Electromagnetic core-mantle coupling - I. Explaining decadal changes in the length of day

Geophysical Journal International

Volumn 132, Issue 1, 1998, Pages 167-180

  Holme, Richard ^a  

^a UNIVERSITY OF EDINBURGH   (United Kingdom)

Author keywords

Core mantle boundary; Earth's magnetic field; Earth's rotation; Geomagnetic variation; Inverse problem

Indexed keywords

CORE/MANTLE BOUNDARY; DAY LENGTH; EARTH ROTATION; ELECTROMAGNETIC COUPLING; GEOMAGNETIC FIELD; INVERSE PROBLEM;

EID: 0031921980     PISSN: 0956540X     EISSN: None     Source Type: Journal    
DOI: 10.1046/j.1365-246x.1998.00424.x     Document Type: Article

References (74)

1. Backus, G.E., 1968. Kinematics of geomagnetic secular variation in a perfectly conducting core, Phil. Trans. R. Soc. Lond., A, 263, 239-266.
2. Backus, G.E., 1983. Application of mantle filter theory to the magnetic jerk of 1969, Geophys. J. R. astr. Soc., 74, 713-746.
3. Backus, G., Parker, R. & Constable, C., 1996. Foundation of Geomagnetism, Cambridge University Press.
4. Benton, E.R. & Whaller, K.A., 1983. Rapod diffision of the poloidal geomagnetic field through the weakly conducting mantle a perturbation solution, Geophys. J. R. astr. Soc., 75, 77-100.
5. Bloxham, J., 1988a. The determination of fluid flow at the surface from geomagnetic observations, in Mathematical Geophysics, a Survey of Recent Developments in Seismology and Geophysics, eds Vlaar, N.J., Nolet, G., Wortel, M.J.R. & Cloetingh, S.A.P.L., Reidel, Dordretch.
6. Bloxham, J., 1988b. The dynamical regime of fluid flow at the core surface, Geophys. Res. Lett., 15, 585-588.
7. Bloxham, J., 1989. Simple models of fluid flow at the core surface derived from geomagnetic field models, Geophys. J. Int., 99, 173-182.
8. Bloxham, J., 1992. The steady part of the secular variation of the Earth's magnetic field, J. geophys. Res., 97, 19 569-19 579.
9. Bloxham, J. & Jackson A., 1991. Fluid flow near the surface of the Earth's outer core, Res. Geophys., 29, 97-120.
10. Bloxham, J. & Jackson, A. 1992. Time-dependent mapping of the magnetic field at the core-mantle boundary. J. geophys. Res., 97, 19 537-19 563.
11. Bloxham, J., Gubbins, D. & Jackson, A., 1989. Geomagnetic secular variation, Phil. Trans. R. Soc. Lond., A. 329, 415-502.
12. Buffett, B.A., 1992. Constraints on magnetic energy and mantle conductivity from the forced nutations of the Earth, J. geophys. Res., 97, 19 581-19 597.
13. Buffett, B.A., 1996a. Effects of a heterogenerous mantle on the velocity and magnetic fields at the top of the core, Geophys. J. Int., 125, 303-317.
14. Buffett, B.A., 1996b. A mechanism for decade fluctuations in the length of day, Geophys. Res. Lett., 23, 3803-3806.
15. Bullard, E.C., Freeman, C., Gellman, H. & Nixon, J., 1950. The westward drift of the Earth's magnetic field. Phil. Trans. R. Soc. Lond., A, 243, 61-92.
16. Cohen, R.E., Mazin, I.I. & Isaak, D.G., 1997. Magnetic collapse in transition metal oxides at high pressure: implications for the Earth, Science, 275, 654-657.
17. Constable, C.G. & Parker, R.L. 1988. Smoothing, splines and smoothing splines: their application in geomagnetism, J. comput. Phys., 78, 493-508.
18. de Boor, C., 1978. A Practical Guide to Splines., Springer, New York.
19. Eubanks, T.M., Steppe, J.A., Dickey, J.O. & Callahan, P.S., 1985. A spectral analysis of the Earth's angular momentum budget, J. geophys. Res., 90, 5385-5404.
20. Gire, C. & Le Mouël J.-L., 1990. Tangentially geostrophic flow at the core-mantle boundary compatible with the observed geomagnetic secular variation: the large-scale component of the flow, Phys. Earth planet. Inter., 59, 259-287.
21. Glatzmaier, G.A. & Roberts, P.H. 1995a. A three-dimensional convectric dynamo solution with rotating and finitely conducting inner core and outer mantle, Phys. Earth planet. Inter., 91, 63-75.
22. Glatzmaier, G.A. & Roberts, P.H. 1995b. A three-dimensional self-consistent computer simultation of a geomagnetic field reversal, Nature, 377, 203-209.
