Just what I’ve been saying for more than 20 years!
“Simulations show magnetic field can change 10 times faster than previously thought,” reads the headline from the University of Leeds.
Here are excerpts from the article:
6 July 2020 – A new study by the University of Leeds and University of California at San Diego reveals that changes in the direction of the Earth’s magnetic field may take place 10 times faster than previously thought.
To capture the evolution of the field back through geological time scientists analyze the magnetic fields recorded by sediments, lava flows and human-made artefacts (sic). Accurately tracking the signal from Earth’s core field is extremely challenging and so the rates of field change estimated by these types of analysis are still debated.
Now, Dr. Chris Davies, associate professor at Leeds and Professor Catherine Constable from the Scripps Institution of Oceanography, UC San Diego, in California have taken a different approach. They combined computer simulations of the field generation process with a recently published reconstruction of time variations in Earth’s magnetic field spanning the last 100,000 years
Their study, published in Nature Communications, shows that changes in the direction of Earth’s magnetic field reached rates that are up to 10 times larger than the fastest currently reported variations of up to one degree per year.
They demonstrate that these rapid changes are associated with local weakening of the magnetic field. This means these changes have generally occurred around times when the field has reversed polarity or during geomagnetic excursions when the dipole axis—corresponding to field lines that emerge from one magnetic pole and converge at the other—moves far from the locations of the North and South geographic poles.
The clearest example of this in their study is a sharp change in the geomagnetic field direction of roughly 2.5 degrees per year 39,000 years ago. This shift was associated with a locally weak field strength, in a confined spatial region just off the west coast of Central America, and followed the global Laschamp excursion—a short reversal of the Earth’s magnetic field roughly 41,000 years ago.
Thanks to Laurel for this link
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July 8, 2020 at 10:53AM