On the relationship between continuing current and positive leader growth

Abstract

AbstractIt has long been speculated that the source of continuing current (CC) for a negative cloud‐to‐ground flash is provided by the growth of its positive leader into negative charge regions. In this study, data from the Langmuir Electric Field Array (LEFA) and Lightning Mapping Array (LMA) are used to investigate these speculations. LEFA and LMA data provide a way to estimate the occurrence and duration of CC and channel growth throughout a flash, respectively. By connecting LMA VHF sources onto contiguous channels, the growth of the positive leader associated with each return stroke is inferred. A linear correlation between positive‐channel growth and CC duration is found, providing evidence that the positive leader grows with a constant velocity, but no obvious correlation of this velocity with CC occurrence is found. Each return stroke is then sorted by its channel growth rate and further identified by its CC type. This analysis also provides no identifiable correlation linking the positive‐channel growth rate to CC occurrence or duration. Finally, the positive‐channel growth rate for the whole flash is calculated in 10 ms windows so that any trends occurring before, during, or after the CC can be observed. This analysis too shows no correlation, which implies that positive‐channel growth is not the primary mechanism that determines CC occurrence and duration.