European satellites reveal magnetic waves "sweeping" Earth's core

The trio of satellites from the European Space Agency's (ESA) Swarm mission have revealed a new type of magnetic wave, which appears to sweep across the "surface" of Earth's outer core every seven years. The mysterious wave moves westward, and travels for up to 1,500 km. The discovery is the result of measurements of the Earth's magnetic field obtained by instruments on the ground, which suggested the existence of some wave, added to the measurements of satellites in space.

The Earth is surrounded by a magnetic field , which acts as a large protective bubble from cosmic rays and charged particles from the solar wind. Most of the magnetic field comes from the dynamo, an ocean of molten iron 3,000 km deep, which forms the core of our planet. The Swarm mission is responsible for collecting magnetic signals from the core and other parts of the Earth, such as the crust and ionosphere.

With measurements from the Swarm satellites combined with data from the Champ (Germany) and Ørsted (Norway) missions, scientists were able to detect the magnetic wave that, until then, was theoretical. "Geophysicists have theorized the existence of these waves, but thought they occurred on much longer timescales than our research has shown," said Nicolas Gillet, the study's lead author.

To try to find out what explained the Earth's magnetic field information obtained by instruments on the ground, they worked with a computer model of the dynamo inside the planet . They found that the waves line up in columns that follow the Earth's axis of rotation, and the motion and changes in the magnetic field associated with them appear to be strongest in the equatorial area of ​​the planet's core.

Gillet explains that the waves are probably caused by disturbances deep in the Earth's core. “Each is specified by its typical period and length scale, and the period depends on the characteristics of the forces at play,” he noted. The study showed that magneto-Coriolis waves have a period of almost seven years, but there may be others, with different periods of oscillation. “For magneto-Coriolis waves, the period indicates the strength of the magnetic field in the core,” he concluded.

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