Features of the Spectrum of Natural VLF Emissions in the Near-Equatorial Region of the Upper Ionosphere from DEMETER Satellite Observations

Abstract : The generation of the U-shaped spectrum, an unusual wave phenomenon observed in the equatorial part of the DEMETER satellite orbit, is studied. This wave phenomenon is explained for the first time based on the assumption that this emission is formed by the waves generated by lightning discharges, while the shape of the spectrum is determined by the features of wave propagation and damping in the near-equatorial region of the upper ionosphere.