The role of the Earth's mantle in controlling the frequency of geomagnetic reversals

Glatzmaier, Gary A.; Coe, Robert S.; Hongre, Lionel; Roberts, Paul

doi:10.1038/44776

Cited by 543 publications

(433 citation statements)

References 45 publications

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“…The fact that they can also undergo reversals was seen as a final prove for their validity (Glatzmaier and Roberts 1995b). Since then, the models have been refined to replicate more and more features of the geomagnetic field and to provide an explanation for the observations.…”

Section: Resultsmentioning

confidence: 99%

Theory and Modeling of Planetary Dynamos

Wicht

Tilgner

2010

Space Sci Rev

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Numerical dynamo models are increasingly successful in modeling many features of the geomagnetic field. Moreover, they have proven to be a useful tool for understanding how the observations connect to the dynamo mechanism. More recently, dynamo simulations have also ventured to explain the surprising diversity of planetary fields found in our solar system. Here, we describe the underlying model equations, concentrating on the Boussinesq approximations, briefly discuss the numerical methods, and give an overview of existing model variations. We explain how the solutions depend on the model parameters and introduce the primary dynamo regimes. Of particular interest is the dependence on the Ekman number which is many orders of magnitude too large in the models for numerical reasons. We show that a minor change in the solution seems to happen at E = 3×10 −6 whose significance, however, needs to be explored in the future. We also review three topics that have been a focus of recent research: field reversal mechanisms, torsional oscillations, and the influence of Earth's thermal mantle structure on the dynamo. Finally we discuss the possibility of tidally or precession driven planetary dynamos.

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Section: Resultsmentioning

confidence: 99%

Theory and Modeling of Planetary Dynamos

Wicht

Tilgner

2010

Space Sci Rev

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“…Heat ®ux absorbed by the mantle will be a function of the spherical polar coordinates and , which is determined mainly by the dynamics of mantle convection (Zhang & Gubbins 1993;Olson & Glatzmaier 1995), and this can a¬ect dynamo action (Sarson et al . 1997a;Glatzmaier et al . 1999).…”

Section: Introductionmentioning

confidence: 99%

“…Very signi cant progress has been achieved; models constructed from solutions of the Navier{Stokes and Maxwell equations can now be sensibly compared with geophysical observations of the actual geomagnetic eld. Results obtained from palaeomagnetic data, such as the nature of the reversals of the main eld, can also be modelled directly from the fundamental equations (Sarson & Jones 1999;Glatzmaier et al . 1999).…”

Section: Introductionmentioning

confidence: 99%

Convection–driven geodynamo models

Jones

2000

Philosophical Transactions of the Royal Society of London. Seri

125

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There has been signi cant progress in the development of numerical geodynamo models over the last ve years. Advances in computer technology have made it possible to perform three-dimensional simulations, with thermal or compositional convection as the driving mechanism. These numerical simulations give reasonable results for the morphology and strength of the eld at the core{mantle boundary, and the models are also capable of giving reversals and excursions which can be compared with palaeomagnetic observations; they also predict di¬erential rotation between the inner core and the mantle.However, there are still a number of fundamental problems associated with the simulations, which are proving hard to overcome. Despite the advances in computing power, the models are still expensive and take a long time to run. This problem may diminish as faster machines become available, and new numerical methods exploit parallelization e¬ectively, but currently there are no practical schemes available which work at low Ekman number.Even with turbulent values of the di¬usivities (and the question of whether isotropic di¬usivities are appropriate is still unresolved), the appropriate dynamical regime has not yet been reached. In consequence, modelling assumptions about the nature of the ®ow near the boundaries have to be made, and di¬erent choices can have profound e¬ects on the dynamics. The nature of large-scale magnetoconvection at small E is still not well understood, and until we have more understanding of this issue, it will be di¯cult to have a great deal of con dence in the predictions of the numerical models.

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“…These correlations are controversial (Dormy et al, 2000) but a single theory can explain all the above features. Several geodynamo computer simulations have incorporated lower mantle seismic shear wave velocity as a proxy for heat flux out of the core (Glatzmaier et al, 1999;Bloxham, 2000a,b;Olson & Christensen, 2002;Christensen & Olson, 2003;Aubert et al, 2007) but the generated fields have fluctuated too rapidly in time to allow a straightforward correlation with the observed geomagnetic field. Correlating the radial component of magnetic field, B r , with the shear wave velocity of the lower mantle is suggestive (Gubbins, 2003) but circumstantial because it does not compare like with like: here we report a more meaningful comparison between two magnetic fields, the observed geomagnetic field and a nearly stationary magnetic field calculated from a geodynamo model incorporating the seismic velocity map in the boundary condition.…”

mentioning

confidence: 99%