While volcanic eruptions and earthquakes are an immediate reminder that the Earth’s interior is anything but peaceful, there are also other, more elusive, dynamic processes taking place deep beneath our feet. Using information from ESA’s Swarm satellite mission, scientists have discovered an entirely new type of magnetic wave that sweeps across the outermost part of the Earth’s outer core every seven years. This fascinating discovery, presented today at ESA’s Living Planet Symposium, opens a new window into a world we will never be able to see.
The Earth’s magnetic field is like a huge bubble that protects us from the onslaught of cosmic radiation and charged particles carried by powerful winds that escape the gravitational pull of the Sun and travel through the solar system. Without our magnetic field, life as we know it could not exist.
Understanding exactly how and where our magnetic field is generated, 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 damage communications networks, 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 generated by a superheated, swirling ocean of liquid iron that makes up the Earth’s outer core 3000 km (1900 miles) below our feet. Acting like the rotating conductor of a bicycle dynamo, it generates electric currents and an ever-changing electromagnetic field.
ESA’s Swarm mission, which includes three identical satellites, measures these magnetic signals from the Earth’s core, as well as other signals from the Earth’s crust, oceans, ionosphere and magnetosphere.
Since the launch of the trio of Swarm satellites in 2013, scientists have analyzed their data to better understand Earth’s many natural processes, from space weather to the physics and dynamics of Earth’s stormy core.
Using information from ESA’s Swarm satellite mission, scientists have discovered an entirely new type of magnetic wave that sweeps across the outermost part of the Earth’s outer core every seven years. This fascinating discovery opens a new window on a world that we will never be able to see. This mysterious wave oscillates every seven years and travels west up to 1,500 kilometers (900 miles) per year. Credit: ESA/Planetary Visions
Measuring our magnetic field from space is the only real way to deeply probe the Earth’s core. Seismology and mineral physics provide information about the material properties of the core, but they do not illuminate the dynamo-generating motion of the liquid outer core.
But now, using data from the Swarm mission, scientists have uncovered a hidden secret.
An article published in the journal Proceedings of the National Academy of Sciences, describes how a team of scientists have detected a new type of magnetic wave that sweeps across the “surface” of the Earth’s outer core, that is, where the core meets the mantle. This mysterious wave oscillates every seven years and travels west up to 1,500 kilometers (900 miles) per year.
Nicolas Gillet, from Université Grenoble Alpes and lead author of the paper, said: “Geophysicists have long theorized the existence of such waves, but they were thought to occur on much longer time scales. than our research has shown.
“Magnetic field measurements from instruments based on the Earth’s surface suggested that there was some sort of wave action, but we needed the global coverage offered by measurements from space to reveal what is really going on.
“We combined satellite measurements from Swarm, as well as those from the previous German Champ mission and the Danish Ørsted mission, with a computer model of the geodynamo to explain what the ground data had produced – and this led to our discovery.”
Due to the rotation of the Earth, 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 research shows magneto-Coriolis waves close to a period of seven years, the question of the existence of such waves oscillating at different periods remains however.
Dr Gillet added: “Magnetic waves are likely to be triggered by disturbances deep in 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 the characteristics of the forces involved. For magneto-Coriolis waves, the period is indicative of the strength of the magnetic field inside the core.
“Our research suggests that other waves of this type are likely to exist, probably with longer periods – but their discovery relies on further research.”
ESA’s Swarm mission scientist Ilias Daras said: “This current research will certainly improve the scientific model of the magnetic field in the Earth’s outer core. It may also give us new insight into the electrical conductivity of the lowest part of the mantle and also into Earth’s thermal history.
Reference: “Satellite magnetic data reveal interannual waves in the Earth’s core” by Nicolas Gillet, Felix Gerick, Dominique Jault, Tobias Schwaiger, Julien Aubert and Mathieu Istas, March 21, 2022, Proceedings of the National Academy of Sciences.
Supported by ESA’s Science for Society programme, this research was presented at ESA’s Living Planet Symposium which took place this week in Bonn, Germany. Attendees hear about the latest scientific discoveries about our planet and how observing Earth from space is supporting environmental research and action to tackle the climate crisis. They also hear about new space technologies and new opportunities emerging in the rapidly evolving Earth observation sector. Some sessions are broadcast live, see ESA Web TV channels.