Open AccessViscomagnetic torque at the core mantle boundary
Author(s) -
Deleplace Bérangère,
Cardin Philippe
Publication year - 2006
Publication title -
geophysical journal international
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.302
H-Index - 168
eISSN - 1365-246X
pISSN - 0956-540X
DOI - 10.1111/j.1365-246x.2006.03180.x
Subject(s) - core–mantle boundary , nutation , geophysics , mantle (geology) , geology , dissipative system , dissipation , boundary layer , torque , inner core , physics , mechanics , geodesy , thermodynamics , astronomy
SUMMARY A magneto‐hydrodynamic model of boundary layers at the core–mantle boundary (CMB) is derived and used to compute the viscous and electromagnetic torques generated by the Earth's nutation forcing. The predicted electromagnetic torque alone cannot account for the dissipation estimated from the observations of the free core nutation. The presence of a viscous boundary layer in the electromagnetic skin layer at the CMB, with its additional dissipative torques, may explain the geodetic data. An apparent Ekman number at the top of the core between 2 and 4 × 10 −11 is inferred depending on the electrical conductivity of the mantle.