Tuning of the Mean-Field Geodynamo Model

摘要

Parker's two-dimensional (2D) dynamo model with an algebraic form of nonlinearity for the a-effect is considered. The model uses geostrophic distributions for the a-effect and differential rotation, which are derived from the three-dimensional (3D) convection models. The resulting configurations of the magnetic field in the liquid core are close to the solutions in Braginsky's Z-model. The implications of the degree of geostrophy observed in the 3D dynamo models for the behavior of the mean magnetic field are explored. It is shown that the reduction in geostrophy leads to magnetic field reversals accompanied by the relative growth of the nondipole component of the field on the surface of the liquid core. The simulations with a random a-effect which causes turbulent pulsations are carried out. The approach is capable of producing realistic sequences of magnetic reversals.