Propagation of VLF Radio Waves on Latitudinal Paths of the East of Russia

The analysis of the amplitude and additional phase of the VLF field of the long-range navigation system (RSLDN-20) during strong magnetic storms and solar flares from September 1 to September 12, 2017 was carried out. Radio paths of latitudinal distribution were investigated: path 1 “Novosibirsk - Ulan-Ude”, length is 1579 km; path 2 “Komsomolsk-on-Amur - Ulan-Ude”, length 2079 km. Daily variations in the amplitudes of the radio signals of 11.9 and 14.9 kHz on paths 1 and 2 obtained after thinning and filtering the measured signal levels through the Savitsky-Golay digital smoothing polynomial filter are considered. The calculations of the field in the Earth-ionosphere waveguide are presented. Analysis of the propagation conditions of VLF radio waves during magnetic storms and solar flares revealed significant differences in the spatial-amplitude-phase phenomena in normal and anomalous geomagnetic conditions at frequencies of 11.9 and 14.9 kHz during propagation along spatially separated radio paths. The main factors that change the parameters of the VLF signal in the Earth-ionosphere waveguide under helio-geophysical disturbances are the increase in the electron concentration in the D-layer of the ionosphere and the change in the height of the upper wall of the waveguide.