ИСТИНА

The experiments of ionosphere heating by a powerful modulated radio signal on high latitudes are conducted to investigate the mechanisms of excitation of low-frequency waves in the Earth-ionosphere waveguide and the physical processes in the ionospheric plasma. The powerful HF radio wave creates a low-frequency ionospheric source. In this work, we show that the electromagnetic field excited in the Earth-ionosphere waveguide by this source can be used for lower ionosphere sounding. We present an approach to solving of the inverse problem of estimation of the ionosphere electron density profiles using ground-based measurements. The basic idea of the approach is that we estimate the profile of the lower ionosphere at altitudes within 60-120 km range comparing the measured phase velocities with those obtained by the full-wave modeling. To find the optimal profile we employed the Monte-Carlo search in which the trial solutions are random modifications of the basic electron density profile preserving its shape and continuity. As a basic profile, we took the profile from the IRI-2016 model. We used ground-based measurements of electromagnetic ELF/VLF fields at the PGI observatories “Lovozero” and “Verkhnetulomsky” at the frequencies 1017 and 3017 Hz to obtain phase velocities of TEM and TE01 waveguide modes. The experiment was conducted by AARI at the EISCAT/Heating facility (Norway) in October 2016. The peculiarities of the solutions to the inverse problem and their confidence intervals are discussed.