Publié le 23 mai 2022
Earth’s magnetic field is like a huge bubble protecting us from the onslaught of cosmic radiation and charged particles carried by powerful winds that escape the Sun’s gravitational pull and stream across the Solar System. Without our magnetic field, life as we know it would not exist.
Understanding exactly how and where our magnetic field is generated, why it fluctuates constantly, how it interacts with solar wind and, indeed, why it is currently weakening, is not only of academic interest but also of benefit to society. For example, solar storms can damage 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 to be prepared.
Most of the field is generated by an ocean of superheated, swirling liquid iron that makes up Earth’s outer core 3000 km under our feet. Acting like the spinning conductor in a bicycle dynamo, it generates electrical currents and the continuously changing electromagnetic field.
The European Space Agency's Swarm mission, which comprises three identical satellites, measures these magnetic signals that stem from Earth’s core, as well as other signals that come from the crust, oceans, ionosphere and magnetosphere.
Since the trio of Swarm satellites were launched in 2013, scientists have been analysing their data to gain new insight into many of Earth’s natural processes, from space weather to the physics and dynamics of Earth’s stormy heart.
Measuring our magnetic field from space is the only real way of probing deep down to Earth’s core. Seismology and mineral physics provide information about the material 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 unearthed a hidden secret.