Effects of propagation on the rise times and the initial peaks of radiation fields from return strokes

摘要

The theoretical solution to the problem of radiation from a pulsed vertical dipole over a flat homogeneous earth is employed to study the changes in rise times and the attenuation of the initial peaks of the radiation fields from lightning constructed according to the most recent experimental data on lightning return stroke radiation fields. Expected changes in rise times and the attenuation of the initial peaks for different values of distances and conductivities are presented. It is shown that for a given initial rise time there is a spread in distant rise times due to the variability of the shapes of the radiation fields. The expected spread in distant rise times for different values of distances and conductivities is calculated. The results show the importance of taking into account the propagation effects in any attempt to estimate return stroke current parameters such as rise time, rate of rise, and peak current from radiation fields which propagated over land. The predictions are compared with the available experimental data, and a good agreement is found between them.