日本地球惑星科学連合2019年大会

講演情報

[E] 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-EM10] Multi-scale Coupling in the Magnetosphere-Ionosphere-Thermosphere System

2019年5月27日(月) 13:45 〜 15:15 ポスター会場 (幕張メッセ国際展示場 8ホール)

コンビーナ:Yue Deng(University of Texas at Arlington)、Toshi Nishimura(Boston 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)、Yanshi Huang(Harbin Institute of Technology, Shenzhen)

[PEM10-P01] 相対論的電子降り込みに対する南北両半球大気のレスポンス

*田中 良昌1,13,14西山 尚典1,14門倉 昭1,13,14尾崎 光紀2三好 由純3大山 伸一郎3,15片岡 龍峰1,14堤 雅基1,14西村 耕司1,13,14佐藤 薫4笠原 禎也2熊本 篤志5土屋 史紀5吹澤 瑞貴5疋島 充6松田 昇也6松岡 彩子6篠原 育6能勢 正仁3長妻 努7篠原 学8藤本 晶子9寺本 万里子3野村 麗子10行松 彰1,14細川 敬祐11小路 真史3Ralph Latteck12 (1.国立極地研究所、2.金沢大学理工研究域、3.名古屋大学宇宙地球環境研究所、4.東京大学大学院理学系研究科、5.東北大学大学院理学研究科、6.宇宙航空研究開発機構宇宙科学研究所、7.情報通信研究機構、8.鹿児島工業高等専門学校、9.九州工業大学、10.国立天文台、11.電気通信大学大学院情報理工学研究科、12.Leibniz-Institute of Atmospheric Physics e.V. at the University Rostock, Germany、13.情報・システム研究機構 データサイエンス共同利用基盤施設 極域環境データサイエンスセンター、14.総合研究大学院大学、15.University of Oulu, Finland)

キーワード:極域中間圏冬季エコー、あらせ衛星、PANSYレーダー、MAARSYレーダー、相対論的電子降り込み、磁気圏プラズマ波動

Relativistic electron precipitation (REP) in the polar atmosphere has been paid attention to because it changes atmospheric composition, causing ozone depletion after migrating to the lower altitude during polar winter. A plausible mechanism for REP is the interaction with magnetospheric plasma waves, such as electromagnetic ion cyclotron (EMIC) waves and whistler-mode chorus waves. Previous studies have already shown that EMIC waves can effectively drive REP, however, observational evidence that chorus waves can drive REP was lacking. In this study we present direct comparison between magnetospheric plasma waves and polar mesosphere winter echoes (PMWE) simultaneously observed with the Arase satellite and high-power Mesosphere, Stratosphere and Troposphere (MST) radars in both hemispheres, PANSY and MAARSY. PMWE can be related to the ionization in the mesosphere due to REP. The PMWE were observed at 03-07 UT on March 21, 2017 during the passage of corotating interaction region (CIR), during which the Arase footprints were close to Syowa Station (SYO; –69.00S, 39.58E), Antarctica, and Husafell (HUS; 65.67N, –21.03E), Iceland.
The observational results are summarized as follows. (1) EMIC waves and whistler-mode chorus waves were observed by Arase near the equatorial magnetosphere during 02:30-04:45 UT and 04:45-07:00 UT, respectively. (2) PMWE were detected with both the MAARSY radar at Andøya (AND; 69.30N, 16.04E), Norway, and the PANSY radar at SYO, Antarctica, during 04:45-07:00 UT, which was the recovery phase of an isolated substorm. We believe this is the first time PMWE have been observed in both hemispheres at exactly the same time. (3) During 04:45-07:00 UT, the temporal variation of the chorus wave power was similar to those of the PMWE power in the both hemispheres. (4) The PMWE observed at SYO during 03:00-04:00 UT before the substorm onset was consistent with the occurrence of the EMIC waves. The item (2) shows direct evidence that chorus waves during the substorm recovery phase cause REP. We estimated the resonance energy of electrons interacting with the observed LBC waves, however, the estimated energy was too low to cause PMWE at an altitude lower than 70 km. However, we found that the resonance energy becomes greater than 1 MeV, if LBC waves propagate to the magnetic latitude greater than 30 degrees and resonate with energetic electrons there. As for item (4), the PMWE observed at SYO during 03:00-04:00 can be related to wave-particle interaction with EMIC waves, which may be generated inside the plasmapause by ring-current hot ions with temperature anisotropy. This anisotropy was caused by magnetospheric compression due to increasing solar wind dynamic pressure during 01:00–06:00 UT just after the arrival of the CIR. Since CIRs are main sources of geomagnetic disturbances during the declining phase of the solar cycle and solar minimum, this event is not rare but rather a common atmospheric response caused by interaction between recurrent large-scale solar wind structures and geospace.