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-EM13] 内部磁気圏

2019年5月29日(水) 15:30 〜 17:00 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:海老原 祐輔(京都大学生存圏研究所)、Danny Summers(Memorial University of Newfoundland)、三好 由純(名古屋大学宇宙地球環境研究所)、齊藤 慎司(名古屋大学 大学院理学研究科)

[PEM13-P17] Relative contribution of ULF and chorus waves to the radiation belt variation: Comparison between multi-point observations and BATSRUS + CRCM simulation

*高橋 直子1関 華奈子1Mei-Ching Fok2Yihua Zheng2三好 由純3David Hartley4松岡 彩子5笠原 禎也6笠羽 康正7東尾 奈々8 (1.東京大学大学院理学系研究科、2.NASA Goddard Space Flight Center、3.名古屋大学宇宙地球環境研究所、4.Department of Physics and Astronomy, University of Iowa、5.宇宙航空研究開発機構 宇宙科学研究所、6.金沢大学総合メディア基盤センター、7.東北大学 惑星プラズマ・大気研究センター、8.宇宙航空研究開発機構)

Earth’s radiation belt is the area where electrons with energies from hundreds of keV to several MeV are trapped. When, where, and how the radiation belt exhibits a dramatic variation during a magnetic storm is of global interest. The dynamic variation of the radiation belt is caused by various wave-particle interactions: (1) the radial diffusion of electrons driven by ultra-low-frequency (ULF) waves in Pc5 frequency ranges (1.6–6.7 mHz) and (2) the local acceleration caused by wave-particle interactions between whistler-mode chorus waves and radiation belt particles. Over the past decade, multi-point observations and numerical simulations have provided evidence to support above physical processes. However, it is debatable how much each wave contributes to the radiation belt variation during a magnetic storm. A few previous studies have quantitatively compared roles of local acceleration and radial transport by calculating diffusion coefficients, whereas the global context between the wave growth and the relativistic electron flux enhancement has not been extensively studied. To address these issues, the comprehensive study using multi-point observations and numerical simulations (not empirical models) makes essential and significant contributions.

We focus on the magnetic storm on 27-30 May 2017. This magnetic storm is triggered by coronal mass ejections and induces a clear interplanetary shock. Fortunately, several satellites are scattered in the inner magnetosphere and detect both ULF and chorus waves during this magnetic storm. Arase and Van Allen Probes also detect variations of relativistic electron fluxes associated with the Dst index variation. We examine L-value dependence of ULF and chorus wave powers and find the difference of wave activity during the recovery phase. The chorus wave activity is large during the early recovery phase, while the ULF wave activity is large during the late recovery phase. The difference of wave activity may contribute to the radial profile in the phase space density of relativistic electrons. To grasp the extent of individual wave contribution, we also perform the comprehensive ring current model (CRCM) coupled with Block-Adaptive-Tree Solar-Wind Roe-Type Upwind Scheme (BATSRUS) simulation. BATSRUS with CRCM well reproduces global characteristics of energetic electron fluxes and wave growth during this magnetic storm. We will further evaluate global distribution of simulated wave power comparing to the observation, and then discuss the temporal and spatial context between each wave growth and the radiation belt variation.