The Earth's magnetic field has a curious anomaly that NASA is closely observing: a vast area of reduced magnetic strength that stretches from South America to southwest Africa.
The South Atlantic Anomaly is a massive, evolving phenomena that has fascinated and alarmed scientists for years, probably none more so than NASA experts. The poor magnetic field strength inside the anomaly and the exposure to charged particles from the Sun that results make the space agency's satellites and spacecraft especially susceptible.
Life on Earth is typically unaffected by the South Atlantic Anomaly (SAA), which NASA has compared to a "dent" in Earth's magnetic field or a kind of "pothole in space." However, orbital spacecraft, such as the International Space Station, which pass through the anomaly directly as they loop around the planet at low-Earth orbit altitudes, are another story.
Due to the weaker magnetic field within the anomaly during these encounters, technical equipment on board satellites are susceptible to short-circuiting and malfunctioning if they are impacted by high-energy protons coming from the Sun.
Although these sporadic collisions often only result in minor malfunctions, they nevertheless have the potential to destroy critical components permanently or lose a lot of data, forcing satellite operators to regularly turn down spacecraft systems before they approach the anomalous zone.
One reason NASA is monitoring the SAA is to reduce those risks in space; a second is that the mystery surrounding the anomaly presents a great opportunity to investigate a complex and challenging phenomenon, and NASA's extensive resources and research groups are particularly well-suited to study the occurrence.
According to geophysicist Terry Sabaka of NASA's Goddard Space Flight Centre in Greenbelt, Maryland, "the magnetic field is essentially a superposition of fields from several current sources."
The principal cause is thought to be a churning ocean of molten iron hundreds of kilometres below the surface in the Earth's outer core. Although not consistently, it appears, the movement of that mass creates electrical currents that produce the Earth's magnetic field.
About 2,900 kilometres (1,800 miles) underneath the African continent, a massive deposit of solid rock known as the African Large Low Shear Velocity Province disrupts the field's creation, resulting in the severe weakening effect, which is exacerbated by the tilt of the planet's magnetic axis.
Weijia Kuang, a geophysicist and mathematician at NASA Goddard, explains that "the observed SAA might alternatively be viewed as a result of declining dominance of the dipole field in the area."
"More precisely, a localised field with reversed polarity rises significantly in the SAA area, resulting in a relatively weak field intensity, weaker than that of the neighbouring regions."
While there is still much that scientists don't completely grasp about the anomaly and its effects, fresh information is constantly illuminating this odd phenomena.
For instance, a study conducted in 2016 under the guidance of NASA heliophysicist Ashley Greeley found the SAA is progressively moving in a northwestern direction.
But it's not simply relocating. Amazingly, the phenomena seems to be splitting in two. This year, researchers found that the SAA appeared to be separating into two unique cells, each of which represents a different centre of lowest magnetic strength inside the larger anomaly.
It is unclear what exactly it signifies for the SAA's future, but there is evidence to support the notion that the anomaly is not a recent development.
According to a research released last month, the phenomena is not a one-time freak occurrence, but rather a periodic magnetic event that may have impacted Earth as long ago as 11 million years ago.
If that's the case, it may mean that the South Atlantic Anomaly is neither the cause or forerunner of the planet's magnetic field flipping as a whole, which does occur, although for periods of thousands or even millions of years at a time.
Although there are still many unanswered concerns about this enormous magnetic anomaly, it is comforting to know that the most powerful space agency in the world is keeping a careful eye on it.
Even if the SAA moves slowly, it is undergoing some morphological change, therefore it's crucial that we continue to observe it via missions, according to Sabaka.
"Because that's how we develop models and forecasts," the speaker said.
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