Groundwave Attenuation Function for Propagation Over A Highly Inductive Earth

Propagation of an electromagnetic groundwave over a plane surface in which the argument of the surface impedance is greater than π/4 but less than π/2 is considered in some detail. The numerical distance, p , over such a surface is characterized by 0 ≤ arg p ≤ π/2. The groundwave behaves in a peculiar manner, and this is attributed to the interaction of two phasor components representing a trapped wave and a Norton surface wave. Approximate expressions are derived which determine the magnitude and phase of the groundwave attenuation function when these two waves are inphase and antiphase. A method is also given for estimating the asymptotic phase for large | p | which was previously not possible except through detailed calculations. Finally, detailed curves are presented which show the amplitude and phase of the groundwave attenuation function versus p .