Deep in the Earth, liquid iron is flowing and creating a magnetic field, according to an article published on July 23 by Live Science. Magnetic fields protect the atmosphere and satellites from harmful radiation from the sun. Magnetic fields change over time and behave differently in different parts of the world. Magnetic fields can even change the poles radically, with north and south poles swapping places. The phenomenon is known as “inversion,” and the last geomagnetic reversal occurred 780,000 years ago.
Between South America and southern Africa lies a mysterious magnetic region called the South Atlantic Anomaly. The magnetic field in the region is much weaker than one would expect. Weak and unstable magnetic fields are thought to be a prelude to geomagnetic reversals, so some think this phenomenon could be evidence that people are facing a geomagnetic reversal.
Now, the new study, published in the proceedings of the National Academy of Sciences, sheds light on the duration of the anomaly in this magnetic region of the South Atlantic and whether it is cause for concern.
The report says weak magnetic fields make people more vulnerable to magnetic storms, which can destroy electronic infrastructure, including power grids. The magnetic field in the south Atlantic anomaly is already so weak that satellites and their technical equipment may be adversely affected as they pass through the region. This strange region is thought to be related to a magnetic field. The field is at a depth of 2,889 kilometers inside the Earth.
To find out, researchers went to St. Helena, an island in the middle of the South Atlantic Ocean. The island is made of volcanic rock, where Napoleon was exiled in 1821 and eventually died.
The results showed that the magnetic field on St Helena had a completely different orientation during the eruption, suggesting that the magnetic field in the region was far less stable than elsewhere. Thus, it challenges the idea that this anomaly has existed only for a few centuries. On the contrary, the whole region is likely to remain unstable for millions of years. That means the current phenomenon is not as rare as some scientists think, reducing the likelihood of a geomagnetic reversal.
So what explains this strange magnetic region? The liquid outer core that produces this magnetic region moves so rapidly that it can change in such a short time. The outer core interacts with the mantle above it. The mantle is moving more slowly, which means it’s unlikely to have changed much in the past 10 million years.
The structure of the mantle is known from seismic waves that pass through the earth. Beneath the African continent lies a vast landform, the underlying mantle. Seismic waves travel very slowly through the earth’s lower mantle — meaning that the lower mantle is most likely an abnormally warm region. This may lead to a different interaction with the outer core at that particular location, thus explaining the singularity of the magnetic field in the south Atlantic anomaly region.