Multi-frequency signatures of space-leader evolution in negative cloud-to-ground lightning stepped leaders

Journal Article · Wed Feb 04 00:00:00 EST 2026 · Atmospheric Research

DOI:https://doi.org/10.1016/j.atmosres.2026.108835· OSTI ID:3017800

Goldberg, Dylan J. ^[1]; Nag, Amitabh ^[2]; Cummins, Kenneth L. ^[1]; Plaisir, Mathieu N. ^[1]; Tempert, Alex ^[1]; Brower, A. Tyler ^[1]; Biagi, Christopher J. ^[3]; Brown, Robert G. ^[1]; Rassoul, Hamid K. ^[1]

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1. Florida Institute of Technology, Melbourne, FL (United States)
2. Florida Institute of Technology, Melbourne, FL (United States); Los Alamos National Laboratory (LANL), Los Alamos, NM (United States)
3. NASA Kennedy Space Center, FL (United States)

In this study, we examined 364 space leaders in 18 negative natural cloud-to-ground lightning strokes whose stepped leaders created new channels to ground. All strokes were captured on ultra-high-speed video cameras operating at frame rates ranging from 400k to 783k frames per second. Additionally, broadband electromagnetic field measurements were available for a subset of these strokes. The median space leader inception-to-attachment-point length and retrograde propagation speed towards the pre-existing leader channel (PELC) were 8.2 m and 4.0 x 10⁶ m/s, respectively. Space leader lengths were longer and retrograde propagation speeds faster for return strokes with higher peak currents. This is likely due to the relative proximity of space leader inception points to the PELC, which makes the electric field produced by the PELC line charge density one of the primary factors in determining space leader characteristics. Space leader characteristics were weakly related to their inception altitude. We observed bursts of very high frequency (VHF) emissions preceding, by around 0.5 – 1 μs, electric field leader-step pulses; visible-frequency-range luminosity pulses started during the step pulses. The median downward leader propagation speed for all 18 strokes was 4.3 x 10⁵ m/s; leader propagation speeds were generally faster for return strokes with higher peak currents. Also, leaders appeared to accelerate (on their way to ground) at altitudes lower than about 200 and 1000 m above ground level for strokes in the 10 – 60 and 84 – 228 kA peak current ranges, respectively.

• Research Organization: Los Alamos National Laboratory (LANL), Los Alamos, NM (United States)
• Sponsoring Organization: National Science Foundation (NSF); USDOE National Nuclear Security Administration (NNSA)
• Grant/Contract Number: 89233218CNA000001
• Other Award/Contract Number: 1934066
• OSTI ID: 3017800
• Report Number(s): LA-UR--25-28755; 10.1016/j.atmosres.2026.108835
• Journal Information: Atmospheric Research, Journal Name: Atmospheric Research Vol. 336; ISSN 0169-8095
• Publisher: Elsevier
• Country of Publication: United States
• Language: English

Related Subjects

54 ENVIRONMENTAL SCIENCES
Lightning space leaders
downward negative stepped leaders
electromagnetic field measurements
lightning
propagation speed
space stems
ultra-high-speed video camera measurements