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GEOPHYSICAL RESEARCH LETTERS, VOL. 31, L12614, doi:10.1029/2004GL020232, 2004

Separating the magnetospheric disturbance magnetic field into external and transient internal contributions using a 1D conductivity model of the Earth

Stefan Maus

Cooperative Institute for Research in Environmental Sciences, University of Colorado, Boulder, Colorado, USA


Peter Weidelt

Institut für Geophysik und extraterrestrische Physik, University of Braunschweig, Braunschweig, Germany


Abstract

Magnetospheric fields and their induced counterparts are the largest source of error in models representing the geomagnetic field. Of particular concern is the current practice of coupling the internal induced field for convenience to the external field by a real constant, independent of the frequency content of the external inducing source. The error introduced into field models by this simplified representation is of the order of 5 nT on average. Here, we propose an accurate representation of the symmetric part of the disturbance field which is easy to implement. Using a 1D conductivity model of the Earth, we split the disturbance D st index into two new indices, E st and I st, which track the transient evolution of the symmetric part of the external and induced disturbance field. The ensuing D st-based transient correction for geomagnetic field models is in remarkable agreement with the transient effect observed in CHAMP, Ørsted and SAC-C satellite magnetic measurements.

Received 12 April 2004; accepted 27 May 2004; published 29 June 2004.

Index Terms: 1515 Geomagnetism and Paleomagnetism: Geomagnetic induction; 1555 Geomagnetism and Paleomagnetism: Time variations—diurnal to secular; 2778 Magnetospheric Physics: Ring current.

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Citation: Maus, S., and P. Weidelt (2004), Separating the magnetospheric disturbance magnetic field into external and transient internal contributions using a 1D conductivity model of the Earth, Geophys. Res. Lett., 31, L12614, doi:10.1029/2004GL020232.