Excitation of an Earth–Ionosphere Waveguide at Frequencies above That of the First Transverse Resonance

The authors consider experimental data on the registering of signals from tweek-atmospherics and an ionospheric source formed by the heating of the ionosphere at frequencies higher than that of the first transverse resonance of the Earth-ionosphere waveguide (~1.8 kHz). It is shown that far from the source, almost complete circular left-hand polarization of the horizontal magnetic field is observed at frequencies near the resonance. The angles of incidence range from 10° to 35°. A joint analysis of observational data and modeling results shows it is possible to calculate the effective altitude of reflection from estimates of the angle of incidence, which can be used to diagnose the lower ionosphere. With an ionospheric source, it is important to allow for the inhomogeneity of its radiation pattern.