Abstract
Here we have monitored the secular variation (s.v.) of the geomagnetic field since the beginning of the century using observatory data. The energy of the s.v. field and the westward drift rate decreased from 1912–13 to 1969. Since 1969 these two parameters have again been increasing. The occurrence of jerks (steps in the second time derivative of the field) has been discovered at these two epochs (1912 and 1969). Moreover, after 1969, the s.v. field tends to have the same geographical distribution it had around 1912.
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Gire, C., Le Mouel, J. & Ducruix, J. Evolution of the geomagnetic secular variation field from the beginning of the century. Nature 307, 349–352 (1984). https://doi.org/10.1038/307349a0
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DOI: https://doi.org/10.1038/307349a0
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