[P-CG19] 惑星大気圏・電磁圏

[PCG19-01] Dynamics of Low-Energy Ions and Electrons in Mercury's Magnetosphere: A Comparison Between Mio's First and Second Flybys

*原田 裕己¹、斎藤 義文²、相澤 紗絵^2,3、André Nicolas³、Hadid Lina⁴、Delcourt Dominique⁴、Persson Moa^3,5、Markus Fraenz⁶、横田 勝一郎⁷、Fedorov Andréi³、三宅 亙⁸、Penou Emmanuel³、Barthe Alain³、Sauvaud Jean-André³、Katra Bruno⁴、Baumjohann Wolfgang⁹、松岡 彩子¹、Magnes Werner¹⁰、Auster Hans-Ulrich¹¹、Schmid Daniel¹⁰、Fischer David¹⁰、篠原 学¹²、田中 良昌¹³、藤本 晶子¹⁴、松島 政貴¹⁵、成田 康人¹⁰、松田 昇也¹⁶、村上 豪² (1.京都大学、2.ISAS, JAXA、3.IRAP, CNRS-UPS-CNES、4.LPP-CNRS-Sorbonne Université-Ecole Polytechnique、5.東京大学、6.Max-Planck-Institute for Solar System Research、7.大阪大学、8.東海大学、9.Austrian Academy of Sciences、10.The Space Research Institute, Austrian Academy of Sciences、11.Institute of Geophysics and Extraterrestrial Physics, Technical University of Braunschweig、12.鹿児島高専、13.国立極地研究所、14.九州工業大学、15.東京工業大学、16.金沢大学)

キーワード：水星、みお、磁気圏

The first two Mercury flybys by Mio have revealed new aspects of the highly dynamic magnetosphere of Mercury. Near the magnetopause and bow shock, rapid fluctuations of particle fluxes were detected at unprecedentedly high-time resolutions. In the nightside magnetotail, we identify periodic variations in the ion and electron fluxes. In the inner part of the magnetosphere, Mio observed complicated energy-time structures such as energy dispersions and inverted V's. A comparison of the data from the two flybys indicates that Mercury's magnetosphere was in completely different states, presumably resulting from different solar wind conditions. The high-quality plasma data with a help of magnetic field measurements obtained by Mio enable us to investigate the boundary dynamics, low-frequency wave activity, and substorm-related processes to an extent not achieved by the previous missions. We report up-to-date results from the ongoing efforts of data analysis regarding Mio's first two Mercury flybys.