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International Geomagnetic Reference Field (IGRF)

The International Geomagnetic Reference Field (IGRF) is a standard mathematical description of the Earth's main magnetic field. It is used widely in studies of the Earth's deep interior, crust, ionosphere, and magnetosphere. While this web page is hosted at NOAA/NCEI, the model itself is developed and maintained by the International Association of Geomagnetism and Aeronomy (IAGA).

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13th Generation Release

The coefficients for the 13th generation of IGRF model were finalized by an IAGA task force in December 2019. The IGRF is the product of a collaborative effort between magnetic field modelers and the institutes involved in collecting and disseminating magnetic field data collected from satellites, observatories, and surveys around the world. Please review the Model Health Warning before using the IGRF.

Citation

International Geomagnetic Reference Field: the 13th generation, Alken, P., Thébault, E., Beggan, C.D. et al. International Geomagnetic Reference Field: the thirteenth generation. Earth Planets Space 73, 49 (2021). doi: 10.1186/s40623-020-01288-x

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Access Methods

Data, Programs, and Software

NCEI provides access to IGRF 13 coefficients, as well as programs with the coefficients integrated into the source code. 

IGRF 13 Calculators

NCEI and the British Geological Survey (BGS) created calculators to compute values for the geomagnetic field and secular variation for specific dates and coordinates.

 

Geomag 7.0 License and Copyright Information

The software code is in the public domain and not licensed or under copyright. The information and software may be used freely by the public. As required by 17 U.S.C. 403, third parties producing copyrighted works consisting predominantly of the material produced by U.S. government agencies must provide notice with such work(s) identifying the U.S. Government material incorporated and stating that such material is not subject to copyright protection.

Older versions of the IGRF may be required in special cases. For example, if a magnetic survey was conducted in 1983, the appropriate predictive IGRF-3 (available at that time) would have been subtracted to make an anomaly map. If the original data are no longer available to update the map, add the IGRF-3 to the anomaly map and then subtract IGRF-13 which includes the required definitive magnetic reference field (DGRF) model for 1980–1985.

Older Versions of IGRF
Model Main Field Secular Variation Release Year
IGRF-1 1965.0 1975.0–1980.0 1965
IGRF-2 1965.0–1975.0 1980.0–1985.0 1975
IGRF-3 1965.0–1980.0 1980.0–1985.0 1980
IGRF-4 1945.0–1985.0 1985.0–1990.0 1985
IGRF-5 1945.0–1985.0 1985.0–1990.0 1987
IGRF-6 1945.0–1990.0 1990.0–1995.0 1991
IGRF-7 1900.0–1995.0 1995.0–2000.0 1995
IGRF-8 1900.0–2000.0 2000.0–2005.0 2000
IGRF-9 1900.0–2000.0 2000.0–2005.0 2003
IGRF-10 1900.0–2005.0 2005.0–2010.0 2005
IGRF-11 1900.0–2010.0 2010.0–2015.0 2010
IGRF-12 1900.0–2015.0 2015.0–2020.0 2015
IGRF-13 1900.0–2020.0 2020.0–2025.0 2020

Specifications

The IGRF is a series of mathematical models of the Earth's main field and its annual rate of change (secular variation). In source-free regions at the Earth's surface and above, the main field, with sources internal to the Earth, is the negative gradient of a scalar potential V which can be represented by a truncated series expansion:

Image contains the following equation:{\displaystyle V(r,\phi ,\theta ,t)=a\sum _{\ell =1}^{L}\sum _{m=0}^{\ell }\left({\frac {a}{r}}\right)^{\ell +1}\left(g_{\ell }^{m}(t)\cos m\phi +h_{\ell }^{m}(t)\sin m\phi \right)P_{\ell }^{m}\left(\cos \theta \right)}

Here, a = 6371.2 km and the degree of truncation is N = 13. The 13th Generation IGRF coefficients were computed from candidate sets of coefficients produced by the participating members of IAGA Working Group V-MOD. Their institutes and the many organizations involved in operating magnetic survey satellites, observatories, magnetic survey programs and World Data Centers are to be thanked for their continuing support of the IGRF project.

Magnetic Repeat Stations Survey

Activities

  • Maintain a catalog of regional and global magnetic surveys, models and charts.
  • Promote and set standards for magnetic repeat station surveys and reporting:
    • Define reporting procedures and classification standards
    • Encourage agencies to submit repeat data in appropriate formats to WDC, Boulder
    • Maintain a catalog of national repeat station network descriptions
  • Promote international interest in surveying, modeling and analysis of the internal geomagnetic field, both globally and on a regional scale.

