マグネトヒドロダイナミックシミュレーションにおける高レイノルズ数での大規模磁場

H Hotta¹, M Rempel², T Yokoyama³

¹Department of Physics, Graduate School of Science, Chiba University, 1-33 Yayoi-cho, Inage-ku, Chiba 263-8522, Japan. High Altitude Observatory, National Center for Atmospheric Research (NCAR), Post Office Box 3000, Boulder, CO 80307, USA. hotta@chiba-u.jp.

Science (New York, N.Y.)

|March 26, 2016

まとめ

高解像度シミュレーションにより,小規模なダイナモが太陽の大規模な磁場を維持する方法が明らかになりました. このダイナモは乱れを抑制し,低磁気拡散率でも地球磁場が持続することを可能にします.

科学分野:

太陽物理学
マグネトヒドロダイナミック
プラズマ物理学

背景:

太陽は11年間の磁気サイクルを示し,乱暴なコンベクションゾーンにもかかわらず一貫した現象です.
以前の磁気水力学シミュレーションでは,低粘度および磁気拡散性を持つ大規模な太陽磁場を維持するのが困難であることが示されました.

研究の目的:

大規模な太陽磁場を維持するメカニズムを調査する.
磁気拡散率の変動が太陽の磁場動態に与える影響を調査する.

主な方法:

高解像度の磁気動力学シミュレーションを使用した.
低拡散度での大規模な磁場エネルギーの減少に関する以前の発見を再現した.
前例のない高解像度で磁場を分析した

主要な成果:

磁場エネルギーが減少していることが確認されました
高解像度で地球規模の磁場の回復を観測した.
小規模な流れを抑制し,高拡散性を模倣する効率的な小規模なダイナモを特定しました.

結論:

この小さなダイナモは地球規模の太陽磁場を維持する上で重要な役割を果たしています
太陽磁場は,小さな磁気拡散率 (大きなレイノルズ数) の条件下でも維持できます.
高解像度シミュレーションは複雑な太陽磁力の動態を理解するために不可欠です

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