Drifts and Intensity Variations of the Geomagnetic Field

Abstract

AbstractThe Briggs' method of correlation analysis of moving random pattern is modified. The characteristics of the westward drift and intensity variations of the non‐dipole geomagnetic field and 6 planetary‐scale geomagnetic anomalies are studied. During 1900‐2000, the non‐dipole field drifted westward at an average speed of 0:15°/α, and intensified by 29%. Six planetary‐scale magnetic anomalies exhibited different characteristics in the drift. The African Anomaly (AF) drifts westward at an average speed of 0:26°/α. The Australia Anomaly (AUS) drifts at an average speed of 0:23°/α. The slowest drift occurs in the Eurasia Anomaly (EA) at an average speed of 0:09°/α. 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 anomalies AUS and SAT in the southern hemisphere slowed down. In the 20 th century, the intensities of AUS, SAT, AF and EA, the largest in area and greatest in intensity anomalies, were increased, while the intensities of other two anomalies were decreased.