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 convection 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, including dipole reversals. However, no dynamo model has yet been run at the spatial resolution 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 dramatically when the solution becomes strongly turbulent. Although these two-dimensional 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.