A new energy budget for the Earth's core

Earth's magnetic field is generated by vigorous motion of the molten iron outer core, which twists and stretches magnetic field lines, a process that requires a significant amount of energy to maintain. The amount of available energy determines the behaviour of the molten iron (just like the behaviour of water in a heated pan depends on the temperature of the stove), which in turn dictates the strength and structure of the magnetic field. Recent work has shown that the energy available to power the molten iron into motion, and hence generate the magnetic field, is presently 2-3 times smaller than previously thought. This result requires drastic revisions to fundamental geophysical quantities such as the age of the inner core and the amount of heat flowing from the core to the overlying mantle. There is presently no coherent model of long term core and geomagnetic field behaviour.

To reestablish a basic theory that explains the long-term existence of the magnetic field requires a model that describes how the outer core has evolved over time and therefore arrived its present-day state. I have recently developed a new mathematical model of outer core evolution that alleviates the technical difficulties encountered by previous models. Over the next five years I will use this model to understand how the Earth has supported its magnetic field for the last 3.5 billion years, thereby providing fundamental new sight into the most remote and enigmatic region of our planet. I will use this information to make computer simulations of the Earth's outer core, which will establish the processes responsible for producing the complex magnetic field behaviour we observe and make predictions about future behaviour of the field including the evolution of the global field strength and patches of weak magnetic field.