The earth’s geomagnetic armor has shrunk and is growing.
Over the past two centuries, a weak spot in the magnetic field of our planet, above the southern Atlantic Ocean, has increased and it has begun to split in two.
This is no cause for concern for those among us on the ground: the protective field still protects the planet from deadly solar radiation.
But the South Atlantic Anomaly, as it is aptly called, does affect satellites and other spacecraft moving through an area between South America and southern Africa.
This is because higher amounts of charged solar particles seep through the field, which can cause errors in computers and circuits.
The source of this growing ‘dive’, as NASA calls it, is a bit of a mystery. But scientists expect it to continue to expand.
“This thing is going to get bigger in the future,” Julien Aubert, a geomagnetism expert at the Paris Institute of Earth Physics, told Insider.
Aubert believes the dent may have a connection with two giant patches of dense rock buried 2,897 kilometers inside the earth. Due to their composition, the stains disturb the liquid metal in the outer core that generates the magnetic field.
Both spots are millions of times larger than Mount Everest in terms of volume, according to Qian Yuan, a researcher studying geodynamics at Arizona State University.
Yuan’s team believes the stains are of other worldly origin: after an ancient, Mars-sized planet entered the Earth, it might have left these pieces behind.
Pieces of a 4.5 billion-year-old planet inside the earth
Nearly 3,219 kilometers below the earth’s surface, whirling iron in the outer core of the planet generates a magnetic field that extends from there into space around our planet.
That vortex is generated in part by a process in which warmer, lighter material rises from the core into the semi-solid mantle above. There it swaps places with cooler, denser mantle material that sinks into the core below. This is known as convection.
The problem is that something at the boundary between the nucleus and the mantle under southern Africa is wreaking havoc on the convection and thus weakening the strength of the magnetic field above it.
It’s plausible, Aubert said, that one of the blobs investigating Yuan’s team gets the blame.
Yuan’s research claims that the stains are remnants of an ancient planet called Theia, which struck the earth 4.5 billion years ago in its infancy. The collision helped create the moon.
After the accident goes the mind, two parts of Theia may have sunk and been preserved in the deepest part of the earth’s mantle.
The animation below, based on a 2016 analysis, shows the location of these planetary fragments.
(Sanne.cottaar / WikimediaCommons / CC-BY-4.0)
Yuan said that these spots – their technical name are large provinces with low shear rates – are between 1.5 and 3.5 denser than the rest of the earth’s mantle, and also warmer.
Thus, if these pieces become involved in convection, it can screw up with the regular flow. This in turn could lead to the iron in the core under southern Africa turning in the opposite direction of iron in other parts of the core.
The orientation of the Earth’s magnetic field depends on the direction in which the iron moves inside. To have a strong magnetic field, the whole thing must be oriented in the same way. Thus, any areas that deviate from the usual pattern weaken the overall integrity of the field.
It is possible, however, that these provinces with a low moving speed are not to blame at all for the field’s weak spot.
“Why does the same weakness not occur in the magnetic field above the Pacific Ocean, where the other province is?” Christopher Finlay, a geophysicist at the Technical University of Denmark, told Insider.
A ‘Hostile Region’
A weaker field enables more charged particles of solar wind to reach satellites and other spacecraft in a low-Earth orbit. This can cause problems with electronic systems, interrupt data collection, and cause expensive computer components to age prematurely.
In the 1970s, 1980s and 1990s, satellite failures were common in the South Atlantic Anomaly, Aubert said.
The European Space Agency still found today that satellites across the region ‘are more likely to encounter technical errors’, such as short-term errors that could disrupt communications.
Therefore, it is common for satellite operators to turn off non-essential components as the objects move through the area.
The Hubble Space Telescope also runs through the anomaly in 10 of its 15 orbits around the Earth every day, spending nearly 15 percent of its time in this ‘hostile region’, according to NASA.
The weak spot is getting weaker and weaker
Researchers use a set of three satellites, collectively nicknamed Swarm, to track the South Atlantic anomaly.
Some studies suggest that the total area of the region has quadrupled in the last 200 years and that it will continue to expand year after year. The anomaly has also weakened by 8 percent since 1970.
In the past decade, Swarm has also noticed that the anomaly has split in half: one area of magnetic weakness has developed across the ocean southwest of Africa, while another sits east of South America.
According to Finlay, this is bad news because it means the hostile space for spacecraft is going to get bigger.
“Satellites will not only have problems over South America, but will also come through southern Africa,” he said.
This article was originally published by Business Insider.
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