Open AccessThe Westward Drift and Geomagnetic Secular Change
Author(s) -
Vestine E. H.,
Kahle Anne B.
Publication year - 1968
Publication title -
geophysical journal of the royal astronomical society
Language(s) - English
Resource type - Journals
eISSN - 1365-246X
pISSN - 0016-8009
DOI - 10.1111/j.1365-246x.1968.tb05743.x
Subject(s) - secular variation , earth's magnetic field , angular momentum , zonal flow (plasma) , earth's rotation , stochastic drift , geophysics , core (optical fiber) , geodesy , dynamo theory , outer core , dipole , inner core , geology , physics , momentum (technical analysis) , rotation (mathematics) , dynamo , magnetic field , geometry , classical mechanics , optics , plasma , statistics , mathematics , quantum mechanics , finance , economics , tokamak
Summary Short‐term fluctuations in the length of the day on the order of a decade are discussed in relation to fluctuations in westward drift of the outer part of the Earth's core. Decreases in the Earth's rotation rate noted near 1910 and 1965 are shown to be correlated with decreases in westward drift of the Earth's magnetic eccentric dipole, which probably originates fairly deep within the Earth's core. If the outer 200‐km thickness of the core moves approximately as does the eccentric dipole field, the changes in angular momentum implied for this part can explain the observed changes in the length of the astronomical second, on the basis of conservation of angular momentum. Other estimates of westward drift in the core based on higher‐degree harmonic terms give a lower westward drift, and also seem to show less precision in the estimates of flow in the core. These discrepancies are unexplained.