Striking distance to flat ground estimated from the bipolar leader model and the influence of the lightning channel radius

Abstract

This paper proposes a physically consistent method to estimate the lightning striking distance to flat ground as a function of the return stroke charge, as well as a function of the prospective return stroke peak current. This method is based on an axisymmetric electrostatic model of charges in thunderstorm clouds used to initiate a vertical bipolar leader that develops bidirectionally from the region of maximum electrical field inside the cloud towards the ground. The leader is assumed as a perfect conductor whose potential is equal to the average cloud potential over its length. The charge simulation method is applied to calculate the leader charge distribution by the numerical solution of the Poisson equation. The striking distance to flat ground is computed when the average potential gradient between the leader tip and the ground is equal to 500 kV/m. This analysis is extended to different leader radius values, in order to evaluate its effect on striking distance, since there are some uncertainties regarding the leader radius reported in literature. Furthermore, the obtained results are compared to models from different authors.