Turbulent 3D MHD dynamo model in spherical shells: Regular oscillations of the dipolar field
arXiv:1102.1092
Abstract
We report the results of three-dimensional numerical simulations of convection-driven dynamos in relatively thin rotating spherical shells that show a transition from an strong non-oscillatory dipolar magnetic field to a weaker regularly oscillating dipolar field. The transition is induced primarily by the effects a stress-free boundary condition. The variation of the inner to outer radius ratio is found to have a less important effect.
http://www.stanford.edu/group/ctr/Summer/SP10/index.html