Evaluation of the candidate Main Field model for IGRF 2000 derived from preliminary Ørsted data

Abstract

On this occasion the selection of the IGRF for 2000 was left to a small Task Force. Before it was accepted by the Task Force as IGRF 2000, the final candidate model (a truncated version of Ørsted(10c/99)) was compared with a comprehensive set of independent surface and satellite data. The method, data selection, and results of this comparison are described.

The working of the IGRF 2000 Task Force

“…The numerical results were very little different from those reported in Lowes et al (2000) for the assessment of the later IGRF2000c Ørsted model, so will not be presented here. An independent look at observatory annual means by Bondar and Golovkov gave similar results.…”

International Geomagnetic Reference Field—the eighth generation

“…As none of these four main-field models was deemed sufficiently accurate for an IGRF model (Macmillan, 2000;Mandea and Langlais, 2000) and because of the successful launch and operation of the Ørsted satellite after the submission deadline, it was decided at the XXII General Assembly of the International Union of Geodesy and Geophysics held in Birmingham (UK) in July 1999 to set up a Task Force to produce and evaluate a new IGRF main-field candidate model for 2000.0 based on Ørsted data. The operation of the Task Force is summarised by Lowes (2000), details of the derivation of this model are given in Olsen and Sabaka (2000) and of its evaluation by Lowes et al (2000). For the secular-variation model for 2000.0-2005.0 the three new candidate models were each given equal weight in the final model as there was insufficient evidence to recommend one model over another.…”

Candidate models for the IGRF-11th generation making use of extrapolated observatory data

“…These successful missions considerably improved the way the magnetic field is described and modeled. Prior to these spacecrafts, and with the exception of the MAGSAT mission, it was indeed difficult to accurately describe the main magnetic field, even in the frame of IGRF models (Lowes et al, 2000).…”