Lightning attachment processes of three natural lightning discharges

摘要: Using a high-speed optical imaging system specifically designed for observing the lightning attachment process, we have documented process six strokes in three natural flashes. All initiate at height above ground and propagate bidirectionally from that height, similar to return of artificially initiated (triggered) previously reported by Wang et al. (2013, 2014). Though data are quite limited, these suggest correlation between larger peak current greater initiation height. Initiation heights determined here span 12–60 m with typical uncertainty less than 10 m. The initial upward stroke luminosity speeds range (0.8 ± 0.2) (2.0 ± 0.4) × 108 m/s. Two first downward assessed as (1.6 ± 0.3) × 107 m/s (1.4 ± 0.3) × 108 m/s. One appeared be stepping pulse discharge its leader an inseparable part stroke.