地磁位谐波振幅的南北非对称性

The North-south asymmetry of amplitude of geomagnetic main field

利用第10代国际参考地磁场模型(IGRF)的资料,研究了地磁位的谐波振幅的纬度分布及其时间变化.结果表明,地磁位偶极子成分的谐波振幅北半球大于南半球,谐波振幅随时间减小,北半球的减小比南半球快,振幅变化率高纬度地区周期小,低纬度地区周期长,平均有60 a左右的周期.非偶极子成分的谐波振幅南半球大于北半球,谐波振幅随时间增大,北半球比南半球增加快,振幅变化率南半球比北半球变化强烈,没有明显的周期规律.地磁位的谐波振幅变化有明显的纬度依赖性,在南北半球的分布及其时间变化与地球赤道非对称.

Using the 10th International Geomagnetic Reference Field （IGRF） models, the latitudinal distribution of harmonic amplitude and its time-variation of geomagnetic potential are investigated. The results indicate that the harmonic amplitude of the dipole component of geomagnetic potential is large in the Northern Hemisphere, small in the Southern, declining with time, which is fast in the Northern Hemisphere, slow in the Southern. And the changing rate periodicity is long in the lower latitude, short in the higher, as well as an average periodic variation of 60-year is available for the changing rate. The harmonic amplitude of the non-dipole component increases with time and more quickly in the Southern Hemisphere than that in the Northern, but not an apparent law of periodicity could be confirmed. A clear latitude-independence can also be obtained for the harmonic amplitude variation of geomagnetic potential, with its distribution and time variation on the north-south hemisphere is asymmetrical with respect to the Equator.