Japan Geoscience Union Meeting 2019

Presentation information

[E] Oral

P (Space and Planetary Sciences ) » P-EM Solar-Terrestrial Sciences, Space Electromagnetism & Space Environment

[P-EM13] Inner magnetosphere: Recent understanding and new insights

Wed. May 29, 2019 10:45 AM - 12:15 PM A04 (TOKYO BAY MAKUHARI HALL)

convener:Yusuke Ebihara(Research Institute for Sustainable Humanosphere, Kyoto University), Danny Summers(Memorial University of Newfoundland), Yoshizumi Miyoshi(Institute for Space-Earth Environmental Research, Nagoya University), Shinji Saito(Graduate School of Science, Nagoya University), Chairperson:Yusuke Ebihara(RISH, Kyoto University), Shinji Saito(ISEE, Nagoya University)

11:55 AM - 12:10 PM

[PEM13-21] Magnetic field disturbances associated with the magnetic dipolarization observed by Arase (ERG) in the inner magnetosphere

*Ayako Matsuoka1, Masahito Nose2, Yoshizumi Miyoshi2, Iku Shinohara1, Mariko Teramoto2, Reiko Nomura3, Akiko Fujimoto4, Yoshimasa Tanaka5, Manabu Shinohara6, Yoshiya Kasahara7, Yasumasa Kasaba8, Keigo Ishisaka9, Shoya Matsuda1, Masafumi Shoji2, Tomoko Nakagawa10, Yoichi Kazama11, Shiang-Yu Wang11, Satoshi Kasahara12, Shoichiro Yokota13, Takefumi Mitani1 (1.Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency, 2.Institute for Space-Earth Environmental Research, Nagoya University, 3.RISE, National Astronomical Observatory of Japan, 4.School of Computer Science and Systems Engineering, Kyushu Institute of Technology, 5.National Institute of Polar Research, 6.National Institute of Technology, Kagoshima College, 7.Information Media Center, Kanazawa University, 8.Planetary Plasma and Atmospheric Research Center, Tohoku University, 9.Faculty of Engineering, Toyama Prefectural University, 10.Faculty of Engineering, Tohoku Institute of Technology, 11.Academia Sinica Institute of Astronomy and Astrophysics, 12.School of Science, The University of Tokyo, 13.School of Science, Osaka University)

Keywords:Arase, magnetic field, dipolarization, Alfven wave

The magneto-hydrodynamic waves propagating in the plasma sheet are recognized to transport substantial energies in the magnetosphere. We investigated magnetic field disturbances of the Alfven waves observed by the Arase spacecraft at about 5 earth-radii distance in the midnight. In the inner plasma sheet Alfven waves were often accompanied by the magnetic dipolarization.
We examined the magnetic disturbances in the plane perpendicular to the ambient magnetic field. In the two events examined in our study, the magnetic field disturbances were linearly polarized and the polarization direction gradually rotated 180 degrees in 200 seconds. It is well interpreted that Arase traversed a magnetic flux tube where torsional Alfven waves propagated. The change of the polarization direction reflected the change of observation location in the flux tube. Torsional-mode is significantly common and natural as the parallel-propagating Alfven wave. It is known that large-scale energy transfer and dissipation of the torsional Alfven waves take place on the solar surface.
Meanwhile, in the boundary plasma sheet adjacent to the lobe, the magnetic field disturbances were linearly polarized again and confined to the dawn-dusk direction. They are interpreted as plane Alfven waves having uniformity in the dawn-dusk direction and propagating obliquely. The kinetic effect of the Alfven waves has been often discussed in previous works in association with the auroral emission at the ionospheric altitude.