Skip to main content


Time evolution of the fluid flow at the top of the core. Geomagnetic jerks

Article metrics


The knowledge of the geomagnetic field and its secular variation allows us to compute the fluid flow at the core surface. The poloidal and toroidal components of the fluid flow at the core-mantle boundary (CMB) have been calculated every year from the Bloxham and Jackson model (1992) and plotted at 50 year intervals over the last three centuries. The flow patterns conserve some broad features over this whole time-span. The time constant of the degree 1 component of the motion is larger than the time constant of the rest of the flow. The average motion over 300 years appears to be in large part symmetrical with respect to the equator. This average flow can be represented by the sum of a few geostrophic vectors. The acceleration fields corresponding to the well documented jerks of 1969, 1979, 1992 have also been computed. The geometry of these acceleration fields is the same, within a change of sign, for the three events. Moreover, this geometry has close connections with the geometry of the flow itself. The spatial and temporal variations of the flow field can be simply described, in a first approximation; it is possible to give an analytical schematic representation of the flow field during the last three decades. Some characteristics of the decadal length-of-day variations follow if the coupling torque between core and mantle is topographic.


  1. Alexandrescu, M., D. Gibert, G. Hulot, J. -L. Le Mouël, and G. Saracco, Detection of geomagnetic jerks using wavelet analysis, J. Geophys. Res., 100(B7), 12557–12572, 1995.

  2. Alexandrescu, M., D. Gibert, G. Hulot, J. -L. Le Mouël, and G. Saracco, Worldwide wavelet analysis of geomagnetic jerks, J. Geophys. Res., 101(B10), 21975–21994, 1996.

  3. Backus, G. E., Poloidal and toroidal fields in geomagnetic field modeling, Rev. Geophys., 24, 75–109, 1986.

  4. Backus, G. E. and J. -L. Le Mouël, The region of the core-mantle boundary where geostrophic velocity fields can be determined from frozen-flux magnetic data, Geophys. J. R. Astron. Soc., 85, 617–628, 1986.

  5. Barraclough, D. R., Spherical harmonic analyses of the geomagnetic field for eight epochs between 1600 and 1910, Geophys. J. R. Astron. Soc., 36, 497–513, 1974.

  6. Benkova, N. P., G. I. Kolomiytseva, and T. N. Cherevko, Analytical model of the geomagnetic field and its secular variation over a period of 400 years (1550–1950), Geomagn. Aeron., 14, 751–755, 1974.

  7. Bloxham, J. and D. Gubbins, The secular variation of Earth’s magnetic field, Nature, 317, 777–781, 1985.

  8. Bloxham, J. and A. Jackson, Time-dependent mapping of the magnetic field at the core-mantle boundary, J. Geophys. Res., 97, 19537–19564, 1992.

  9. Braginsky, S. I., Spherical analyses of the main geomagnetic field in 1550–1800, Geomag. Aeron., 12, 524–529, 1972.

  10. Carlut, J. and V. Courtillot, Geomagnetic paleosecular variation in the last 5 million years: How many multipoles are actually resolvable? (abstract), EOS Suppl., 76(46), 166, 1995.

  11. Carlut, J. and V. Courtillot, How complex is the time-averaged geomagnetic field over the past 5 Myr?, Geophys. J. Int, 134, 527–544, 1998.

  12. Chulliat, A. and G. Hulot, Local computation of the geostrophic pressure at the top of the core, Phys. Earth Planet. Inter., 117, 309–328, 2000.

  13. Courtillot, V. and J. -L. Le Mouël, Geomagnetic secular variation impulses, Nature, 311, 709–716, 1984.

  14. Courtillot, V, J. Ducruix, and J. -L. Le Mouël, Sur une accélération récente de la variation séculaire du champ magnétique terrestre, C. R. Acad. Sci. Paris, 287, Série D., 1095–1098, 1978.

  15. De Michelis, P., L. Cafarella, and A. Meloni, Worldwide character of the 1991 jerk, Geophys. Res. Lett., 25, 377–380, 1998.

  16. Forte, A. M., J. X. Mitrovica, and R. L. Woodward, Seismic-geodynamic determination of the origin of excess ellipicity of the core-mantle boundary, Geophys. Res. Lett., 22(9), 1013–1016, 1995.

  17. Fritsche, H., Atlas des Erdmagnetismus, pp. 1–26, Riga, 1903.

  18. Gavoret, J., D. Gibert, M. Menvielle, and J. -L. Le Mouël, Long-term variations of the external and internal components of the Earth’s magnetic field, J. Geophys. Res., 91(B5), 4787–4796, 1986.

  19. Gire, C. and J. -L. Le Mouël, 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, 1990.

  20. Gire, C., J. -L. Le Mouël, and J. Ducruix, Evolution of the geomagnetic secular variation field from the beginning of the century, Nature, 307, 349–352, 1984.

  21. Gire, C., J. -L. Le Mouël, and T. Madden, Motions at the core surface derived from secular variation data, Geophys. J. R. Astron. Soc., 84, 1–29, 1986.

  22. Golovkov, V. P., T. I. Zvereva, and A. O. Simonyan, Common features and differences between “jerks” of 1947,1958 and 1969, Geophys. Astrophys. Fluid Dyn., 49, 81–96, 1989.

  23. Gubbins, D. and J. Bloxham, Morphology of the geomagnetic field and implications for the geodynamo, Nature, 325, 509–511, 1987.

  24. Gubbins, D. and L. Tomlinson, Secular variation from monthly means from Apia and Amberley magnetic observatories, Geophys. J. R. Astron. Soc., 86, 603–616, 1986.

