|
|
|
|
|||||
|
||||||
Subject: Anomalies hint at magnetic pole flip
From: Young, Derrick (NCR) (youngd@XXX.XXX)
Date: Fri Apr 12 2002 - 11:26:47 EDT
don't know how many of you are aware of this - makes interesting reading -
and another good reason to study/practice CELNAV. This is from the New
Scientist (a British publication) -
http://www.newscientist.com/news/news.jsp?id=ns99992152
derrick
Anomalies hint at magnetic pole flip
19:00 10 April 02 Exclusive from New Scientist-The Earth's magnetic poles
might be starting to flip say researchers who have seen strange anomalies in
our planet's magnetic field.
The magnetic field is created by the flow of molten iron inside the Earth's
core. These circulation patterns are affected by the planet's rotation, so
the field normally aligns with the Earth's axis - forming the north and
south poles.
But the way minerals are aligned in ancient rock shows that the planet's
magnetic dipole occasionally disappears altogether, leaving a much more
complicated field with many poles all over the planet. When the dipole comes
back into force, the north and south poles can swap places.
The last reversal happened about 780,000 years ago, over a period of several
thousand years. Now Gauthier Hulot from the Institute of Earth Sciences in
Paris and his colleagues think they have spotted early signs of another
reversal.
South African anomaly
They used data from the Ørsted satellite to study strange variations in the
Earth's magnetic field. In particular, one large patch under South Africa is
pointing in the opposite direction from the rest of the Earth's field and
has been growing for hundreds of years.
The anomalies have already reduced the overall strength of the planet's
magnetic field by about 10 per cent. If they continue to grow at the same
rate, the Earth's dipole will disappear within just two millennia.
But Ørsted is the first satellite to take a snapshot of the Earth's magnetic
field for 20 years, and such scant data makes it difficult to predict future
shifts.
"We can't really tell what will happen," says Hulot. "But we speculate that
we're in an unusual situation that might be related to a reversal."
Journal reference: Nature (vol 416, p 620)
|