地磁场的漂移运动和强度变化

在修正了Briggs提出的移动变形图案相关分析法基础上,对全球非偶极子磁场以及6个行星尺度磁异常区的漂移特性和强度变化进行了研究.结果表明,在1900-2000年期间,全球非偶极子磁场以0.15°/a的平均速度向西漂移,强度累计增长了29%;6个行星尺度异常区的西漂运动存在明显差异,其中漂移最快的是赤道附近的非洲异常,平均西漂速度为0.26°/a,其次是南半球的澳大利亚异常(0.23°/a),最慢的是欧亚异常(0.09°/a).除西漂外,大多数异常区还有较小的北向漂移.在1940-1955年期间北半球的欧亚、北美和北大西洋3个异常区以及赤道地区的非洲异常几乎同时由西漂或西南漂转为西北向漂移;紧接着,南半球的南大西洋和澳大利亚两个异常区的漂移特征也发生明显变化,主要是漂移明显减慢,而不是漂移方向的转折.在6个异常区中,澳大利亚、南大西洋、非洲和欧亚4个异常区的强度有明显增加,而北美和北大西洋两个异常区的强度则显示了减小的趋势.

DRIFTS AND INTENSITY VARIATIONS OF THE GEOMAGNETIC FIELD

In this paper we modified the Briggs' method of correlation analysis of moving random pattern and studied the characteristics of the westward drift and intensity variations of the non dipole geomagnetic field and 6 planetary scale geomagnetic anomalies. During 1900-2000,the non dipole field has drifted westward at an average speed of 0 15°/a, and has intensified by 29%. Six planetary scale magnetic anomalies exhibit different characteristics in the drift. The African anomaly （AF） drifts westward at an average speed of 0 26°/a. The Australia anomaly drifts at an average speed of 0 23°/a. The slowest drift occurs in the Eurasia anomaly at an average speed of 0 09°/a . As drifting westward, most anomalies drift northward slowly. During 1945-1955,the anomalies EA,NAM,NAT in the northern hemisphere and AF near the equator changed its drift directions, from the westward to northwestward; a little later, the drifts of the anomalies AUS and SAT in the southern hemisphere slowed down. In the 20th century, the intensities of AUS, SAT, AF and EA have been increased, while the intensities of other two anomalies have been decreased.