Unravelling earth’s magnetic history and processes
We wish to understand how magnetic fields are generated in the cores of planets. This process is called the dynamo mechanism, whose understanding remains one of the geophysical grand challenges. In cores of rocky planets and in gas giants, thermal forcing results in convection and the resulting flow of liquid metal transports heat and generates magnetic fields as a result of the electrical currents that are induced by their motion. Magnetic field generation affects heat transport and cooling, controlling planetary history and evolution (on Earth it is connected with the growth of the inner core); and ultimately the presence or not of magnetic fields can control the existence of life. To understand the process, the momentum, induction and heat equations must be solved in three dimensions as a function of time in a spherical geometry and linked to the numerous extant data sets that are available. Present-day computer simulations do this by implementing fluid viscosities that are too large by many orders of magnitude. Our aim is to correct this by creating a working computer code that correctly implements a novel theory for the dynamo process in which viscosity and inertia have negligible effects, as is correct for the planets. These dynamos are likely to be different from any previous computational dynamo presented over the last 25 years. The potential rewards of such a correct theory and implementation will be great. We will understand how self-sustained dynamos equilibrate in this never-explored regime, and discover strengths and geometries of generated magnetic fields as a function of forcing. We will discover how to find reversing dynamos, just like on Earth, and understand the mechanisms at play. We will understand the energy requirements, ultimately understand core cooling and also be able to make more accurate predictions of future field evolution. We also aim to understand the new data returning from missions to the giant planets.