There is an area stretching from Africa to South America in which the magnetic field gradually weakens. This area is known as the South Atlantic magnetic anomaly and is further proof that the Earth’s magnetic field is not static , and that, furthermore, the processes involved in its generation are quite complex.
The strange behavior of the magnetic field in the area of the anomaly intrigues the scientific community and also causes technical problems in the satellites that orbit the Earth. Now, the European Space Agency (ESA) is using the satellites of the Swarm mission to collect more data about what happens there: its spacecraft are designed to accurately identify and measure the different magnetic signals that make up the Earth’s magnetic field.
The anomaly could be fragmenting
Between 1970 and 2020, the minimum intensity in this zone decreased from around 24,000 to 22,000 nanoteslas, while at the same time the area of the anomaly grew and moved westward at a rate of about 20 kilometers per year. In the past five years, a second center of least intensity has emerged in southwestern Africa, indicating that the South Atlantic anomaly could divide into two separate cells.
The Earth’s magnetic field is usually represented as a powerful dipole magnet in the center of the planet, which is also inclined about eleven degrees with respect to the axis of rotation. However, the growth of the South Atlantic anomaly indicates that the processes involved in the generation of the field are much more complex, since simple dipole models cannot explain the recent development of the second minimum.
“The new eastern minimum of the South Atlantic anomaly has been forming for a decade, although its development has accelerated in recent years. We are very lucky to have the Swarm satellites to investigate its evolution. The challenge now is to understand the processes in the Earth’s core that cause these changes ”, explained Jürgen Matzka, researcher at the German Research Center for Geosciences.
Towards a magnetic reversal?
It has been speculated whether the current weakening of the field is a sign that the Earth is heading towards the next magnetic reversal. Throughout the history of our planet, the magnetic poles have been reversed several times, and the last episode is known as the Brunhes-Matuyama magnetic inversion. In any case, the current drop in intensity in the South Atlantic is within the usual fluctuation levels.
The existence of this anomaly is not a reason to be alarmed either. However, satellites and other spacecraft flying over the area are more likely to experience technical failures, given the greater weakness of the magnetic field in that region, which allows charged particles to penetrate to the altitudes of satellites in low Earth orbit.
The mystery of the origin of the South Atlantic anomaly remains, but scientists are hoping that observations of Swarm’s magnetic field will help clarify it and offer new data on unclear processes that occur inside the Earth.
Source: European Space Agency (ESA)
