Constraints on the couplings at the core-mantle and inner core boundaries inferred from nutation observations (Invited)

Details Constraints on the couplings at the core-mantle and inner core boundaries inferred from nutation observations (Invited) Constraints on the couplings at the core-mantle and inner core boundaries inferred from nutation observations (Invited)

Dec 2009

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2009agufm.p44a..06k&link_type=abstract

American Geophysical Union, Fall Meeting 2009, abstract #P44A-06

Physics

[1213] Geodesy And Gravity / Earth'S Interior: Dynamics, [1239] Geodesy And Gravity / Earth Rotation Variations

Scientific paper

The rotational motion of the Earth depends on its internal structure. Because Earth rotation is measured very accurately with advanced space geodetic techniques, those observations can be used to infer properties of the Earth's interior. In particular, nutation observations allow to get information on the couplings at the core-mantle and inner core boundaries (CMB and ICB). In this work, we perform an inversion of nutation observations obtained by the very long baseline interferometry (VLBI) technique. Two important characteristics of our inversion strategy are that (1) the observations are used directly in time series, avoiding the loss of information occurring when only some important terms in frequency are used, and (2) we use a Bayesian inversion method, which allows to deal with the high non-linearity of the nutation model. In order to test the robustness of the estimation, we use several VLBI nutation data sets, each produced by a different VLBI analysis center. We obtain estimations of parameters characterizing Earth interior properties, among which, two complex parameters, named coupling constants, characterizing the intensity of the couplings at the CMB and ICB, as well as the amount of dissipation arising from these couplings. We use this estimation of the coupling constants at the CMB and ICB together with a theoretical model of the visco-magnetic coupling at those boundaries in order to obtain constraints on the coupling mechanisms at the CMB and ICB and on physical properties of those boundaries, such as the intensity of the radial magnetic field and the viscosity of the fluid outer core close to those boundaries.

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