Contribution of the discrete modes to the current propagating along a wire parallel to a moderate conducting earth

Previous theoretical work on the propagation of electromagnetic waves along a thin wire parallel to the air-ground interface is applied to determine the current propagating along the line when a moderate conducting earth is assumed. We only consider the discrete modes due to residue contributions of the modal equation. The results show the limit of validity of the quasi-TEM approximation and that the fast-wave mode excited by a delta-function voltage generator at the centre of an antenna above a moderate conducting earth cannot be a priori neglected.