The magnetic leakage field distribution above linear defects of a tube sample under the geomagneticfield was modeled according to magnetic dipole theory.
利用磁偶极子理论，建立稳恒微弱地磁场作用下管类试件线状缺陷段产生的漏磁场模型。
2
With geomagneticfield model records, several kinds of secular variation of geomagneticdipole moment and the position of the geomagnetic North Pole during the year 0 ~ 2000 a.
利用地磁场模型资料，计算和分析了公元0 ~ 2000年的地磁场偶极子磁矩和地磁北极位置的长期变化。
3
Results shown the continued attenuation of the dipole moment in the last 50 years, and the variation of spatial spectrum of geomagneticfield continuously decreased.