[P-EM15] 太陽地球系結合過程の研究基盤形成

[PEM15-11] High-speed thermospheric winds with strong shear driven by fast ion flows in high-latitude polar regions

*藤原 均¹、野澤 悟徳²、小川 泰信³、三好 勉信⁴、堤 雅基³ (1.成蹊大学サステナビリティ教育研究センター/理工学部、2.名古屋大学宇宙地球環境研究所、3.国立極地研究所、4.九州大学大学院理学研究院地球惑星科学部門)

キーワード：熱圏、電離圏、EISCAT

Among the planets and moons of the solar system, it is believed that supersonic winds blow in the atmospheres of Jupiter, Saturn, Neptune, and Titan. On Neptune, it has been pointed out that the winds that create the Great Dark Spot may reach Mach number 1.6. Even in the Earth's atmosphere, there are observational reports of supersonic winds in the thermosphere although they are very few. Gardner and Schunk (Radio Science, 2009) pointed out by numerical simulation that when the strong polar electric field, the Mach number of the thermospheric wind can reach as high as 1.2, mainly in the polar cap region. However, it has not been confirmed by observations.
A supersonic ion flow was observed by the Earth observation satellite SWARM, and the results were presented by the European Space Agency (ESA) in 2017. According to our previous EISCAT observations, fast ion flows (> 1000 m/s), which are thought to be the momentum source of high-speed thermospheric winds, are often found in the polar cap region. We will clarify generation of high-speed/super sonic thermospheric winds with strong shear from the EISCAT observations. The EISCAT_3D system will enable us to investigate the fast ion flows and spatio-temporal variations of the strong electric field. In this presentation, we summarize our previous EISCAT observations of the fast ion flows and thermospheric modeling activities to investigate driving mechanisms of high-speed thermospheric winds.