Hydrodynamic and magnetohydrodynamic computations inside a rotating sphere

The code lacks the resolution to probe high Reynolds numbers, but nevertheless interesting dynamo regimes turn out to be plentiful in those parts of parameter space in which the code is accurate. The key control parameters seem to be mechanical and magnetic Reynolds numbers, the Rossby and Ekman numbers (which in our computations are varied mostly by varying the rate of rotation of the sphere) and the amount of mechanical helicity injected.

Magnetic energy levels and magnetic dipole behaviour are exhibited which fluctuate strongly on a timescale of a few eddy turnover times. These seem to stabilize as the rotation rate is increased until the limit of the code resolution is reached.