International Geomagnetic Reference Field, 1991 Revision: International Association of Geomagnetism and Aeronomy (IAGA) Division V, Working Group 8: Analysis of the main field and secular variation

Geophysics ◽  
1992 ◽  
Vol 57 (7) ◽  
pp. 956-956 ◽  
Author(s):  
R. A. Langel
Keyword(s):  
Secular Variation ◽  
Working Group ◽  
International Association ◽  
Legendre Function ◽  
Radial Distance ◽  
Reference Field ◽  
International Geomagnetic Reference Field ◽  
The Earth ◽  
International Geomagnetic Reference ◽  
Associated Legendre Function

The International Geomagnetic Reference Field (IGRF) is a series of mathematical models of the main geomagnetic field and its secular variation. Each model consists of a set of spherical harmonic (or Gauss) coefficients, g and h in a series expansion of the geomagnetic potential [Formula: see text], where a is the mean radius of the Earth (6371.2 km); r the radial distance from the center of the Earth; ϕ the east longitude measured from Greenwich; θ the geocentric colatitude; and [Formula: see text] the associated Legendre function of degree n and order m, normalized according to the convention of Schmidt [see, e.g., Langel (1987)]. In principle, N should be ∞ but the Working Group is of the opinion that in practice the available data for most epochs do not justify N greater than 10. This value is chosen to maintain consistency between models at different epochs. The coefficients are in units of nanotesla (nT).

International Geomagnetic Reference Field 1980 A Report by IAGA Division I, Working Group I

Geophysics ◽  
1982 ◽  
Vol 47 (5) ◽  
pp. 841-842 ◽  
Author(s):  
Norman W. Peddie
Keyword(s):  
Secular Variation ◽  
Working Group ◽  
Field Model ◽  
International Association ◽  
Division I ◽  
Reference Field ◽  
Main Field ◽  
International Geomagnetic Reference Field ◽  
International Geomagnetic Reference ◽  
Group I

IGRF 1965, the first international geomagnetic reference field, was adopted by the International Association of Geomagnetism and Aeronomy (IAGA) in 1968 (IAGA Commission 2, Working Group 4, 1969). It consists of a model of the main field at 1965.0, along with a model of secular variation for use in extending the main field model in time, both backward (not earlier than 1955.0) and forward (not later than 1975.0). IGRF 1975, adopted later, consists of IGRF 1965 extended to 1975.0, along with a revised model of secular variation for use in extending the main field model up to 1980.0 (IAGA Division I Study Group, 1976).

AD HOC COMMITTEE ON MAGNETIC FIELD MODELS

Geophysics ◽  
1976 ◽  
Vol 41 (4) ◽  
pp. 796-797
Keyword(s):  
Magnetic Field ◽  
Working Group ◽  
Ad Hoc ◽  
Field Model ◽  
International Association ◽  
Geological Survey ◽  
Reference Field ◽  
International Geomagnetic Reference Field ◽  
International Geomagnetic Reference ◽  
Purdue University

An SEG ad‐hoc committee on Magnetic Field Models was formed as one result of the Zmuda Memorial Field Model Conference (Regan and Cain, 1975a). The chairman of the committee is Michael S. Reford, Geoterrex Ltd., and committee members are William J. Hinze, Purdue University, Peter J. Hood, Geological Survey of Canada, and Robert D. Regan, U.S. Geological Survey. The main objective of the committee was to produce an SEG resolution on the revision of the International Geomagnetic Reference Field (IGRF) to be submitted to the International Association of Geomagnetism and Aeronomy’s (IAGA) working group 1.1.

scholarly journals Evaluation of candidate models for the 13th generation International Geomagnetic Reference Field

2020 ◽  
Author(s):  
Patrick Alken ◽  
Erwan Thebault ◽  
Ciaran Beggan ◽  
Julien Aubert ◽  
Julien Baerenzung ◽  
...  
Keyword(s):  
Secular Variation ◽  
Task Force ◽  
International Association ◽  
Research Centre ◽  
Reference Field ◽  
International Geomagnetic Reference Field ◽  
British Geological Survey ◽  
International Geomagnetic Reference ◽  
Geographical Regions ◽  
Weighted Model

