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A brief description of the multipath coherent radio technique installation is presented. Its goal is continuous monitoring of the dynamical processes in the ionosphere caused by space weather variations and the impact of high-energy sources in the Earth–atmosphere–ionosphere–magnetosphere system. The variations of radio-wave characteristics (the Doppler spectra and signal amplitudes) in the HF range and the ionospheric parameters over China during the ionospheric storm of August 26, 2018, are described. An ∼50–100 km ascent in the radio-wave reflection region and its oscillations with an amplitude of ∼30–40 km were observed many times during the storm on all paths. The ascents were followed by descents of the radio-wave reflection region by many tens of kilometers. The ascents and descents of the reflection region were caused by a decrease in the electron concentration by a factor of 1.5–2 and its increase by a few times, respectively. The maximal increase in the electron concentration in the E and F regions reached a factor of 1.5 and 3, respectively. The relative amplitude of oscillations in the electron concentration reached many tens of percent. The amplitude of oscillations of frequency Doppler shift was several times lower on the reference days. The observed oscillations in the frequency Doppler shift were apparently caused by generation of the atmospheric gravity waves and their subsequent propagation to the latitudes of the means of observation. The velocity of wave disturbances was ∼275–480 m/s, whereas their period was ∼60 min. The ionospheric disturbances of August 27, 2018, were insignificant despite the repeated magnetic storm.

We acquired measurements with the oblique HF Doppler technique in the city of Harbin during the super typhoon Lekima event of 4 – 12 August 2019. The ionospheric response was observed by the Harbin...

A brief description of multi-frequency multipath passive radar dedicated to sounding the ionosphere at oblique incidence is presented. Observations of variations caused by the ionospheric storms in the Doppler spectra and in amplitudes of the signal reflected from the ionosphere in 2018 – 2019 are described.

The observation of disturbances in the ionosphere during moderate (M ≈ 5.9 – 6.6) earthquakes of July 7, 2018, September 5 2018, and April 11, 2019 in Japan are described. Analysis of the signal amplitude, of the Doppler spectra variations, and of the Doppler shift of frequency in the signals traveling along the main ray path on the reference days and on the day when the earthquakes occurred have revealed that they are different. The disturbance propagation exhibits two apparent speeds, of 3 km/s characteristic of seismic waves and of ~300 – 1000 m/s characteristic of acoustic and atmospheric gravity waves in the Earth’s ionosphere. The amplitude of electron density disturbances caused by the infrasonic and atmospheric gravity waves has been estimated to be ~0.15 – 9% and 7 – 55%, respectively.