NASA tracks large growing anomaly in Earth’s magnetic field

NASA is actively monitoring a strange anomaly in Earth’s magnetic field: a giant region of weaker magnetic intensity in the sky above the planet, stretching between South America and southwest Africa.

This vast developing phenomenon, called the South Atlantic Anomaly, has puzzled and preoccupied scientists for years, and perhaps no more than NASA researchers. The space agency’s satellites and spacecraft are particularly vulnerable to the strength of the weakened magnetic field in the anomaly and the resulting exposure to charged particles from the Sun.

The South Atlantic Anomaly (SAA) – compared by NASA to a “ bump ” in Earth’s magnetic field, or some kind of “ pothole in space ” – n ‘ Usually does not affect life on Earth, but the same cannot be said for orbit. spacecraft (including the International Space Station), which pass directly through the anomaly circling the planet at low Earth orbit altitudes.

During these encounters, the reduction in the strength of the magnetic field inside the anomaly means that the technological systems on board the satellites can short-circuit and malfunction if struck by high-energy protons. emanating from the Sun.

These random strikes can usually only produce low-level problems, but they carry the risk of causing significant data loss or even permanent damage to key components – threats forcing satellite operators to systematically shut down machine systems. before the spacecraft enter the anomaly zone.

Mitigating these dangers in space is one of the reasons NASA follows SAA; another is that the mystery of the anomaly represents an excellent opportunity to study a complex and difficult to understand phenomenon, and NASA’s vast resources and research groups are uniquely suited to study the occurrence.

“The magnetic field is actually a superposition of fields from many sources of current,” says geophysicist Terry Sabaka of NASA’s Goddard Space Flight Center in Greenbelt, Maryland.

The main source is thought to be a swirling ocean of molten iron inside the Earth’s outer core, thousands of miles below the ground. The movement of this mass generates electric currents that create the Earth’s magnetic field, but not necessarily uniformly, it seems.

A huge reservoir of dense rock called the Great African Low Shear Velocity Province, located about 2,900 kilometers (1,800 miles) below the African continent, disrupts the generation of the field, resulting in a dramatic weakening effect – which is facilitated by the tilt of the planet’s magnetic field. axis.

“The observed AAS can also be interpreted as a consequence of the weakening of the dipole field dominance in the region,” explains Weijia Kuang, geophysicist and mathematician of NASA Goddard.

“Specifically, a localized field with reversed polarity grows strongly in the SAA region, thus making the field strength very weak, weaker than that of the surrounding regions.”

Satellite data suggests that SAA is dividing. (Geomagnetism division, DTU space)

Although many scientists still do not fully understand the anomaly and its implications, new knowledge is continually shedding light on this strange phenomenon.

For example, a study conducted by NASA heliophysicist Ashley Greeley in 2016 found that SAA was slowly drifting in a northwest direction.

It’s not just on the move, however. Most notably, the phenomenon appears to be splitting in two, with researchers this year discovering that AAS appears to be dividing into two distinct cells, each representing a distinct center of minimum magnetic intensity within the larger anomaly.

What this means for the future of SAA remains unknown, but in any case, there is some evidence to suggest that the anomaly is not a new appearance.

A study published last month suggested that the phenomenon is not an unusual event of recent times, but a recurring magnetic event that may have affected Earth since 11 million years ago.

If so, it could indicate that the South Atlantic anomaly is not a trigger or precursor to the reversal of the entire planet’s magnetic field, which is actually happening, if not for hundreds of thousands of days. years at a time.

Obviously, huge questions remain, but with so much going on with this vast magnetic quirk, it’s good to know that the world’s most powerful space agency is watching it as closely as they are. .

“Even though SAA evolves slowly, it undergoes a change in morphology, so it is also important that we continue to observe it as we continue with its missions,” says Sabaka.

“Because that’s what helps us make models and predictions.”