Effects of Ionospheric Reflection Height and Ground Conductivity on Earth-Ionosphere Waveguide Mode and Ground-Wave Attenuation Rates

摘要

A surviving ground-wave signal has previously been assumed to represent the minimum expected for vlf and lf systems operating in a severely disturbed environment. The authors show that for propagation over poorly conducting soil and under a depressed ionosphere, path losses may markedly exceed those predicted by the normal ground-wave attenuation rates. This is shown to be caused by the invasion of the ionosphere into the presupposed free-space region of the diffraction mode (ground-wave) 'dust.' Because of inherent uncertainties in the ground-wave model for some propagation conditions, the authors recommend that estimates of system performance in severe environments be based on earth-ionosphere waveguide mode computational models. (Author)