Propagation of lightning generated transient electromagnetic fields over finitely conducting ground

This paper elucidates the propagation effects on lightning generated electric fields. The mathematics of the problem is described and a simple procedure that can be used to predict the propagation effect is outlined together with its experimental confirmation. This procedure is used to analyse the propagation effects, over distances less than about 300 km, on the radiation fields of negative first return strokes, positive first return strokes and subsequent return strokes in triggered lightning flashes. From the results, empirical equations that can be used to correct for the propagation effects are extracted. The results show that the attenuation due to propagation effects of the initial peak amplitudes may differ in negative and positive return strokes and that the data from triggered lightning flashes should be applied with caution in correcting for the propagation effects of natural lightning flashes. (C) 2000 Elsevier Science Ltd. All rights reserved.