The effect of a horizontally stratified ground on lightning electromagnetic fields

This paper proposes a formulation for the evaluation of the lightning electromagnetic fields in presence of a horizontally stratified soil. The formulation is based on a suitable mathematical modification of the Sommerfeld's exact formulas for the case of a homogeneous ground, in order to account for the dependence of the ground conductivity and permittivity on the vertical coordinate. Numerical simulations are presented to analyse the influence of the soil stratification on the above-ground lightning electromagnetic field components. The results obtained for a two-layered ground configuration are compared with those related to a homogeneous soil.