On Representation of Lightning Return Stroke as a Lossy Monopole Antenna With Inductive Loading

In this paper, a modification of the antenna theory (AT) model of the lightning return stroke to include inductive loading is presented. The distributed inductive energy-storing elements are used in the modified AT model (designated as ATIL model, where IL stands for inductive loading) to control the propagation speed of the upward traveling current wave without using an artificial, higher permittivity dielectric medium, as done in the original AT model. The variation of the propagation speed along the channel is also considered in the proposed model. As in the original AT model, resistive loading is used to account for the current attenuation with height. Numerical solution of the electric field integral equation in the time domain using the with appropriate boundary conditions yields a time-space distribution of current along the lightning channel. This current distribution and the resultant electromagnetic fields for the ATIL model are compared with those predicted by other time-domain and frequency-domain electromagnetic models. The current distribution predicted by the ATIL model exhibits features (such as current dispersion) that are more consistent with optical observations of lightning compared to the predictions of the original AT model.