ESA's Swarm spots a fast-growing anomaly in the Earth’s magnetic field

Since its launch in November 2013, Swarm has been measuring the Earth’s magnetic field. Swarm is a satellite constellation consisting of three identical satellites. It has now broken the record for the longest continuous magnetic field measurement from space.

The satellite constellation revealed new findings about the South Atlantic Anomaly. The South Atlantic Anomaly is an area where the Earth’s magnetic field is weak. Swarm has shown that there has been a steady expansion of this weak spot between 2014 and 2025. The region has grown by an area comparable in size to continental Europe.

While that weakening spot is concerning enough, Swarm revealed a region with even more rapid decline in magnetic strength. That region is located southwest of Africa. It has experienced a more rapid weakening of Earth’s magnetic field since 2020.

These Swarm data also showed areas of higher magnetic strength. While the southern hemisphere has one such area, the northern hemisphere has two — one around Canada and the other around Siberia. Over the years, though, the magnetic field over Siberia has grown even stronger while the one over Canada has weakened.

Swarm’s data is helping scientists understand the Earth’s magnetic field better. With more information, they can dig deeper to find out the cause of the changes in the field’s strength in certain areas. The Earth’s magnetic field is what protects us from cosmic radiation and charged particles from the Sun. So understanding it is crucial for space safety. These findings were published in the journal Physics of the Earth and Planetary Interiors.