Horizontal electric field at the surface of layered earth due to lightning

This paper presents a time-domain method for the calculation of the electric field at the surface of earth due to lightning, when the earth structure is made of two parallel horizontal layers of finitely conducting earth. The method is based on the assessment of the electric field at the surface considering the earth as homogeneous and with the electrical parameters of the first layer. The contribution of the second layer is considered by computing the waves reflected from this layer, after they have propagated in the first layer. The paper also shows that the displacement currents could be neglected during the reflection of the waves, which leads to a simple expression for the reflection coefficient. The results from the method presented in this paper agree with reference results calculated from a frequency-domain expression proposed by Wait.