Dynamos generated by wave turbulence and mechanical forcing

Rotating fluids subject to tidal deformation are prone to elliptical instability due to the the resonance of two inertial waves with the (elliptically strained) base flow. Upon saturation, the resulting turbulent state consists of interacting inertial waves and geostrophic vortices. When both the amplitude of the tide and the fluid viscosity are weak, a limit which is relevant for planetary interiors, recent results @Fludyco suggest the existence of a flow regime dominated by inertial waves turbulence.

The first question is : Is this flow regime a fertile ground for a dynamo ? Theoretical studies showed that random inertial waves in a rotating fluid could lead to dynamo action. Our first task is to check if this mechanism can be reproduced numerically, and then characterize the suitable conditions to start a dynamo. To that end, a parameter study is performed using local numerical models solving the induction equation in a periodic box.

The second question is whether these suitable conditions can be satisfied by a mechanically forced flow and how does it affect the dynamo efficiency ? The properties of the resulting fields can then be identified.

The last question is what are the limitations of this mechanism ? This is a crucial point as it would reveal if it can be applied to astrophysical bodies.

Local direct numerical simulations have been performed in a shearing box using the 3D spectral code SNOOPY, developed by Geoffroy Lesur (IPAG, Grenoble) and adapted by Adrian Barker (University of Leeds, UK) for the study of the elliptical instability.

Right: Axial component of a magnetic field sustained by inertial waves turbulence, using the SNOOPY code.