前言各地的地磁正常场是由地球深部(主要是地核)的电流系统产生的;一般又认为它由两部分组成,即中心偶极磁场和非偶场。前者根据n=1的三个球谐系数(g_1~0、g_1~1和h_1~1)、各地的地理座标和中心偶极子磁场表示式计算;后者为各地的地磁正常场减去相应的中心偶极磁场。 INTRODUCTION Geomagnetic normal fields are formed by current systems in the deep part of the earth (mainly the earth’s core); they are generally considered to be composed of two parts, namely, a central dipole magnetic field and a non-even magnetic field. The former is calculated based on the three spherical harmonic coefficients (g_1 ~ 0, g_1 ~ 1 and h_1 ~ 1) of n = 1, the geographical coordinates and the center dipole magnetic field of each place, and the latter is calculated by subtracting the geomagnetic normal field The corresponding center dipole field.