JpGU-AGU Joint Meeting 2020

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[E] Oral

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

[P-EM13] Dynamics of Magnetosphere and Ionosphere

convener:Aoi Nakamizo(Applied Electromagnetic Research Institute, National Institute of Information and Communications Technology), Mitsunori Ozaki(Faculty of Electrical and Computer Engineering, Institute of Science and Engineering, Kanazawa University), Akiko Fujimoto(Kyushu Institute of Technology), Yuka Sato(Nippon Institute of Technology)

[PEM13-22] Feedback instability theory extended to the magnetosphere-ionosphere coupling with field-aligned inhomogeneity

*Tomo-Hiko Watanabe1, Junya Hiwatari1, Shinya Maeyama1 (1.Graduate School of Science, Nagoya University)

Keywords:feedback instability, Alfven wave, magnetosphere-ionosphere coupling

The feedback instability theory for Alfvenic coupling of the magnetosphere and the ionosphere has been extended by introducing inhomogeneous profiles of the ionospheric collision frequency and the magnetospheric Alfven speed. The eigenvalue analysis clarifies the stabilizing mechanism of high frequency components of the ionospheric Alfven resonator (IAR) mode for the strongly inhomogeneous collision frequency profile in the ionosphere. The stabilization is brought by an effective internal resistivity due to the ionospheric inhomogeneity, not by a shear of the ionospheric current. Low frequency components of the field line resonance (FLR) mode remain unstable even when the high frequency components are stabilized. The theoretical results demonstrate a robustness of the feedback instability mechanism providing spontaneous growth of the auroral arc structure in the magnetosphere-ionosphere coupling.