中文摘要：

为计算地球磁极处的磁感应强度，建立地球的磁场是由带电的地球外核的旋转产生的模型．先根据毕奥-萨伐尔定律计算球形模型绕自转轴旋转时在自转轴直径上产生的磁感应强度；再利用已知的地球外核的内外半径及地球半径和磁极处的磁感应强度值，计算出地球外核的电荷体密度及面密度．结果表明：若外核的电荷呈均匀的体密度分布，则其电荷体密度为3．5507C／m^2；若外核的电荷均匀分布在外核的外表面，则其面密度为2．4581×10^6C／m^2．通过地球表面的磁感应强度信息利用物理规律和地球物理数据推测地球内部难以直接进行探测的相关信息，具有实际意义．根据地震学方法对地球外核厚度、转向等变化的最新研究数据按该文模型可推测地球磁场强度、极性等的变化．而地球磁场的变化对地球上的人类生活颇有影响．

英文摘要：

For calculation of the magnetic induction at the Earth＇s magnetic pole, a model of the rotation of the Earth＇s outer core has been established. According to Biot-Savart law, the magnetic induction at the diameter position of the spin axis is calculated. Furthermore, using the internal and external radius of the Earth＇s outer core as well as the radius of the Earth and the magnetic induction at the Earth＇ s magnetic pole, the volume charge density and surface charge density of the Earth＇s outer core have been obtained. Results show that the charge density is 3. 5507 C/m^3 for uniform volume distribution. The charge density is 2. 4581 × 10^6 C/m^2 for uniform surface distribution. The information of the Earth＇s interior can be inferred by surface magnetic induction and its physical laws as well as earth physical data. It is practical because the information is difficult measured directly. New dada about the thickness, deflect of the Earth＇s outer core obtained by seismological methods can reveal the varieties of the earth magnetic intensity and the polarity. Variations of the earth magnetic field affects much the human being on the earth.