Ultra‐Slow Discharges That Precede Lightning Initiation

We report on ultra-slowly propagating discharge events with speeds in the range 1–13 km/s, much lower than any known lightning process. The propagation of these discharges are orders magnitude slower leader or streamer speeds, but faster ion drift speed. For one particular event, a forms about 40 ms later within 50 m discharge, likely same high field region. A second slow event 9 prior to initiation, and leads into negative leader. Most appear not be directly involved initiation. This suggests that classic cascade model initiation is always definitive In this work we describe displaying unique behavior, their relation common discharges, implications for