[P-EM12] Coupling Processes in the Atmosphere-Ionosphere System

[PEM12-11] Largest thermospheric wind ever observed with a Fabry-Perot interferometer in Tromsø, Norway since 2009 during the March 2023 storm

*大山 伸一郎^1,2、Vanhamaki Heikki³、Cai Lei³、新堀 淳樹¹、細川 敬祐⁴、坂野井 健⁵、塩川 和夫¹、Aikio Anita³、Virtanen Ilkka³、西谷 望¹、小川 泰信²、三好 由純¹、栗田 怜⁶ (1.名古屋大学宇宙地球環境研究所、2.国立極地研究所、3.オウル大学、4.電気通信大学、5.東北大学惑星プラズマ・大気研究センター、6.京都大学生存圏研究所)

キーワード：熱圏風、磁気嵐、ファブリペロー干渉計、イオンドラッグ、ジュール加熱、極域

Solar cycles 24-25 were quiet until a geomagnetic storm with a Sym-H index of -170 nT occurred in late March 2023. On March 23-24, a Fabry-Perot interferometer (FPI; 630 nm) in Tromsø, Norway, recorded the highest thermospheric wind speed of over 500 m/s since 2009. Comparisons with magnetometer readings in Scandinavia showed that a large amount of electromagnetic energy was transferred to the ionosphere-thermosphere system. Total electron content maps suggested an enlarged auroral oval and revealed that the FPI observed winds near the polar cap instead of inside the oval for a long period during the storm main phase. The FPI wind had a strong equatorward component during the storm, likely because of the powerful anti-sunward ionospheric plasma flow in the polar cap. The positive Y-component of the IMF for six days before the storm caused a successive westward component of the FPI-measured wind during the storm main phase. On March 24, the first day of the storm recovery phase, thermospheric wind disturbed and the ionospheric density decreased significantly at high latitudes. This density depression lasted for several days, and a large amount of electromagnetic energy during the storm modified the thermospheric dynamics and ionospheric plasma density.