Disturbances in the ionosphere that accompanied typhoon activity in the vicinity of China in September 2019

We have acquired HF Doppler measurements and studied the dynamics of the ionosphere in the ∼100–300 km altitude range during the 1–10 September 2019 period of typhoon activity near the People's Republic of China (PRC). The multifrequency multiple path system located at the Harbin Engineering University campus, the PRC, and probing the ionosphere at oblique incidence was used to identify the effects from the typhoons. The response of the ionosphere to the Typhoon Lingling was detected along three adjacent radio-wave propagation paths where chaotic and quasiperiodic variations in the Doppler shift and a significant (from −1 to 1 Hz or greater) Doppler spectrum broadening were observed to occur. The Doppler spectrum chaotic variations are due to plasma turbulence generated by typhoons in the ionosphere, and the Doppler shift quasiperiodic variations along the main ray are due to infrasound and atmospheric gravity waves (AGWs) launched by the typhoons. The relative amplitude of quasiperiodic variations in the electron density in the field of the infrasound wave reached several percent, and in the field of the AGW attained from ten to a few tens of percent. The effects of the Typhoon Faxai during 9/10 and 10/11 September 2019 nights were accompanied by a 27% decrease in the electron density in the ionospheric E and F regions. At the closest approach of the Typhoon Faxai to the ionosonde during 8/9 September 2019 night, when it had the largest energy, a 56% increase was detected in the ionospheric F region electron density.