**Shigeo Kida**

Kyoto University, Japan

### Super-Rotation Flow in a Precessing Spherical Cavity

The flow inside a precessing spherical cavity exhibits
a variety of states, either steady, periodic, or chaotic, depending
on the spin and precession angular velocities.

Here we present our recent numerical study on the stability characteristics and structure of the flow in a precessing spherical cavity whose spin
and precession axes are orthogonal to each other. After discussing
the stability boundary of the steady states and the toral structure
of streamlines, we concentrate our attention on the super-rotation
flow. When both the Reynolds number and the Poincare number are
large, two different flow regions appear in the cavity, i.e. the
thin boundary layer and the inner region. The majority of the cavity
volume is occupied by the latter, and the flow there is almost uniform
along the precession axis (the Taylor-Proudman theorem holds) and
swirls around it nearly as a solid-body rotation. Interestingly enough,
this swirl flow is faster than the precession rotation. We consider
the generation mechanism of this super-rotation flow.