Quantitative analysis of a lightning return stroke for diameter and luminosity changes as a function of space and time
Richard E. Orville, John H. Helsdon, W. H. Evans · Journal of Geophysical Research Atmospheres · 1974
Two hundred twenty-four images of a lightning return stroke have been obtained with a high-speed framing camera. The exposure time for each frame is 2 μs, and the time between frames is 77 μs. Channel diameters corrected for overexposure and image density are measured as a function of space and time for the first 1.6 ms of the stroke. The channel diameter has a mean value of 6.5 cm, and it is not observed to change significantly within the period of measurement. The image density generally decreases with time except for a momentary increase at approximately 0.6 ms. Sections of the return stroke channel remain luminous for at least 17.7 ms, an order of magnitude greater than that previously reported by Evans and Walker.