Unraveling the coil of Earth’s magnetic core

Japanese researchers reporting in this week’s Nature have used one of the fastest supercomputers in the world, the Earth Simulator, to numerically model the ‘geodynamo’ that generates the Earth’s magnetic field. The simulation is the closest yet to the real thing and reveals a new twist for our understanding of magnetism of the Earth.

The Earth’s magnetic field is created through strong electrical currents generated by a dynamo process within its liquid, iron-rich outer core. Scientists have previously modeled this outer core to show these convections as columnar cell structures. Further modeling was hampered by the inability of computers to handle the extremely large and small numbers required to simulate parameters, particularly those associated with the viscosity of the fluid core.

To overcome this limitation, Akira Kageyama and colleagues from the Japan Agency for Marine-Earth Science and Technology in Yokohama used 4,096 processors at the Earth Simulator to generate high-resolution computer simulations of how this flow field is organized.

The team’s simulations show that both the convection flow and magnetic field structures are qualitatively different from the columnar form found in earlier lower-resolution simulations. Instead the convection takes the form of thin sheets radiating out from Earth’s axis — which explains some, but not all, aspects of Earth’s magnetic field.

“Kageyama et al. have penetrated territory previously inaccessible to simulation,” notes Ulrich R. Christensen of the Max Planck Institute for Solar System, Germany, in a related ‘News and Views’ article. Christensen also suggests that a full understanding of the Earth’s dipolar geometry is still a long way off, saying: “The next step will be even more demanding: scouting this new terrain to identify the true path through parameter space to understanding.”