Numerical dynamo models

We numerically study the generation and evolution of Earth's magnetic field which takes place in the liquid iron outer core. This geodynamo process supplies our planet with its shield against the solar wind. We use numerical simulations to investigate the physics of the geodynamo. Topics of interest include zonal flow generation, heat transport, Ohmic heating, magnetic saturation, anelasticity, stable stratification at the CMB, and anisotropy of the solid inner core related to Maxwell stresses at the ICB.

A subject of particular interest is the origin and mechanism underlying geomagnetic reversals. According to paleomagnetic data, reversals (when the north and south magnetic poles change hemisphere) occur on average 2-3 times per million years, though the time between reversals varies in an aperiodic manner. In comparison, the reversal event itself is fast. We are investigating the details of how such reversals occur.

We also use geodynamo models to gain insight into likely mechanisms of secular variation. These include zonal flows, hydromagnetic waves, flux expulsion and magnetic diffusion. We aim to test such mechanisms using improved time-dependent field models derived from geomagnetic observations.

We run our computer codes on ETH Zurich's new parallel cluster Gonzales and on the Cray XT3 at Swiss National Supercomputing Centre. The codes are continuously being expanded when we address new aspects of the geodynamo. At the moment we are also developing 2.5D models of the geodynamo.

People involved: Andrew Jackson, Chris Finlay,


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