The intensity of Earth’s geomagnetic field has been dropping for the
past 200 years, at a rate that some scientists suspect may cause the
field to bottom out in 2,000 years, temporarily leaving the planet
unprotected against damaging charged particles from the sun. This drop
in intensity is associated with periodic geomagnetic field reversals, in
which the Earth’s North and South magnetic poles flip polarity, and it
could last for several thousand years before returning to a stable,
shielding intensity.
With a weakened geomagnetic field, increased
solar radiation might damage electronics — from individual pacemakers to
entire power grids — and could induce genetic mutations. A reversal may
also affect the navigation of animals that use Earth’s magnetic field
as an internal compass.
But according to a new MIT study in the Proceedings of the National Academy of Sciences,
the geomagnetic field is not in danger of flipping anytime soon: The
researchers calculated Earth’s average, stable field intensity over the
last 5 million years, and found that today’s intensity is about twice
that of the historical average.
This indicates that the current
field intensity has a long way to fall before reaching an unstable level
that would lead to a reversal.
“It makes a huge difference,
knowing if today’s field is a long-term average or is way above the
long-term average,” says lead author Huapei Wang, a postdoc in MIT’s
Department of Earth, Atmospheric and Planetary Sciences. “Now we know we
are way above the unstable zone. Even if the [field intensity] is
dropping, we still have a long buffer that we can comfortably rely on.”
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