An already gigantic hole in Earth’s natural force field has grown by nearly half the size of Europe in 10 years, according to a new study.
The Earth is protected by the cosmic equivalent of cling film called the magnetic field, generated by swirling iron currents in the liquid outer core.
The magnetosphere protects us against dangerous galactic and solar rays, yet it has been weakening by about 10% over the last 200 years or so.
Adding to the strangeness is the South Atlantic Anomaly, a roughly 4.3million square mile-sized magnetic weak spot.
Discovered in 1958, the region stretches from South America across the southern Atlantic Ocean toward southwestern Africa.
But a new paper has revealed that the gap has expanded by about two million square miles since 2014.
The study, published in the journal Physics of the Earth and Planetary Interiors, says the hole has even changed shape.
But what does this mean exactly? Metro spoke with the study’s co-author, a European space official and an independent expert to find out.
What is the South Atlantic anomaly?
You can think of the Earth’s magnetic field a bit like a dynamo bike lamp, where light is generated by the cyclist’s pedalling.
Instead of a cyclist’s feet, it’s an ocean of molten iron 1,900 miles below your feet that creates a magnetic field that flows upwards, forming two rings that join near the north and south poles.
But over the South Atlantic, the magnetic field only reaches about 120 miles high, far lower than the field’s average altitude of about 400 miles.
The hole allows particles from a band of intense radiation surrounding the Earth, called the Van Allen belts, to get closer to touching the surface.
The anomaly doesn’t have a fixed location or shape but the centre is just off the coast of Brazil, where it is unusually weak, said study lead author Chris Finlay.
‘By “unusually weak” we mean the strength in this region is only about half what would be expected if it were a simple tilted dipole,’ the professor of geomagnetism at the Technical University of Denmark said to Metro.
Why is it growing?
To answer this question, Finlay and his team analysed 11 years of measurements from a group of three satellites launched in 2013.
The probes were launched by the European Space Agency as part of its Swarm mission.
The mission’s manager, Anja Strømme, told Metro that the anomaly is caused by a quirk in our planet’s liquid core and the rocky mantle.
‘Beneath the South Atlantic Anomaly, the magnetic field lines are going in the “wrong” direction, they are going into the core instead of coming out of the core as they should normally do in the southern hemisphere,’ she says.
‘These reversed magnetic flux regions have moved in the past years, having separated the regions under South America from those located under southern Africa. This is leading to the overall South Atlantic Anomaly growing.
‘This shows us that the processes in the Earth’s core and the core-mantle boundary are very complex and a reminder that the Earth’s magnetic field is not a simple dipole.’
The data also revealed that since 2014, the field has torn a lobe towards Africa, where the field is weakening rapidly.
It has also shrunk by about the size of India over Canada, while Siberia’s has swelled by an area the size of Greenland.
These changes, the study found, were likely due to Earth’s north pole shifting towards Siberia.
Finlay said that the Earth’s magnetic field is pretty strange and as much as it might seem that we know a lot, scientists have a lot more to learn.
‘We are working to better understand this process, but don’t yet know all the details,’ he added.
Should we be worried?
Cosmic rays can short-circuit satellites or even cause electrical surges, leading to blackouts down below, Richard Holme, professor of geophysics at the University of Liverpool, told Metro.
Some satellites passing over the anomaly have suffered malfunctions because particles were able to pierce the magnetic bubble.
‘Astrophysics satellites are routinely switched off when they fly over that area,’ Holme said.
‘For Earth observing satellites, this is more difficult – if you want to look at the Amazon, then turning off every time you fly over it doesn’t work!
‘More chance of damage, yes, but not doom – certainly if Elon Musk is anything to go by, there is plenty of money to launch new ones.’
Some scientists have suggested that the anomaly hints that the magnetic field may be about to disappear.
The reason sounds almost like the stuff of science fiction – the planet’s north and south poles are flipping, called a reversal.
That, or it’s just a run-of-the-mill fluctuation that’s nothing to worry about, says Holme.
‘This has happened many times in Earth’s history, and it hasn’t been shown to be associated with anything particularly nasty like a mass extinction,’ he adds.
‘There is strong evidence that, although weakening, the field is not actually reversing at the moment, but will recover its strength.’
Until then, Holme says people are going to keep asking him if the magnetic field is reversing and, if so, are we all going to die?
‘I would say no to the first question, and yes to the second,’ Holme said, ‘although it has nothing to do with the magnetic field.’
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