An entirely new type of magnetic wave sweeping through the Earth’s outer core has been discovered

While volcanic eruptions and earthquakes are instant reminders that the Earth’s interior is not peaceful, there are also other elusive dynamic processes occurring deep within our feet. Using information from the European Space Agency’s Swarm satellite mission, scientists have discovered an entirely new type of magnetic wave that sweeps across the outer part of Earth’s outer core every seven years. This remarkable discovery, presented today at the European Space Agency’s Living Planet symposium, opens a new window into a world we can never see.

Earth’s magnetic field It is like a huge bubble that protects us from the onslaught of cosmic radiation and charged particles carried by strong winds that escape the sun’s gravity and flow through the solar system. Without our magnetic field, life as we know it could not exist.

constellation swarm. Credit: ESA/ATG Medialab

Understanding exactly how and where our magnetic field is created, why it constantly fluctuates, how it interacts with the solar wind, and, in fact, why it is currently weakening, is not only of academic interest but also beneficial to society. for example, Solar storms can destroy communication networks And navigation systems and satellites, so while we can’t do anything about changes in the magnetic field, understanding this invisible force helps us prepare.

Most of the field is created by an ocean of superheated, swirling liquid iron that forms the Earth’s outer core 3,000 kilometers (1,900 miles) below our feet. Acting like a spinning conductor in a bike dynamo, it generates electric currents and an ever-changing electromagnetic field.

The European Space Agency’s Swarm mission, consisting of three identical satellites, measures these magnetic signals that originate from the Earth’s core, as well as other signals that come from the crust, oceans, ionosphere and magnetosphere.

Since the launch of three Swarm satellites in 2013, scientists have been analyzing their data to gain new insight into many of Earth’s natural processes, from space climate to me Physics and dynamics The stormy heart of the earth.

Using information from the European Space Agency’s Swarm satellite mission, scientists have discovered an entirely new type of magnetic wave that sweeps across the outer part of Earth’s outer core every seven years. This remarkable discovery opens a new window into a world we can never see. This mysterious wave oscillates every seven years and spreads westward at speeds of up to 1,500 kilometers (900 miles) per year. Credit: ESA/Planet Insights

Measure our magnetic field from space It is the only real way to investigate the depths of the Earth’s core. Seismology and mineral physics provide information about the physical properties of the core, but they do not shed any light on the dynamo-generating motion of the liquid outer core.

But now, using data from the Swarm mission, scientists have discovered a hidden secret.

A paper published in the magazine Proceedings of the National Academy of Sciences, describes how a team of scientists has discovered a new type of magnetic wave that sweeps across the ‘surface’ of Earth’s outer core – where the core meets the mantle. This mysterious wave oscillates every seven years and spreads westward at speeds of up to 1,500 kilometers (900 miles) per year.

“Geophysics have long theorized about the existence of such waves, but they have been thought to occur over much longer timescales than our research has shown,” said Nicholas Gillet, of Grenoble Alps University and the paper’s lead author.

Magnetic field measurements from Earth-based instruments suggested that there was some kind of wave motion, but we needed the global coverage that measurements from space provide to reveal what’s really going on.

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

Because of the Earth’s rotation, these waves line up in columns along the axis of rotation. The motion and magnetic field changes associated with these waves are strongest near the equatorial region of the core.

While the research displays Coriolis magnetic waves near a seven-year period, the question of the existence of such waves that would oscillate at different periods, however, remains.

Dr Gillette added: “Magnetic waves are likely caused by disturbances deep within Earth’s fluid core, possibly related to buoyancy plumes. Each wave is determined by its duration and a typical length scale, and the period depends on the characteristics of the forces acting. For magnetic-Coriolis waves, the period denotes on the strength of the magnetic field inside the heart.

“Our research suggests that there may be other waves like this, possibly with longer durations – but their discovery depends on further research.”

Elias Daras, ESA’s Swarm mission scientist, noted, “This current research will certainly improve the scientific model of the magnetic field within the Earth’s outer core. It may also give us new insight into the electrical conductivity of the lower mantle as well as for the Earth’s thermal history.”

Reference: “Satellite Magnetic Data Reveal Interannual Waves in the Earth’s Core” By Nicholas Gillett, Felix Gerek, Dominic Gault, Tobias Schweiger, Julian Ober, and Matthew Estas, March 21, 2022 Available here Proceedings of the National Academy of Sciences.
DOI: 10.1073/pnas.2115258119

Supported by the European Space Agency’s Science for Society programme, this research was presented at the European Space Agency’s Planet Biology Symposium taking place this week in Bonn, Germany. Attendees hear about the latest scientific findings on our planet and how observing Earth from space supports environmental research and action to combat the climate crisis. They also hear about new space technologies and about new opportunities emerging in the rapidly changing Earth observation sector. Selected sessions are broadcast, see ESA Web TV Channels.