A New Inversion Algorithm for Estimating the Return-Stroke Velocity

To study the lightning return-stroke process, this paper proposed a new inversion algorithm for evaluating the average return-stroke velocity. As the Gaussian function covers a frequency range wider than the typical channel-base current, the main step of this method was to treat the channel-base current representing using the Gaussian function and the corresponding azimuthal magnetic field at close distance as the inputs and outputs, respectively, to establish the transfer functions. We have verified the proposed method using the azimuthal magnetic field with/without noises at different distances from the lightning channel. In addition, we compared the evaluated results using different return-stroke models including the transmission line (TL) model, the modified TL model with linear (MTLL) current decay with height, and the modified TL model with exponential (MTLE) current decay with height. The evaluated results are in agreement with the simulated return-stroke velocity, indicating the effectiveness and robustness of this method for predicting the return-stroke velocity. The proposed inversion method is effective in estimating the return-stroke velocity, which can be applied in lightning physics research.