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The purpose of the present paper is to describe the observations of the variations in the parameters of HF radio waves propagating through the ionosphere when the action of the super typhoon Hagibis on 6–13 October 2019 occurred. The observations have been made with the Harbin Engineering University (the People's Republic of China) multi-frequency multiple path radio system involving the software-defined technology. The action of the super typhoon has been shown to be accompanied by enhanced atmospheric wave activity acting to generate wave processes with periods of 10 to 120 min. Coupling in the atmosphere–upper-atmosphere–ionosphere system has been confirmed to be carried out with atmospheric gravity waves. The ionosphere underwent the greatest impact on those days when the supertyphoon had maximum energy, on 8, 10, and especially 9 October 2019, and when it was found to be in an ∼2,500–3,000-km distance range from the propagation path midpoints. Under the action of wave processes, the height of the reflection region was observed to oscillate within the ±(30–90 km) limits. The amplitude of the quasi-periodic variations in the ionospheric F-region electron density was estimated to be 10–12% for periods of ∼20 min, and 30–60% for periods of ∼60–120 min. The joint action of the dusk terminator and the supertyphoon has been confirmed to enhance wave activity in the ionosphere. Similar effects for the dawn terminator have not been detected. more...

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. more...