Evaluation of candidate models for the 14th generation International Geomagnetic Reference Field

In November 2024, the 14th revision of the International Geomagnetic Reference Field (IGRF) was issued 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 2020.0 (DGRF-2020) and 2025.0 (IGRF-2025) and a model of the predicted secular variation for the interval 2025.0-2030.0 (SV-2025-2030), all provided as internal Gauss coefficients to degree and order 13 for DGRF-2020 and IGRF-2025, and degree and order 8 for SV-2025-2030. The models were produced from candidates submitted by nineteen international teams. The candidate models were evaluated by an expert international volunteer Taskforce. Comparisons between all candidates as well as to mean, median and Huber-weighted averages of all candidates were made using well-established statistical criteria. These analyses were used to identify, for example, the variation between Gauss coefficients or geographical regions where the candidate models strongly differed. The majority of candidates were sufficiently close that the differences can be explained primarily by individual modelling methodologies and data selection strategies. None of the candidates were sufficiently different to warrant their exclusion. The IAGA V-MOD Taskforce thus voted for two approaches: the median of the Gauss coefficients of the candidates for the DGRF-2020 and the computed Huber mean in space for the IGRF-2025 and SV-2025-2030 models. In this paper, we document the evaluation of the candidate models and provide details of the approach used to derive the final IGRF-14 products.