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Scale model of Earth reveals clues about the planet’s magnetic field
Friday 01 November 2024
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Researchers at the Centre for Fluid and Complex Systems (FCS) used a scale model of the Earth’s liquid core to learn more about the formation of the planet’s magnetic field.
The magnetic field is important to life on Earth because it protects against harmful cosmic and solar radiation. It is formed by convection and the planet’s rotation, which generate an electric current in a layer of liquid iron that surrounds the solid core of the Earth.
For years, researchers have been trying to describe how this liquid flow sustains the planet's magnetic field, but experimental models usually ignore the fact that the magnetic field itself also influences the current. Alban Pothérat, Professor of Fluid Mechanics and FCS Centre Director, said:
There are some problems in astrophysics where the magnetic field does not influence the flow, but for planets the effects are comparable, so you can’t ignore the magnetic field.
Professor Alban Pothérat
Pothérat's research group explored how the magnetic field affects flow in the core using the Little Earth Experiment: a scale model of the Earth’s liquid core placed inside a large magnetic field at the European Magnetic Field Laboratory location in Grenoble, France.
The dome-shaped model represents one half of the core of the Earth, with a liquid layer surrounding a solid core. To represent the conductive properties of liquid iron, the dome was filled with sulphuric acid. Crucially, this is a transparent liquid, so that the flow movement inside the dome could be followed with cameras and mirrors while the system rotates around a vertical axis.
To infer flow patterns in the Earth, researchers often picture a cylinder that follows the width of the solid core along the planet's rotation axis. This cylinder divides flow patterns into two separate regions that don't interact. But in the Little Earth Experiment, Pothérat saw that the flow can cross this boundary. The same phenomenon has also previously been observed from satellite measurements of geomagnetic data and numerical simulations.
Professor Pothérat added:
We realized that the magnetic field breaks the constraint that separates these regions, so I went back to the drawing board and adjusted the theory to include the effect of the magnetic field. This is a big change in our understanding of these flows.
The results of this research, now published in Physical Review Letters, can be of interest to astrophysicists who study exoplanets, because the presence of a magnetic field might indicate the possibility of life.
Closer to home, studying the Earth’s magnetic field will help researchers understand what happens when it disappears, for example when the magnetic poles flip.
Professor Pothérat concluded:
It's very important to understand how it's generated, because it’s possible that the magnetic field could suddenly shut down, what makes it shut down is directly linked to what happens inside the core.
While these observations bring researchers a step closer to understanding magnetic field formation, the model will still need to be further refined to address fluctuations in the magnetic field and other factors.
Credit: Eva Amsen, Science Communicator and Writer: https://evaamsen.com/
This research was funded by the Leverhulme Trust. The Little Earth Experiment was developed by Kélig Aujogue, one of Pothérat’s former PhD students. His thesis on the development of this experimental setup was awarded the Royal Astronomical Society's Patricia Thompkins Prize.
