3D COMPUTATION OF LIGHTNING ELECTROMAGNETIC FIELDS IN THE PRESENCE OF A HORIZONTALLY STRATIFIED GROUND

Kaddour Arzag, Zin-Eddine Azzouz, Yoshihiro Baba, and Boualem Ghemri

Keywords

3D finitedifference timedomain method, lightning, lightning returnstroke model, stratified ground, lightning electromagnetic fields

Abstract

In this paper, the three-dimensional finite difference in time-domain method is applied to compute electromagnetic fields above and in a uniform or horizontally stratified ground in the vicinity of a vertical lightning return-stroke channel. In the computations, the return-stroke channel is represented with engineering and electromagnetic models. Engineering models used here are the modified transmission-line model with linear current decay with height and the modified transmission-line model with exponential current decay with height. Electromagnetic models employed include a vertical resistive wire having additional series distributed inductance and a vertical resistive wire coated by a fictitious material having high relative permittivity and permeability. Fields above ground computed with each lightning return-stroke model are not much influenced by the ground stratification, but those in the ground are influenced more by it. It appears that each model yields reasonably accurate results of close electromagnetic fields.

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