The influence of magnetic fields in planetary dynamo models

Soderlund, K. M.; King, E. M.; Aurnou, J. M.

doi:10.1016/j.epsl.2012.03.038

Cited by 107 publications

(182 citation statements)

References 55 publications

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“…The data appears to deviate away from the steep scaling law near to where rotating convection columns lose their strong axial coherence. This is relevant to our understanding of present-day (E ∼ 10 −4 ) planetary dynamo models because Earth-like dipolar dynamo action has been shown to fail in the vicinity of the heat transfer transition in these models , where rotating convection columns also lose their axial coherency (Soderlund et al 2012). Thus, we hypothesize that the heat transfer transition in our extreme rotating convection data will provide a proxy for behavioural transitions in more extreme dynamo models.…”

Section: O M Pa R I N G R E G I M E T R a N S I T I O N H Y P O T Hmentioning

confidence: 99%

“…In fact, typical E ∼ 10 −4 models cannot generate Earth-like magnetic fields without the presence of axially coherent columns (e.g. Sreenivasan & Jones 2006b;Christensen 2010;Miyagoshi et al 2010;Soderlund et al 2012Soderlund et al , 2013.…”

Section: Rotating Convectionmentioning

confidence: 99%

“…We hypothesize then that rotating convection and dynamo studies, carried out at sufficiently extreme parameter values, will also be able to access theoretically predicted regimes of behaviour (e.g. Soderlund et al 2012). In particular, asymptotically reduced rotating convection models by Julien et al (2012a) predict distinct heat transfer scalings corresponding to each of the regimes visualized in Figs 3(b)-(d).…”

Section: Rotating Convectionmentioning

confidence: 99%

“…Over 10 orders of magnitude larger than estimates for Earth's core, the viscous diffusion in current numerical dynamo models ultimately removes all but the largest scale motions in the system (e.g. Soderlund et al 2012). Small-scale turbulence and turbulent fluxes between large-and small-scale processes cannot exist in these models (cf.…”

Section: Introductionmentioning

confidence: 99%

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Laboratory-numerical models of rapidly rotating convection in planetary cores

Cheng

Stellmach

Ribeiro

et al. 2015

Geophysical Journal International

116

203

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Section: O M Pa R I N G R E G I M E T R a N S I T I O N H Y P O T Hmentioning

confidence: 99%

Section: Rotating Convectionmentioning

confidence: 99%

Section: Rotating Convectionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Laboratory-numerical models of rapidly rotating convection in planetary cores

Cheng

Stellmach

Ribeiro

et al. 2015

Geophysical Journal International

116

203

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“…In dynamos, which tend to exhibit significant temporal variability, it is more appropriate to approximate the current density using Ampere's law under the MHD approximation, J ∼ B/μ o B where B is the characteristic length scale of magnetic field variations (e.g., Cardin et al 2002;Soderlund et al 2012). In this dynamic case, Eq.…”

Section: Introductionmentioning

confidence: 99%

The competition between Lorentz and Coriolis forces in planetary dynamos

Soderlund

Sheyko

King

et al. 2015

Prog. in Earth and Planet. Sci.

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Fluid motions within planetary cores generate magnetic fields through dynamo action. These core processes are driven by thermo-compositional convection subject to the competing influences of rotation, which tends to organize the flow into axial columns, and the Lorentz force, which tends to inhibit the relative movement of the magnetic field and the fluid. It is often argued that these forces are predominant and approximately equal in planetary cores; we test this hypothesis using a suite of numerical geodynamo models to calculate the Lorentz to Coriolis force ratio directly. Our results show that this ratio can be estimated by * d i Rm −1/2 ( i is the traditionally defined Elsasser number for imposed magnetic fields and Rm is the system-scale ratio of magnetic induction to magnetic diffusion). Best estimates of core flow speeds and magnetic field strengths predict the geodynamo to be in magnetostrophic balance where the Lorentz and Coriolis forces are comparable. The Lorentz force may also be significant, i.e., within an order of magnitude of the Coriolis force, in the Jovian interior. In contrast, the Lorentz force is likely to be relatively weak in the cores of Saturn, Uranus, Neptune, Ganymede, and Mercury.

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Multiscale convection in a geodynamo simulation with uniform heat flux along the outer boundary

Matsui

King

Buffett

2014

Geochem Geophys Geosyst

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It is generally expected that Earth's magnetic field, which is generated by convecting liquid metal within its core, will substantially alter that convection through the action of Lorentz forces. In most dynamo simulations, however, Lorentz forces do very little to change convective flow, which is predominantly fine-scaled. An important exception to this observation is in dynamo models that employ uniform heat flux boundary conditions, rather than the usual uniform temperature conditions, in which multiscale convection is observed. We investigate the combined influence of thermal boundary conditions and magnetic fields using four simulations: two dynamos and two nonmagnetic models, with either uniform temperature or heat flux fixed at the outer boundary. Of the four, only the fixed-heat-flux dynamo simulation produces multiscale convective flow patterns. Comparison between the models suggests that the fixed-flux dynamo generates large patches of strong azimuthal magnetic field that suppress small-scale convective motions. By allowing temperature to vary along the outer boundary, the fixed-flux dynamo generates stronger azimuthal flow and, in turn, stronger magnetic field, and the resulting Lorentz forces alter the nature of convective flow. Extrapolation of the analyses presented here suggests that magnetic fields may also suppress small-scale convection in the Earth's core.

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The influence of magnetic fields in planetary dynamo models

Cited by 107 publications

References 55 publications

Laboratory-numerical models of rapidly rotating convection in planetary cores

Laboratory-numerical models of rapidly rotating convection in planetary cores

The competition between Lorentz and Coriolis forces in planetary dynamos

Multiscale convection in a geodynamo simulation with uniform heat flux along the outer boundary

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