Abstract
Annual mean data from worldwide magnetic observatories show that there was a jerk1 (step-change in the second time derivative) in the geomagnetic field, which took place over an interval of <2 yr around 1970. If such a short-lived phenomenon originated in the Earth's core, and were still detectable after passing through the mantle to the surface, this would imply a much lower conductivity for the lower mantle than had been believed previously. Here we show by an objective test that most of the jerk has an internal origin.
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Malin, S., Hodder, B. Was the 1970 geomagnetic jerk of internal or external origin?. Nature 296, 726–728 (1982). https://doi.org/10.1038/296726a0
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DOI: https://doi.org/10.1038/296726a0
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