2018 Fiscal Year Final Research Report
Theoretical studies on magnetohydrodynamic waves and implications for inferring Jupiter's internal structure
| Project/Area Number |
17H06859
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| Research Category |
Grant-in-Aid for Research Activity Start-up
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| Allocation Type | Single-year Grants |
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| Research Field |
Solid earth and planetary physics
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| Research Institution | Kobe University |
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Principal Investigator |
Hori Kumiko 神戸大学, システム情報学研究科, 助教 (30636858)
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| Research Collaborator |
Teed Robert J. University of Glasgow, School of Mathematics and Statistics, Lecturer
Jones Chris A. University of Leeds, Department of Applied Mathematics, School of Mathematics, Professor
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| Project Period (FY) |
2017-08-25 – 2019-03-31
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| Keywords | 地球惑星内部物理学 / 磁気流体波動 / 木星探査 / ダイナモ / 国際研究者交流 |
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| Outline of Final Research Achievements |
Theory suggests the metallic hydrogen region in Jupiter's deep interior may host waves. We considered a special class of waves whose transverse motions are confined to cylindrical surfaces aligned with the rotation axis of the gas giant and travel in radius perpendicular to the axis. This wave mode has been shown to travel within Earth's liquid iron core. Performing three-dimensional spherical numerical simulations for the Jupiter's magnetohydrodynamic fluid, we predicted its excitation on timescales of several years. The waves were found to be reflected at a transition to the molecular hydrogen region. Our simulations demonstrated that changes in zonal flow nearer the planet's surface, and possibly in the rotation period, might reveal its signal.
We further analysed the models to yield Rossby waves, which are best known to play a role in Earth's atmosphere, could travel eastwardly on timescales of months-years inside the gaseous planet.
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| Free Research Field |
地球惑星内部物理学、地球惑星流体力学
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| Academic Significance and Societal Importance of the Research Achievements |
地球の除く他惑星では、その基本的な内部構造も十分にわかっているとは言えない。木星を現在周回中の NASA 探査機 Juno も、木星の内部構造の探査を課題の一つに掲げている。本研究では、木星深部で起きる波動やその反射を捉えることによって、金属水素層と分子水素層との境界がある深さを特定できる可能性を示した。これらは、惑星磁場の生成メカニズムや惑星進化の歴史の解明に向けて、重要な制約を与えると期待できる。
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