  25. Gubbins, D. and P. Kelly, Persistent patterns in the geomagnetic field over the past 2.5 Myr, Nature, 365, 829–832, 1993.

  26. Hide, R., Fluctuations in the Earth’s rotation and the topography of the core-mantle interface, Phil. Trans. R. Soc. Lond., A328, 351–363, 1989.

  27. Hide, R., R. W. Clayton, B. H. Hager, M. A. Speith, and C. V. Voorhies, Topographic core-mantle coupling and fluctuations in the Earth’s rotation, in Relating Geophysical Structures and Processes: The Jeffreys Volume, edited by K. Aki and R. Dmowska, Geophys. Monog., Amer. Geophys. Un., 76, 107–120, 1993.

  28. Hulot, G. and J. -L. Le Mouël, A statistical approach to the Earth’s main magnetic field, Phys. Earth Planet. Inter., 82, 167–183, 1994.

  29. Hulot, G., J. -L. Le Mouël, and D. Jault, The flow at the core-mantle boundary: symmetry properties, J. Geomag. Geoelectr., 42, 857–874, 1990.

  30. Hulot, G., J. -L. Le Mouël, and J. Wahr, Taking into account truncation problems and geomagnetic model accuracy in assessing computed flows at the core-mantle boundary, Geophys. J. Int., 108, 224–246, 1992.

  31. Jault, D. and J. -L. Le Mouël, The topographic torque associated with a tangentially geostrophic motion at the core surface and inferences on the flow inside the core, Geophys. Astrophys. Fluid Dyn., 48, 273–296, 1989.

  32. Jault, D. and J. -L. Le Mouël, Core mantle boundary shape: constraints inferred from the pressure torque acting between the core and the mantle, Geophys. J. Int., 101, 233–241, 1990.

  33. Jault, D. and J. -L. Le Mouël, Exchange of angular momentum between the core and the mantle, J. Geomag. Geoelectr., 43, 111–129, 1991.

  34. Jault, D. and J. -L. Le Mouël, Comment on ‘On the dynamics of topographical core-mantle coupling’ by Weijia Kuang and Jeremy Bloxham, Phys. Earth Planet. Inter., 114, 211–215, 1999.

  35. Kelly, P. and D. Gubbins, The geomagnetic field over the past 5 million years, Geophys. J. Int., 128, 315–330, 1997.

  36. Kerridge, D. J. and D. R. Barraclough, Evidence for geomagnetic jerks from 1931 to 1971, Phys. Earth Planet. Inter., 39, 228–236, 1985.

  37. Le Mouël, J.-L., Outer-core geostrophic flow and secular variation of Earth’s geomagnetic field, Nature, 311, 734–735, 1984.

  38. Le Mouël, J. -L., C. Gire, and T. Madden, Motions at the core surface in the geostrophic approximation, Phys. Earth Planet. Inter., 39, 270–287, 1985.

  39. Le Huy, M., M. Alexandrescu, G. Hulot, and J. -L. Le Mouël, On the characteristics of successive geomagnetic jerks, Earth Planets Space, 50, 723–732, 1998.

  40. Macmillan, S., A geomagnetic jerk for the early 1990’s, Earth Planet. Sci. Lett., 137, 189–192, 1996.

  41. Malin, S. R. C., Geomagnetic secular variation and its changes, 1942.5 to 1962.5, Geophys. J. R. Astron. Soc., 17, 415–441, 1969.

  42. Malin, S. R. C. and A. D. Clark, Geomagnetic secular variation, 1962.5 to 1967.5, Geophys. J. R. Astron. Soc., 36, 11–20, 1974.

  43. Malin, S.R. C. and B.M. Hodder, Was the 1970 geomagneticjerk of internal or external origin?, Nature, 296, 726–728, 1982.

  44. Malin, S. R. C., B. M. Hodder, and D. R. Barraclough, Geomagnetic secular variation: a jerk in 1970, in 75th Anniversary Volume of Ebro Observatory, edited by J. O. Cardús, pp. 239–256, Ebro Obs., Tarragona, Spain, 1983.

  45. McLeod, M. G., On the Geomagneticjerk of 1969, J. Geophys. Res., 90, 4597–4610, 1985.

  46. Morelli, A. and M. Dziewonski, Topography of the core-mantle boundary and lateral homogeneity of the liquid core, Nature, 325, 678–683, 1987.

  47. Pais, A., G. Hulot, M. Mandea Alexandrescu, Does the geomagnetic secular variation anticipate or correlate with decade length of day variations? (Abstract), IUGG Birmingham, 1999.

  48. Roberts, P. H. and S. Scott, On the analysis of the secular variation. 1. A hydromagnetic constraint: theory, J. Geomag. Geoelectr., 17, 137–151, 1965.

  49. Stewart, D. N. and K. Whaler, Geomagnetic disturbance fields: An analysis of observatory monthly means, Geophys. J. Int., 108, 215–223, 1992.

  50. Whaler, K. A., A new method for analysing geomagnetic impulses, Phys. Earth Planet. Inter., 48, 221–240, 1987.

Download references

Author information

Correspondence to Minh Le Huy.

Rights and permissions

Reprints and Permissions

About this article

Verify currency and authenticity via CrossMark

Cite this article

Le Huy, M., Mandea, M., Le Mouël, J. et al. Time evolution of the fluid flow at the top of the core. Geomagnetic jerks. Earth Planet Sp 52, 163–173 (2000) doi:10.1186/BF03351625

Download citation


  • Secular Variation
  • Core Surface
  • Antisymmetric Part
  • Core Mantle Boundary
  • Geomagnetic Jerk