A Note on the Groundwave Phase Velocity Over a Plane Earth

Abstract

Equations are derived for the phase velocity of an electromagnetic groundwave propagating over. a plane earth having a constant surface impedance. The equations are found to differ in essence from one previously derived by King and Schlak (1967). As a result of the interpretation made here, it is concluded that the local phase velocity over a highly inductive surface exceeds the velocity of light in free space under certain conditions. For strongly capacitive surfaces, the phase velocity is expected to exceed the velocity in free space at all distances.