日本地球惑星科学連合2018年大会

講演情報

[EE] Evening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-EM16] Dynamics of Earth's Inner Magnetosphere and Initial Results from Arase

2018年5月22日(火) 17:15 〜 18:30 ポスター会場 (幕張メッセ国際展示場 7ホール)

コンビーナ:Danny Summers(Memorial University of Newfoundland)、三好 由純(名古屋大学宇宙地球環境研究所)、細川 敬祐(電気通信大学大学院情報理工学研究科、共同)、海老原 祐輔(京都大学生存圏研究所)

[PEM16-P21] Flux decrease of outer radiation belt electrons associated with solar wind pressure pulse: A Code coupling simulation of GEMSIS-RB and GEMSIS-GM

*伊藤 大輝1三好 由純1齊藤 慎司4松本 洋介2天野 孝伸3林 昌広1 (1.名古屋大学宇宙地球環境研究所、2.千葉大学大学院理学研究科、3.東京大学 地球惑星科学専攻、4.名古屋大学 大学院理学研究科)

キーワード:マグネットポーズシャドウィング

Relativistic electron flux of the outer radiation belt dynamically changes in response to solar wind variations. There exist several conditions to cause the flux drop-out of outer belt electrons. The magnetopause shadowing (MPS) is one of the process to cause the rapid loss of outer belt electrons (e.g.,Kim et al.,2008). In this study, we performed a code-coupling simulation using GEMSIS-RB test particle simulation code (Saito et al., 2010) and GEMSIS-GM global MHD magnetosphere simulation code (Matsumoto et al., 2010) to specify which electrons of the outer belt will be lost due to the MPS, by investigating pitch angle and MLT dependences. We calculated the guiding center equation of each particle with initial L-shells 7.5 Re to 9.0 Re, energies 300 keV to 3 MeV and pitch angles 60 degrees to 120 degrees. The initial dynamic pressure of the solar wind is 1.0 nPa. The standoff distance of magnetopause at the subsolar point was 12 Re as an initial state. The magnetopause moved to 9 Re due to the dynamic pressure enhancement when the solar wind pressure became 2.5 nPa. After the enhancement of the dynamic pressure for 40 sec, the L-values of the magnetopause moved back to 10 Re due to the dynamic pressure decrease. We found that electron flux decreased during the period, which strongly depended on MLT and pitch angle of electrons. The simulation showed that more than 80% of lost electrons lost from the magnetopause at 8 ~ 11 MLT. The pitch angles of 90% of lost electrons are 85 ~ 95 degrees. Because the MPS process causes loss of electrons at L values higher than 6.75, it is suggested that other loss processes are necessary for the loss at lower L-values. After the MPS, the electron fluxes at lower L-shells decreased through outward motion of trapped electrons due to E x B drift. Our simulation results suggest that the dominant loss processes of electron flux in the MPS at L > 6.75, while the outward motion at L < 6.75.