Earth's magnetic field dramatically flipped a little more than 40,000 years ago. We can now experience this epic upheaval, thanks to a clever interpretation of information collected by the European Space Agency's Swarm satellite mission.
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Earth's magnetosphere formed by the interaction between the
planet's geomagnetic field and solar winds. (NASA's Scientific Visualization
Studio) |
Combining the satellite data with evidence of magnetic field
line movements on Earth, European geoscientists mapped the so-called Laschamps
event and represented it using natural noises like the creaking of wood and the
crashing of colliding rocks.
The resulting compilation – unveiled in 2024 by the
Technical University of Denmark and the German Research Center for Geosciences
– is unlike anything you've ever heard.
Generated by the swirling liquid metals in our planet's
core, Earth's magnetic field reaches tens to hundreds of thousands of
kilometers into space, protecting us all by deflecting atmosphere-stripping
solar particles.
In its current orientation, the field lines form closed
loops that are directed south to north above the planet's surface, and then
north to south deep within it. Yet every so often the field randomly flips its
polarity. Were this to happen again today, our north-pointing compasses would
point to the South Pole.
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Strength of the magnetic field at Earth's surface. (ESA) |
The last such cataclysmic event occurred about 41,000 years
ago, leaving a signature in the Laschamps lava flows in France. As the field
weakened to only 5 percent of its current strength the reversal process allowed
a surpluss of cosmic rays to pass into Earth's atmosphere.
Ice and marine sediment preserve isotopic signatures of this
higher-than-normal solar bombardment, with levels of beryllium-10 isotopes
doubling during the Laschamps event, according to a study published last year.
These altered atoms are formed when cosmic rays react with
our atmosphere, ionizing the air and frying the ozone layer. With global
climate change being a potential consequence, it's speculated the extinction of
Australia's megafauna as well as changes in human cave use may have been
associated with this event.
"Understanding these extreme events is important for
their occurrence in the future, space climate predictions, and assessing the
effects on the environment and on the Earth system," German Research
Center for Geosciences geophysics Sanja Panovska explained at the time.
It took 250 years for the Laschamps reversal to take place
and it stayed in the unusual orientation for about 440 years. At most, Earth's
magnetic field may have remained at 25 percent of its current strength as the
north polarity drifted to the south.
Recent magnetic field anomalies like the weakening over the
Atlantic ocean have led to questions about an impending reversal today, but
recent research suggests these anomalies are not necessarily connected to
flipping events.
The South Atlantic anomaly is, however, exposing satellites
in the area to higher levels of radiation.
Since 2013, ESA's Swarm constellation has been measuring
magnetic signals from Earth's core, mantle, crust, oceans, ionosphere, and
magnetosphere so we can better understand our planet's geomagnetic field and
predict its fluctuations.