Abstract In December 2019, the 13th revision of the International Geomagnetic Reference Field (IGRF) was released by the International Association of Geomagnetism and Aeronomy (IAGA) Division V Working Group V-MOD. This revision comprises two new spherical harmonic main field models for epochs 2015.0 (DGRF-2015) and 2020.0 (IGRF-2020) and a model of the predicted secular variation for the interval 2020.0 to 2025.0 (SV-2020-2025). The models were produced from candidates submitted by fifteen international teams. These teams were led by the British Geological Survey (UK), China Earthquake Administration (China), Universidad Complutense de Madrid (Spain), University of Colorado Boulder (USA), Technical University of Denmark (Denmark), GFZ German Research Centre for Geosciences (Germany), Institut de physique du globe de Paris (France), Institut des Sciences de la Terre (France), Pushkov Institute of Terrestrial Magnetism, Ionosphere and Radio Wave Propagation (Russia), Kyoto University (Japan), University of Leeds (UK), Max Planck Institute for Solar System Research (Germany), NASA Goddard Space Flight Center (USA), University of Potsdam (Germany), and Universit\'e de Strasbourg (France). The candidate models were evaluated individually and compared to all other candidates as well to the mean, median and a robust Huber-weighted model of all candidates. These analyses were used to identify, for example, the variation between the Gauss coefficients or the geographical regions where the candidate models strongly differed. The majority of candidates were sufficiently close that the differences can be explained primarily by individual modeling methodologies and data selection strategies. None of the candidates were so different as to warrant their exclusion from the final IGRF-13. The IAGA V-MOD task force thus voted for two approaches: the median of the Gauss coefficients of the candidates for the DGRF-2015 and IGRF-2020 models and the robust Huber-weighted model for the predictive SV-2020-2025. In this paper, we document the evaluation of the candidate models and provide details of the approach used to derive the final IGRF-13 products. We also perform a retrospective analysis of the IGRF-12 SV candidates over their performance period (2015-2020). Our findings suggest that forecasting secular variation can benefit from combining physics-based core modeling with satellite observations.

scholarly journals Evaluation of candidate models for the 13th generation International Geomagnetic Reference Field

2021 ◽  
Vol 73 (1) ◽  
Author(s):  
P. Alken ◽  
E. Thébault ◽  
C. D. Beggan ◽  
J. Aubert ◽  
J. Baerenzung ◽  
...  
Keyword(s):  
Secular Variation ◽  
Task Force ◽  
International Association ◽  
Research Centre ◽  
Reference Field ◽  
International Geomagnetic Reference Field ◽  
British Geological Survey ◽  
International Geomagnetic Reference ◽  
Geographical Regions ◽  
Weighted Model

AbstractIn December 2019, the 13th revision of the International Geomagnetic Reference Field (IGRF) was released by the International Association of Geomagnetism and Aeronomy (IAGA) Division V Working Group V-MOD. This revision comprises two new spherical harmonic main field models for epochs 2015.0 (DGRF-2015) and 2020.0 (IGRF-2020) and a model of the predicted secular variation for the interval 2020.0 to 2025.0 (SV-2020-2025). The models were produced from candidates submitted by fifteen international teams. These teams were led by the British Geological Survey (UK), China Earthquake Administration (China), Universidad Complutense de Madrid (Spain), University of Colorado Boulder (USA), Technical University of Denmark (Denmark), GFZ German Research Centre for Geosciences (Germany), Institut de physique du globe de Paris (France), Institut des Sciences de la Terre (France), Pushkov Institute of Terrestrial Magnetism, Ionosphere and Radio Wave Propagation (Russia), Kyoto University (Japan), University of Leeds (UK), Max Planck Institute for Solar System Research (Germany), NASA Goddard Space Flight Center (USA), University of Potsdam (Germany), and Université de Strasbourg (France). The candidate models were evaluated individually and compared to all other candidates as well to the mean, median and a robust Huber-weighted model of all candidates. These analyses were used to identify, for example, the variation between the Gauss coefficients or the geographical regions where the candidate models strongly differed. The majority of candidates were sufficiently close that the differences can be explained primarily by individual modeling methodologies and data selection strategies. None of the candidates were so different as to warrant their exclusion from the final IGRF-13. The IAGA V-MOD task force thus voted for two approaches: the median of the Gauss coefficients of the candidates for the DGRF-2015 and IGRF-2020 models and the robust Huber-weighted model for the predictive SV-2020-2025. In this paper, we document the evaluation of the candidate models and provide details of the approach used to derive the final IGRF-13 products. We also perform a retrospective analysis of the IGRF-12 SV candidates over their performance period (2015–2020). Our findings suggest that forecasting secular variation can benefit from combining physics-based core modeling with satellite observations.

