 Simulating the geodynamo requires numerically solving a set of nonlinear partial differential equations for the magnetohydrodynamics (MHD) of the Earth's interior.Simulation of the MHD equations is performed on a 3D grid of points and the fineness of the grid, which in part determines the realism of the solutions, is limited mainly by computer power.For decades, theorists were confined to creating "kinematic dynamo" computer models in which the fluid motion is chosen in advance and the effect on the magnetic field calculated.