Scientists have discovered a rapidly expanding weak spot in Earth's magnetic field, posing a significant threat to satellites and spacecraft. This phenomenon, known as the South Atlantic Anomaly, has grown by an area nearly half the size of continental Europe since 2014, with the field weakening the fastest in the direction of Africa. The anomaly was first detected in the 19th century, and its magnetic field dips to an altitude of about 120 miles above the planet's surface, much lower than the average altitude of about 400 miles. This poses a risk to satellites and spacecraft, as they are exposed to more charged solar particles and incoming X-ray and ultraviolet radiation. The anomaly is growing and spreading eastward due to strange fluxes at the limit between Earth's mantle and outer core, with patterns known as reverse flux patches migrating and expanding. The magnetic field above Canada has weakened slightly, and the magnetic field above Siberia has strengthened, with the strong region over Canada shrinking by an area nearly the size of India and the strong region over Siberia growing by an area the size of Greenland. The Swarm mission, using three identical satellites to measure magnetic signals, has revealed these changes and more, providing valuable data for understanding Earth's dynamic magnetic field.
