地磁気ダイナモとマントルダイナミクス Geodynamo and Mantle Dynamics

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Recent progress of numerical simulations on the dynamo process in the core and the mantle convection provides a clue to understanding the origin of global variations of the Earth system during the last 150 Ma, in which long-term variations of geomagnetic reversal frequency and mantle activity are closely related in time. Recent MHD dynamo simulations suggest that the increase of the total heat flow through the CMB changes the geodynamo from stable dipolar dynamos to unstable multipolar dynamos, and on axially symmetric and equatorial symmetric pattern of heat flux produces stable dipolar dynamos. Numerical modelings of mantle convection indicate 3 convection regimes, whole-mantle, intermittent, and 2-layer convections, in a parameter space of the Rayleigh number (Ra) and the Clapeyron slope (dP/dT) of the phase transition at a depth of 660 km. In the intermittent convection regime, the convection vacillates between wholelayer and the 2-layer regimes, and the surface and CMB heat flows fluctuate with time. The global variation of the Earth system might be attributed to this intermittent convection mode of the present Earth. However, the apparent out of phase variation of the total heat flow through the CMB inferred from the reversal frequency and the mantle activity requires some mechanism for the phase shift of the variations..

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  • 地學雜誌

    地學雜誌 114(2), 142-150, 2005-04-25

    公益社団法人 東京地学協会

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各種コード

  • NII論文ID(NAID)
    10017472916
  • NII書誌ID(NCID)
    AN00322536
  • 本文言語コード
    JPN
  • 資料種別
    REV
  • ISSN
    0022135X
  • NDL 記事登録ID
    7366328
  • NDL 雑誌分類
    ZM41(科学技術--地球科学)
  • NDL 請求記号
    Z15-169
  • データ提供元
    CJP書誌  NDL  J-STAGE 
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