Abstract

The origin of the Earth’s magnetic field is an apparently simple, yet challenging problem. In terms of mathematical models, dynamo action in a rotating spherical domain is the now well established model to account for the magnetic field of planets and stars. Whereas the relevant equations are easily written, the parameters regime relevant to the Earth’s core is so extreme that a numerical solution with these parameters is out of reach of today’s largest computers. This raises the daunting question of the relevance of today’s state-of-the-art numerical models to the mechanisms at work within our planet. Several issues, on which researchers often disagree, naturally follow: What can we learn by comparing models with observations? Can we test numerical models against theoretical results? Can the relevant forces balance in the Earth’s core be approached in numerical models? Could the unresolved small scale and rapidly varying flow be important? In this talk, I will try to place the emphasis on open and controversial issues.