Constraining the geodynamo by sequences of field reversals

Using a spherically symmetric mean field dynamo model with a quenched helical turbulence parameter alpha under the influence of noise and external periodic forcing we try to constrain its essential parameters by typical features of field reversal. Our results indicate that the geodynamo works in a highly supercritical state, that the relative strength of the periodic forcing due to the Milankovic cycle of the Earth’s orbit eccentricity is approximately 15 per cent of the general dynamo strength, and that the magnetic diffusion time is significantly reduced in comparison with the diffusion time resulting from the molecular conductivity.