An analysis of the fluctuations of the geomagnetic dipole

K. Brendel, J. Kuipers, G. T. Barkema, P. Hoyng*

*Corresponding author for this work

Research output: Contribution to journalArticleAcademicpeer-review

Abstract

The time evolution of the strength of the Earth's virtual axial dipole moment (VADM) is analyzed by relating it to the Fokker-Planck equation, which describes a random walk with VADM-dependent drift and diffusion coefficients. We demonstrate first that our method is able to retrieve the correct shape of the drift and diffusion coefficients from a time series generated by a test model. Analysis of the Sint-2000 data shows that the geomagnetic dipole mode has a linear growth time of 20(-7)(+13) kyear, and that the nonlinear quenching of the growth rate follows a quadratic function of the type [1 - (x/x(0))(2)]. On theoretical grounds, the diffusive motion of the VADM is expected to be driven by multiplicative noise, and the corresponding diffusion coefficient to scale quadratically with dipole strength. However, analysis of the Sint-2000 VADM data reveals a diffusion which depends only very weakly on the dipole strength. This may indicate that the magnetic field quenches the amplitude of the turbulent velocity in the Earth's outer core. (C) 2007 Elsevier B.V. All rights reserved.

Original languageEnglish
Pages (from-to)249-255
Number of pages7
JournalPhysics of the Earth and Planetary Interiors
Volume162
Issue number3-4
DOIs
Publication statusPublished - 16 Jul 2007

Keywords

  • geodynamo
  • reversals
  • secular variation
  • sint-2000 record
  • turbulent convection
  • stochastic processes
  • MAGNETIC-FIELD
  • SIMULATION
  • REVERSAL

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