[P-EM10] Dynamics of Magnetosphere and Ionosphere

[PEM10-P15] Characteristics of the precipitating electron energy of omega band auroras

森井 雄大¹、*三好 由純¹、栗田 怜²、中村 るみ³、細川 敬祐⁴、大山 伸一郎¹、小川 泰信⁵、今城 峻²、齊藤 慎司⁶、浅村 和史⁷ (1.名古屋大学宇宙地球環境研究所、2.京都大学、3.オーストリア宇宙科学研究所、4.電気通信大学、5.国立極地研究所、6.情報通信研究機構、7.JAXA)

キーワード：オメガバンド、エネルギー推定、EMCCDカメラ

Omega band auroras often appear during the late expansion and recovery phase of the substorms, consisting of various types such as the discrete aurora, diffuse aurora, and pulsating aurora. Omega band auroras have a large scale field aligned current structure on the ionospheric side, and it has been suggested that Omega band auroras are related to the BBF. Therefore, omega band auroras are considered phenomena that appears in the magnetosphere ionosphere coupling process. One of the unknown properties of omega band auroras is the characteristics of precipitating electrons. Since the precipitation mechanism depends on the type of auroras, it is expected that the characteristics of precipitating electron in omega band auroras differ from another aurora. Moreover, the corresponding generation mechanism on the magnetospheric side is also different. In this study, we analyze images of omega band auroras at two wavelengths on the ground and estimate the spatial distribution of characteristic energy and downward energy flux of the omega band auroral electrons using the intensity ratio of these images. Our findings reveal that the characteristic energy varies depending on the types of each aurora. Moreover, the downward energy flux is larger in the discrete/diffuse auroral region on the western side of the torch structure. The two omega-band events are established as conjugate observations with satellites in the magnetospheric side. In one of the events, a high-speed earthward ion flow (BBF) exceeding 100 km/s is observed in the region where the footprint is near the torch structure of the omega band aurora. Together with the results on the downward energy flux, these results are consistent with the streamer model, indicating east-west differences in auroral brightness expected from the downward/upward field aligned currents in the east west side of BBFs.