J. Wicht
Institute of Geophysics, Georg-August-University, Goettingen, Germany
An issue of special interest for geodynamo modelling is the influence of the inner-core conductivity. It has been suggested that the finite magnetic diffusivity of the inner core prevents more frequent reversals of the Earth's magnetic field. We explore this possible influence by comparing convection-driven 3d dynamo simulations with insulating or conducting inner cores at various parameters. In order to gain conclusions of some statistical relevance we consider long runs of up to 100 magnetic diffusion times that undergo several reversals. Besides reversals we also examine excursions and try to estimate the typical length of both types of events. Reversal rates range from 1 to 6 per million year and excusions are slighly more frequent for a conducting as well as for an insulating inner core. The duration of excursions and reversals is of the order of 10 000 years with a minimum length of about 1000 years for both inner-core models. We conclude that the influence of inner-core conductivity on the time behaviour and in particular on reversals and excursions is only marginal for the dynamo model considered here.