Not only iron, but also another metal is crucial for Earth’s magnetic field, scientists find

Not only iron, but also another metal is crucial to Earth’s magnetic field, according to a new study.

Earth’s iron core and the planet’s rotation creates a magnetic field but these alone cannot explain the effect in its entirety, scientists say. A team of researchers, led by Prof. Alessandro Toschi and Prof. Karsten Held from TU Wien and Prof. Giorgio Sangiovanni form Würzburg University has now published a new study in the journal “Nature Communications”, which argues that the theory of the geodynamo has to be revised in order to include another metal which is crucial to forming the Earth’s magnetic field.

Under their calculations, for the dynamo effect to be fully explained, the scientists have to take into account the fact that our planet’s core contains up to 20% nickel – a metal, which under extreme conditions behaves quite differently from iron.

In order to understand what metals due under the extreme conditions they are under, deep in our planet‘s core, scientists used computer simulations.

 “Under these extreme conditions, materials behave in a way which may be quite different from what we are used to”, says Karsten Held. “It is hardly possible to recreate these conditions in a lab, but with sophisticated computer simulations, we are able to calculate the behaviour of metals in the earth’s core on a quantum mechanical level.”

The Earth‘s core is hot as the sun and big as the moon and the heat stored has to escape. So the hot material rises to the outer layers of the globe, creating convection currents. At the same time, the planet’s rotation created strong Coriolis forces. The combination of these effects leads to a complicated spiralling flow of hot material, the scientists explain. But researchers had a hard time explaining how these convection currents emerge in the first place.

“If the earth’s core consisted only of iron, the free electrons in the iron could handle the heat transport by themselves, without the need for any convection currents”, says Karsten Held. “Then, earth would not have a magnetic field at all.”

This is where nickel comes in, according to the new study.

“Under pressure, nickel behaves differently from iron”, says Alessandro Toschi. “At high pressure, the electrons in nickel tend to scatter much more than the electrons in iron. As a consequence, the thermal conductivity of nickel and, thus, the thermal conductivity of the earth’s core is much lower than it would be in a core consisting only of iron.”

And the proportion of nickel is also important as it prevents the high-temperature of flowing towards the surface by motion of electrons alone and thus leads to the creation of convection currents.

To obtain these results, different metallic structures had to be analysed in large-scale computer simulations, and the behaviour of their electrons had to be calculated.

“Together with our colleagues from Würzburg, we did not only have a look at iron and nickel, but also at alloys of these two materials. We also had to take imperfections and irregularities into account, which made the computer simulations even more challenging”, says Karsten Held.

The new analysis helps scientists not only better understand Earth’s magnetic field but offers new insight into the electronic scattering processes in different materials and it could be applied in other fields of study like chemistry, biology, industry and technology.