JpGU-AGU Joint Meeting 2017

講演情報

[EE] ポスター発表

セッション記号 P (宇宙惑星科学) » P-EM 太陽地球系科学・宇宙電磁気学・宇宙環境

[P-EM11] [EE] Mesosphere-Thermosphere-Ionosphere Coupling in the Earth's Atmosphere

2017年5月24日(水) 15:30 〜 17:00 ポスター会場 (国際展示場 7ホール)

コンビーナ:Chang Loren(Institute of Space Science, National Central University)、Liu Huixin(九州大学理学研究院地球惑星科学専攻 九州大学宙空環境研究センター)、齊藤 昭則(京都大学大学院理学研究科地球物理学教室)、Tzu-Wei Fang

[PEM11-P09] Seasonal and spatial variation of He+ column density in the evening topside ionosphere observed by ISS-IMAP/EUVI

*穂積 裕太1齊藤 昭則2吉川 一朗3山崎 敦4村上 豪4吉岡 和夫3 (1.電気通信大学大学院、情報理工学研究科、2.京都大学大学院、理学研究科、3.東京大学、4.宇宙航空研究開発機構 宇宙科学研究所)

The seasonal, longitudinal and latitudinal variations of He+ distribution in the evening topside ionosphere in 2013 - 2015 are elucidated with data of He+ resonant scattering obtained by Extreme Ultra Violet Imager (EUVI) onboard the International Space Station (ISS). EUVI provides a data set of the column density of He+ in the topside ionosphere. The data set provides a unique opportunity to study He+ distribution in the topside ionosphere from a different perspective of past studies using in-situ measurement data. During the solstice seasons, an enhancement of He+ column density in the winter hemisphere is observed. The magnitude of this hemispheric asymmetry shows a longitudinal variability. Around the June solstice, the hemispheric asymmetry was greater in the longitude sector where the geomagnetic declination angle is negative and smaller in the longitude sector where the geomagnetic declination angle is positive. Around the December solstice, on the other hand, this longitudinal variation of the asymmetry magnitude had opposite tendency. The hemispheric asymmetry of the effective neutral wind well explains this behavior of He+. The field-aligned component of neutral wind in the F-region is varied in longitude under the presence of finite geomagnetic declination angle and large zonal wind. We examined the seasonal and longitudinal variation of the effective wind with HWM14 model. In the equinox seasons, two longitudinal maxima were observed at around 140ºE and 30ºE. The longitudinal variation of the effective neutral wind is a candidate of these two maxima of He+ concentration. These results suggest that the transport of ions in the topside ionosphere is strongly affected by the F-region neutral wind.