17:15 〜 18:45
[PEM10-P16] Temporal variations of intense low-energy electron precipitation near the nightside polar cap boundary
キーワード：オーロラ、極冠境界、電子降下
The red aurora near the nightside polar cap boundary is highly dynamic and often shows poleward expansion. This poleward expansion is the result of the rapid motion of the region of intense low-energy electron precipitation, which is thought to be accelerated by Alfvén waves along the magnetic field lines associated with the plasma sheet boundary layer. Previous studies based on satellite observations have revealed the detailed energy profiles of this low-energy electron precipitation and its spatial characteristics. However, the evolution of the low-energy precipitation, which plays a crucial role in the dynamic poleward motion of the red aurora, is still unknown. To understand the temporal characteristics of the intense low-energy electron precipitation associated with the poleward expansion of red auroras near the nightside polar cap boundary, we have derived a method that can estimate the two-dimensional distribution of the energy flux of the low-energy electron precipitation by incorporating 630-nm all-sky imager data and the Global Airglow model. Specifically, we used the data from the all-sky imager at Longyearbyen, Svalbard, and applied the Global Airglow model to a three-dimensional spatial domain up to 500 km altitude within the imager's field of view. We report on the temporal characteristics of the variability of the intense low-energy electron precipitation revealed by applying our method to a large number of all-sky image data. We also discuss the validity of the method by comparing it with the in-situ observation of low-energy electron precipitation by the DMSP.