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Crustal and upper Mantle Electrical Conductivity Structures and the South Atlantic Magnetic Anomaly: Simultaneous Research on Eletromagnetic Induction and Geomagnetic Variations


Observations of electromagnetic induction and magnetic variations of the external geomagnetic field are being carried out simultaneously in Brazil. The former provides the knowledge of the electrical conductivity distribution in the crust and upper mantle which can be useful in refined studies of the South Atlantic Magnetic Anomaly (Sama) and the Equatorial Electrojet (Eej). Similarly, the knowledge of the characteristics of these geomagnetic peculiarities can be used to verify their effects on the induction studies. This study combines ground-based geomagnetic data from permanent observatories, one dedicated mobile array of digitally recording magnetometers (GDS) and magnetotelluric (MT) campaigns. Thus, the conductivity structure of the lithosphere and the peculiarities of the Sama and the Eej can be well delineated as well as the source effects on the electromagnetic induction studies. In terms of geomagnetic induction, the areas to be studied are the southeastern coastal belt, from southern Rio de Janeiro (tertiary basins of Taubaté, São Paulo, Curitiba, Sete Barras, Volta Redonda, Resende, Guanabara and Itaboraí) to Santa Catarina (torres sincline), the northern border of the Paraná sedimentary basin and the Parnaíba basin at the Brazilian northern region. On the other hand, the geomagnetic micropulsations and daily variations recorded at the earth s surface are used to study the physical processes involving transfer of solar energy to the magnetosphere/ionosphere, i.e. solar-terrestrial relaionship, at low geomagnetic latitudes. (AU)

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