[SIT31-02] Anomalous is normal in planetary dynamos: A case of Mercury
Keywords:Mercury, dynamo, offset dipole, equatorial symmetry
Here we use numerical dynamo models to see why Mercury has such an anomalous magnetic field. In the model, convection is thermocompositionally-driven in the liquid core with a thermally stably stratified upper layer. The present models well produce the magnetic field similar to observations. The dynamo-generated magnetic fields force the flows via the Lorentz force to interact so as to break the equatorial symmetry. As a consequence, core flows have significantly north-south asymmetric helicity, resulting in the maintenance of the asymmetric magnetic field due to biased dynamo action. This symmetry breaking magnetic self-regulation causes the flow to generate and maintain the Mercury’s axially offset dipolar field. The result indicates that the Mercury’s anomalous magnetic field is a natural consequence of the dynamo mechanism in the core.