[P-PS07] 惑星科学

[PPS07-12] Magnetic field observations of a deformed bow shock and a highly dynamic magnetotail during BepiColombo’s second Mercury flyby

*Daniel Schmid¹、David Fischer¹、Ali Varsani¹、Werner Magnes¹、Yasuhito Narita¹、Martin Volwerk¹、Wolfgang Baumjohann¹、Ayako Matsuoka²、Manabu Shinohara³、Yoshimasa Tanaka⁴、Akiko Fujimoto⁵、Masaki Matsushima⁶、Go Murakami⁷、Hans-Ulrich Auster⁸、Ingo Richter⁸、Daniel Heyner⁸、Ferdinand Plaschke⁸、Rumi Nakamura¹ (1.Space Research Institute, Austrian Academy of Sciences, Graz, Austria、2.Data Analysis Center for Geomagnetism and Space Magnetism, Graduate School of Science, Kyoto University、3.National Institute of Technology, Kagoshima College、4.National Institute of Polar Research、5.Kyushu Institute of Technology、6.Department of Earth and Planetary Sciences, School of Science, Tokyo Institute of Technology、7.Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency、8.IGEP, Technische Universit¨at Braunschweig, Braunschweig, Germany)

キーワード：Mercury, Magnetosphere, BepiColombo

Due to Mercury’s proximity to the Sun, the in-depth understanding of its magnetospheric structure remains challenging post MESSENGER-Mariner10 era. The calibrated magnetic field data from BepiColombo’s flyby-2 at Mercury in June 2022, facilitate an unique opportunity for in-situ study of the magnetosphere, and its boundaries such as the bow shock, magnetosheath and magnetopause. Our analysis on the shock crossing reveals that the shock normal direction was significantly deviated during the inbound crossing, while in contrast the outbound crossing is conforming to the statistical or steady-state bow shock shape. The highlight of this research is the detection of a magnetic field depression in the midnight sector before BepiColombo’s closest approach to the planet. This depression layer is thought to be the evidence for either a transient event, or alternatively the crossing of the spacecraft through a current layer which separates the tail-like magnetic field orientation from the dipolar field. The analysis of such transient events in Mercury magnetosphere is a key to understanding of its highly dynamic and unique plasma environment.