Models of geomagnetic secular variations on recent times for South America
Palaeosecular variations of the geomagnetic field obtained from palaeomagnetic and radiometric studies carried out on the bottom sediments from three lakes in southwestern Argentina (records extend back to about 6000 years by 14C dating) were compared with results from different theoretical models,...
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| Formato: | JOUR |
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| Acceso en línea: | http://hdl.handle.net/20.500.12110/paper_00319201_v64_n2-4_p133_Sinito |
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| Sumario: | Palaeosecular variations of the geomagnetic field obtained from palaeomagnetic and radiometric studies carried out on the bottom sediments from three lakes in southwestern Argentina (records extend back to about 6000 years by 14C dating) were compared with results from different theoretical models, which suggested the possible sources of the field. Attempts were then made to simulate long period secular variations using modified Alldredge and Hurwitz's models. The Alldredge and Hurwitz model uses a central dipole and eight radial dipoles, all at the same distance from the centre of the Earth, as a first approximation to the sources of the geomagnetic field. The modified models, which have been used to describe the northern hemisphere data, comprise eight radial dipoles, which oscillate sinusoidally and/or drift. The different parameters of the models were fitted to the palaeomagnetic data from southwestern Argentina. The best fit was obtained with a mixed model; between 6000 and 3000 years BP all radial dipoles oscillate and some of them drift as well. Later the drift rates become lower and, finally, between 1700 years BP and present times, all radial dipoles only oscillate. © 1990. |
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