Low Frequency Magnetic Field Observations of Natural Positive Leaders Featuring Stepwise Propagation

Abstract

We examine the low‐frequency (LF) magnetic pulses recorded for the positive leader in two natural lightning flashes as recorded on the high‐speed video camera. The captured positive leader in both cases propagated in a stepwise manner at least over several milliseconds according to the concurrent sequence of LF magnetic pulses. By comparing with previous studies on positive leaders under different situations, the average inter‐pulse intervals (11.7 and 20.3 μs, respectively) obtained for our natural cases are shorter than that of upward positive leaders in rocket‐triggered (typically >25 μs) and tower‐initiated lightning (62 μs in one case). Hence, the stepwise propagation of positive leaders in natural lightning is likely more frequent than that in object‐induced lightning, reflecting a possible influence of ambient electric field and other meteorological factors on the stepwise feature of positive leader. The stepwise extension might be common for positive leaders developing in various scenarios.

Effects of Applied Voltage on Branching of Positive Leaders in Laboratory Long Sparks

“…The research on positive leader has been primarily focused on investigating fundamental physical processes, initiation meteorological conditions, velocity‐current relationships, and analysis of two‐dimensional (2‐D) velocity (Kitagawa & Michimoto, 1994; Nag & Rakov, 2009; Saba et al., 2009; Yuan et al., 2017). Extensive studies have been conducted to explore leader stepping, cloud charge configurations, electric field ( E ‐field) waveforms, multiplicity and transferred charge (Qie et al., 2005; Lu et al., 2009, 2016; Saba et al., 2010; S. Huang et al., 2022; Wang et al., 2023). Nag and Rakov (2012) reported on the investigation of cloud charge configurations, identifying at least six configurations capable of producing downward positive lightning discharges.…”

“…Extensive studies have been conducted to explore leader stepping, cloud charge configurations, electric field (E-field) waveforms, multiplicity and transferred charge (Qie et al, 2005;Lu et al, 2009Lu et al, , 2016Saba et al, 2010;S. Huang et al, 2022;Wang et al, 2023). Nag and Rakov (2012) reported on the investigation of cloud charge configurations, identifying at least six configurations capable of producing downward positive lightning discharges.…”