Representation of a Lightning Return-Stroke Channel as a Nonlinearly Loaded Thin-Wire Antenna

Distributed nonlinear resistive elements are incorporated into an antenna theory (AT) model with fixed inductive loading (ATIL-F) to realistically model the current wave propagation along the lightning return-stroke channel (RSC). Resistive elements are considered as a nonlinear distributed load whose resistance is a function of both current and time. This is adopted from the numerical models of a spark channel and consequent shockwave from a lightning discharge, yielding a changing value of the channel radius from the base to the cloud along the RSC. It is demonstrated that the proposed model is more consistent with the nonlinear behavior of a lightning channel inferred from experimental physical observations. The model also satisfies most of the well-known characteristics of RSC, including the temporal and spatial current and charge distributions, some important features observed in radiated electromagnetic fields, and wave propagation speed profiles along the channel when compared with those predicted by the ATIL-F model.