VLF propagation across discontinuous daytime-to nighttime transitions in anisotropic terrestrial waveguide

Discontinuity effects are analyzed after referring the ionospheric surface impedance of daytime and nighttime waveguide portions to the same common altitudeh. The properties of the waveguide junction are determined by field matching, and the resulting linear equations are rearranged in a form that permits a sequential determination of transmission and reflection coefficients. Simple dominant mode approximations of the transmission and reflection coefficients are also developed. Field calculations of reciprocal geometries illustrate the consistency of the formulation and reflection coefficients are found to be of negligible magnitudes. The discontinuous surface impedance tends to excite higher order waveguide modes of larger amplitudes than a ground based source in homogeneous waveguide.