[P-EM13] Coupling Processes in the Atmosphere-Ionosphere System

[PEM13-P02] Sporadic E characteristics over Japan from long-term ionosonde observations

*寺岡 宙惟¹、Liu Huixin²、西岡 未知³ (1.九州大学、2.九州大学理学研究院地球惑星科学専攻　九州大学宙空環境研究センター、3.（独）情報通信研究機構)

Sporadic E (Es) is an important ionosphere irregularity that affects wireless communications. In this study, we analyze long-term ionosonde observations during 2001-2020 at three locations: Wakkanai (45.16°N, 141.75°E), Kokubunji (35.71°N, 139.49°E), Okinawa(26.68°N, 128.15°E). We examined the long-term (solar cycle, inter-annual, seasonal) and short-term (below one-month) variations of the Es density, occurrence frequency and altitudes, and their latitudinal dependence. The analysis revealed a clear latitudinal difference in the occurrence of the Es layer, with Es occurring mainly in May and June at Okinawa, while mainly in June-July at Kokubunji and Wakkanai. Furthermore, Es shows a higher occurence rate at solar minimum than at solar maximum. The Es occurring altitude also shows a solar activity dependence which is different at different locations. The analysis also revealed strong day-to-day variability in the Es occrrrence, which is likely driven by low atmosphere forcing.