Influence of return stroke speed and leader line charge density on lightning corona sheath dynamics

Positive transferred charge inside the lightning channel core during the return-stroke stage dominates the total charge when the speed of the return stroke current wave is relatively low and negative leader line charge density is less than typical values inferred from field measurements. As a result, the positive charge inside the channel during the return-stroke stage can be temporarily greater than the negative charge deposited by the preceding leader. This may explain significant positive overshoots in radial electric fields measured close to the lightning attachment point at ground.