Strong field dynamo action in rapidly rotating convection with no inertia

Abstract

The Earth's magnetic field is generated by dynamo action driven by convection in the outer core. For numerical reasons, inertial and viscous forces play an important role in geodynamo models; however, the primary dynamical balance in the Earth's core is believed to be between buoyancy, Coriolis and magnetic forces. The hope has been that by setting the Ekman number to be as small as computationally feasible, an asymptotic regime would be reached in which the correct force balance is achieved. However, recent analyses of geodynamo models suggest that the desired balance has still not yet been attained. Here we adopt a complementary approach consisting of a model of rapidly rotating convection in which inertial forces are neglected from the outset. Within this framework we are able to construct a new branch of solutions in which the dynamo generates a strong magnetic field that satisfies the expected force balance. The resulting strongly magnetized convection is dramatically different to the corresponding solutions in which the field is weak.

Published in Physical Review E (Rapid Communications)

Cited by in corpus (9)

• Dynamo theories
• The Turbulent Dynamo
• Approaching a realistic force balance in geodynamo simulations
• Three Branches of Dynamo Action
• Rossby and Magnetic Prandtl Number Scaling of Stellar Dynamos
• Large-scale-vortex dynamos in planar rotating convection
• Inertia-less convectively-driven dynamo models in the limit of low Rossby number and large Prandtl number
• Asymptotic behaviour of rotating convection-driven dynamos in the plane layer geometry
• Dynamo saturation down to vanishing viscosity: strong-field and inertial scaling regimes