Illustration showing the interaction of the solar wind (red) with the Earth’s magnetic field (blue, not … [+] to climb).
getty
The Earth’s magnetic field acts as an invisible shield against the life-threatening environment in space, especially radiation and charged particles emitted by the Sun. However, the magnetic field is not stable and, at irregular intervals, polarity reversals occur on average every 200,000 years. This means that the magnetic north and south poles exchange places.
Over the past 180 years, the strength of the Earth’s magnetic field has decreased by about 10 percent. At the same time, an area with an unusually weak magnetic field has grown in the South Atlantic off the coast of South America. This area, where satellites have malfunctioned several times due to exposure to highly charged particles from the sun, is called the South Atlantic Anomaly. These developments have led to speculation that we could be heading for a reversal of polarity.
Intensity map of the Earth’s magnetic field in 2015. Source: … [+]:
NOAA
However, a new study suggests that may not be the case.
Using data from around the planet, researchers at Lund University reconstructed the Earth’s magnetic field over the past 9,000 years, showing that these magnetic anomalies are common.
“We have developed a new modeling technique that connects these indirect observations of different time periods and places in a global reconstruction of the magnetic field over the last 9,000 years,” said Andreas Nilsson, a geologist at Lund University and lead author of study.
The results are based on analyzes of archaeological artifacts, volcanic rocks and sediment drilling cores, all of which carry information about the Earth’s magnetic field. Using sensitive instruments, researchers have been able to measure the residual magnetization found in these samples and recreate the direction and strength of the magnetic field at specific places and times.
“We have mapped changes in the Earth’s magnetic field over the last 9,000 years, and anomalies such as the South Atlantic are likely to be recurring phenomena related to the corresponding variations in the strength of the Earth’s magnetic field,” says Nilsson.
“Based on the similarities with the recreated anomalies, we predict that the South Atlantic anomaly is likely to disappear in the next 300 years and that the Earth is not moving toward a polarity reversal,” Nilsson concludes.
By studying how the magnetic field has changed, researchers can learn more about the processes underlying the Earth’s core that generate the field. The new model can also be used to date archaeological and geological records, by comparing measured and modeled variations in the magnetic field. And, reassuringly, it has led them to a conclusion about speculation about an imminent polarity reversal.
The paper, “Recurring Anomalies in the Ancient Geomagnetic Field Illuminates the Future Evolution of the South Atlantic Anomaly,” is published in Proceedings of the National Academy of Sciences (2022). Materials provided by Lund University.