NASA watches as weird 'dent' in Earth's magnetic field splits in two

There's something very strange happening high above South America and the nearby Atlantic Ocean, and NASA is on the case.

Meet the South Atlantic Anomaly, a strange dent in Earth's magnetic field that is growing and splitting. It's been there for decades, but over time the anomaly has slowly changed. Although you'd never notice anything was wrong from the ground, for satellites, changes to the magnetic field that envelopes Earth can be a big deal — hence NASA's interest in the anomaly and its activities.

The connection comes because the magnetic field blocks charged particles spewed out by the sun from reaching Earth. But at the South Atlantic Anomaly, the field is dented, lowering the protective barrier above that part of Earth. The lower barrier means that more radiation bombards satellites as they fly over this region, triggering occasional shutdowns to avoid potential damage to the hardware, according to a NASA statement.

Video: South Atlantic Anomaly in Earth's magnetic field described in detail
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An artist's depiction of Earth's magnetic field, with the sun in the background. (Image credit: NASA's Goddard Space Flight Center)

The International Space Station is one of the many spacecraft that fly through the anomaly, but it carries extra shielding to protect the astronauts who live and work in orbit from radiation. Other spacecraft that fly through the anomaly send NASA valuable observations about how the feature is changing, like the Ionospheric Connection Explorer (ICON), which the agency launched last year in part to monitor the weak spot in the field after the retirement of its Solar, Anomalous, and Magnetospheric Particle Explorer (SAMPEX) mission in 2012. Among other changes, those observations have shown that the "dent" is moving westward and splitting in two.

These observations are valuable because of the complexity of studying the magnetic field, which traces its roots to liquid metal moving within Earth's core, then is shaped by a range of phenomena as it ripples out from the center of the planet, according to NASA. 

Those interactions mean that more data about changes in the magnetic field can lead to a host of valuable results — not just a better understanding of what the anomaly is doing now in order to warn approaching satellites, but also more nuanced models of what's happening deep inside the Earth, and of course, more accurate predictions of how the anomaly will change into the future.

"Even though the SAA [South Atlantic Anomaly] is slow-moving, it is going through some change in morphology, so it's also important that we keep observing it by having continued missions," Terry Sabaka, a geophysicist at NASA's Goddard Space Flight Center in Maryland, said in the statement. "Because that's what helps us make models and predictions."

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Meghan Bartels
Senior Writer

Meghan is a senior writer at and has more than five years' experience as a science journalist based in New York City. She joined in July 2018, with previous writing published in outlets including Newsweek and Audubon. Meghan earned an MA in science journalism from New York University and a BA in classics from Georgetown University, and in her free time she enjoys reading and visiting museums. Follow her on Twitter at @meghanbartels.