Regional Magnetic Survey Results
Countries contacted (no. organisations if > 1) Response Observatories Current status of absolute observation network
ALBANIA Yes 0 10 repeat stations occupied 1994-1996 with assistance from Italy
ALGERIA   1  
ANGOLA   0  
ARGENTINA   3  
AUSTRALIA Yes 8 15 repeat stations occupied every 1-2 years
AUSTRIA   1  
BELGIUM   2  
BOLIVIA   1  
BOTSWANA Yes 0 5 repeat stations occupied in 1998-2000 with assistance from South Africa
BRAZIL   2  
BULGARIA   1  
CANADA Yes 12 5 primary repeat stations occupied every 2 years, 7 secondary stations occupied every 3-4 years and 2 tertiary stations whenever possible
CHINA (2)   18  
COLOMBIA Yes 1 ~ 80 stations at least every 5 years
COSTA RICA   1  
CROATIA Yes 0 no network but plans to establish 1-2 stations
CUBA Yes 1 ~35 stations occupied whenever possible
CZECH REPUBLIC Yes 1 6 repeat stations occupied every 2 years
DENMARK Yes 4 no network
DOMINION REPUBLIC OF CONGO   0  
EGYPT   1  
ESTONIA Yes 0 no network
ETHIOPIA Yes 1 no network
FINLAND (2) Yes 2 4 pulsation stations, at least one absolute
FRANCE Yes 1 33 repeat stations occupied every 5 years
FRANCE – OVERSEAS Yes 7 4 stations occupied in Antarctic and sub-Antarctic islands whenever possible
GEORGIA Yes 1 13-station network lapsed
GERMANY (2) Yes 3 ~40 repeat stations occupied every 4 years
GREECE Yes 1 100 stations occupied by the military – data published as D chart only
HUNGARY (2) Yes 2 195 stations occupied in 1994-5. Plans to occupy 20 primary stations every 5 years and remaining secondary stations every 15 years.
ICELAND Yes 1 3 repeat stations occupied every 1-4 years
INDIA (3) Yes 10 no network
INDONESIA Yes 2 53 stations occupied 1994-6, plans to resurvey every 5 years, Australia assisting
IRAN Yes 0 no vector observations, intermittent F observations at Tehran observatory
IRAQ   0  
IRELAND Yes 1 9 stations occupied in 1995
ISRAEL Yes 1 3 repeat stations occupied every 3-5 years
ITALY Yes 3 8 repeat stations occupied in 1998, ~2500 vector observations 1977-82
JAPAN (4) Yes 8 12 repeat stations occupied every 5 years (Maritime Safety Agency) and ~100 repeat stations occupied at a rate of ~3/year (Geographical Survey Institute)
KAZAKHSTAN Yes 1 no network
KENYA Yes 0 no network
KOREA Yes 0 F observations at 4 sites
LUXEMBURG   0  
MADAGASCAR   1  
MALAWI Yes 0 no network
MALAYSIA Yes 0 no network
MEXICO   1  
MONGOLIA   0  
MOROCCO   0  
MOZAMBIQUE Yes 1 network lapsed
NEW ZEALAND Yes 3 30 repeat stations occupied every 3 years
NIGERIA Yes 0 no network
NORWAY (2)   4  
PAKISTAN (2) Yes 2 no network
PAPUA NEW GUINEA   0  
PERU Yes 2 7 stations occupied 1992-3 as part of International Equatorial Electrojet Year
PHILIPPINES   0  
POLAND   3  
PORTUGAL Yes 1 no network
ROMANIA Yes 1 28 repeat stations occupied every 5 years
RUSSIA (3) Yes 14 network lapsed
SLOVAK REPUBLIC Yes 1 12 repeat stations occupied every 2 years
SLOVENIA   0  
SOUTH AFRICA Yes 3 63 repeat stations occupied every 5 years
SPAIN (3) Yes 5 40 repeat stations occupied every 3 years
SUDAN   0  
SWEDEN (2)   4  
SWITZERLAND   0  
TAIWAN, REPUBLIC OF CHINA   1  
TANZANIA   0  
THAILAND Yes 0 ~15 repeat stations occupied in 1996
TUNISIA   0  
TURKEY (2)   1 85 repeat stations occupied every 5 years, data confidential
U.K. Yes 6 51 repeat stations occupied every 3-5 years
U.S.A. Yes 13 24 repeat stations occupied every 3-5 years
UKRAINE Yes 4 network lapsed
VENEZUALA   0  
VIETNAM Yes 1 56 repeat stations occupied every 6 years
YUGOSLAVIA Yes 1 5 repeat stations occupied every 3 years
ZAMBIA Yes 0 no network
ZIMBABWE   0