Numerische Simulationen des Geodynamos mit thermo-chemischem Antrieb

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Fluid motions in the Earth’s liquid core driving a dynamo are thought to be the main source for its internal magnetic field. The liquid outer core is assumed to be composed of a mixture of predominantly iron and nickel and a small fraction of lighter elements (e.g. sulphur, oxygen or silicon). Two potential sources are available for driving convection and thereby the dynamo in the liquid outer core: density variations due to temperature and due to compositional differences inducing buoyancy. Temperature differences result from secular cooling of the planet. Once the planet has cooled enough to grow a solid inner core the latent heat being released in the solidification process provides another source for thermal convection. The additional compositional differences arise from light elements being released from the solidifying material at the inner core boundary. So far, Geodynamo simulations do not take into account the effects that may arise from the presence of two buoyancy sources with significantly different diffusion time scales. For this reason the aim of this proposal is to study thermo-chemically driven dynamos in rotating spherical shells by means of a numerical model. By considering different thermal to chemical forcing ratios we hope to get a better general understanding of magnetic field generation within the Earth’s core and the spatio-temporal behavior of the Geodynamo.