NASA is actively monitoring an early anomaly in the Earth’s magnetic field: a gigantic region with lower magnetic intensity in the skies above the planet, which extends between South America and southwest Africa.
This large, evolving phenomenon, called the South Atlantic Anomaly, has intrigued and troubled scientists for years, and perhaps none other than NASA researchers. The space agency’s satellites and spacecraft are particularly vulnerable to the attenuated strength of the magnetic field within the anomaly, and the resulting exposure to charged particles from the sun.
The South Atlantic Anomaly (SAA) – compared by NASA to a ‘dent’ in the Earth’s magnetic field, as a kind of ‘pothole in space’ – generally does not affect life on Earth, but the same can not be said for orbital spaceships (including the International Space Station), which pass directly through the anomaly as they ascend the planet at low Earth orbital heights.
During these meetings, the reduced strength of the magnetic field in the anomaly technological systems on board satellites can short circuit and malfunction if they are hit by high energy protons coming from the sun.
These random hits usually produce only low-level glitches, but they carry the risk of causing significant data loss, or even permanent damage to key components – threats that require satellite operators to routinely shut down spacecraft systems before spacecraft enters the anomaly zone.
Reducing these hazards in space is one reason NASA is following the SAA; another is that the mystery of the anomaly represents a great opportunity to investigate a complex and difficult-to-understand phenomenon, and NASA’s broad resources and research groups are uniquely well appointed to study its performance.
“The magnetic field is actually a superposition of fields from many current sources,” explains geophysicist Terry Sabaka of NASA’s Goddard Space Flight Center in Greenbelt, Maryland.
The primary source is considered to be a heated ocean of molten iron in the outer core of the earth, thousands of miles below the ground. The motion of that mass generates electric currents that make the Earth’s magnetic field, but not necessarily uniform, it seems.
An enormous reservoir of dense rock called the African Large Low Shear Velocity Province, about 2,900 kilometers (1,800 miles) below the African continent, disrupts the generation of the field, resulting in the dramatic weakening effect – which is aided by the tilt of ‘ the magnetic planet as.
“The observed SAA can also be interpreted as a result of weakening of dominance of the dipole field in the region,” says NASA Goddard geo-physicist and mathematician Weijia Kuang.
“More specifically, a localized field with reverse polarity grows strongly in the SAA region, making the field intensity very weak, weaker than that of the surrounding regions.”
Satellite data suggesting the SAA is splitting. (Department of Geomagnetism, DTU space)
While many scientists do not yet fully understand the anomaly and its implications, new insights are constantly shedding light on this strange phenomenon.
For example, one study led by NASA heliophysicist Ashley Greeley in 2016 found that the SAA is slowly drifting in a northwest direction.
However, it is not just moving. Even more remarkable is the phenomenon in the process of splitting in two, with researchers discovering this year that the SAA seems to divide into two distinct cells, each representing a separate center of minimal magnetic intensity within the larger anomaly.
Exactly what this means for the future of the SAA remains unknown, but in any case there is evidence to suggest that the anomaly is not a new appearance.
A study published last month suggested that the phenomenon is not a freak event of recent times, but a recurring magnetic event that may have affected Earth since 11 million years ago.
If so, it could signal that the South Atlantic Anomaly is not a trigger as a precursor to the entire magnetic field of the planet, which is something that actually happens, if not hundreds of thousands of years at a time.
Of course, enormous questions remain, but with so much going on with this incredible magnetic imbalance, it’s good to know that the world’s most powerful space agency is looking at it as closely as they are.
“Even though the SAA is moving slowly, it is going through some change in morphology, so it is also important that we continue to observe it,” Sabaka says.
“Because that’s what helps us make models and predictions.”
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