Tiny magnetic waves detected in the Earth’s core could help elucidate what’s going on inside our planet.
The Earth’s core has a solid inner layer and an outer layer of liquid metal. The temperature difference between the hot centre and the cooler exterior layer creates convection currents in the liquid, and the movement of charged particles in the metal produced the planet’s magnetic field.
The motion is turbulent & chaotic, and but the magnetic field varies over time. Nicolas Gillet of the University of Grenoble Alpes and his colleagues observed the earth’s magnetic field between 1999 and 2021 using data from satellites and ground-based observatories.
The team found that the magnetic field fluctuated regularly around the core’s equatorial region. These fluctuations repeat every seven years and move west around the equator at speeds of about 1,500 kilometers per year.
“What’s important to know that the magnetic field in the core evolves on very long time-scales,” says Gillet. “And what we witnessed is just small wiggles on top of this.”
Although they’re relatively small, studying these waves may help to improve our understanding of the inner workings of the Earth.
Whether there’s a thin layer of rock between the outer core and the overlying mantle that might be responsible for changes in the magnetic field has been debated, says Gillet, but these findings suggest that layer isn’t necessary.
The team even believes that it is possible to image the geo-magnetic field in depth at the core with the newly discovered waves and predict the future evolution of the field.
“It is fascinating that by recording the Earth’s magnetic field with satellites, we can be able to images of what is going on greater than 3,000 metres below our feet,” says Gillet.
“This study is a mind-blowing advance in our understanding of how the Earth’s magnetic field works on timescales of less than a decade,” says Chris Finlay of the Technical University of Denmark. “Much longer time series that require continuous observations of the Earth’s magnetic field from space. In the decades to come, they will be essential to fully test this new model and realize their potential for exploring the depths of the earth.”
The findings are published in the journal of PNAS.
