講演情報
[PEM13-P20]地上光学・電波機器とあらせ衛星・Van Allen Probes衛星の同時観測に基づくサブオーロラ帯の３種類のオーロラの複数例解析：Coulomb衝突によるHeat fluxの見積り
*椙村 怜1、塩川 和夫1、大塚 雄一1、大山 伸一郎1、Connors Martin2、門倉 昭3、Poddelsky Alexey4、Poddelsky Igor4、西谷 望1、Shepherd Simon5、Ruohoniemi J6、Smith Charles7、MacDowall Robert8、Spence Harlan7、Reeves Geoff9、Funsten Herbert9、三好 由純1、篠原 育10、笠原 禎也11、土屋 史紀12、熊本 篤志12、中村 紗都子1、新堀 淳樹1、浅村 和史13、横田 勝一郎14、Yoichi Kazama15、Jun Chae-Woo1、Shiang-Yu Wang15、Sunny Tam16、笠原 慧17、桂華 邦裕18、堀 智昭1、Ayako Matsuoka10 (1.名古屋大学宇宙地球環境研究所、2.アサバスカ大学、3.国立極地研究所、4.Institute of Cosmophysical Research and Radiowave Propagation, Far Eastern Branch of the Russian Academy of Sciences、5.Thayer School of Engineering, Dartmouth College、6.Bradley Department of Electrical and Computer Engineering, Virginia Tech、7.Institute for the Study of Earth, Oceans, and Space, University of New Hampshire、8.NASA Goddard Space Flight Center, Greenbelt、9.Los Alamos National Laboratory、10.宇宙科学研究所, 宇宙航空研究開発機構、11.金沢大学自然科学研究所、12.Graduate School of Science, Tohoku University、13.宇宙航空研究開発機構、14.Department of Earth and Space Science, Graduate School of Science, Osaka University、15.Academia Sinica Institute of Astronomy and Astrophysics、16.Institute of Space and Plasma Sciences, National Cheng Kung University、17.Department of Earth and Planetary Science, School of Science, University of Tokyo、18.Graduate School of Science, Tokyo University)
キーワード：
STEVE、SARアーク、あらせ衛星
Strong Thermal Emission Velocity Enhancement (STEVE) is a latitudinally-narrow, purple band of emission seen at subauroral latitudes, which was discovered in 2016. Well-known Stable Auroral Red (SAR) arcs also occurs at subauroral latitude. Red and green arcs, which are similar to SAR arcs at subauroral latitudes but accompanied by green (557.7 nm) emission, have also been reported. However, the characteristics of the magnetospheric plasma and electromagnetic field variations as a source of these three types of optical emissions have not fully been studied, because of limited conjugate observations between magnetospheric satellites and ground-based optical and radio instruments. In this study, we report the auroral morphology as seen in all-sky image data obtained at seven ground stations (Athabasca, Gakona, Husafell, Kapuskasing, Magadan, Nyrola and Tromsø) during about four years from January 2017 to April 2021. By referring to the optical images as well as the ionospheric footprint of magnetospheric satellites (Arase and Van Allen Probes) calculated with the Tsyganenko magnetic field model (TS04), we have identified four cases of STEVE, four cases of SAR arc, three cases of green and red arcs in which these satellites were located in the conjugate regions in the magnetosphere of the optical emissions. For all three types of optical emissions, satellite data showed that the plasmasphere and ring-current particles spatially overlapped in the conjugate regions of the magnetosphere. Some electromagnetic waves in mHz to kHz were observed for STEVE and red and green arc events. SuperDARN radar data showed a strong westward plasma flow in the ionosphere, especially during the STEVE events, while the plasma flows associated with SAR arcs and red and green arcs are relatively weak and variable. Heat fluxes due to Coulomb collisions were larger for STEVE compared to SAR arc. However, the heat flux may have been underestimated for events that low-energy electrons were not measured. These analyses have provided the first-ever comparison of magnetospheric particle and electromagnetic field characteristics for the three types of optical emissions in the subauroral region. In the presentation, we will discuss the differences and similarities of the magnetospheric and ionospheric processes responsible for producing these three-types of emissions.