VLF Wave Propagation Along a Mixed Path in the Curved Earth‐Ionosphere Waveguide

An investigation of VLF radio‐wave propagation across a land‐sea boundary has been completed. The influence of the homogeneous ionosphere and the curvature of the earth, as well as the ground discontinuity, are considered. The problem of finding the field strength due to a horizontal line source is first formulated as a Wiener‐Hopf type problem via the concept of equivalent surface impedance and is subsequently solved in the Fourier‐transform plane. This solution has direct correspondence with that for dipole excitation and is expressed analytically in terms of the reflection and transmission coefficients of modes in the two sections of the earth‐ionosphere waveguide.