Global Changes of the Non-Dipole Magnetic Field for 1900-2000

Abstract

Based on the seventh generation of International Geomagnetic Reference Field(IGRF), the non-dipole magnetic fields for each 5 years during the period of 1900–2000 were calculated and analyzed. The location and intensity of each magnetic anomaly center at different epoch were computed and analysed. There are five magnetic anomalies with large spatial coverage and strong intensity, they are Eastern Asian positive magnetic anomaly, Oceanian negative magnetic anomaly, Southern Atlantic positive magnetic anomaly, African negative magnetic anomaly, and Northern American positive magnetic anomaly. The intensity of Southern Atlantic positive anomaly is the biggest. The intensity of Eastern Asian positive anomaly is the second before 1990.The intensity of African negative anomaly has exceeded Eastern Asian positive anomaly and becomes the second since 1990. The increasing rate of magnetic anomaly intensity (absolute value) of African negative anomaly is the largest(average annual variation rate is 67.1nT/a.), that of Southern Atlantic positive anomaly is the second (64.8nT/a.), that of Oceanian negative anomaly is the third (49.6nT/a.). The changes of magnetic anomaly centers of African and Southern Atlantic anomaly are the fastest compared with other magnetic anomalies.