The current status of the IGRF and its relation to magnetic surveys

Geophysics ◽  
1983 ◽  
Vol 48 (7) ◽  
pp. 997-998 ◽  
Author(s):  
Robert D. Regan
Keyword(s):  
Geomagnetic Field ◽  
Working Group ◽  
International Association ◽  
Current Status ◽  
Reference Field ◽  
Summary Report ◽  
International Geomagnetic Reference Field ◽  
Significant Time ◽  
International Geomagnetic Reference ◽  
Geomagnetic Field Models

As aeromagnetic surveys covered increasingly larger areas and as the need arose for the compilation of adjacent surveys with significant time differences, there has been an increase in the use of geomagnetic field models for regional field definition. Indeed, few aeromagnetic contracts exist today without some provision for removal of the International Geomagnetic Reference Field (IGRF). Yet, as publications indicate (Regan and Cain, 1975a, 1975b; Reford et al, 1976; Regan, 1977, 1978), the IGRF is far from perfect for this application despite the considered attention of the IAGA (International Association of Geomagnetism and Aeronomy) working group charged with its upkeep and maintenance. One reason for this is that the model is meant to serve all areas of geomagnetism and, as such, is not specifically tailored to the needs of the exploration community. The recent summary report of the IAGA committee (Peddie, 1982) could lead to some confusion because there are seven IGRF models published. A rational question for those involved in aeromagnetic surveys is “Which model should be used for regional field definition?”

scholarly journals Geomagnetic core field models and secular variation forecasts for the 13th International Geomagnetic Reference Field (IGRF-13)

2020 ◽  
Author(s):  
Ingo Wardinski ◽  
Diana Saturnino ◽  
Hagay Amit ◽  
Aude Chambodut ◽  
Benoit Langlais ◽  
...  
Keyword(s):  
Secular Variation ◽  
Geomagnetic Field ◽  
Singular Spectrum Analysis ◽  
Reference Field ◽  
Candidate Model ◽  
Main Field ◽  
International Geomagnetic Reference Field ◽  
Core Field ◽  
International Geomagnetic Reference ◽  
Continuous Models

Abstract Observations of the geomagnetic field taken at Earth's surface and at satellite altitude were combined to construct continuous models of the geomagnetic field and its secular variation from 1957 to 2020. From these parent models, we derive candidate main field models for the epochs 2015 and 2020 to the 13th generation of the International Geomagnetic Reference Field (IGRF). The secular variation candidate model for the period 2020 - 2025 is derived from a forecast of the secular variation in 2022.5, which results from a multi-variate singular spectrum analysis of the secular variation from 1957 to 2020.

International Geomagnetic Reference Field Revision 1985

Geophysics ◽  
1986 ◽  
Vol 51 (4) ◽  
pp. 1020-1023 ◽  
Author(s):  
◽  
Norman W. Peddie
Keyword(s):  
Working Group ◽  
Theory And Practice ◽  
Division I ◽  
Magnetic Survey ◽  
Reference Field ◽  
International Geomagnetic Reference Field ◽  
International Geomagnetic Reference ◽  
Secular Variations ◽  
Field Revision ◽  
Group 1

IAGA Division I, Working Group 1 deals with the topic “Analysis of the Main Field and Secular Variations.” One of the more important functions of the working group is the periodic revision of the International Geomagnetic Reference Field (IGRF). The thirteen members of the working group have professional interests covering a broad spectrum of geomagnetic science, including the theory and practice of geomagnetic analysis and modeling, the theory of the origin of the magnetic fields of the Earth and other bodies, the theory of geomagnetic secular variation, the application of field models in magnetic survey data processing, and geomagnetic charting.

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