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| IGRF | |
|---|---|
| Name | IGRF |
| Abbreviation | IGRF |
| Discipline | Geophysics |
| Established | 1968 |
| Maintainer | International Association of Geomagnetism and Aeronomy |
| Scope | Earth's main magnetic field |
| Type | Spherical harmonic model |
IGRF
The International Geomagnetic Reference Field is a standard mathematical representation of the Earth's main magnetic field used across NOAA, NASA, European Space Agency, British Geological Survey, USGS, CSIRO, and many national laboratories. It provides a time-dependent spherical harmonic model adopted by scientific bodies such as the International Union of Geodesy and Geophysics and the International Association of Geomagnetism and Aeronomy to support operations in geophysics, navigation, satellite mission planning, and studies of the magnetosphere, ionosphere, and core dynamics.
The model summarizes the internal geomagnetic field through Gauss coefficients expressed as spherical harmonics, enabling calculations of declination, inclination, and total intensity for locations cited in standards by International Organization for Standardization committees and operational centers like NOAA and ESA. Users include researchers from institutions such as University of Cambridge, MIT, Caltech, ETH Zurich, Columbia University, University of Tokyo, Peking University, and agencies including JAXA, ISRO, CNSA, and Roscosmos. The IGRF is widely used alongside regional models from agencies like British Geological Survey and global reconstructions used in paleomagnetism by teams at Scripps Institution of Oceanography and Lamont–Doherty Earth Observatory.
Initiated in 1968 following recommendations at meetings of the International Union of Geodesy and Geophysics and panels involving experts from NOAA, USGS, NASA, European Space Agency, and national observatories such as Greenwich Observatory and Paris Observatory, the model evolved through collaborative workshops at Woods Hole Oceanographic Institution, INGV, and the Royal Observatory of Belgium. Successive iterations incorporated data from satellite missions Ørsted (satellite), Magsat, CHAMP, Swarm, Pioneer, Voyager, and observatory networks maintained by INTERMAGNET and universities including University of Alaska Fairbanks and GEOMAGIA50 contributors. Committees including members from International Association of Geomagnetism and Aeronomy, International Union of Geodesy and Geophysics, and national agencies coordinated consensus releases.
IGRF expresses the main field with Gauss coefficients g_n^m and h_n^m up to a specified spherical harmonic degree, typically degree 13, employing least-squares fitting and regularization techniques developed in studies at Princeton University, Massachusetts Institute of Technology, University of Oxford, and University of Cambridge. The methodology draws on mathematical foundations from Carl Friedrich Gauss's potential theory and numerical approaches refined by researchers at Stanford University, University of California, San Diego, ETH Zurich, and Imperial College London. Time dependence is encoded via secular variation coefficients estimated using temporal basis functions and spline fits as used in studies by groups at Institut de Physique du Globe de Paris and GFZ German Research Centre for Geosciences.
Primary inputs are satellite magnetometer records from missions such as Magsat, Ørsted (satellite), CHAMP, Swarm, and ground observatory data from networks like INTERMAGNET, observational centers including Geophysical Institute, University of Alaska and British Geological Survey, and marine and airborne surveys conducted by institutions including NOAA and Geological Survey of Canada. Calibration and selection protocols reference standards from International Council for Science-sponsored workshops and employ techniques developed at Scripps Institution of Oceanography, Lamont–Doherty Earth Observatory, University of Toronto, and Australian National University to mitigate external field contamination from the magnetosphere and ionosphere.
Operational users include aviation and maritime navigation authorities, spaceflight mission planners at ESA, NASA, Roscosmos, and JAXA, geomagnetic observatories in networks like INTERMAGNET, and researchers in paleomagnetism at Scripps Institution of Oceanography and University of Liverpool. Scientific applications span core dynamics investigations at Institut de Physique du Globe de Paris, space weather forecasting by NOAA's Space Weather Prediction Center, archeomagnetic studies by teams at University of Oxford and University of Cambridge, and lithospheric studies used by the British Geological Survey and Geological Survey of India. Engineering uses include magnetometer calibration for missions by Lockheed Martin, Airbus Defence and Space, and navigation systems in platforms built by Boeing and Thales Group.
The model represents the main field produced by the Earth's core and excludes rapid external variations from the magnetosphere and ionosphere unless specifically modeled; such separation relies on data selection and correction methods developed at GFZ German Research Centre for Geosciences and National Institute for Space Research (INPE). Uncertainties arise from spatial aliasing, temporal sampling, and limited high-latitude coverage; these issues are addressed with methods from Carnegie Institution for Science, Princeton University, and University of Colorado Boulder but remain inherent. Regional crustal anomalies mapped by the Geological Survey of Canada or British Geological Survey may not be fully captured by the global spherical harmonic truncation, and ongoing research at ETH Zurich and Imperial College London seeks improved modelling.
Releases are coordinated by working groups under the International Association of Geomagnetism and Aeronomy and the International Union of Geodesy and Geophysics with versions issued periodically (e.g., 2015, 2020) to incorporate new satellite and observatory data, following procedures established at meetings involving NOAA, NASA, ESA, British Geological Survey, and GFZ German Research Centre for Geosciences. Each update refines Gauss coefficients and secular variation estimates using inputs from missions such as Swarm and CHAMP, and from networks like INTERMAGNET and observatories at Greenwich Observatory and Paris Observatory. Future updates will integrate data from upcoming missions proposed by ESA and national agencies like JAXA and ISRO.
Category:Geomagnetism