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In the Hollywood blockbuster "The Core", the planet's nucleus suddenly stops rotating, causing the earth's magnetic field to collapse. Then deadly microwaves bake the Coliseum and melt the Golden Gate Bridge.
While "almost everything in the film is wrong," according to seismologist Justin Revenaugh of the University of Minnesota, it is true that the Earth's magnetic field protects the planet from deadly and destructive solar rays. Without it, solar winds could deprive the Earth of its oceans and atmosphere.
But the magnetic field of the planet is not static.
The north magnetic pole of the Earth (which is not the same as the geographic north) has led scientists to a sort of goose hunting over the last century. Each year, it moves north about 30 miles on average.
This movement made the global magnetic model (WMM) – which tracks the terrain and informs compasses, GPS on smartphones and navigation systems on board aircraft and ships – imprecise. Since the next scheduled update of the MMM was not expected to occur until 2020, the US military requested an unprecedented rapid update to take into account the acceleration of the Gambol magnetic north.
Today, the authors of a new study have understood why magnetic north could move and have learned to predict these changes.
Follow the movement in the Earth's core
The magnetic field of the Earth exists thanks to the swirls of nickel and liquid iron in the outer core of the planet, 1,800 kilometers below the surface. Anchored in the north and south magnetic poles (which tend to move and even invert every million years or so), the field gains strength and strength, waving according to what is happening goes into the kernel.
Periodic and sometimes random changes in the distribution of this turbulent liquid metal can cause idiosyncrasies in the magnetic field. If you imagine the magnetic field as a series of elastics that sneak between the magnetic poles and the Earth's core, changes in the core essentially cause different elastics at various locations.
These geomagnetic tugs then influence the migration of the north magnetic pole and can even divert it from its current position.
Read more: The north magnetic pole of the Earth has moved – here is what it means for our navigation systems
Until now, predicting these magnetic field changes has been a challenge. But in the new study, geophysicists Julien Aubert and Christopher Finlay attempted to simulate the physical conditions of the Earth 's core by asking supercomputers to perform calculations of a duration of 4 million years. hours.
Researchers knew that the movement of heat from the inside of the planet could influence the magnetic field. In general, this occurs at a speed of 6 miles per year. But their results revealed that sometimes there are pockets of liquid iron in the core that are much warmer and lighter than the surrounding fluid. If the difference between these hot and less dense fluid particles and their colder and denser counterparts is sufficient, the hot liquid can rise very rapidly.
This rapid movement then triggers magnetic waves that break off towards the surface of the nucleus, causing geomagnetic jolts.
"Think of these waves as vibrating strings of a musical instrument," Aubert told Business Insider.
Magnetic north is important for navigation models
Keeping an eye on magnetic north is imperative for European and American armies as their navigation systems rely on the MMM. Commercial airlines and smartphone GPS apps also rely on this model to help pilots and users locate their locations and navigate accordingly.
This is why the British Geological Survey and NOAA update the MMM every five years. The first update requested by the US Army was completed on February 4th.
But even with these periodic updates, geomagnetic shaking makes it difficult to maintain model accuracy, Aubert said.
The new model of his group could solve this problem by helping to predict how the Earth's magnetic field could evolve.
"In the coming years, we anticipate that this should actually be possible for our groups […] to capture the shakes of the past and predict futures with improved accuracy, "said Aubert.
Could the magnetic field ever collapse?
The Earth's magnetic field protects its atmosphere, which represents "an important part of the work" aimed at preventing solar radiation, as Revenaugh said. If we lose our magnetic field, we will finally lose our atmosphere.
But according to Revenaugh, it's very unlikely to happen, because the Earth's core would never stop spinning.
Even if the field has collapsed, the devastating effects described in "The Core" (dead pacemakers, uncontrollable thunderstorms, eviscerated national landmarks) would not follow.
According to Revenaugh, a much more likely scenario would involve the reversal of magnetic poles, as was the case 780,000 years ago. When such reversals occur (there have been several in the history of the Earth), the magnetic field drops to about 30% of its total force, he said.
Although this is a distant scenario, Revenaugh added that it was always important to improve scientists' understanding of the magnetic field.
"The better we can model it, the better we can understand what is going on," he said.
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