Lightning Initiation From Fast Negative Breakdown is Led by Positive Polarity Dominated Streamers

Evidence of positive polarity dominated streamers preceding fast negative breakdown (FNB) and of simultaneous positive and negative polarity streamer development in lightning initiation is reported. Observations of lightning initiation as FNB have remained a puzzle because simulations of lightning initiation have shown that negative streamers are not produced in virgin air without simultaneous positive streamers. Here, the authors observe positive streamer development forms first or at least simultaneously with negative streamers. Further evidence comes from observations of mixed fast breakdown (FB). The overall trajectory of the positive breakdown during such mixed events indicates that the positive streamers continuously propagate during the burst of strong negative breakdown. These observations indicate that even when negative streamers dominate the overall very high frequency (VHF) emissions, both positive and negative streamers are propagating simultaneously from the initiation point. These findings on the structure and dynamics of FB provide key new insight to our understanding of lightning initiation.

Automated summary

Evidence shows that positive polarity dominated streamers precede fast negative breakdowns and both positive and negative polarity streamers develop simultaneously during lightning initiation. Observations indicate that positive streamers continuously propagate during strong negative breakdowns, even when negative streamers dominate the overall emissions. These findings provide new insight into the structure and dynamics of fast breakdowns during lightning initiation.