Issue
EPL
Volume 83, Number 4, August 2008
Article Number 49001
Number of page(s) 6
Section Geophysics, Astronomy and Astrophysics
DOI http://dx.doi.org/10.1209/0295-5075/83/49001
Published online 09 July 2008
EPL, 83 (2008) 49001
DOI: 10.1209/0295-5075/83/49001

The geodynamo as a low-dimensional deterministic system at the edge of chaos

D. A. Ryan and G. R. Sarson

School of Mathematics and Statistics, Newcastle University - Newcastle upon Tyne, NE1 7RU, UK, EU

g.r.sarson@ncl.ac.uk

received 28 June 2008; accepted in final form 1 July 2008; published August 2008
published online 9 July 2008

Abstract
We perform non-linear time series analysis tests on the SINT 2000 paleomagnetic record of the Earth's virtual axial dipole moment for the past 2 Ma, and find evidence of low-dimensional deterministic chaos. We reconstruct the phase space attractor using embedded time delay vectors, and compare the result with reconstructions from time series of a turbulent mean-field dynamo model, which exhibits a similar attractor structure. Considered alongside evidence of 1/f noise and lognormality in the paleomagnetic record, this suggests an important role for multiplicative noise, which may maintain the dynamo at the edge of chaos. In contrast to characterisations of geomagnetic reversals as stochastic processes, this work supports their interpretation as the outcome of a deterministic dynamical system.

PACS
91.25.Cw - Origins and models of the magnetic field; dynamo theories.
05.45.Ac - Low-dimensional chaos.
05.45.Tp - Time series analysis.

© EPLA 2008