2023 Fiscal Year Final Research Report

Imaging of radiation belt loss during plasmasphere extreme erosion

Research Project

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Project/Area Number	19H01958
Research Category	Grant-in-Aid for Scientific Research (B)
Allocation Type	Single-year Grants
Section	一般
Review Section	Basic Section 17010:Space and planetary sciences-related
Research Institution	Kyushu University (2021-2023) Osaka Electro-Communication University (2019-2020)
Principal Investigator	Obana Yuki 九州大学, 国際宇宙惑星環境研究センター, 学術研究員 (50398096)
Co-Investigator(Kenkyū-buntansha)	坂口歌織国立研究開発法人情報通信研究機構, 電磁波研究所電磁波伝搬研究センター, 主任研究員 (60598994) 細川敬祐電気通信大学, 大学院情報理工学研究科, 教授 (80361830) 能勢正仁名古屋市立大学, データサイエンス学部, 教授 (90333559)
Project Period (FY)	2019-04-01 – 2024-03-31
Keywords	放射線帯 / 内部磁気圏 / EMIC波動 / 孤立オーロラ
Outline of Final Research Achievements	In order to verify that radiation belt particle losses due to EMIC waves occur even at mid- and low-latitudes, we conducted the following research. We installled an all-sky aurora camera and a 64-Hz sampling induction magnetometer at Middlemarch, New Zealand as well as 1-Hz sampling fluxgate magnetometers. Green and red auroras respectively corresponding to the 557.7 nm and 630.0 nm emissions were observed on the night of 5 Aug 2019. Pc1 pulsations were observed in the frequency range of ~0.2-1 Hz before and after a small geomagnetic storm during 4-6 October 2020. The Ionospheric Alfven Resonator (IAR) was also identified with spectral resonance structures during this magnetic storm. Lower harmonic modes of IAR were present throughout the local nighttime, but higher harmonic modes with frequency of 5-15 Hz seemed to disappear at the onset time of substorms. This is the first report of IAR at such a high frequency range and this is the first IAR observation in the southern hemisphere.
Free Research Field	磁気圏物理学
Academic Significance and Societal Importance of the Research Achievements	本研究は、磁気嵐前後に大きく変動する放射線帯の変動について、特に粒子損失メカニズムを明らかにするうえで重要な研究である。これまで注目されてこなかった深内部磁気圏におけるEMIC波動による粒子拡散に着目した点が独創的であり、これを実証するために、磁気的な中低緯度にあたるニュージーランドに新しい観測体制を構築した。放射線帯は宇宙機や宇宙飛行士に被ばくという害悪を与えるものであり、本研究は宇宙の安全利用にも貢献するものである。