Libration driven elliptical instability

TL;DR

This paper demonstrates that elliptical instability can be driven by libration, periodic oscillations of differential rotation, which may cause turbulence in planetary liquid cores and subsurface oceans.

Contribution

It provides the first numerical and experimental evidence that libration can induce elliptical instability, expanding understanding beyond constant differential rotation scenarios.

Findings

Libration-driven elliptical instability can generate turbulence.

Intermittent turbulence may occur in planetary liquid cores.

Evidence includes numerical simulations and experiments.

Abstract

The elliptical instability is a generic instability which takes place in any rotating flow whose streamlines are elliptically deformed. Up to now, it has been widely studied in the case of a constant, non-zero differential rotation between the fluid and the elliptical distortion with applications in turbulence, aeronautics, planetology and astrophysics. In this letter, we extend previous analytical studies and report the first numerical and experimental evidence that elliptical instability can also be driven by libration, i.e. periodic oscillations of the differential rotation between the fluid and the elliptical distortion, with a zero mean value. Our results suggest that intermittent, space-filling turbulence due to this instability can exist in the liquid cores and sub-surface oceans of so-called synchronized planets and moons.