地磁気軸対極の熱核-マントルの相互作用に対する感度
1Department of Earth and Planetary Sciences, Harvard University, Cambridge, Massachusetts 02138, USA. jeremy_bloxham@harvard.edu
Nature
|May 16, 2000
まとめ
地球の磁場は,常に地球中心軸二極 (GAD) モデルに従うとは限りません. 数学的シミュレーションは,内核の大きさではなく,コア・マントルの境界における熱流動の変動を示唆し,初期の地球の磁場における偏差を説明する可能性がある.
科学分野:
- 地質物理学 地質物理学とは地質物理学です.
- 地球科学 地球科学 地球科学
- パレオマグネティズムは,古磁気学です.
背景:
- 古代磁気論の中心である地球中心的軸性二極体 (GAD) 仮説は,地球の磁場は,その軸に沿った中央二極体であると仮定しています.
- GADは過去1億年にわたって十分にサポートされていますが,2億5000万年前よりも早くフィールドを正確に記述することはできません.
- 以前の理論では,より小さな内核が,以前の期間のGAD偏差を説明できると示唆されていました.
研究 の 目的:
- 地球の初期の磁場に関するGAD仮説の妥当性を調査する.
- 内核のサイズとコア・マントルの境界の熱流の変化が磁場に与える影響をテストするために.
主な方法:
- 地球の磁場をシミュレートするために数値ジオダイナモモデルを使用した.
- シミュレートされた内核のサイズが変化した.
- 核-マントルの境界で妥当な熱流動の変動を導入した.
主要な成果:
- 内核の縮小は,磁場の性質にはほとんど影響しなかった.
- メソゾイク以前の状態と一致するシミュレートされた熱流の変化は,重要な八極成分を誘発した.
- この八極の貢献は,初期の地球に関する単純なGADモデルに異議を唱える.
結論:
- 内核の大きさは,地球の初期の歴史におけるGAD仮説の崩壊の主な理由である可能性は低い.
- コア・マントル境界における熱流の変化は,GADモデルからの偏差についてより妥当な説明を提供する.
- これらの発見は,メソゾーイク時代以前の時代からの古磁気データの改訂された解釈を必要とします.
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