Drifts and Intensity Variations of the Geomagnetic Field

Abstract

The 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 • /a, 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 • /a. The Australia Anomaly (AUS) drifts at an average speed of 0.23 • /a. The slowest drift occurs in the Eurasia Anomaly (EA) at an average speed of 0.09 • /a. As drifting westward, most anomalies drift northward slowly. During 1945During -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.

Regional Features of the Secular Variation of the Geomagnetic Field in China Area

“…On the main field SV and its regional features, many important results have been obtained. For instance, geomagnetic jerks and their geodynamic significances have been examined [20,21] , the global pattern of westward drift in the MF and its regional differences have been analyzed by using various techniques [22∼24] , differential rotation in the global magnetic field and its dispersion phenomena have been studied [25,26] , the magnetic energy distribution within the Earth and its variations have been calculated [27] , the relationship between the annual rate of westward drift and the variations in the magnetic field intensity has been searched [28] . In addition, a possible correlation between the earthquake occurrence and geomagnetic field variations has become a attractive topic.…”

The Secular Variation of the Center of Geomagnetic South Atlantic Anomaly and Its Effect on the Distribution of Inner Radiation Belt Particles

“…From Figure we can see that the longitudinal variation of MFSAA center is similar at different altitudes and close to the result of 0.18 ∘ /year given by Heynderickx (). Wei and Xu () used IGRF7 model to study six main geomagnetic anomalies. All the six anomalies were found to drift toward west, and the average drift speed of the South Atlantic Anomaly during 1900–2000 is 0.12 ∘ /year, close to the result in our study.…”

Role of the Africa Magnetic Anomaly in Controlling the Magnetic Configuration and its Secular Variation

“…The drift rates of the main field have been estimated by many researchers using different techniques. The globally average westward drift rate is 0.2( • )/a, while the northward drift rate is much smaller [3,13] . Using Briggs method [14] , Wei and Xu obtained the globally averaged westward drift rate of 0.185( • )/a and the northward drift rate of 0.031( • )/a for 1900∼2005, on the basis of which the global SV is calculated, as shown in Fig.…”