Physics
Scientific paper
Apr 2002
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2002pepi..130..143h&link_type=abstract
Physics of the Earth and Planetary Interiors, Volume 130, Issue 3-4, p. 143-157.
Physics
14
Scientific paper
We present a detailed analysis of the Sint-800 virtual axial dipole moment (VADM) data in terms of an /αΩ mean field model of the geodynamo that features a non-steady generation of poloidal from toroidal magnetic field. The result is a variable excitation of the dipole mode and the overtones, and there are occasional dipole reversals. The model permits a theoretical evaluation of the statistical properties of the dipole mode. We show that the model correctly predicts the distribution of the VADM and the autocorrelation function inferred from the Sint-800 data. The autocorrelation technique allows us to determine the turbulent diffusion time τd=R2/β of the geodynamo. We find that τd is about 10-15kyr. The model is able to reproduce the observed secular variation of the dipole mode, and the mean time between successive dipole reversals. On the other hand, the duration of a reversal is a factor /~2 too long. This could be due to imperfections in the model or to unknown systematics in the Sint-800 data. The use of mean field theory is shown to be selfconsistent.
Hoyng Peter
Ossendrijver A. J. H. M.
Schmitt Denis
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