At a Glance

A thermal anomaly was documented in the middle of the Atlantic Ocean during a scan in July 2017.Scientists say the South Atlantic Magnetic Anomaly (SAMA) caused the anomaly.SAMA is a weakness in Earth's magnetic field that allows exposure to an extra dose of radiation to the area.

When the Visible Infrared Imaging Radiometer Suite (VIIRS) on the Suomi NPP satellite scans the Earth's surface each night, itproduces thousands of red dots, each signifying a thermal anomaly.

The majority of those anomalies are caused by fires. But every now and then, you get one that's a little bit harder to explain, like onein the middle of the ocean.

"," Patricia Olivia, a Universidad Mayor scientist, said in a NASA release dated July 2017 when VIIRS spotted an anomaly a few hundred miles off the coast of Brazil.

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Other events that can trip the scanner are natural gas flares and volcanic activity, but gas flares are only found in shallow waters near the coast and there are no volcanoes to be found nearthe blipon the scan.

"It is almost certainly SAMA," said Olivia.

The thermal signal in the bottom right-hand corner of the image above shows the South American Magnetic Anomaly in the South Atlantic. These anomalies may look like fires in the middle of the ocean, but they're actually areas of increased radiation.

(NASA Earth Observatory)

SAMA stands for the South Atlantic Magnetic Anomaly, a over South America and the South Atlantic that allows exposure to an extra dose of radiation, according to NASA's Atmospheric Science Data Center.

The atmosphere takes care of most of the high-energy particles so that they don't cause problems at the surface, but there are enough in space close enough to Earth to affect electronic systems on spacecraft.

The International Space Station has been layered with extra protection because of SAMA, and the Hubble Space Telescope shuts down when it traverses the area.

With VIIRS, the abundance of particles in the atmosphere causes its extremely sensitive radiometer to pick some up. When the team developing the fire data product first began to process data, .

“Each night, the sensor was detecting several dozen thermal anomalies over the Atlantic Ocean in places that didn’t make sense,” said Wilfrid Schoeder, the principal investigator for VIIRS's fire product.

The team formed an algorithm that would removeany suspicious anomaly with signs of being caused by SAMA — a signal that was substantiallyweak, sat over the ocean or was short-lived.

The rare blip or two on the radar caused by SAMA will still slip through the system every night, Schroeder said, but that pales in comparison to the thousands of real thermal anomalies VIIRS documents.

"In developing an algorithm like this for a global data product, we had to find a balance. If we are too aggressive with our filtering, there is a risk that we will remove real fires from the data record,” Olivia said. “I don’t think people realize that most satellite data products go through a whole battery of calibration and validation tests to address issues like this.”