The geomagnetic armor of the Earth has a crack and it is growing.
A weak spot in our planet’s magnetic field, located over the South 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 aptly called, affects satellites and other spacecraft passing through an area between South America and southern Africa.
This is because larger quantities of charged solar particles seep through the field there, which can cause malfunctions in computers and circuits.
The source of this growing ‘dent’, as NASA calls it, is a bit of a mystery. But scientists expect it to continue to grow.
“This thing will grow in size in the future,” Julien Aubert, a geomagnetism expert at the Paris Institute of Earth Physics, told Insider.
Aubert thinks the dent may be related to two giant blobs of dense rock buried 2,897 kilometers (1,800 miles) into the earth. Due to their composition, the blobs disrupt the liquid metal in the outer core that generates the magnetic field.
Both blobs are “millions of times larger than Mount Everest in terms of volume,” said Qian Yuan, a researcher studying geodynamics at Arizona State University.
Yuan’s team thinks the blobs are of alien origin: After an ancient planet the size of Mars entered Earth, it may have left these pieces behind.
Chunks from a planet 4.5 billion years old in the Earth
Almost 3,219 kilometers below the Earth’s surface, swirling iron in the planet’s outer core generates a magnetic field that extends from there all the way to space around our planet.
That vortex is generated in part by a process in which hotter, lighter material rises from the core into the semi-solid mantle above. There it changes places with cooler, denser jacket material, which sinks into the underlying core. This is known as convection.
The problem is, something on the boundary between the core and mantle underneath southern Africa is doing great damage to that convection, weakening the strength of the magnetic field above it.
It’s plausible, Aubert said, that one of the blobs Yuan’s team is investigating is to blame.
Yuan’s research states that the blobs are remnants of an ancient planet called Theia, which hit Earth 4.5 billion years ago. The collision helped create the moon.
After that crash, it is believed, 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 these blobs – their technical name is low-shear large counties – are between 1.5 and 3.5 percent denser than the rest of the mantle, and hotter too.
So when these chunks come into convection, they can rotate with the normal flow. That, in turn, can cause the iron in the core beneath southern Africa to swirl in the opposite direction from iron in other parts of the core.
The orientation of the Earth’s magnetic field depends on the direction the iron is moving within. To have a strong magnetic field, the whole thing has to be oriented the same way. So any areas that deviate from the usual pattern will weaken the overall integrity of the field.
Still, these low shear rate provinces may not be to blame for the field’s weakness at all.
“Why doesn’t the same weakness occur in the magnetic field over 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 allows more charged particles from solar wind to reach satellites and other spacecraft in 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 disturbances were common in the South Atlantic anomaly, Aubert said.
Even today, the European Space Agency has discovered that satellites flying through the region are “more likely to experience technical glitches”, such as brief glitches that can disrupt communications.
Therefore, it is common for satellite operators to turn off non-essential components when the objects pass through the area.
The Hubble Space Telescope also passes the anomaly in 10 of its 15 orbits around Earth every day and spends nearly 15 percent of its time in this “hostile region,” according to NASA.
The weak spot is getting weaker
Researchers use a set of three satellites, collectively nicknamed Swarm, to keep an eye on the South Atlantic anomaly.
Some studies suggest that the total area of the region has quadrupled in the last 200 years and continues to grow year after year. The anomaly has also weakened by 8 percent since 1970.
Over the past decade, Swarm also noted that the anomaly has split in two: an area of magnetic weakness has developed over the ocean southwest of Africa, while another area is east of South America.
According to Finlay, this is bad news because it means that the hostile spacecraft region will get bigger.
“Satellites will not only have problems over South America, but will also be affected when they come over southern Africa,” he said.
This article was originally published by Business Insider.
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