New Clues to Earth's Mangetic Flip-Flops

[Ivan Seeking]

When North Becomes South: New Clues to Earth's Mangetic Flip-Flops

Next time Earth's magnetic field flips, compass needles will point South instead of North. But scientists can't say when it will occur, and until now they've disagreed on how long the transitions take.

A new study pins down how long it took for the last four reversals to play out. It also finds that the dramatic turnarounds occur more quickly nearer the equator than at higher latitudes closer to the poles.

...In the past 15 million years, there have been four reversals every 1 million years, or about one shift each 250,000 years, Clement explained. The last one, however, was 790,000 years ago. That might suggest we're overdue for a big change. Not necessarily so, Clement says. The flips are not periodic, meaning they don't adhere to a schedule of even intervals.

Yet the intensity of the magnetic field has been dropping for the last 2,000 years, and "it has dropped significantly" during the past two decades, Clement said. One recent study shows the decline in strength amounts to 10 percent over the last 150 years. [continued]

http://space.com/scienceastronomy/earth_poles_040407.html

 

[Andre]

I wonder what "mangnetic" is? Maybe-A-No-Go-netic?

Anyway, yes the magnetic field strength is decreasing, quite natural, considering that it has never been registrated being stronger than nowadays. It can only go down after that. But it's not a clear sign of a magnetic flip. It's even more likely that a (Palaeo) Magnetic Excurion (PME) could follow. They seem to happen about every 100,000 years on a global level. The field strength reduces very strongly and the bipolarity (N and S) changes apparently to multiple poles. A PME seem to last some 5000-10,000 years
This (fig 1) seems to be the current consensus about the palaeo magnetic field strenght in the current "Brunhes chron" as this period with the "normal" magnetic polarity is called. There are many more reports of (local?) Palaeo-Magnetic-Excursions like this perhaps 10,000 years ago and whether or not the Mono Lake excursion (26,000 years ago) is identical to the Lachamps excursion (40,000 years ago).

Anyway, the alleged Gothenburg Paleo Magnetic Flip (12,000 years ago) has been debunked. This is the last reference that I could google up with.

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