International Geomagnetic Reference Field

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The International Geomagnetic Reference Field (IGRF) is a standard mathematical description of the large-scale structure of the Earth's main magnetic field and its secular variation. It was created by fitting parameters of a mathematical model of the magnetic field to measured magnetic field data from surveys, observatories and satellites across the globe. The IGRF has been produced and updated under the direction of the International Association of Geomagnetism and Aeronomy (IAGA) since 1965.[1]

Spherical Harmonics[edit]

The IGRF models the geomagnetic field as a gradient of a magnetic scalar potential

The magnetic scalar potential model consists of the Gauss coefficients which define a spherical harmonic expansion of [1]

where is radial distance from the Earth's center, is the maximum degree of the expansion, is East longitude, is colatitude (the polar angle), is the Earth's radius, and are Gauss coefficients, and are the Schmidt normalized associated Legendre functions of degree and order . The Gauss coefficients are assumed to vary linearly over the time interval specified by the model.

IGRF models are standardized for a particular year, reflecting the most accurate measurements available at that time, and indicating a small-scale, slow time variation of the Earth's overall magnetic field. The 12th edition of the IGRF model covers the 2015 epoch.[1]

See also[edit]


  1. ^ a b c Thébault, Erwan; Finlay, Christopher C; Beggan, Ciarán D; Alken, Patrick; Aubert, Julien; Barrois, Olivier; Bertrand, Francois; Bondar, Tatiana; Boness, Axel; Brocco, Laura; Canet, Elisabeth; Chambodut, Aude; Chulliat, Arnaud; Coïsson, Pierdavide; Civet, François; Du, Aimin; Fournier, Alexandre; Fratter, Isabelle; Gillet, Nicolas; Hamilton, Brian; Hamoudi, Mohamed; Hulot, Gauthier; Jager, Thomas; Korte, Monika; Kuang, Weijia; Lalanne, Xavier; Langlais, Benoit; Léger, Jean-Michel; Lesur, Vincent; Lowes, Frank J; Macmillan, Susan; Mandea, Mioara; Manoj, Chandrasekharan; Maus, Stefan; Olsen, Nils; Petrov, Valeriy; Ridley, Victoria; Rother, Martin; Sabaka, Terence J; Saturnino, Diana; Schachtschneider, Reyko; Sirol, Olivier; Tangborn, Andrew; Thomson, Alan; Tøffner-Clausen, Lars; Vigneron, Pierre; Wardinski, Ingo; Zvereva, Tatiana (27 May 2015). "International Geomagnetic Reference Field: the 12th generation". Earth, Planets and Space. 67 (1). Bibcode:2015EP&S...67...79T. doi:10.1186/s40623-015-0228-9. 

External links[edit]