Ionospheric storm effects over the People’s Republic of China on 14 May 2019: Results from multipath multi-frequency oblique radio sounding

Abstract

Results obtained from observations of ionospheric disturbances over the People’s Republic of China during the course of the geospace storm of 14 May 2019, one of the largest storms in 2019, are presented. The Harbin Engineering University operates the multi-frequency multipath radio wave diagnostics employing software defined technology and continuously monitoring dynamic process acting in the ionosphere at oblique incidence since April 2018. The basic premise upon which this instrument operation is based is that the digital re-sampling remains coherent with radio frequency for each propagation path, which permits Doppler spectra and signal amplitudes to be calculated along each of the 14 propagation paths. UT dependences of the Doppler spectra, the main mode Doppler shifts of frequency, and signal amplitudes that were measured on the day of the ionospheric storm and on the reference days of 13 and 15 May 2019 have been analyzed. After the magnetic storm onset, the Doppler shift of frequency exhibits an abrupt –1-Hz decrease, indicating the ionospheric storm onset. In addition, quasi-periodic variations in the Doppler shift of frequency, with 5-, 15-, 20-, and 30-min periods and the amplitudes in the range from 0.05 Hz to 0.15 Hz, occur in the course of the storm. These variations are due to modulation by infrasound (5-min period oscillation) and atmospheric gravity waves (15-, 20-, and 30-min period oscillations). In the electron density, the corresponding waves have amplitudes equal to 0.7% and 4–8%, respectively.