A new lightning return stroke model based on antenna theory

A new approach based on antenna theory is presented to describe the lightni ng return-stroke process. The lightning channel is approximated by a straig ht and vertical monopole antenna with distributed resistance (a so-called l ossy antenna) above a perfectly conducting ground. The antenna is fed at it s lower end by a voltage source such that the antenna input current, which represents the lightning return-stroke current at the lightning channel bas e, can be specified. An electric field integral equation (EFIE) in the time domain is employed to describe the electromagnetic behavior of this lossy monopole antenna. The numerical solution of EFIE by the method of moments ( MOM) provides the time-space distribution of the current and line charge de nsity along the antenna. This new antenna-theory (or electromagnetic) model with specified current at the channel base requires only two adjustable pa rameters: the return-stroke propagation speed for a nonresistive channel an d the channel resistance per unit length, each assumed to be constant (inde pendent of time and height). The new model is compared to four of the most commonly used "engineering" return-stroke models in terms of the temporal-s patial distribution of channel current, the line charge density distributio n, and the predicted electromagnetic fields at different distances. A reaso nably good agreement is found with the modified transmission line model wit h linear current decay with height (MTLL) and with the Diendorfer-Uman (DU) model.