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Leading modes of torsional oscillations within the Earth's core
Author(s) -
Dickey Jean O.,
de Viron Olivier
Publication year - 2009
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/2009gl038386
Subject(s) - physics , earth's magnetic field , amplitude , inner core , geophysics , core (optical fiber) , earth's rotation , rotation (mathematics) , geology , geodesy , magnetic field , geometry , optics , mathematics , quantum mechanics
The fluid core motion cannot be observed directly, however, it can be deduced from magnetic observations. This motion can be approximated as a set of coaxial cylinders rotating along the Earth rotation axis. Our study shows that the actual motion in the core corresponds to a set of oscillations propagating from the core‐mantle boundary to the inner core (with diminishing amplitude) at period of 85, 50, 35 and 28 years, respectively. These oscillations appear to be very robust in our study, moreover two weaker modes have also been isolated and require further study. Zatman and Bloxham (1997) isolated two modes with periods that correspond to our first two modes. Comparing the theoretically predicted modes of Mound and Buffett (2007), all three analyses (one theoretically based and two based on geomagnetic observations) agree on the periods of the isolated modes; this concurrence is exceptional and provides strong evidence of the existence of the modes.