Cloud influence in evaluating the electric field of a lightning return stroke

A theoretical model to evaluate the electric field of a lightning return-stroke by taking into account the presence of the cloud, is illustrated. The cloud-lightning channel system is modelled by employing a perfectly conducting sphere placed above a thin-wire vertical antenna excited by a lightning current at the ground level. The current distribution in the channel is derived by a transmission line model found in technical literature. The ground is considered perfectly conductive. Different examples related to various channel lengths and sphere radii are reported in the paper, by stressing the different behaviour with and without the cloud. A comparison with recorded data available in literature, enables to qualitatively validate the results computed by means of the proposed model.