The effect of relativistic electrons precipitating on the RSDN-20 system signal characteristics during the event on March 28, 2017

Based on the experimental data of the EISCAT radar and numerical modeling methods, the influence of the fluxes of subrelativistic (relativistic) electrons of the Earth's outer radiation belt on the operation of the RSDN-20 long-range navigation system operating at frequencies of 11.905 kHz, 12.649 kHz and 14.881 kHz has been studied. As a result of computational experiments, a slight decrease in attenuation under perturbed conditions was obtained at a frequency of 14.881 kHz with a slight, less than an order of magnitude increase in the electron concentration in the D- and E-layers of the ionosphere. At lower frequencies and in the case of an increase in concentration in the reflection region, an increase in signal attenuation is observed. It is shown that the violation of monotonicity in the frequency dependence of signal attenuation is associated with the position of the boundary between regions with different types of signal attenuation and the height of the signal reflection from the ionosphere. In the case when the intersection point of the high-altitude profile of the electron collision frequency υe with the profile of the doubled plasma frequency 2ωe is inside the signal reflection region, a nonlinear type of attenuation dependence on frequency is observed. The phases of RSDN-20 signals are weakly affected by the precipitation of relativistic energy electrons into the atmosphere. A comparison of the amplitudes of the signals obtained in computational experiments and the signals recorded at the observatories of the Polar Geophysical Institute Lovozero and Barentsburg showed partial agreement in most of the changes recorded during the precipitation of subrelativistic electrons in the polar ionosphere. The presented estimates can be used on short radio paths of 100–200 km in the high latitude region to monitor the state of the ionosphere.