A MODEL FOR SUBSEQUENT RETURN STROKES

In this paper a new return stroke model is introduced which is capable of predicting the temporal and spatial variation of the return stroke current and return stroke velocity. The model predictions concerning the electromagnetic fields, return stroke current and return stroke velocity are in good agreement with experimental observations. The model predicts that the peak radiation field increases approximately linearly with increasing peak current at ground level and that the peak radiation field derivative increases approximately linearly with increasing peak current derivative at ground level. The Transmission Line Model equations can, therefore, be used to derive the distribution of peak currents and peak current derivatives from the measured fields. However, an effective velocity of about 1.5 x 10(8) m/s should be used to calculate the peak currents from the measured peak radiation fields and an effective velocity of about 2.3 x 10(8) m/s should be used to calculate the peak current derivatives from the measured peak radiation field derivatives.