1985-1997年中国地磁场长期变化的正交模型

选取中国地区20个地磁台,日本地区3个地磁台的基本数据,使用自然正交分量方法(简称NOC方法)求得1985-199年中国地区地磁场三分量(X ,Y,Z)的自然正交分量的时间函数,即地磁场时间变化的正交模型. 对阶数从1-9的正交分量进行了试验计算,并计算出这23个地磁台分量的均方根偏差(RMS)值. 以1995年为例 ,取kNOC=1-3,将23个地磁台的正交模型值绘出了平面等值线图. 结果显示X , Y,Z长期变化速度的等值线非常平滑,分布均匀,且均具有明显的分区特征,这反映了主磁场的长期变化规律,而其中长期变化速率比较大的地区,反映地磁场的局部特征和有关的地球物理现象.

REGIONAL ORTHORGONAL MODEL OF SECULAR VARIATION OF THE GEOMAGNETIC FIELD IN CHINA DURING 1985-1997

An natural orthogonal component model of secular variation of the geomagnetic field in China was established for the period of 1985_1997 by means of natural orthogonal component methods (NOC's),on the basis of the data of 20 geomagnetic observatories in China and 3 geomagnetic observatories in Japan. The root mean square (RMS) of geomagnetic field components of 23 observatories were calculated for NOC truncation levels 1_9,the contour maps of orthogonal model values for k NOC =1_3 were constructed for 1995 epoch. The results show that the contours of secular variation of X,Y and Z components are very smooth and uniform in distribution and have obvious regional feature. In some areas,the secular variations are very large,reflecting local feature of geomagnetic field and the related geophysics phenomena.