20世纪地磁长期变化场分析

THE ANALYSIS OF THE GEOMAGNETIC SECULAR VARIATION IN THE 20TH CENTURY

利用IAGA(国际地磁与高空物理学协会 )编制的IGRF(国际地磁参考场 )研究了 2 0世纪地磁场变化规律 .2 0世纪地磁长期变化场的四极子 (n =2的高斯系数所表示 )变化最为显著 ,与主磁场相比长期变化场的球谐级数收敛较慢 ,利用追踪异常焦点位置随时间的变化的方法 ,发现地磁非偶极子长期变化场的垂直分量Z的等值图上有五大异常 ,其漂移情况不太统一 ,但是基本上是西向漂移 .这种西向漂移的不一致性 ,在某种程度上证明了地磁场模型的正确性 .2 0世纪地磁场长期变化的能量谱与主磁场的不同 ,偶极子。

Using IGRF(International Geomagnetic Reference Field) workout by IAGA (International Association of Geomagnetism and Aeronomy), this paper investigates the geomagnetic field in the 20th century. The quadrupole field ( n =2) is the most significant one of the geomagnetic secular variation in the 20th century. The Gauss series of the geomagnetic secular variation is converged slower than that of the main field. Using the method of tracing the change of the position of the anomaly focus, it is found that there are 5 anomalies in the chats of Z (vertical component) of the secular variation of the non dipole field. Their drifting is not consolidate in a few degrees. But they are drifting westward basically. This inconsistency of the westward drifting of the geomagnetic secular variation proves the Wang's geomagnetic model in some degrees. Different from the geomagnetic main field, the power spectra of the dipole, quatrupole and the eighthpole field of the secular variation have significant changes.