using high‐speed camera videos and data from a lightning location system. The results show that the final and average speed of the leaders are well correlated to the return stroke current, the return stroke current being more closely related to the final speed than the average speed. In contrast, dart leaders showed a weak correlation between their speed and the return stroke current. It also shows that most stepped leaders sped up as they got closer to the ground. Key Points The return stroke peak current is better correlated with final speed than with the average speed of the stepped leader No significant correlation was found between dart leaders speed and stroke peak current The stepped leaders increase their propagation speed near the ground