Reconstruction of lightning currents and return stroke model parameters using remote electromagnetic fields

Estimating parameters of a lightning return stroke model and the current at the base of the lightning channel from measurements of remote electromagne tic fields is an important practical problem. In the present paper we apply a genetic algorithm (a global optimization technique) to the above problem . Firstly, we use the genetic algorithm to reconstruct the return stroke mo del parameters using the channel-base current and the remote electromagneti c field measured simultaneously. The channel-base current is used to calcul ate the electric field at the measurement point. The difference between the calculated and the measured fields is minimized using the genetic algorith m, which finds the optimal solution for the return stroke parameters. The t ransmission line and Diendorfer-Uman return stroke models are used in the i llustrations. Secondly, we develop a method to reconstruct the return strok e model parameters and channel-base current from electric or magnetic field s measured at two different distances, one of which is a far-field and the other is a near field. The Diendorfer-Uman model is used in the reconstruct ion. Thirdly, we develop a method to reconstruct the return stroke model pa rameters and channel-base current from two magnetic fields at two different distances, one of which is an intermediate field and the other is a near f ield. For doing the above with the Diendorfer-Uman model we derive an expli cit inversion formula using both the induction and the radiation terms of t he magnetic field.