Dear Friends,
Be Well.
David
Earth’s magnetic field overdue for a chaos-causing (possibly life-altering) flip
NASA/THEMIS
Illustration showing magnetic
reconnection in the magnetotail triggering the onset of substorms.
Substorms are the sudden violent eruptions of space weather that release
solar energy trapped in the Earth's magnetic field. The reconnections
trigger dynamic changes in the auroral displays seen near Earth's
northern and southern magnetic poles, causing a burst of light and
movement in the Northern and Southern Lights.
LONDON — The discovery by NASA
rover Curiosity of evidence that water once flowed on Mars – the most
Earth-like planet in the solar system – should intensify interest in
what the future could hold for mankind.
The only thing stopping Earth having a lifeless environment like Mars
is the magnetic field that shields us from deadly solar radiation and
helps some animals migrate, and it may be a lot more fragile and febrile
than one might think.
Scientists say earth’s magnetic field is weakening and could all but
disappear in as little as 500 years as a precursor to flipping upside
down.
It has happened before – the geological record suggests the magnetic
field has reversed every 250,000 years, meaning that, with the last
event 800,000 years ago, another would seem to be overdue.
“Magnetic north has migrated more than 1,500 kilometres over the past
century,” said Conall Mac Niocaill, an earth scientist at Oxford
University. “In the past 150 years, the strength of the magnetic field
has lessened by 10 percent, which could indicate a reversal is on the
cards.”
While the effects are hard to predict, the consequences may be
enormous. The loss of the magnetic field on Mars billions of years ago
put paid to life on the planet if there ever was any, scientists say.
Mac Niocaill said Mars probably lost its magnetic field 3.5-4.0
billion years ago, based on observations that rocks in the planet’s
southern hemisphere have magnetisation.
The northern half of Mars looks younger because it has fewer impact
craters, and has no magnetic structure to speak of, so the field must
have shut down before the rocks there were formed, which would have been
about 3.8 billion years ago.
“With the field dying away, the solar wind was then able to strip the
atmosphere away, and you would also have an increase in the cosmic
radiation making it to the surface,” he said.
“Both of these things would be bad news for any life that might have
formed on the surface – either wiping it out, or forcing it to migrate
into the interior of the planet.”
RIGHT HERE, RIGHT NOW
Earth’s magnetic field has always restored itself but, as it
continues to shift and weaken, it will present challenges – satellites
could be more exposed to solar wind and the oil industry uses readings
from the field to guide drills.
In nature, animals which use the field could be mightily confused –
birds, bees, and some fish all use the field for navigation. So do sea
turtles whose long lives, which can easily exceed a hundred years, means
a single generation could feel the effects.
Birds may be able to cope because studies have shown they have
back-up systems that rely on stars and landmarks, including roads and
power lines, to find their way around.
The European Space Agency is taking the issue seriously. In November,
it plans to launch three satellites to improve our fairly blurry
understanding of the magnetosphere.
The project – Swarm – will send two satellites into a 450 kilometre
high polar orbit to measure changes in the magnetic field, while a third
satellite 530 kilometres high will look at the influence of the sun.
DESCENT INTO CHAOS
Scientists, who have known for some time the magnetic field has a
tendency to flip, have made advances in recent years in understanding
why and how it happens.
The field is generated by convection currents that churn in the
molten iron of the planet’s outer core. Other factors, such as ocean
currents and magnetic rocks in the earth’s crust also contribute.
The Swarm mission will pull all these elements together to improve
computer models used to predict how the magnetic field will move and how
fast it could weaken.
Ciaran Beggan, a geomagnetic specialist at the British Geological
Survey in Edinburgh, said studies have also refined our understanding of
how the field reverses.
They have focused on lava flows. When these cool and form crystals
the atoms in iron-rich molten rock align under the influence of the
magnetic field, providing a geological memory of the earth’s field.
But that memory looks different in various locations around the
world, suggesting the reversal could be a chaotic and fairly random
process.
“Rather than having strong north and south poles, you get lots of
poles around the planet. So, a compass would not do you much good,” said
Beggan.
While the whole process takes 3,000-5,000 years, latest research
suggests the descent into a chaotic state could take as little as 500
years, although there are significant holes in scientific understanding.
“Although electricity grids and GPS systems would be more vulnerable,
we are not really sure how all the complex things that are linked
together would react,” Beggan said.
© Thomson Reuters 2012
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