North will remain North for now, say geo-magnetic boffins

Much-feared magnetic field 'flip' not happening anytime soon

Earth's magnetic field flips from time to time, but boffins are now confident it won't happen again any time soon.

Research published April 30 in the Proceedings of the National Academy of Sciences of the United States of America (PNAS) says Earth scientists' assessment of our magnetosphere suggest we're more likely to see a wobble than a flip.

Which is rather good news: a reversal of the field would be pose many and stern challenges. As this piece from The Conversation in 2017 explained, a reversal would be accompanied by a weaker magnetic field surrounding the Earth, at least for a while. That would reduce our protection against cosmic rays, with other effects on electrical grids, electronics, aviation, or even living organisms over-exposed to energetic particles.

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The international group of researchers* reached a reassuring conclusion in their work: “Earth’s magnetic field is not in an early stage of a reversal or excursion.”

While the geomagnetic field is undeniably declining – around five per cent per century since at least 1840 – and while there's a particularly pronounced anomaly over the South Atlantic ocean, neither of these guarantee an imminent reversal, the authors concluded.

They used two geologically-recent events as their model: one at Laschamp around 41,000 years ago, and the other at Mono Lake, 34,000 years ago. Both of those events featured multiple magnetic anomalies, and both lasted more than a thousand years.

Those two events, the paper said, were the most extreme disruptions of the geomagnetic field in the last 50,000 years, yet still didn't end in catastrophe. The field settled down again, providing its protection against cosmic rays and leaving North and South where they still remain.

Yes, Earth appears “overdue” for a reversal, since they happen on average a few times per million years (with very wide error bars – The Conversation's piece noted gaps can last up to ten million years), and it hasn't happened since the Brunhes-Matuyama reversal around 780,000 ago.

Even if a reversal did take place, the timescale would be so long people would have time to prepare: even the Laschamp event, which The Conversation described as a “temporary reversal”, took 250 years to develop and lasted 1,000 years. ®

* Authors were Maxwell Brown (University of Iceland and the German Research Centre for Geosciences), Monika Korte (German Research Centre for Geosciences), Richard Holme (University of Liverpool and the Max Planck Institute for Solar System Research), Ingo Wardinski (German Research Centre for Geosciences and the Université de Nantes) and Sydney Gunnarson (University of Iceland)

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