Modeling the Earth’s dynamo

For the past decade, three-dimensional time-dependent computer models have been used to predict and explain how the geomagnetic field is maintained by con-vection in the Earth’s fluid core. Geodynamo models have simulated magnetic fields that have surface structure and time dependence similar to the Earth’s field, includ-ing dipole reversals. However, no dynamo model has yet been run at the spatial res-olution required to simulate a broad spectrum of turbulence, which surely exists in the Earth’s fluid core. Two-dimensional simulations of magnetoconvection show how the structure and time dependence of even the large-scale features change dra-matically when the solution becomes strongly turbulent. Although these two-dimen-sional turbulent simulations lack the important effects of three-dimensional spherical geometry, based on their results one must question how geophysically realistic the large-scale dynamo mechanism is in current three-dimensional laminar simulations. Whatever the answer, we look forward to new discoveries from the next generation of turbulent dynamo models. 1. BASIC GEODYNAMO THEOR