RADIO PHYSICS AND RADIO ASTRONOMY

Subject and Purpose. The study of the effect that each new Solar eclipse (SE) has on radio wave characteristics is an actual scientific and technical issue. Th e purpose of the present work is to analyze the variations in Doppler spectra (DS), Doppler shift of frequency (DSF), and in the reflected wave amplitude (RWA) that were observed during the SE of June 21, 2020 over the People’s Republic of China.

Methods and Methodology. The observations of HF radio wave characteristics were made using the Harbin Engineering University multi-frequency multipath coherent radio system. The temporal variations in DS, DSF of the main ray and RWA are analyzed further. The variations in the DSF were subjected to a systematic spectral analysis that involved joint application of the windowed Fourier transform, adaptive Fourier decomposition, and the Morlet mother-function-based wavelet transformation.

Results. The SE was accompanied by DS diffuseness resulting from an increase in the number of rays. The DSF temporal variations were observed to be bi-polar and asymmetrical, with extreme DSF magnitudes varying from –11 to –40 mHz and from 22 to 56 mHz. The duration of processes with negative DSF values varied from 50 to 80 min, and the duration of processes with positive DSF changed from 30 to 80 min. The multi-hop propagation (from two to five hops) took place along all propagation paths, with a 360 to 560 km one-hop range. The 4...5 min period quasi-periodic DSF variations showed 20...50 mHz amplitude, and the 8...18 min period variations exhibited 40...100 mHz amplitude. The relative amplitudes of the 4...5 min period quasi-periodic variations in the electron density were observed to be in the 0.3...6.2% range, and the amplitudes of the 8...18 min period variations were found to be in the 1.1...21.7% range. A decrease in the electron density along different propagation paths was observed to vary from –(12...16)% to – (20...26)%.

Conclusions. The characteristic features of the variations in HF radio wave parameters in the ionosphere have been studied during the SE of June 21, 2020 over the People’s Republic of China.

Keywords: Solar eclipse, HF radio wave, ionosphere, oblique radio sounding, Doppler spectrum, Doppler shift, reflected wave amplitude.

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