Physics-based secular variation candidate models for the IGRF

Abstract Each International Geomagnetic Reference Field (IGRF) model released under the auspices of Association Geomagnetism and Aeronomy comprises a secular variation component that describes evolution main magnetic field anticipated for 5 years to come. Every Gauss coefficient, up spherical harmonic degree order 8, is assumed undergo its own independent linear evolution. With mathematical core time rate change constructed from geomagnetic observations at hand, standard prediction (SV) consists taking each coefficient final analysis as predicted change. The last three generations IGRF have additionally witnessed growing number candidate SV models relying upon physics-based forecasts. This surge motivated by satellite data now span more than two decades concurrent progress in numerical modelling Earth’s dynamics. Satellite reveal rapid (interannual) features whose imprint can be detrimental quality prediction. calls forecasting frameworks able incorporate least part processes responsible short-term variations. In this letter, we perform retrospective performance past candidates over 35 years; emphasize era, 5-year forecasts worsens times changes. After definition scales are relevant exercise, cover strategies followed candidates, which categorize into “‘core–surface flow” family “dynamo” family, noting both resort “input” observations. We next review practical lessons learned our previous attempts. Finally, discuss possible improvements on current state affairs directions: feasibility incorporating physical one accuracy quantification uncertainty impacting input other hand.