A Procedure to Infer Lightning Return-Stroke Current Waveform From Far-Field Waveform for the Case of Lossy Ground

We proposed expressions for reconstructing the waveform of channel-base current from the corresponding far electric field waveform (radiation field component only) on perfectly conducting ground for the modified transmission line models with linear and exponential current decay with height. Waveforms of vertical electric field on lossy ground at far distances (50-200 km) were computed using the finite-difference time-domain (FDTD) method for solving discretized Maxwell's equations in the 2-D cylindrical coordinate system. The FDTD-computed waveforms of vertical electric field on lossy ground were compensated for propagation effects and used in the proposed field-to-current conversion expressions for inferring the channel-base current waveform. The reconstructed currents are in excellent agreement with the current used in computing the fields on lossy ground.