コロナ質量放出の発生機構及び発生後の惑星間空間への影響についての数値的観測的研究

日冕物质抛射机制及其发生后对行星际空间影响的数值观测研究

• 批准号: 05J01664
• 负责人: 塩田 大幸
• 金额: $ 1.15万
• 依托单位: Kyoto University
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for JSPS Fellows
• 财政年份: 2005
• 资助国家: 日本
• 起止时间: 2005 至 2006
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-05J01664/
• 关键词: 電磁流体力学; 太陽コロナ; 太陽フレア; コロナ質量放出; 宇宙天気; 磁気リコネクション; 数値シミュレーション

本研究では、「宇宙天気予報」の基礎となる太陽フレアやコロナ質量放出(CME)初期の物理過程の解明及び観測データに基づく現実的なモデリングを行うための三次元シミュレーションコードの開発を行った。太陽フレアやCMEのエネルギー蓄積機構やトリガー機構伝播過程において、磁場のねじれなどの磁場の三次元構造が本質的に重要であると考えられる。特に、大局的な磁場構造はCME発生・進化過程に大きく影響するため、フレア・CMEの現実的なモデリングのためには、周囲の磁極が球面上に分布する効果を考慮したモデルである必要がある。以上の要求から本研究では、HLLD近似リーマン解法と有限体積法を用いた三次元球座標電磁流体シミュレーションコードの開発を行った。球座標系におけるシミュレーションの弊害の一つに、極域で方位角方向の格子点間隔が小さくなることにより時間間隔が小さくなる弊害がある。我々はこの弊害を回避するために、方位角方向のグリッドを結合した新たな手法の開発に成功した。さらに、観測結果を取り入れる、任意の速度場を与えるなど制御可能にした磁場・速度場の太陽表面境界条件の開発にも成功した。上記の計算コードを用いて、単純な双極磁場の太陽表面境界に磁場を捻る速度場と、その後磁極を押し付ける速度場を与えて磁力線のつなぎ変えによりCMEを発生させる三次元磁気流体シミュレーションを行った。また、軸対象二次元シミュレーションも行い、三次元性の効果の検証を行っているところである。研究計画では、コード開発の後、フレア・CMEの物理過程を明らかにする研究を行う予定であったが時間が足りず、今後も本研究を継続していく予定である。しかし、本研究で開発した電磁流体コードは、長時間安定に計算を続けることができる非常に優れたコードであり、降着円盤など他の電磁流体現象への幅広い発展も期待できる。

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项目成果

Self-Consistent Magnetohydrodynamic Modeling of a Coronal Mass Ejection, Coronal Dimming, and a Giant Cusp-shaped Arcade Formation

• DOI: 10.1086/496943
• 发表时间: 2005-08
• 期刊: The Astrophysical Journal
• 作者: D. Shiota;H. Isobe;P. Chen;Tetsuya T. Yamamoto;Takuma Sakajiri;K. Shibata