23. Gubbins, D., 1981. Finding core motions from magnetic observations, Phil. Trans. R. Soc. Lond., A, 306, 247-254.
24. Gubbins, D., 1983. Geomagnetic field analysis - I. Stochastic inversion, Geophys. J. R. astr. Soc., 73, 641-652.
25. Gubbins, D. & Kelly, P., 1996. A difficulty with using the frozen flux hypothesis to find steady core motions, Geophys. Res. Lett., 23, 1825-1828.
26. Gubbins, D. & Roberts, P.H., 1987. Magnetohydrodynamics of the Earth's core, in Geomagnetism, Vol. 2, Ch. I, ed. Jacobs, J.A., Academic, San Diego.
27. Hide, R. 1969. Interaction between the Earth's liquid core and solid mantle, Nature, 222, 1055-1056.
28. Hide, R., 1977. Towards a theory of irregular variation in the length of day and core-mantle coupling, Phil. Trans. R. Soc. Lond., A. 284, 547-554.
29. Hide, R., 1995a. Reply to comment on 'The topographic torque on a bounding surface of a rotating gravitating fluid and the excitation by core motions of decadal fluctuations in the Earth's rotation', Geophys. Res. Lett., 22, 3563-3565.
30. Hide, R., 1995b. The topographic torque on a bounding surface of a rotating gravitating fluid and the excitation by core motions of decadal fluctuations in the Earth's rotation, Geophys. Res. Lett., 22, 961-964.
31. Hide, R. & Dickey, J.O., 1991. Earth's variable rotation, Science, 253, 629-637.
32. Hide, R., Clayton, R.W., Hager, B.H. Spieth, M.A. & Voorhies, C.V., 1993. Topographic core-mantle coupling and fluctuations in the Earth's rotation, in Relating Geophysical Structures and Processes: the Jeffreys Volume, pp. 121-127, eds Aki, K. & Dmowska, R., AGU/IUGG.
33. Hills, R.G., 1979. Convection in the Earth's mantle due to viscous shear at the core-mantle interface and due to large-scale bouyancy, FhD thesis, New Mexico State University, Las Cruces.
34. Holme, R., 1997. Electromagnetic core-mantle coupling II: probing deep mantle conductance, AGU Geophysical Monograph on the Core-Mantle Region, submitted.
35. Jackson, A., 1989. The Earth's Magnetic Field at the Core-Mantle Boundary, PhD thesis, Cambridge University.
36. Jackson, A., 1997. Time dependency of geostropic core surface motions, Phys. Earth planet. Inter., in press.
37. Jackson, A., Bloxham, J. & Gubbins, D., 1993. Time-dependent flow at the core surface and conservation of angular momentum in the coupled core-mantle system, in Dynamics of the Earth's Deep Interview and Earth Rotation, pp. 97-107, eds Le Mouël, J.-L., Smylie, D.E. & Herring, T., AGU/IUGG.
38. Jault, D. & Le Mouël, J.L., 1989. The topographic torque associated with a tangentially geostrophic motion at the core surface and inferences on flow inside the core, Geophys. astrophys. Fluid Dyn., 48, 273-296.
39. Jault, D. & Le Mouël, J.L., 1990. Core-mantle boundary shape: constraints inferred from the pressure torque acting between the core and the mantle, Geophys. J. Int., 101, 233-241.
40. Jault, D. & Le Mouël, J.L., 1991. Exchange of angular momentum between the core and the mantle, J. Geomag. Geoelectr., 43, 111-129.
41. Jault, D., Gire, C. & Le Mouël, J.L., 1988. Westward drift, core motions and exchanges of angular momentum between core and mantle, Nature, 333, 353-356.
42. Jeanloz, R., 1990. The nature of the Earth's core, Ann. Rev. Earth planet. Sci., 357-386.
43. Jeanloz, R., 1993. Chemical reactions at the Earth's core-mantle boundary: summary of evidence and geomagnetic implications, in Relating Geophysical Structures and Processes: the Jeffreys Volume, pp. 121-127, eds Aki, K. & Dmowska, R., AGU/IUGG.
44. Kuang, W. & Bolxham, J., 1993. On the effect of boundary topography on flow in the Earth's core, Geophys. astrophys. Fluid Dyn., 72, 161-195.
45. Kuang, W. & Bloxham, J., 1997a. Convective MHD flow in a rapidly rotating spherical shell I: numerical modelling, J. Comput. Phys., submitted.
46. Kuang, W. & Bloxham, J., 1997b. On the dynamics of topographical core-mantle coupling. Phys. Earth planet. Inter., 99, 289-294.
