경희대학교 BK21

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● 날짜 : 2014년 05월 22일 (목요일)
● 시간 : 오후 4시 30분
● 장소 : 천문대 영상실
● 강사 : Dr. Hyuck-Jin Kwon, School of Space Research, Kyung Hee Univ.
● 주제 : Plasmapause locations identified by THEMIS spacecraft under very quiet geomagnetic conditions (Kp ≤ 1)

 

 Abstract

In this study, we used cold electron density data observed by THEMIS probes to investigate the plasmapause location under quiet geomagnetic conditions (Kp≤1) from 2008 to 2009. The observation of THEMIS during two years provided good statistical coverage of all magnetic local times between and L shell of 3 to 13. We identified over 2000 plasmapause crossing events for all Kp and a total 1193 events were observed when Kp≤1. We assumed that plasmapause is not a layer, but it has thickness. Therefore, we separated plasmapause into two boundaries, inner and outer. We found that the outer boundary of plasmapause is observed near the geosynchronous orbit under extremely quiet geomagnetic conditions and this result is larger than model results. By contrast, inner boundary location is comparable with model results contrast to outer boundary. And bulge rotating profile on the observation coincides with the result of global core plasma model [{\it Gallagher et al.}, 2000]. We also examined the property of plasmapause between two boudnaries. As a result, the thickness of plasmapause is slightly difference between quiet and moderate geomagnetic conditions and electron density gradient increases as geomagnetic activity is enhanced except plasmasphere plume region. This results support that the property of plasmapause also depends on geomagnetic conditions.