Correlation between speed of the stepped leader and peak current of the return stroke of lightning flashes

This study analyzes the two-dimensional speed profiles of 107 stepped leaders and 93 dart leaders recorded by high-speed cameras in Utah (USA), together with data from lightning location system (NLDN). The results show that the stepped leader speed right before the ground contact (final speed) has a very strong correlation (R = 0.85) with the peak current of the initiated return stroke. It also shows that the correlation between the average speed and the peak current of the return stroke is strong (R = 0.73). The same analysis for dart leaders did not show any significant correlation with the peak current of the prospective return stroke (R = 0.41 to average speed and R = 0.29 to final speed). This paper discusses why stepped leaders exhibit a significant correlation, while dart leaders do not. In addition, why final speed is better correlated with peak current than average speed.