The modelling of positive return strokes in lightning flashes

A simple model is introduced to represent positive return strokes so that the electromagnetic field environment created by them at different distances and at ionospheric heights can be calculated. The model parameters were selected in such a way that they can be directly connected to the observed features of the electromagnetic fields. This removed the guess work that is sometimes necessary in attributing values to the parameters of models. The model is then used to evaluate the electromagnetic fields created by positive return strokes at locations, such as in the immediate vicinity of the lightning flash and in the ionosphere, where it is difficult to perform field measurements. (C) 2000 Published by Elsevier Science Ltd. All rights reserved.