The Combined Effect of Precession and Convection on the Dynamo Action

Wei, Xing

doi:10.3847/0004-637x/827/2/123

Cited by 8 publications

(5 citation statements)

References 31 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Obviously, as for even the most recent convectively driven dynamos (see, e.g., Schaeffer et al, 2017), the dimensionless parameters of our simulations, like the Reynolds and the Ekman numbers, remain far from the planetary ones: turbulence and dynamo thresholds have thus been reached by artificially increasing the amplitude of the mechanical forcings and of the magnetic Prandtl number, respectively. Note in particular that while the models of convectively driven and mechanically driven dynamos are often presented as antithetical, they could actually coexist and even collaborate to produce planetary magnetism (Wei, 2016), a behavior up to now largely unexplored. But we want to stress the following three points.…”

Section: Resultsmentioning

confidence: 99%

“…Finally, the results presented here are expected to open new horizons and stimulate additional studies, that we hope will lead to rapid progress in our understanding of those mechanically-driven dynamos. Note in particular that while the models of convectivelydriven and mechanically-driven dynamos are often presented as antithetical, they could actually co-exist and even collaborate to produce planetary magnetism [Wei , 2016], a behavior up to now largely unexplored.…”

Section: Discussionmentioning

confidence: 99%

See 1 more Smart Citation

Turbulent Kinematic Dynamos in Ellipsoids Driven by Mechanical Forcing

Reddy

Favier

Bars

2018

Geophysical Research Letters

View full text Add to dashboard Cite

Dynamo action in planetary cores has been extensively studied in the context of convectively driven flows. We show in this letter that mechanical forcings, namely, tides, libration, and precession, are also able to kinematically sustain a magnetic field against ohmic diffusion. Previous attempts published in the literature focused on the laminar response or considered idealized spherical configurations. In contrast, we focus here on the developed turbulent regime and we self‐consistently solve the magnetohydrodynamic equations in an ellipsoidal container. Our results open new avenues of research in dynamo theory where both convection and mechanical forcing can play a role, independently or simultaneously.

show abstract

Section: Resultsmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Turbulent Kinematic Dynamos in Ellipsoids Driven by Mechanical Forcing

Reddy

Favier

Bars

2018

Geophysical Research Letters

View full text Add to dashboard Cite

show abstract

“…Evidence is also given here for precession energy contributing to driving the dynamo. Finally, a model based upon the combined effect of convection and precession, as the energy source of the geodynamo has already been proposed and suggests that neither source is adequate to drive the geodynamo alone [4].…”

Section: Introductionmentioning

confidence: 99%

Evidence for a Geodynamo Driven by Thermal Energy in the Outermost Core and by Precession Deeper in the Outer Core

D¹

2017

Int J Earth Sci Geophys

View full text Add to dashboard Cite

VGP (Virtual Geomagnetic Pole) paths during reversals are preferentially located in roughly north south circum-Pacific arcs, where the temperature of the mantle at the core mantle boundary is lowest. This indicates that the movement of magnetic flux concentrations in the outermost core responds to thermal constraints during the reversal. Hence thermal energy plays a role in driving the geodynamo. The preponderance of the occurrence of reversals when the obliquity is lower than the average within the last 5 Ma and their preferential onset during the decreasing half of the obliquity cycle provide evidence for a role of precession in driving the dynamo. The geodynamo therefore appears to involve a combination of thermal and precessional energy. A reversal with its decay of the dipole intensity by almost an order of magnitude, the polarity switch, and regrowth of the new axial dipole involves an intermediate equatorial field source, whose polarity also switches with the axial dipole. The whole reversal process for each of the last two reversals falls within approximately one obliquity cycle of 41,000 years and the polarity switch is close to the midpoint of the cycle.

show abstract

“…They found that a stable stratification suppresses possible precessional instabilities, whereas an unstable stratification can lead to both stabilization and destabilization, depending on the parameters. This approach was later extended to the hydromagnetic case in Wei (2016), where it was shown that dynamos with a combined forcing are possible even when one forcing by itself leads to a failed dynamo. Here, we consider a non-uniform temperature stratification that is imposed by the temperature boundary conditions and we neglect the magnetic field.…”

Section: Introductionmentioning

confidence: 99%