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

地磁场的特征：基于观测数据和发电机理论的综合认识

基本信息

批准号：
12304024
负责人：
KONO Masaru
金额：
$ 26.78万
依托单位：
Okayama University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (A)
财政年份：
2000
资助国家：
日本
起止时间：
2000 至 2003
项目状态：
已结题

项目摘要

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.

在该研究计划中，我们试图将观察性（古磁）和理论（发电机仿真）结果结合起来。换句话说，我们旨在了解地磁场的各种特征（极性逆转，世俗变化，强度变化）如何由模型再现，如果是这些行为的物理原因是什么。我们获得了以下结果。在古磁研究中，我们通过K-AR方法将来自中国东北蒙古的玄武岩岩石日期。结果表明，这些岩石在白垩纪晚期，在所谓的白垩纪长正常超校立中爆发。我们的实验产生了大约当天价值的1/4的古敏，我们从过去500万年的古磁数据中构建了现场模型。 Kelly和Gubbins（1997）和Johnson and Constable（1997）已经报道了类似的模型，但是我们的模型是新的，因为它同时考虑了该领域变化的影响。因此，我们的模型同时表达了平均值和波动场。迄今已发布和审查了3D，非线性发电机模型。我们的结果表明，尽管模型中使用的参数与真实地球的参数之间存在显着差异，但数值模型还是重现了地磁场的许多特征行为。