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Does nickel drive Earth’s magnetic field?

13 Jul 2017 Hamish Johnston
Deep thinkers: Giorgio Sangiovanni, Michael Karolak and Andreas Hausoel

A theoretical study of nickel at high temperatures and high pressures suggests that the metal could play a crucial role in generating the Earth’s magnetic field. That’s the conclusion of Giorgio Sangiovanni of the University of Würzburg and an international team, which has done calculations suggesting that the thermal conductivity of nickel is much lower than that of iron under these extreme conditions.

The geodynamo model says that the Earth’s magnetic field is created by the flow of liquid iron in the outer core of the Earth. This flow is driven by the convection of heat from the inner core to the mantle. A problem with this model is that the thermal conductivity of iron is predicted to be very high at the relevant pressures and temperatures – and this means that convection should not occur.

Crystal structure

Compared to some other metals, iron and nickel are relatively poor thermal conductors under ambient conditions. At high pressures and temperatures, however, the crystal structure of iron is expected to change – resulting in a large increase in its thermal conductivity. By performing calculations at Germany’s Leibniz Supercomputing Centre, Sangiovanni and colleagues have shown that nickel is likely to retain its crystal structure – and poor thermal conductivity – at high pressures and temperatures.

Writing in Nature Communications, the team suggests that further research is needed into the possible contributions of nickel and iron/nickel alloys to the convection that is believed to be driving the Earth’s magnetic field.

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