基于第四代地磁场综合模型(CM4)改善模型边界效应的研究

Analysis of improvement of boundary effects based on the fourth generation comprehensive models (CM4) of the Earth's magnetic field

一般通过在国界外围均匀添加一定数量的IGRF点以改善区域地磁场模型的边界效应.而最新的地磁场综合模型(Comprehensive Model 4,CM4)可以计算1960～2002年内全球任意区域的地核场、地壳场、磁层场及其感应场、电离层场及其感应场,其内源场比IGRF更适合作为边界补充点以提高模型精度.本文对CM4和IGRF10的地核场网格图进行了比较,并以Taylor多项式模型为例,通过将34个CM4的内源场数据点和34个IGRF10的数值点分别作为边界补充点代入计算出网格值,并将其相减以分析差异.结果显示:各分量在国内大部分区域差异很小,几乎都为0值,在境外区域除了北向分量(X),其余分量均是正值,说明结合IGRF10建立的模型在国界外区域的数值偏小.

Generally, a number of IGRF points are uniformly added outside the boundary for improve the boundary effects. So far to now, the newest updated version of comprehensive model CM4, which could sophisticatedly divide the earth＇s magnetic field into main field, crustal field, ionospheric field and its induced field, magnetospheric field and its induced field, during 1960~2002 globally,was adopted in this study. Comparing to IGRF10, the internal field of CM4 could better be as supplementary points to enhance the modelrs precision. This paper compared the CM4＇ s core field grids charts to that of IGRF10, and the Taylor polynomial method was taken as a example, moreover, 34 points values outside the boundary were taken of this two model, respectively, to figure out the grids values correspondingly. Finally, the anomaly values between two kinds of grids were analyzed. Results showed that anomalyvalues in most region of China were relatively small, the values basically equal to 0, outside the boundary, expect for component X and H, the other components were positive values, with which implicitly indicated the values calculated by IGRF smaller than CM4 in regions outside China.