Scientists Detect Weakened Area in Earth’s Magnetic Field

Unexplained phenomenon disrupts spacecraft.

South Atlantic Anomaly. (Image courtesy of ESA.)

South Atlantic Anomaly. (Image courtesy of ESA.)

Data from the European Space Agency (ESA) indicates that a large area in the South Atlantic from South America to Africa where the Earth’s magnetic field is continuously getting weaker. Swarm, ESA’s operational mission to study the Earth’s magnetic field, has coined the area as the “South Atlantic Anomaly.” Earth’s magnetic field is vital to the persistence of life because it forms an invisible protective shield against deadly radiation that’s constantly streaming toward the planet from both the Sun and other parts of the universe. The field is generated from extremely hot molten iron contained within the outer core deep under the Earth’s crust, and connects the magnetic North and South poles. Unlike the geographic poles, the locations of the magnetic poles vary. The magnetic North Pole has been documented as “wandering” since 1831.

Such changes, including the estimated 9 percent drop in the overall strength of the magnetic field over the last 200 years, has implications that are not yet fully understood. According to ESA, the field strength also dropped between 1970 and 2020 by 2,000 nanoteslas, and the South Atlantic Anomaly has expanded to the west at a rate of 20 kilometers per year. Since 2015, the field has started to weaken at a second focal point near the cost of Africa, and could eventually split into two anomalous areas. These changes remain unexplained.

“The new, eastern minimum of the South Atlantic Anomaly has appeared over the last decade and in recent years is developing vigorously,” said Jürgen Matzka from the German Research Centre for Geosciences. “We are very lucky to have the Swarm satellites in orbit to investigate the development of the South Atlantic Anomaly. The challenge now is to understand the processes in Earth’s core driving these changes.”

Satellite Disruption

Although ESA scientists do not necessarily regard the changes as alarming, the South Atlantic Anomaly is already having an impact on satellites and spacecraft that fly through the area. Because the magnetic field is weaker in that area, it can cause devices to malfunction due to the increased amount of radiation in the form of charged particles hitting anything within 1,200 miles of the Earth’s surface. Such radiation can damage sensitive electronic components. According to NASA, satellites and spacecraft passing through the South Atlantic Anomaly are bombarded by protons exceeding energies of 10 million electron volts at a rate of 3,000 hits per square centimeter per second. One such spacecraft is the Hubble Space Telescope, which passes through the area 10 times per day, accounting for 15 percent of its orbit. Spacecraft that pass through the area may have to be designed to withstand higher amounts of radiation to increase their longevity.

It’s also notable that a large portion of the South Atlantic Anomaly is currently above the South American continent, meaning that people and other organisms could be exposed to slightly higher levels of radiation despite being much farther away from the danger than satellites located high up in the atmosphere.

Pole Reversal

The magnetic North and South Poles flip roughly once every 250,000 years, though such an event is long overdue. There’s been some discussion about whether recent changes in the magnetic field could be related to an upcoming pole reversal, but that has also not been determined. During a pole shift event, the Earth’s entire magnetic field would become much weaker, potentially doing grave harm to life as well as communication systems.