The westward drift of the Earth's magnetic field

• BULLARD E. C.

抄録

The westward drift of the non-dipole part of the earth’s magnetic field and of its secular variation is investigated for the period 1907-45 and the uncertainty of the results discussed. It is found that a real drift exists having an angular velocity which is independent of latitude. For the non-dipole field the rate of drift is 0.18 ± 0-015°/year, that for the secular variation is 0.32 ±0-067°/year. The results are confirmed by a study of harmonic analyses made between 1829 and 1945. The drift is explained as a consequence of the dynamo theory of the origin of the earth’s field. This theory required the outer part of the core to rotate less rapidly than the inner part. As a result of electromagnetic forces the solid mantle of the earth is coupled to the core as a whole, and the outer part of the core therefore travels westward relative to the mantle, carrying the minor features of the field with it.

収録刊行物

• Philosophical Transactions of the Royal Society of London. Series A, Mathematical and Physical Sciences

  Philosophical Transactions of the Royal Society of London. Series A, Mathematical and Physical Sciences 243 (859), 67-92, 1950-10-27

  The Royal Society

詳細情報

• CRID: 1363951794530027136
• NII論文ID: 30035330156
• DOI: 10.1098/rsta.1950.0014
• ISSN: 20540272
• ISSN: 00804614
• Web Site: https://royalsocietypublishing.org/doi/pdf/10.1098/rsta.1950.0014
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