Swarm probes weakening of Earth's magnetic field

In an area stretching from Africa to South America, Earth's magnetic field is gradually weakening. This strange behaviour has geophysicists puzzled and is causing technical disturbances in satellites orbiting Earth. Scientists are using data from ESA's Swarm constellation to improve our understanding of this area known as the 'South Atlantic Anomaly.'

Earth's magnetic field is vital to life on our planet. It is a complex and dynamic force that protects us from cosmic radiation and charged particles from the Sun.

The magnetic field is largely generated by an ocean of superheated, swirling liquid iron that makes up the outer core around 3000 km beneath our feet. Acting as a spinning conductor in a bicycle dynamo, it creates electrical currents, which in turn, generate our continuously changing electromagnetic field.

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The objective of the Swarm mission is to provide the best ever survey of the geomagnetic field and its temporal evolution, and gain new insights into improving our knowledge of the Earth's interior and climate.

The Swarm concept consists of a constellation of three satellites in three different polar orbits between 400 and 550 km altitude.

The multi-satellite Swarm mission will be able to take full advantage of a new generation of magnetometers enabling measurements to be taken over different regions of the Earth simultaneously.

The Earth's magnetic field has lost about 15% of its strength over the last 150 years. For example, the South Atlantic Anomaly has a particularly weak magnetic field, which is only half as strong as over Europe.

Furthermore, the magnetic north pole was moving at about 10 km a year before 1994, but the rate has increased to around 65 km a year since 2001.