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Characteristics of the geomagnetic field : comprehensive understanding based on observational data and the dynamo theory

Research Project

Project/Area Number 12304024
Research Category

Grant-in-Aid for Scientific Research (A)

Allocation TypeSingle-year Grants
Section一般
Research Field 固体地球物理学
Research InstitutionOkayama University

Principal Investigator

KONO Masaru  Okayama University, Institute for Study of the Earth's Interior, Professor, 固体地球研究センター, 教授 (20011596)

Co-Investigator(Kenkyū-buntansha) HATAKEYAMA Tadahiro  Okayama University of Science, Information Processing Center, Lecturer, 情報処理センター, 講師
KANZAKI Masami  Okayama University, Institute for Study of the Earth's Interior, Associate Professor, 固体地球研究センター, 助教授 (90234153)
TANAKA Hidefumi  Kochi University, Faculty of Education, Professor, 教育学部, 教授 (80108191)
Project Period (FY) 2000 – 2003
Project Status Completed (Fiscal Year 2003)
Budget Amount *help
¥41,840,000 (Direct Cost: ¥37,100,000、Indirect Cost: ¥4,740,000)
Fiscal Year 2003: ¥3,120,000 (Direct Cost: ¥2,400,000、Indirect Cost: ¥720,000)
Fiscal Year 2002: ¥2,990,000 (Direct Cost: ¥2,300,000、Indirect Cost: ¥690,000)
Fiscal Year 2001: ¥14,430,000 (Direct Cost: ¥11,100,000、Indirect Cost: ¥3,330,000)
Fiscal Year 2000: ¥21,300,000 (Direct Cost: ¥21,300,000)
Keywordssecular variation / paleointensities / dynamo / average field / ダイナモモデル / 対流渦 / ヘリシティ / エクマン収束 / 白亜紀 / 平均磁場と変動成分 / レーリー数 / 古地磁気永年変化 / 逆問題解法
Research Abstract

In this research program, we tried to combine the observational (paleomagnetism) and theoretical (dynamo similation) results about the geomagnetic field. In other words, we aimed at understanding how various features of the geomagnetic field (polarity reversals, secular variation, intensity variation) are reproduced by the models, and if so what are the physical causes for these behaviors. We obtained the following results.
In Paleomagnetic studies, we dated the basaltic rocks from Inner Mongolia, northeast China, by K-Ar method. The results indicated that these rocks erupted in late Cretaceous, in the so-called Cretaceous Long Normal superchron. Our experiments yielded the paleointensities which are about 1/4 of the present day value.
We constructed the field model from the Paleomagnetic data of the last 5 million years. Similar models were already reported by Kelly and Gubbins (1997) and Johnson and Constable (1997), but our model is new in that it considers the effect of the variation of the field at the same time. Consequently our model express both the mean and the fluctuating field at the same time.
The 3D, nonlinear dynamo models so far published are compared and reviewed. Our results show that, despite the significant difference between the parameters used in the models and those of the real earth, the numerical models reproduce many of the characteristic behaviors of the geomagnetic field.

Report

(5 results)
  • 2003 Annual Research Report   Final Research Report Summary
  • 2002 Annual Research Report
  • 2001 Annual Research Report
  • 2000 Annual Research Report
  • Research Products

    (25 results)

All Other

All Publications (25 results)

  • [Publications] Kono, M., H.Tanaka, H.Tsunakawa: "Spherical harmonic inversion of paleomagnetic data : The case of linear mapping"Journal of Geophysical Researach. 105. 5817-5833 (2000)

    • Description
      「研究成果報告書概要(和文)」より
    • Related Report
      2003 Final Research Report Summary
  • [Publications] Hatakeyama, T., M.Kono: "Shift of the mean magnetic field values : Effect of scatter due to secular variation and errors"Earth, Planets, and Space. 53. 31-44 (2001)

    • Description
      「研究成果報告書概要(和文)」より
    • Related Report
      2003 Final Research Report Summary
  • [Publications] Zheng, A., H.Tanaka, Y.Tatsumi, M.Kono: "Basalt platform in Inner Mongolia and Hebei Province : New K-Ar ages, geochemistries, and revision of paleomagnetic results"Geophysical Journal International. 151. 654-662 (2002)

    • Description
      「研究成果報告書概要(和文)」より
    • Related Report
      2003 Final Research Report Summary
  • [Publications] Tanaka, H., M.Kono: "Paleointensities from a Cretaceous basalt platform in Inner Mongolia, northeastern China"Physics of the Earth and Planetary Interiors. 133. 147-157 (2002)

    • Description
      「研究成果報告書概要(和文)」より
    • Related Report
      2003 Final Research Report Summary
  • [Publications] Hatakeyama, T., M.Kono: "Geomagnetic field model for the last 5 My : Time-averaged field and secular variation"Physics of the Earth and Planetary Interiors. 133. 181-215 (2002)

    • Description
      「研究成果報告書概要(和文)」より
    • Related Report
      2003 Final Research Report Summary
  • [Publications] Kono, M., P.H.Roberts: "Recent geodynamo simulations and observations of the geomagnetic field"Reviews of Geophysics. 40(4). 4-1-4-53 (2002)

