Earth's magnetic field could form even with a fully liquid core

Earth's magnetic field could form even with a fully liquid core
by Robert Schreiber
Berlin, Germany (SPX) Aug 01, 2025

A team of geophysicists has demonstrated that Earth's magnetic field could have originated even before the planet's solid inner core formed. The new research from ETH Zurich and SUSTech, China, addresses a long-standing question in geoscience by using high-fidelity computer simulations to test conditions present over a billion years ago.

According to the well-established dynamo theory, the Earth's magnetic field is generated by convection currents in its liquid outer core. These currents, composed mainly of molten iron and nickel, are twisted by the planet's rotation into helical flows, which generate electric currents and thus magnetic fields. This theory, however, has left scientists wondering how the magnetic field existed when the Earth's core was entirely liquid, before the solid inner core crystallized roughly a billion years ago.

Using advanced computer modeling and high-performance calculations performed on the Piz Daint supercomputer in Lugano, the researchers showed that a magnetic field could indeed be generated under fully liquid core conditions. The team succeeded in simulating the early Earth's dynamo in a regime where the influence of core viscosity is negligible-something no prior study had achieved.

"Until now, no one has ever managed to perform such calculations under these correct physical conditions," said lead author Yufeng Lin.

"This finding helps us to better understand the history of the Earth's magnetic field and is useful in interpreting data from the geological past," added Andy Jackson, Professor of Geophysics at ETH Zurich.

These insights have implications beyond Earth's past. They provide a framework to study magnetic fields on other planets and stars, including gas giants like Jupiter and Saturn, as well as the Sun.

The study also underscores the importance of the magnetic field in supporting life and technology. Earth's magnetosphere protects the planet from cosmic radiation and solar wind and is crucial for satellite navigation and communication. Understanding its origins and evolution is key to forecasting future changes in the magnetic field, including the rapid movement of the magnetic north pole observed in recent decades.

Research Report:Invariance of dynamo action in an early-Earth model