Earth's magnetic field has a hole over 11 million square kilometers and it's growing
An already gigantic hole in Earth's natural force field has grown to nearly half the size of Europe in 10 years, according to a new study.
Earth is protected by a magnetic field, generated by currents of iron swirling in the liquid outer core. The magnetosphere protects against dangerous galactic and solar radiation, but it has weakened by about 10 percent over the past 200 years.
Adding to the puzzle is the South Atlantic Anomaly, a weak magnetic spot measuring over 11 million square kilometers.
Discovered in 1958, the region stretches from South America across the southern Atlantic Ocean to southwest Africa. But a new paper has found that the gap has widened by about five million square kilometers since 2014.
The study, published in the journal Physics of the Earth and Planetary Interiors, says the hole has even changed shape. But what exactly does that mean?
You can think of the Earth's magnetic field a bit like a bicycle dynamo, where the light is generated by the cyclist's pedaling. Instead of a cyclist's legs, it's an ocean of molten iron 3 km below your feet that creates a magnetic field that flows upward, forming two rings that meet near the north and south poles.
But over the South Atlantic, the magnetic field reaches only about 305 km high, far below the average field height of about 644 km. The hole allows particles from a band of intense radiation that surrounds the Earth, called the Van Allen belts, to come closer to touching the surface.
The anomaly has no specific location or shape, but the center is just off the coast of Brazil where it is extremely weak, lead author of the study Chris Finlay told Metro.
Finlay and his team analyzed 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.
Mission manager Anja Strømme told Metro that the anomaly is caused by a feature in our planet's liquid core and rocky mantle.
“These regions of reversed magnetic flux have been moving in recent years, separating the regions under South America from those located under southern Africa. This is leading to the overall increase in the South Atlantic Anomaly. This tells us that the processes in the Earth's core and at the core-mantle boundary are very complex.”
The data also revealed that since 2014, the magnetic field has split into a lobe toward Africa, where the field is rapidly weakening. It has also shrunk by about the size of India over Canada, while that over Siberia has expanded by an area the size of Greenland.
The study found that these changes are likely due to the shift of the Earth's north pole towards Siberia, but there is no danger to humanity.
"This has happened many times in Earth's history and has not been shown to be associated with anything particularly bad like a mass extinction. There is strong evidence that, although it is weakening, the field is not actually reversing but will recover its strength," said Richard Holme, professor of geophysics at the University of Liverpool.
