Part of Earth's Magnetic Field is Getting Weaker in 'Vigorously' Developing Anomaly, Scientists Say

Part of Earth's magnetic field appears to be getting weaker, scientists have said. Using satellite data, researchers believe an "anomaly" in the South Atlantic may have split in two, with the eastern section "developing vigorously."

Earth's magnetic field is generated by movements within the planet's molten iron core. It stretches out into space and provides a barrier around us that protects Earth against harmful radiation from the sun. When the magnetic field is stronger, it blocks more radiation. When it is weaker, more radiation reaches the planet's surface.

The magnetic field is constantly moving. It strengthens and weakens as part of normal fluctuations. According to the European Space Agency (ESA), the magnetic field has lost around 9 percent of its strength over the preceding two centuries. One section of the magnetic field has been found to have weakened considerably since 1970.

This patch, called the South Atlantic Anomaly, sits between Africa and South America. Over the last 50 years, it has grown and moved farther west at a rate of roughly 12 miles per year. However, in the last five years, part of the anomaly appears to have split off into a cell which the ESA calls a "second center of minimum intensity" located southwest of Africa.

Jürgen Matzka, who is in charge of geomagnetic observations at the GFZ German Research Centre for Geosciences, is one of the scientists tracking the South Atlantic Anomaly. He and other scientists use ground based observations coupled with data from the ESA's Swarm satellite constellation to better understand changes to the magnetic field.

"It is important to monitor because firstly we use the magnetic field for navigation, having accurate maps of the geomagnetic field allows for accurate navigation, secondly our data tells us a lot about processes in the upper atmosphere and in space that can be relevant for operating satellites and the electric power network," Matzka told Newsweek in an email. "Thirdly, it is important to investigate the structure of the Earth's core and the physical processes relevant there to generate the geomagnetic field, this is important for understanding Earth and other planets."

Matzka said the South Atlantic Anomaly is caused by parts of Earth's core that sit beneath South Africa, the South Atlantic and South America, where the geomagnetic field is going into the wrong direction.

"We call these areas 'reversed flux patches,'" he said. "The 'normal flux patches' produce the field that we measure at the surface, while the reversed flux patches decrease it, causing the low field intensity in the anomaly. So there must be further reversed flux patches at the core of the earth that cause the split into different cells at the surface."

In a statement, Matzka said the eastern minimum has been "developing vigorously" in recent years. "The challenge now is to understand the processes in Earth's core driving these changes," he said.

Matzka said the newly-developed patch is nothing to worry about at ground level as the atmosphere protects us from the sun's radiation. However, satellites may need more protection in the future as increased radiation as a result of a weaker magnetic field may lead to more technical malfunctions.

Nathan Case, a senior research associate at the Department of Physics, University of Lancaster, U.K., studies the interaction between Earth's magnetic field and the solar wind—the stream of charged particles coming from the sun. Case, who was not involved in the ESA's Swarm observations, said Earth's magnetic field is currently weakening by around five percent per century.

"These new data from the ESA Swarm mission are allowing scientists to better understand the dynamic processes going on within the Earth which create our magnetic shield," he told Newsweek in an email. "The new result of a second minimum peak, an area of especially weak field in the anomaly, is something that will test our current understanding of what generates the anomaly."

He said that even if the magnetic field in this region is weak, it is still strong enough to prevent harmful radiation from hitting Earth's surface. Satellites orbiting hundreds of miles above may be bombarded with radiation.

"Even the International Space Station has to have extra radiation shielding to protect the astronauts on-board when it passes through this region," Case said. "As the anomaly expands, and the field weakens further, the risk to spacecraft and crewed space missions increases."

Correction 05/26 03.25 a.m. ET: This article has been corrected to say the SAA is moving 12 miles per year, not miles per hour.

earth magnetic field
Stock image representing Earth's magnetic field. Researchers have found part of the South Atlantic Anomaly has developed a “second center of minimum intensity,” the ESA says. iStock