MECHANISM FOR GEOMAGNETIC POLARITY REVERSALS

被引:131
作者
GUBBINS, D
机构
[1] Bullard Lab, Cambridge, Engl, Bullard Lab, Cambridge, Engl
关键词
MAGNETISM; -; Theory;
D O I
10.1038/326167a0
中图分类号
O [数理科学和化学]; P [天文学、地球科学]; Q [生物科学]; N [自然科学总论];
学科分类号
07 ; 0710 ; 09 ;
摘要
Recent studies of old magnetic observations and the seismic velocity of the lower mantle suggest that at least part of the geomagnetic secular variation is driven by temperature anomalies in the solid mantle. In particular, a patch of flux of opposite sign to that expected for a dipole field occurs beneath southern Africa. It has intensified throughout the twentieth century, by a process that is believed to be flux expulsion associated with a particularly hot part of the lowermost mantle, and is drifting westwards. A similar patch lies beneath South America. It is shown in this paper that the present fall in the dipole moment is directly related to the intensification and southward movement of these patches, and it is suggested that the fall occasionally leads to polarity reversal. The almost linear increase in the frequency of polarity reversals that has occurred since the Cretaceous quiet interval is attributed to the growth of the hot patch of mantle presently under southern Africa.
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页码:167 / 169
页数:3
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