ABSTRACT
Traditional linearized theory of contained, rotating, homogeneous fluids ignored phenomena with Rossby number, ε<<1, for E→0 where E=v/ΩL2 is the Ekman number defined in terms of v, the fluid’s kinematic viscosity, Ω, its rotation speed and L, its length scale. We are reminded of the error produced by this assumption when we see the onset of a parametric instability, even when the Rossby number, ε≈E1/2. This inertial instability provides a mechanism to produce very long time-scale response from a shortperiod perturbation. If one ignores the possibility of an instability, a class of possible explanations of an observed phenomena will be overlooked: this is precisely why some of the early experiments in precession were incompletely interpreted and part of the basis for rejecting precession as a way to maintain the geodynamo.
