A geomagnetic field model for year 2001 with daily estimations of dipole terms

Lesur, Vincent; Thomson, Alan; Macmillan, Susan. 2003 A geomagnetic field model for year 2001 with daily estimations of dipole terms. [Poster] In: EGS-AGU-EUG Joint Assembly, Nice, France, 7-11 April 2003. (Unpublished)

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We describe derivations of spherical harmonic models of the main field (up to degree/order 20) and its secular variation (up to degree/order 10) using a full year of Ørsted data and applying new modelling techniques for degree 1 internal and external Gauss coefficients. The magnetospheric contributions and the internal dipole Gauss coefficients are re-calculated for each day where there are sufficient data, and therefore, there is no need to introduce annual/ semi-annual periodicity or the Dst index to describe the fast variations in time of these terms. The data set used consists of year 2001 Ørsted data, augmented for one model, with observatory data. The models are estimated using an iterative re-weighted least-squares algorithm to account for non-Gaussian data error distributions. Comparisons are made with the usual approach where the magnetospheric contributions are modelled up to degree/order 2; the zonal external terms varying with annual/semi-annual periodicity and the degree 1 external and associated induced internal terms modulated using the Dst index. Preliminary results indicate improvements to the fit to the data when this new technique is used.

Item Type: Publication - Conference Item (Poster)
Programmes: BGS Programmes > Seismology and Geomagnetism
NORA Subject Terms: Earth Sciences
Date made live: 21 Nov 2012 13:08 +0 (UTC)

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