Magnetic Rossby waves in the stratified ocean of the core, and topographic core-mantle coupling
Earth, Planets and Space volume 50, pages 641–649 (1998)
A new model of the stably stratified layer at the top of the core is proposed. The existence of a stably stratified layer (we name it the stratified ocean) at the top of the core makes possible the propagation of the waves akin to the Rossby waves (also named “planetary waves”), well known in oceanology and meteorology. These waves are modified and experience significant decay, due to the core’s magnetic field. The “magnetic Rossby waves” are considered here, using a simple planar model, to reveal their qualitative features without going into significant mathematical complications. The core-mantle coupling, which originates from the interaction of the surface flow with the topography of the core-mantle boundary, is strongly influenced by the stably stratified layer. We consider the topographic core-mantle coupling arising due to generation of motion resembling the magnetic Rossby waves in the stably stratified layer. A simple expression is obtained for the topographic tangential stress on the core-mantle boundary.
Anufriev, A. P. and S. I. Braginsky, Effect of irregularities of the boundary of the earth’s core on the velocity of the liquid and on the magnetic field, Geomagn. Aeron., 15, 754–757, 1975.
Anufriev, A. P. and S. I. Braginsky, Influence of irregularities of the boundary of the earth’s core on fluid velocity and the magnetic field, II, Geomagn. Aeron., 17, 78–82, 1977a.
Anufriev, A. P. and S. I. Braginsky, Effect of irregularities of the boundary of the earth’s core on the speed of the fluid and on the magnetic field, III, Geomagn. Aeron., 17, 492–496, 1977b.
Bergman, M. I., Magnetic Rossby waves in a stably stratified layer near the surface of the Earth’s outer core, Geophys. Astrophys. Fluid Dyn., 68, 151–176, 1993.
Braginsky, S. I., Short-period geomagnetic secular variation, Geophys. Astrophys. Fluid Dyn., 30, 1–78, 1984.
Braginsky, S. I., Generation of a 65-year oscillation in the Earth’s core, Izv. Acad. Sci. USSR, Earth Physics, 23, No. 9, 745–748, 1987a.
Braginsky, S. I., Waves in a stably stratified layer on the surface of the terrestrial core, Geomagn. Aeron., 27, 410–414, 1987b.
Braginsky, S. I., MAC-oscillations of the hidden ocean of the core, J. Geomag. Geoelectr., 45, 1517–1538, 1993.
Braginsky, S. I., Dynamics of the stably stratified ocean at the top of the core, Phys. Earth Planet. Inter., 1998 (submitted).
Braginsky, S. I. and J. L. Le Mouël, Two-scale model of a geomagnetic field variation, Geophys. J. Int., 112, 147–158, 1993.
Brekhovskikh, L. and V. Goncharov, Mechanics of Continua and Wave Dynamics, 342 pp., Spriner-Verlag, Berlin, 1985.
Cushman-Roisin, B., Introduction to Geophysical Fluid Dynamics, 320 pp., Prentice Hall, London, 1994.
Dziewonski, A. M. and Don L. Anderson, Preliminary reference Earth model, Phys. Earth Planet. Inter., 25, 297–356, 1981.
Fearn, D. R. and D. E. Loper, Compositional convection and stratification in Earth’s core, Nature, 289, 393–394, 1981.
Frank, S., Ascending droplets in the Earth’s core, Phys. Earth Planet. Inter., 27, 249–254, 1982.
Garnero, E. J., D. V. Helmberger, and S. P. Grand, Constraining outermost core velocity with SmKS waves, Geophys. Res. Lett., 20, 2463–2466, 1993.
Gill, A. E., Atmosphere-Ocean Dynamics, 662 pp., Academic Press, London, 1982.
Gubbins, D., C. J. Thompson, and K. A. Whaler, Stable regions in the Earth’s liquid core, Geophys. J. R. Astron. Soc., 68, 241–251, 1982.
Hide, R., Interaction between the earth’s liquid core and solid mantle, Nature, 222, 1055–1056, 1969.
Hulot, G., M. Le Huy, and J.-L. Le Mouël, Influence of core flows on the decade variations of the polar motion, Geophys. Astrophys. Fluid Dyn., 82, 35–67, 1996.
Kuang, W. and J. Bloxham, On the effect of boundary topography on flow in the Earth’s core, Geophys. Astrophys. Fluid Dyn., 72, 162–195, 1993.
Lambeck, K., The Earth’s Variable Rotation, 449 pp., Cambridge Univ. Press, London, 1980.
Landau, L. D. and E. M. Lifshitz, Fluid Mechanics, 2nd ed., 539 pp., Pergamon, Oxford, 1987.
Lay, T. and C. J. Young, The stably-stratified outermost core revisited, Geophys. Res. Lett., 17, 2001–2004, 1990.
Lister, J. R. and B. A. Buffett, How much of the Earth’s core would be stably stratified if Nu < 1?, Proceedings of the 4th SEDI Symposium on Earth’s Deep Interior, Whistler Mountain, British Columbia, Canada, 1994.
Loper, D. E. and T. Lay, The core-mantle boundary region, J. Geophys. Res., 111, B4, 6397–6420, 1995.
Moffatt, H. K., Topographic coupling at the core-mantle interface, Geophys. Astrophys. Fluid Dyn., 9, 279–288, 1978.
Pedlosky, J., Geophysical Fluid Dynamics, 710 pp., Springer-Verlag, Berlin, 1987.
Peyronneau, J. and J. P. Poirier, Electrical conductivity of the Earth’s lower mantle, Nature, 342, 537–539, 1989.
Roberts, P. H., On topographic core-mantle coupling, Geophys. Astrophys. Fluid Dyn., 44, 181–187, 1988.
Shearer, M. J. and P. H. Roberts, The hidden ocean at the top of Earth’s core, Dyn. Atmos. Oceans, 27, 631–647, 1997.
Souriau, A. and G. Poupinet, A study of the outermost liquid core using differential travel times of the SKS, SKKS and S3KS phases, Phys. Earth Planet. Inter., 68, 183–199, 1991.
Sylvander, M. and A. Souriau, Mapping S-velocity heterogeneous in the D region, from SmKS differential travel times, Phys. Earth Planet. Inter., 94, 1–21, 1996.
Whaler, K. A., Does the whole of the Earth’s core convect?, Nature, 287, 528–530, 1980.
Yokoyama, Y., Thirty year variation in the Earth rotation and the geomagnetic Gauss coefficients, Geophys. Res. Lett., 20, 2957–2960, 1993.
Yukutake, T., A stratified core motion inferred from geomagnetic secular variations, Phys. Earth Planet. Inter., 24, 253–258, 1981.
About this article
Cite this article
Braginsky, S.I. Magnetic Rossby waves in the stratified ocean of the core, and topographic core-mantle coupling. Earth Planet Sp 50, 641–649 (1998). https://doi.org/10.1186/BF03352159