[P-EM10] Dynamics of Magnetosphere and Ionosphere

[PEM10-P02] Temporal variations of 2-D distributions of precipitating low-energy electron fluxes associated with the auroral arc near the nightside polar cap boundary

*八島 和輝¹、田口 聡¹、細川 敬祐² (1.京都大学大学院地球物理学専攻、2.電気通信大学報理工学研究科 情報・ネットワーク工学専攻)

キーワード：オーロラ、ブロードバンド型電子降下、極冠境界

Near the nightside polar cap boundary there often occurs intense low-energy electron precipitation as well as the inverted-V type electron precipitation. The intense low-energy electron precipitation, which is thought to be associated with Alfvenic electron acceleration, produces a tall red aurora. Previous satellite observations have shown the detailed energy profiles of that low-energy electron precipitation, and their spatial features. However, we still do not understand how the low-energy component of the electron precipitation grows or decays near the nightside polar cap boundary. In this study, to understand the temporal characteristics of the low-energy electron fluxes near the nightside polar cap boundary we have developed an automated method for deriving 2-D distributions of the low-energy electron fluxes by comparing 630-nm auroral image data obtained by an all-sky imager (located at Longyearbyen, Svalbard) with 630-nm emission distributions calculated by the Global Airglow model. The result from this automated method has revealed the energy fluxes of the low-energy electron precipitation are enhanced intermittently. We discuss this feature in terms of the motion of the auroral arc.