Westward Drift of the Geomagnetic Anomaly in East Asia

Wei, Zigang; Xu, Weihua

doi:10.1002/cjg2.7

Cited by 7 publications

(1 citation statement)

References 7 publications

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“…Different results have been obtained for different epochs and different components of the field by different researchers, although an average westward drift velocity 0.2 degree/year is widely accepted (Bullard et al, 1950;Yukutake, 1962Yukutake, , 1981Malin, 1969;Malin and Saunder, 1973;Jault et al, 1988;Tank, 2000). Using the eighth generation of IGRF and Briggs method (Briggs, 1968a, b), Wei and Xu (2000, 2001, 2002 obtained the average drift rate of 0.15 degree/year in the MG-field for last century.…”

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confidence: 99%

Westward drift in secular variation of the main geomagnetic field inferred from IGRF

Wei

2014

Earth Planet Sp

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Westward drift is apparent not only in the Main Geomagnetic field (MG-field) but also in its Secular Variation (SV-field). The eighth generation of International Geomagnetic Reference Field (IGRF) is used in this paper to study westward drift in the SV-field. The magnetic potential of the SV-field shows a simple spatial distribution and steady variation tendency. An average westward drift rate (0.43 degree/year) is obtained from the SV potential for 1900-2005, which is much greater than the slow westward drift of the MG-field itself (about 0.15 degree/year) for the same period. Magnetic components Y and Z of the SV-field show complicated patterns, from which the average rates of westward drift are roughly estimated as 0.39 degree/year and 0.43 degree/year, respectively. The spatial distribution of component X shows much more complicated pattern with many small-scale vertices, especially for the period 1940-1960, giving a larger drift rate (0.51 degree/year). The unusual behaviors of the high-degree Gauss coefficients in IGRF 1945IGRF , 1950IGRF and 1955 slightly affect the spatial pattern of the potential, although they greatly distort the distribution of components X , Y and Z .

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Section: Introductionmentioning

confidence: 99%

Westward drift in secular variation of the main geomagnetic field inferred from IGRF

Wei

2014

Earth Planet Sp

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Secular Variations of the Planetary‐Scale Geomagnetic Anomalies

Xu¹

2001

Chinese J of Geophysics

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The characteristics of a planetary-scale geomagnetic anomaly are described by using "unsigned magnetic flux" through the anomaly region. The eighth generation of the international geomagnetic reference filed (IGRF) is analyzed to study the secular variations of 5 planetary-scale geomagnetic anomalies during the 1900-2000 period. The results show that the magnetic fluxes through the southern Atlantic anomaly (SAT), Australian anomaly (AUS), and African anomaly (AF) have increased by more than 200 MWb, the increase of the flux through the Eurasian anomaly (EA) is smaller (157 MWb), while the flux through the North America anomaly (NAM) has decreased by 50 MWb. On the other hand, the variations of the anomaly areas are within 10%. The westward drift at the core-mantle boundary (CMB) is less than 0.1 • /a, being much slower than that at the Earth's surface (0.2 • /a). This contrast may be attributed to the different westward drift velocities of the various harmonics in the geomagnetic field: the westward drift at the Earth's surface is controlled by the dominant low-degree harmonics, while the westward drift at the CMB largely depends on high-degree harmonics. Consequently, it should be careful to take the westward drift velocity at the Earth's surface as the characteristic velocity of the fluid flow in the outer core.

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Preliminary Study on the Mechanism of the Geomagnetic Secular Variations in Beijing Since 12000 Years

Zhu¹,

Liu²,

Guo³

2001

Chinese J of Geophysics

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The paleomagnetic secular variation (PSV) in Beijing over the last 12000 years can be divided into long-term (> 1000 a) and short-term (500-1000 a) components. The longterm variations are mainly controlled by changes in the drifting field, while the short-term variations are most probably caused by the fluctuation of the standing field. Compared to the PSV in Japan a remarkable feature in Beijing is a short geomagnetic excursion occurring between (5110 − 4670) ± 110 a, which might have been induced by the anomalous movement of the fluid in the Earth's outer core.

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Westward Drift of the Geomagnetic Anomaly in East Asia

Cited by 7 publications

References 7 publications

Westward drift in secular variation of the main geomagnetic field inferred from IGRF

Westward drift in secular variation of the main geomagnetic field inferred from IGRF

Secular Variations of the Planetary‐Scale Geomagnetic Anomalies

Preliminary Study on the Mechanism of the Geomagnetic Secular Variations in Beijing Since 12000 Years

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