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.

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):  
Task Force ◽  
International Association ◽  
Research Centre ◽  
Reference Field ◽  
Max Planck ◽  
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 eld 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 fteen 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 Universite 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 coecients or the geographical regions where the candidate models strongly di ered. The majority of candidates were suciently close that the di erences can be explained primarily by individual modeling methodologies and data selection strategies. None of the candidates were so di erent to warrant their exclusion from the nal IGRF-13. The IAGA V-MOD task force thus voted for two approaches: the median of the Gauss coecients 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 nal IGRF-13 products.

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).

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).

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 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 1987

Geophysics ◽  
1988 ◽  
Vol 53 (4) ◽  
pp. 576-578 ◽  
Author(s):  
D. R. Barraclough
Keyword(s):  
Charged Particle ◽  
Mathematical Models ◽  
Secular Variation ◽  
Spherical Harmonic ◽  
Geomagnetic Field ◽  
Magnetic Anomalies ◽  
Reference Field ◽  
International Geomagnetic Reference Field ◽  
International Geomagnetic Reference ◽  
Field Revision

The International Geomagnetic Reference Field (IGRF) is a series of mathematical models of the main geomagnetic field and its secular variation, the models consisting of sets of spherical harmonic (or Gauss) coefficients. The IGRF has become a widely used means of deriving values of geomagnetic field components in, for example, studies of magnetic anomalies and investigations of charged particle motions in the ionosphere and the magnetosphere.

scholarly journals The new WMM2020 and IGRF-13 models, and a retrospective analysis of IGRF secular variation

2020 ◽  
Author(s):  
William Brown ◽  
Ciarán Beggan ◽  
Grace Cox ◽  
Susan Macmillan
Keyword(s):  
Retrospective Analysis ◽  
Secular Variation ◽  
Task Force ◽  
Reference Field ◽  
Coordinate Systems ◽  
International Geomagnetic Reference Field ◽  
The North ◽  
The Us ◽  
The World ◽  
Magnetic Model

<p>2020 marks the start of a new 5-year cycle and updated releases of the World Magnetic Model (WMM) and International Geomagnetic Reference Field (IGRF). These models provide a reference for the up-to-date internal geomagnetic field in 2020, and a prediction of its secular variation for the next 5 years, to 2025. While similar in some aspects, the two models have different specifications and many different users across diverse fields. They provide references to be used primarily for navigation (WMM) and geomagnetic coordinate systems (IGRF).</p><p>BGS produces the WMM in collaboration with the US’ NOAA/NCEI, while the IGRF is produced by an IAGA Div. V-MOD task force, this time consisting of fifteen teams across nine nations, including BGS. Here we present a summary of the production of the updated WMM2020 and IGRF-13, and BGS efforts to enable access to these models.</p><p>We also present a retrospective analysis of the predictive components of the candidate models for previous IGRF epoch’s secular variation. Recent epochs have seen notable geomagnetic jerks and the acceleration of the North magnetic dip pole, features not well represented by the constant SV format of models such as the IGRF. We assess the range of candidate models submitted for previous IGRF epochs, assess the accuracy of physically derived predictions versus mathematical extrapolations, and discuss the implications given the range of candidate models submitted for IGRF-13 secular variation over the next five years.</p>

scholarly journals International Geomagnetic Reference Field: the thirteenth generation

2021 ◽  
Vol 73 (1) ◽  
Author(s):  
P. Alken ◽  
E. Thébault ◽  
C. D. Beggan ◽  
H. Amit ◽  
J. Aubert ◽  
...  
Keyword(s):  
Field Model ◽  
International Association ◽  
Rate Of Change ◽  
Generation Model ◽  
Reference Field ◽  
Main Field ◽  
International Geomagnetic Reference Field ◽  
Group V ◽  
International Geomagnetic Reference ◽  
Time Period

AbstractIn December 2019, the International Association of Geomagnetism and Aeronomy (IAGA) Division V Working Group (V-MOD) adopted the thirteenth generation of the International Geomagnetic Reference Field (IGRF). This IGRF updates the previous generation with a definitive main field model for epoch 2015.0, a main field model for epoch 2020.0, and a predictive linear secular variation for 2020.0 to 2025.0. This letter provides the equations defining the IGRF, the spherical harmonic coefficients for this thirteenth generation model, maps of magnetic declination, inclination and total field intensity for the epoch 2020.0, and maps of their predicted rate of change for the 2020.0 to 2025.0 time period.

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