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

在本研究计划中，我们试图联合收割机观测（古地磁学）和理论（发电机模拟）的结果有关的地磁场。换句话说，我们的目的是了解地磁场的各种特征（极性反转，长期变化，强度变化）是如何被模型再现的，如果是这样，这些行为的物理原因是什么。在古地磁研究中，对内蒙古地区玄武岩进行了K-Ar法测年。结果表明，这些岩石的喷发时代为晚白垩世，即白垩纪长正超时。实验得到的古地磁场强度约为现今的1/4，我们根据近500万年的古地磁数据建立了场模型。Kelly和Gubbins（1997）以及约翰逊和康斯特布尔（1997）已经报道了类似的模型，但我们的模型是新的，因为它同时考虑了场变化的影响。因此，我们的模型表达的平均和脉动场在同一时间。三维，非线性发电机模型迄今已发表的比较和评论。我们的研究结果表明，尽管模型中使用的参数与真实的地球的参数之间存在显着差异，但数值模型再现了地磁场的许多特征行为。

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.