Characterisation of lightning flashes from changing electric field measurements in Johannesburg, South Africa

Presented are results obtained from changing electric field measurements and high-speed video analysis on lightning flashes over Johannesburg, South Africa. A flat-plate antenna and integrator were used to record changing electric fields and the high-speed footage was recorded using Phantom v310 and v7.1 (15,000 fps and 5,000 fps respectively) cameras. A total of 34 negative strokes and 3 positive strokes were analysed. The recorded negative strokes presented an average peak intensity of 8.0 V/m, 0 - 100 % rise time of 3.3 μs, 10 - 90 % rise time of 1.8 μs and pulse duration of 6.4 μs. The positive strokes presented an average peak intensity of 36.7 V/m, 0 - 100 % rise time of 22.9 μs, 10 - 90 % rise time of 7.4 μs and pulse duration of 33.4 μs. The average continuing current durations, determined using high-speed videos, was 6.3 ms for the negative strokes and 81.5 ms for the positive strokes.