47. Langel, R.A., 1987. The main field, in Geomagnetism, Vol. 1, Ch. 4, ed. Jacobs, J.A., Academic, San Diego.
48. Lanzerotti, L.J., Medford, L.V., Maclennan, C.G., Thomson, D.J., Meloni, A., & Gregori, G.P., 1985. Measurements of the large-scale direct-current Earth potential and possible implications for the geomagnetic dynamo, Science, 229, 47-49.
49. Le Mouël, J.-L., 1984. Outer core geostrophic flow and secular surface in the geostropic approximation, Phys. Earth planet. Inter., 39, 270-287.
50. Le Mouël, J-L., Hulot, G. & Poirier, J.-P., 1997. Core-mantle interaction, in Earth's Deep Interior, pp. 197-221, ed. Crossley, D.J., Gordon and Breach, Amsterdam.
51. Lloyd, D. & Gubbins, D., 1990. Toroidal fluid motion at the top of the Earth's core, Geophys. J. Int., 100, 455-467.
52. Love, J.J. & Bloxham, J., 1994. Electromagnetic coupling and the toroidal magnetic field at the core-mantle boundary, Geophys. J, Int., 117, 235-256.
53. Manga, M. & Jeanloz, R., 1996. Implications of a metal-bearing chemical boundary layer in D″ for mantle dynamics, Geophys. Res. Lett., 23, 3091-3094.
54. McCarthy, D.D. & Babcock, A.K., 1986. The length of day since 1656, Phys. Earth planet. Inter., 44, 281-292.
55. Parker, R.L., 1994. Geophysical Inverse Theory, Princeton University Press, Princeton, NJ.
56. Poirier, J.-P. 1993. Core-infiltrated mantle and the nature of the D″ layer, J. Geomag. Geoelectr., 45, 1221-1227.
57. Poirier, J.-P. & Le Mouël, J.-L., 1992. Does infiltration of core material into the lower mantle affect the observe geomagnetic field?, Phys. Earth planet. Inter., 73, 29-37.
58. Poirier, J.-P., Goddat, A. & Peyronneau, J., 1996. Ferric iron dependence of the electrical conductivity of the Earth's lower mantle material, Phil. Trans. R. Soc. Lond., A, 354, 1361-1369.
59. Press, W.H., Flannery, B.P., Teukolsky, S.A. & Vetterling, W.T., 1986. Numerical Recipes, Cambridge University Press.
60. Roberts, P.H., 1972. Electromagnetic core-mantle coupling. J. Geomag. Geoelectr., 24, 231-259.
61. Roberts, P.H. & Scott, S., 1965. On the analysis of secular variation, I, a hydromagnetic constraint: theory. J. Geomag. Geoelectr., 17, 137-151.
62. Rochester, M.G., 1960. Geomagnetic westward drift and irregularities in the Earth's rotation, Phil. Trans. R. Soc. Lond., A, 252, 531-555.
63. Rochester, M.G., 1984. Causes of fluctuation in the rotation of the Earth, Phil. Trans. R. Soc. Lond., A., 313, 95-105.
64. Roden, R.B., 1963. Electromagnetic core-mantle coupling, Geophys. J. R., astr. Soc., 7, 361-374.
65. Sclater, J.G., Jaupart, C. & Galson, D., 1980. The heat flow through oceans and continents, Rev. Geophys. Space Phys., 18, 269-311.
66. Shure, L., Parker, R.L., & Backus, G.E., 1982. Harmonic splines for geomagnetic modelling, Phys. Earth planet. Inter., 28, 215-229.
67. Stephenson, F.R. & Morrison, L.V., 1984. Long-term changes in the rotation of the Earth: 700 B.C. to A.D. 1980, Phil. Trans. R. Soc. Lond., A, 313, 47-70.
68. Stewart, D.N., 1991. Geomagnetic impulses and the electrical conductivity of the lower mantle, PhD thesis, University of Leeds.
69. Stewart, D.N. Busse, F.H., Whaler, K.A. & Gubbins, D., 1995. Geomagnetism, Earth rotation and the electrical conductivity of the lower mantle, Phys. Earth planet. Inter., 92, 199-214.
70. Stix, M. & Roberts, P.H., 1984. Time-dependent electromagnetic core-mantle coupling, Phys. Earth planet. Inter., 36, 49-60.
71. Voorhies, C.V., 1986. Steady surficial core motions: an alternate method, Geophys. Res. Lett. 13, 1537-1540.
72. Whaler, K.A., 1980. Does the whole of the Earth's core convect?, Nature, 287, 528-530.
73. Whaler, K.A., 1986. Geomagnetic evidence for fluid upwelling at the core-mantle boundary, Geophys. J. R. astr. Soc., 86, 563-588.
74. Whaler, K.A. & Gubbins, D., 1981. Spherical harmonic analysis of the geomagnetic field: an example of a linear inverse problem, Geophys. J. R. astr. Soc., 65, 645-693.