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Turbulent structure in Earth's fluid core inferred from time series of geomagnetic dipole moment
Author(s) -
Sakuraba Ataru,
Hamano Yozo
Publication year - 2007
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 - 10.1029/2007gl029898
Subject(s) - wavenumber , earth's magnetic field , geophysics , physics , dipole , magnetohydrodynamic turbulence , dynamo , computational physics , outer core , inner core , magnetic dipole , cosmic microwave background , moment (physics) , core–mantle boundary , geomagnetic pole , mantle (geology) , magnetohydrodynamics , magnetic field , classical mechanics , anisotropy , optics , quantum mechanics
The physical grounds are discussed for assessing turbulent structures hidden inside the Earth's liquid core by using a time series of the geomagnetic dipole moment obtained from historical and paleomagnetic data. We propose the idea that the time‐averaged wavenumber spectra of electric current density at the core‐mantle boundary (CMB) and also velocity near the CMB have relation to the frequency spectrum of the dipole moment. We performed computer simulations of a magnetohydrodynamic spherical dynamo to verify this idea. We show that the frequency spectrum of the dipole moment in the simulation is similar to that inferred by paleomagnetic observations. The simulation results indicate that the underlying kinetic energy spectrum is proportional to m −5/3 in a high wavenumber range, where m is the azimuthal wavenumber. We speculate that a similar turbulent energy spectrum may exist in the Earth's core with a peak near m = 5.