Rotational dynamics of planetary cores: instabilities driven by precession, libration and tides

Abstract

In this chapter, we explore how gravitational interactions drive turbulent flows inside planetary cores and provide an interesting alternative to convection to explain dynamo action and magnetic fields around terrestrial bodies. In the first section, we introduce tidal interactions and their effects on the shape and rotation of astrophysical bodies. A method is given to derive the primary response of liquid interiors to these tidally-driven perturbations. In the second section, we detail the stability of this primary response and demonstrate that it is able to drive resonance of inertial waves. As the instability mechanism is introduced, we draw an analogy with the parametric amplification of a pendulum whose length is periodically varied. Lastly, we present recent results regarding this instability, in particular its non-linear saturation and its ability to drive dynamo action. We present how it has proved helpful to explain the magnetic field of the early Moon.

arXiv comment4th chapter of the book "Fluid Mechanics of Planets and Stars", 33 pages, 16 figures

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Cited by in corpus (5)

• Parallel finite volume simulation of the spherical shell dynamo with pseudo-vacuum magnetic boundary conditions
• Internal shear layers generated by a vertically oscillating cylinder in unbounded and bounded rotating fluids
• Symmetric instability in a Boussinesq fluid on a rotating planet
• Dancing rivulets in an air-filled Hele-Shaw cell
• The reflection-transmission problem for inertial waves on geostrophic shear layers