Phys. Earth Planet. Inter. (2014)

Over Earth's history, the geomagnetic field has intermittently reversed direction, so that the positions of the magnetic north and magnetic south poles swap. Numerical simulations of Earth's dynamo — the driver of the magnetic field — suggest that the frequency of these magnetic reversals is linked to convection in the lower mantle.

Peter Olson at Johns Hopkins University, USA, and Hagay Amit at the University of Nantes, France, use calculations to assess how the turbulent movements in Earth's liquid outer core that power the dynamo are affected by the flux of heat across the boundary between the core and mantle. They use seismic images of the present-day lower mantle, which identify patches of warmer and cooler mantle, to constrain the pattern of heat flux across the core–mantle boundary. The researchers find that when the transfer of heat across the boundary is high and heterogeneous, convection in the outer core becomes very turbulent, causing the magnetic field to destabilize and reverse more frequently.

Because the heat flux at the core–mantle boundary is regulated by convection in the mantle, reversals of Earth's magnetic field must also be linked to changes in the vigour and pattern of mantle convection.