Evaluation of the Return-Stroke Current Attenuation Function from the Vertical Electric Field by Means of the Regularization of an Inverse Problem

The behavior of the return-stroke current along the lightning channel is extremely important for the evaluation of the electromagnetic fields radiated at various distances, since such fields may cause disturbances or faults on electric and electronic equipment. It is commonly known that lightning current attenuates while propagating along the channel and several models have been adopted in an attempt to reproduce the characteristics of the electromagnetic fields at different distances. This work proposes a method that can reconstruct the attenuation of the current along the channel, starting from the knowledge of the channel-base current and of the vertical electric field measured by a sensor located five km away from the discharge location. The method relies upon the Tikhonov regularization technique applied to an ill-posed problem in the frequency domain and is mainly based on the hypothesis of long-time measurement windows.