No CrossRef data available.
Article contents
On the ellipticity of the core-mantle boundary from Earth nutations and gravity
Published online by Cambridge University Press: 03 August 2017
Abstract
Core share and HTML view are not available for this content. However, as you have access to this content, a full PDF is available via the ‘Save PDF’ action button.
A change in the core free nutation period from its hydrostatic value of 466d to about 433d has been inferred from analysis of both earth's annual nutation amplitude from Polaris VLBI data (Herring et al., 1986) and surface gravity in the diurnal tidal band (Zürn et al., 1986; Neuberg et al., 1986). Gwinn et al. (1986) interpret this shift as due to an excess nonhydrostatic ellipticity ed, equivalent to a change in the equatorial minus polar radius of 0.5 km. In this paper, the effect of a layer at the core-mantle boundary (CMB) on σf (and hence ed) is examined. Although the potential effect of this layer on σf is found to be large, constraints imposed from gravimetry limit changes in ed to 10%. In addition, the annual nutation has a significant out-of-phase component. Mantle solid friction accounts for a large fraction of the out-of-phase nutation.
- Type
- V. Precession & Nutation
- Information
- Copyright
- Copyright © Reidel 1988
References
Chinnery, M. A., Static deformation of an earth with a fluid core: a physical approach, Geophys. J. R. Astr. Soc., 42, 461–475, 1975.Google Scholar
Christodoulidis, D. C., Smith, D. E., Klosko, S. M. and Dunn, P. J., Solid earth and ocean tide parameters from LAGEOS, Proc. 10th Symp. Earth Tides, in press, 1986.Google Scholar
Duxbury, T. C. and Callahan, J. D., Pole and prime meridian expressions for Phobos and Deimos, Astron. J., 86, 1722–1727, 1981.Google Scholar
Gwinn, C. R., Herring, T. A. and Shapiro, I. I., Geodesy by radio interferometry: Studies of the forced nutation of the earth, 2. Interpetation, J. Geophys. Res.
91, 4745–4754, 1986.Google Scholar
Herring, T. A., Gwinn, C. R. and Shapiro, I. I., Geodesy by radio interferometry: Studies of the forced nutation of the earth, 1. Data analysis, J. Geophys. Res.
91, 4755–4765, 1986.Google Scholar
Himwich, E. and Harder, E., Direct estimation of nutation coefficients from VLBI data, this proceedings, 1988.Google Scholar
Melbourne, W., Anderle, R., Feissel, M., King, R., McCarthy, D., Smith, D., Tapley, B. and Vicente, R., Project MERIT standards, United States Naval Observatory Circular No. 167, 1983.Google Scholar
Neuberg, J., Hinderer, J. and Zurn, W., Stacking gravity tide observation in central Europe for the retrieval of the complex eigen frequency of the nearly diurnal wobble, preprint, 1986.Google Scholar
Sasao, T., Okubo, S. and Saito, M., A simple theory on dynamical effects of a stratified fluid core upon nutational motion of the earth, in Proc. IAU Symp. No. 78. Nutation and the earth rotation, Kiev, May
1977, (eds. Fedorov, E.P., Smith, M.L., Bender, P.L.), Reidel, Dordrecht, 165–183, 1980.Google Scholar
Wahr, J. and Bergen, Z., The effects of mantle anelasticity on nutations, earth tides and tidal variations in rotation rate, Geophys. J. R. Astr. Soc., 87, 633–668, 1986.Google Scholar
Yoder, C. F., Spherical harmonic decomposition of M. E. Parke's ocean tidal model, Jet Propulsion Laboratory Engineering Memorandum, 335–30, 1982.Google Scholar
Zürn, W., Rydelek, P. A. and Richter, B., The core-resonance effect in the record from the superconducting gravimeter at Bad Homburg, Proc. 10th Int. Symp. Earth Tides, in press, 1986.Google Scholar
You have
Access