Multi-Frequency Multiple Path Oblique Incidence Sounding of the Ionosphere Disturbed by Super Typhoon Motion

The aim of this study is to observe the changes in the characteristics of HF radio waves traveling through the ionosphere perturbed by the super typhoon Hagibis during October 6–13, 2019 period. The measurements have been taken with the Harbin Engineering University (the People's Republic of China) multi-frequency multiple path software defined radio system. The super typhoon acted to enhance wave activity in the atmosphere and to generate wave processes with 10 to 120-min periods. The atmospheric gravity waves have been confirmed to conduct coupling within the atmosphere-upper-atmosphere-ionosphere system. The impact on the ionosphere was the largest when the super typhoon energy was a maximum, i.e., on October 8, 10, and particularly 9, 2019, and when the typhoon was at distances of ~2,500 km to ~3,000 km from the midpoints of the propagation paths. The wave processes acted to excite oscillations in the reflection level height from 30–50 km to 60–90 km. In the $F$ region, the ~20-min period harmonic in electron density changes were seen with amplitude of 10-12%, while the ~60-120-min period harmonics with amplitudes of 30-60%.