New magnetic wave type found in Earth’s core
Scientists have detected a completely new type of magnetic wave that surges through Earth’s outer core every seven years, warping the strength of our planet’s magnetic field. Dubbed ‘Magneto-coriolis waves’ because they move along Earth’s axis of rotation per the Coriolis effect, they creep from east to west in columns that can travel up to 930 miles per year. Using a fleet of European Space Agency (ESA) satellites, a team pinpointed the mysterious waves to the outermost layer of Earth’s liquid outer core, roughly 1,800 miles below the planet’s surface.
The existence of these waves could help explain mysterious fluctuations in the planet’s magnetic field, which is generated by the movement of liquid iron in the planet’s outer core. Satellite measurements of the magnetic field taken over the last 20 years show that the field’s strength dips every seven years or so, coinciding with the oscillations of these newfound waves. “Geophysicists have long theorised over the existence of such waves, but they were thought to take place over much longer timescales,” said Nicolas Gillet, a researcher at Université Grenoble Alpes in France. “Our research suggests that other such waves are likely to exist – probably with longer periods – but their discovery relies on more research.”
Earth’s outer core is an orb of molten iron that churns with constant motion. The flow of
this rotating, electrically conducting fluid is thought to be the source of Earth’s magnetic field. The planet’s magnetic field is always changing, both on short and long-term timescales. Long-term, the magnetic field has been gradually weakening for hundreds of years. Recent measurements taken by ground and satellite-based instruments also show regular variations in the magnetic field’s strength and shape that occur every few years. Scientists have long thought that these short-term variations in the field’s strength are influenced by activity in the planet’s outer core. This new study may provide the long-sought proof.
Researchers looked at more than 20 years of magnetic field data collected by the ESA’S Swarm satellite mission between 1999 and 2021. Swarm is a fleet of three identical satellites deployed to measure magnetic signals from Earth’s core, crust, oceans and atmosphere. The team combined this satellite data with earlier magnetic field measurements taken by ground-based sensors and then used a computer model to simulate the geodynamo, or the convective flow of fluid in Earth’s outer core. Through these combined measurements, the team identified the presence of Magneto-coriolis waves in the planet’s core for the first time. The source of these waves remains a mystery for now, but they likely stem from “disturbances deep within Earth’s [outer] core,” Gillet said.