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Tide‐driven shear instability in planetary liquid cores
Author(s) -
Sauret Alban,
Le Bars Michael,
Le Gal Patrice
Publication year - 2014
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1002/2014gl061434
Subject(s) - instability , physics , mechanics , turbulence , rotational symmetry , shear (geology) , classical mechanics , jet (fluid) , nonlinear system , forcing (mathematics) , geology , atmospheric sciences , petrology , quantum mechanics
We present an experimental study on the shear instability driven by tidal forcing in a model planetary liquid core. The experimental setup consists of a water‐filled deformable sphere rotating around its axis and subjected to an elliptical forcing. At resonant forcing frequencies, the nonlinear self‐interaction of the excited inertial mode drives an intense and localized axisymmetric jet. The jet becomes unstable at low Ekman number because of a shear instability. Using particle image velocimetry measurements, we derive a semiempirical scaling law that captures the instability threshold of the shear instability. This mechanism is fully relevant to planetary systems, where it constitutes a new route to generate turbulence in their liquid cores.