Evaluation of Lightning Current and Return Stroke Velocity Using Measured Far Electric Field Above a Horizontally Stratified Ground

This paper proposed an inverse procedure for evaluating the channel-base current and return stroke velocity using measured far electric fields over a two-layer horizontally stratified ground, where the lightning current along lightning channel adopt the modified transmission line model with linear current decaying with height (MTLL) model. Moreover, the proposed method has been validated using two numbers of measured electric field obtained from triggered lightning, where the velocity is considered to be variable along lightning channel and the average value along lightning channel, respectively. The results show that the evaluated channel-base current is in good agreement with the corresponding measured channel-base current, and the average evaluated return stroke velocity is among 1/3 to 2/3 of the speed of light in free space. Also, we compare the evaluated results using transmission line (TL) model or adopting single-layer soil model. The results both show that the method, which combines the MTLL model and the two-layer stratification soil model, is more suitable to evaluate the channel-base current and return stroke velocity in this paper. The proposed inverse procedure can evaluate the lightning current as well as return stroke velocity, this is useful for studies on lightning characteristics and lightning protection.