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Authors: Gregori, G. P.* 
Dong, W. J.* 
Gao, X. Q.* 
Gizzi, F. T.* 
Title: The separation of the geomagnetic field originated in the core, in the asthenosphere, and in the crust
Issue Date: Apr-1999
Series/Report no.: 2/42 (1999)
Keywords: dynamo
spatial spectrum
white spectrum
Nevanlinna’s law
Hamilton’s principle
geomagnetic anomalies
inner core
outer core
Subject Classification04. Solid Earth::04.05. Geomagnetism::04.05.01. Dynamo theory 
Abstract: The separation of the field produced by different internal sources can be accomplished by means of the so-called spatial spectrum of the geomagnetic field of internal origin. It is shown how such a rationale, when suitably interpreted, allows to recognize the field that is originated by electric currents that flow either on the Inner-Core Boundary (ICB), or on the Core-Mantle Boundary (CMB), or on the Asthenosphere-Lithosphere Boundary (ALB). It appears crucial, however, to rely on satellite measurements alone, because ground-based and ship- and air-borne records are severely perturbed by the crustal field. Therefore, it is shown, on the basis of a critical reconsideration of a few key-papers in the literature, that the best approach is to avoid mixing together all kinds of measurements. Satellite data are best suited for recognizing the dynamo field, while ground-based, ship- and air-borne records, which are measured much closer to crustal sources, are best suited, after subtraction of the satellite-derived dynamo field, for inferring the geomagnetic anomalies that are to be associated with crustal sources alone.
Appears in Collections:Annals of Geophysics

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