Completely New Type of Magnetic Wave Discovered Sweeping Across Earth’s Outer Core

While volcanic eruptions and earthquakes serve as stark reminders that the Earth's core is far from tranquil, there are also other, more mysterious, dynamic processes at work deep under our feet. Scientists have identified an entirely new sort of magnetic wave that sweeps over the outermost region of Earth's outer core every seven years using data from the ESA's Swarm satellite mission. This remarkable discovery, announced today at the ESA's Living Planet Symposium, provides a new window into a planet we'll never be able to view.

The magnetic field of the Earth acts as a giant shield, shielding us from cosmic radiation and charged particles carried by tremendous winds that escape the Sun's gravitational pull and travel throughout the Solar System. Life as we know it would not be possible without our magnetic field.

Understanding how and where our magnetic field is formed, why it varies so much, how it interacts with solar wind, and why it is currently diminishing is not just of academic interest but also of societal importance. Solar storms, for example, can disrupt communication networks, navigation systems, and satellites, so while we can't control changes in the magnetic field, knowing it can help us prepare.

The majority of the field is produced by an ocean of superheated, whirling liquid iron that makes up Earth's outer core, which is 3000 kilometers (1900 miles) under our feet. It creates electrical currents and a constantly changing electromagnetic field by acting like the spinning conductor in a bicycle dynamo.

The Swarm mission of the European Space Agency (ESA), which consists of three identical satellites, monitors these magnetic signals as well as signals from the crust, seas, ionosphere, and magnetosphere.

Since the launch of the trio of Swarm satellites in 2013, scientists have been studying their data to learn more about a variety of Earth's natural processes, ranging from space weather to the physics and dynamics of Earth's turbulent core.

The only genuine way to probe deep into Earth's core is to measure our magnetic field from orbit. Seismology and mineral physics give information on the core's material qualities, but they don't reveal anything about the liquid outer core's dynamo-generating motion.

However, scientists have discovered a hidden secret using data from the Swarm expedition.

A team of scientists discovered a new sort of magnetic wave that sweeps across the'surface' of Earth's outer core - where the core meets the mantle – according to a research published in the journal Proceedings of the National Academy of Sciences. This unexplained wave occurs every seven years and travels westward at a speed of up to 1500 kilometers per year.

“Geophysicists have long theorized over the existence of such waves, but they were thought to take place over much longer time scales than our research has shown,"  said Nicolas Gillet, lead author of the report.

“Measurements of the magnetic field from instruments based on the surface of Earth suggested that there was some kind of wave action, but we needed the global coverage offered by measurements from space to reveal what is actually going on."

“We combined satellite measurements from Swarm, and also from the earlier German Champ mission and Danish Ørsted mission, with a computer model of the geodynamo to explain what the ground-based data had thrown up – and this led to our discovery.”

These waves align in columns along the axis of rotation due to the Earth's rotation. The velocity and magnetic field changes caused by these waves are most pronounced in the core's equatorial region.

While the research shows magneto-Coriolis waves with a seven-year duration, the question of whether such waves exist that oscillate at various times remains unanswered.

“Magnetic waves are likely to be triggered by disturbances deep within the Earth’s fluid core, possibly related to buoyancy plumes. Each wave is specified by its period and typical length-scale, and the period depends on characteristics of the forces at play. For magneto-Coriolis waves, the period is indicative of the intensity of the magnetic field within the core", Dr. Gillet continued.

“Our research suggests that other such waves are likely to exist, probably with longer periods – but their discovery relies on more research.”

“This current research is certainly going to improve the scientific model of the magnetic field within Earth’s outer core. It may also give us new insight into the electrical conductivity of the lowermost part of the mantle and also of Earth’s thermal history,” said Ilias Daras, an ESA Swarm project scientist.