A group of geomagnetic field modellers associated with the International Association of Geomagnetism and Aeronomy (IAGA) Division V Working Group 8, periodically examines various geomagnetic field representations from which the Earth's main field and its secular variation can be computed. They produce a set of coefficients to represent the main field at a particular epoch, usually every 5 years, and name it the International Geomagnetic Reference Field (IGRF). Also, if a previous IGRF is re-derived using new data not available at the time of its production and agreed upon when it is clear that no additional data are likely to emerge, it is called a Definitive Geomagnetic Reference Field (DGRF). For similar reasons, no DGRF model for 1995 has yet been adopted by the IAGA, Division V Working Group 8. Note that, when referring to these models, the designation “IGRF” refers to all available models, viewed collectively. If a particular model is intended, the reference must be specific; i.e., IGRF2000 or DGRF1990, rather than simply IGRF or DGRF
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