  Orbital dynamics that lead to longitudinal libration of celestial bodies also
result in an elliptically deformed equatorial core-mantle boundary. The
non-axisymmetry of the boundary leads to a topographic coupling between the
assumed rigidmantle and the underlying low viscosity fluid.The present
experimental study investigates theeffect of non axisymmetric boundaries on the
zonal flow driven by longitudinal libration. For large enough equatorial
ellipticity, we report intermittent space-filling turbulence in particular
bands of resonant frequency correlated with larger amplitude zonal flow. The
mechanism underlying the intermittent turbulence has yet to be unambiguously
determined. Nevertheless, recent numerical simulations in triaxial and biaxial
ellipsoids suggest that it may be associated with the growth and collapse of an
elliptical instability (Cebron et al., 2012). Outside of the band of resonance,
we find that the background flow is laminar and the zonal flow becomes
independent of the geometry at first order, in agreement with a non linear
mechanism in the Ekman boundary layer (e.g. Calkins et al.; 2010, Sauret and Le
Dizes, 2012b).
