You might not be driving in space anytime soon, but one extraterrestrial pothole could still cause you a headache back on Earth. The “pothole” in question is called the South Atlantic Anomaly (SAA): a weak spot in Earth’s magnetic field that extends over South Africa, South America and the Pacific Ocean, disrupting satellites that pass through it. At NASA, researchers are working to better understand and mitigate the effects of the SAA – and they’re using supercomputing to do it.

Earth’s magnetic field originates from its outer core, which produces the field by way of the electric currents that emanate from the unceasing motion of the molten metals it contains. However, these forces are not perfectly aligned, and Earth’s magnetic field fluctuates as a result. This effect can express itself in big ways – like the gradual shifting of the magnetic poles themselves – and in smaller ways, like the SAA.

“The observed SAA can also be interpreted as a consequence of weakening dominance of the dipole field in the region,” explained Weijia Kuang, a geophysicist and mathematician in the Geodesy and Geophysics Laboratory at NASA’s Goddard Space Flight Center (GSFC). “More specifically, a localized field with reversed polarity grows strongly in the SAA region, thus making the field intensity very weak, weaker than that of the surrounding regions.”

The “pothole” impact of the SAA comes into play via high-energy emissions of solar wind, hot plasma and radiation constantly barraging the Earth’s protective fields. Normally, the magnetosphere distributes these emissions safely – but the SAA allows them to dip closer to the Earth’s surface, introducing a dangerous variable. Crucially, of course, the SAA is also changing – and those changes introduce unpredictability that could impact important satellite missions.

To better understand these changes in the SAA, NASA researchers worked with several other institutions to model 125 years of the anomaly. To do this, they used NASA’s in-house Geomagnetic Ensemble Forecasting System (GEMS), running a 512-member ensemble simulation ranging from 1900 to 2025. The simulations were powered by the Blue Waters supercomputer at the National Center for Supercomputing Applications (NCSA), which completed all of the massive simulations in a matter of weeks.

Based on the results, the researchers anticipate that the SAA will continue its westward expansion, weakening in intensity – and, it turns out, split into two separate anomalies. 

But, of course, supercomputing can’t do all of the work.

“Even though the SAA 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,” said Terry Sabaka, a geophysicist at GSFC. “Because that’s what helps us make models and predictions.”