    • Description
      「研究成果報告書概要(和文)」より
    • Related Report
      2003 Final Research Report Summary
  • [Publications] Kono, M., H.Tanaka, H.Tsunakawa: "Spherical harmonic inversion of paleomagnetic data : The case of linear mapping"Journal of Geophysical Research. 105. 5817-5833 (2000)

    • Description
      「研究成果報告書概要(欧文)」より
    • Related Report
      2003 Final Research Report Summary
  • [Publications] Hatakeyama, T., M.Kono: "Shift of the mean magnetic field values : Effect of scatter due to secular variation and errors"Earth, Planets, and Space. vol.53. 31-44 (2001)

    • Description
      「研究成果報告書概要(欧文)」より
    • Related Report
      2003 Final Research Report Summary
  • [Publications] Zheng, A., H.Tanaka, Y.Tatsumi, M.Kono: "Basalt platform in Inner Mongolia and Hebei Province : New K-Ar ages, geochemistries, and revision of paleomagnetic results"Geophysical Journal International. vol.151. 654-662 (2002)

    • Description
      「研究成果報告書概要(欧文)」より
    • Related Report
      2003 Final Research Report Summary
  • [Publications] Tanaka, H., M.Kono: "Paleointensities from a Cretaceous basalt platform in Inner Mongolia, northeastern China"Physics of the Earth and Planetary Interiors. vol.133. 147-157 (2002)

    • Description
      「研究成果報告書概要(欧文)」より
    • Related Report
      2003 Final Research Report Summary
  • [Publications] Hatakeyama, T., M.Kono: "Geomagnetic field model for the last 5 My : Time-averaged field and secular variation"Physics of the Earth and Planetary. vol.133. 181-215 (2002)

    • Description
      「研究成果報告書概要(欧文)」より
    • Related Report
      2003 Final Research Report Summary
  • [Publications] Kono, M., P.H.Roberts: "Recent geodynamo simulations and observations of the geomagnetic field"Reviews of Geophysics. vol.47(4). 4-1-4-53 paper 1013, 2000RG00102 (2002)

    • Description
      「研究成果報告書概要(欧文)」より
    • Related Report
      2003 Final Research Report Summary
  • [Publications] 河野 長, David Stevenson: "ダイナモ作用と地球・惑星の磁場"地震. 56-4. 311-325 (2003)

    • Related Report
      2003 Annual Research Report
  • [Publications] Zheng, Z., Tanaka, H., Tatsumi, Y., Kono, M.: "Basalt platform in Inner Mongolia and Hebei Province, northeastern China : New K-Ar ages geochemistries and revision of paleaomagnetic results"Geophysical Journal International. 128. 654-662 (2002)

    • Related Report
      2002 Annual Research Report
  • [Publications] Tanaka, H., Kono, M.: "Paleointensities from a Cretaceous basalt platform in Inner Mongolia, northeast China"Physics of Earth and Planetary Interiors. 133. 147-157 (2002)

    • Related Report
      2002 Annual Research Report
  • [Publications] Hatakeyama, T., Kono, M.: "Geomagnetic field model for the last. 5 My : Time-averaged secular variation"Physics of Earth and Planetary Interiors. 133. 181-215 (2002)

    • Related Report
      2002 Annual Research Report
  • [Publications] Kono, M., Roberts, P.H.: "Recent geodynamo simulations and observations of the geomagnetic field"Reviews of Geophysics. 40(4). 4-1-4-53 (2002)

    • Related Report
      2002 Annual Research Report
  • [Publications] Hatakeyama, T., Kono, M.: "Shift of the mean magnetic field values : Effect of scatter due to secular variation and errors"Earth.Planets and Space. 53. 31-44 (2001)

    • Related Report
      2001 Annual Research Report
  • [Publications] Kono, M., Roberts, P.H.: "Definition of the Rayleigh number for geodynamo simulation"Physice of Earth and Planetary Interiors. 128. 13-24 (2001)

    • Related Report
      2001 Annual Research Report
  • [Publications] Christensen, U.R., Kono, M.ほか14名: "A numerical dynamo benchmark"Physics of Earth and Planetary Interiors. 128. 25-34 (2001)

    • Related Report
      2001 Annual Research Report
  • [Publications] Kono, M., Roberts, P.H.: "Recent geodynamo simulations and observations of the geomagnetic field"Review of Geophysics. 40(印刷中). (2002)

    • Related Report
      2001 Annual Research Report
  • [Publications] 河野 長: "ガウスと地球磁気"数学セミナー. 41. 46-50 (2001)

    • Related Report
      2001 Annual Research Report
  • [Publications] Kono M,H.Tanaka,and H.Tsunakawa: "Spherical harmonic inversion of paleomagnetic data : The case of linear mapping"J.Geophys.Res.. 105. 5817-5833 (2000)

    • Related Report
      2000 Annual Research Report
  • [Publications] Kono M,A.Sakuraba,and M.Ishida: "Dynamo simulation and paleosecular variation models"Phil.Trans.Roy.Soc.Lond.. A358. 1123-1139 (2000)

    • Related Report
      2000 Annual Research Report
  • [Publications] Sakuraba,A.and M.Kono: "Effect of a uniform magnetic field on nonlinear magnetoconvection in a rotating fluid spherical shell"Geophys.Astrophys.Fluid Dynam.. 92. 255-287 (2000)

    • Related Report
      2000 Annual Research Report

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Published: 2000-04-01   Modified: 2016-04-21  

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