[P-EM15] Study of coupling processes in solar-terrestrial system

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

*Hitoshi Fujiwara¹, Satonori Nozawa², Yasunobu Ogawa³, Yasunobu Miyoshi⁴, Masaki Tsutsumi³ (1.Education and Research Center for Sustainable Development/Faculty of Science and Technology, Seikei University, 2.Institute for Space-Earth Environmental Research, Nagoya University, 3.National Institute of Polar Research, 4.Department of Earth and Planetary Sciences, Faculty of Sciences, Kyushu University)

Keywords:thermosphere, ionosphere, 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.