Earth’s geomagnetic armor has a crack and is growing.
A weak point in our planet’s magnetic field, located over the southern Atlantic Ocean, has grown in size over the past two centuries and is beginning to split in two.
For those of us on the ground, this is not a cause for concern: the protective field continues to protect the planet from deadly solar radiation.
But the South Atlantic Anomaly, as it is appropriately called, does affect satellites and other spacecraft traversing an area between South America and South Africa.
That’s because there are higher amounts of charged solar particles leaking through the field, which can cause computer and circuit failures.
The source of this growing “dent,” as NASA calls it, is a bit of a mystery. But scientists hope it will continue to expand.
“This thing is going to get bigger in the future,” Julien Aubert, a geomagnetism expert at the Institute of Earth Physics in Paris, told Insider.
Aubert believes the dent may have a connection to two giant blobs of dense rock buried 2,897 kilometers (1,800 miles) inside Earth. Due to their composition, the stains alter 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 that the spots have an otherworldly origin: After an ancient planet the size of Mars hurtled toward Earth, it could have left these pieces behind.
Chunks of a 4.5 billion-year-old planet inside Earth
Almost 3,219 kilometers below Earth’s surface, the swirling iron in the planet’s outer core generates a magnetic field that extends from there to the space surrounding our planet.
That eddy is generated, in part, by a process in which the hotter and lighter material in the core rises up into the semisolid mantle above. There, it swaps places with colder, denser mantle material, which sinks into the core below. This is known as convection.
The problem is that something at the core-mantle boundary below southern Africa is wreaking havoc on that convection, thus weakening the strength of the magnetic field above it.
It’s plausible, Aubert said, that one of the blemishes Yuan’s team is investigating is to blame.
Yuan’s research posits that the spots are remnants of an ancient planet called Theia, which struck Earth in its infancy 4.5 billion years ago. The collision helped create the Moon.
After that accident, it is thought, two parts of Theia may have sunk and preserved deep in the Earth’s mantle.
The animation below, based on an analysis from 2016, shows the location of these planetary fragments.
Yuan said that these patches (their technical name is large low-shear-speed provinces) are 1.5 to 3.5 percent denser than the rest of the Earth’s mantle, and also hotter.
So when these chunks get involved in convection, they could interfere with regular flow. That, in turn, can drive iron in the core below southern Africa to spin in the opposite direction to iron elsewhere in the core.
The orientation of the Earth’s magnetic field depends on the direction in which the iron moves inside it. To have a strong magnetic field, everything must be oriented the same way. Therefore, any area that deviates from the usual pattern weakens the overall integrity of the field.
Still, these low-cutting speed provinces may not be to blame for the field’s weak point at all.
“Why doesn’t the same weakness occur in the magnetic field over the Pacific, where the other province is?” Christopher Finlay, a geophysicist at the Technical University of Denmark, told Insider.
A ‘hostile region’
A weaker field allows the more charged particles from the solar wind to reach satellites and other spacecraft in low Earth orbit. That can cause problems with electronic systems, disrupt 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.
Even today, the European Space Agency has found that satellites flying through the region are “more likely to experience technical failures,” such as brief failures that can disrupt communications.
That is why it is common for satellite operators to turn off nonessential components when objects pass through the area.
The Hubble Space Telescope also traverses the anomaly in 10 of its 15 orbits around Earth each day, spending nearly 15 percent of its time in this “hostile region,” according to NASA.
The weak point is weakening
Researchers use a set of three satellites, collectively dubbed the Swarm, to monitor the South Atlantic Anomaly.
Some studies suggest that the total area of the region has quadrupled in the last 200 years and that it continues to expand year after year. The anomaly has also weakened by 8 percent since 1970.
In the last decade, Swarm also observed that the anomaly has been split in half: one area of magnetic weakness has developed over the ocean in southwestern Africa, while another is located east of South America.
This is bad news, according to Finlay, because it means that the hostile region for spacecraft will get bigger.
“The satellites will not only have problems in South America, but they will also be affected when they reach southern Africa,” he said.
This article was originally published by Business Insider.
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