LIGHTNING RETURN STROKE ELECTRIC-FIELDS ABOVE GROUND

The vertical and horizontal field wave shapes derived from the Lienard -Wiechert potentials for a lightning return stroke are presented. The calculations were performed for ranges from 50 m to 5 km and altitudes from ground level up to 10 km, assuming a finitely conducting ground. It was found that the finite ground conductivity affects the fields a t close ranges and lower altitudes. It was also found that the effect introduced by considering the Lienard-Wiechert potentials is to increa se the initial field peaks and the time to peak. The maximum deviation in peak fields observed due to this effect is 40%.