2003 Fiscal Year Final Research Report Summary
Characteristics of the geomagnetic field : comprehensive understanding based on observational data and the dynamo theory
| Project/Area Number |
12304024
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| Research Category |
Grant-in-Aid for Scientific Research (A)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
固体地球物理学
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| Research Institution | Okayama University |
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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)
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| 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)
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| Project Period (FY) |
2000 – 2003
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| Keywords | secular variation / paleointensities / dynamo / average field |
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| 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.
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