Bootstrapping Swarm and observatory data to generate candidates for the DGRF and IGRF-13

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Marsal, Santiago
Torta, J. Miquel
Catalán, Manuel
Tordesillas, J. Manuel
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As posted by the Working Group V of the International Association of Geomagnetism and Aeronomy (IAGA), the 13th generation of the International Geomagnetic Reference Field (IGRF) has been released at the end of 2019. Follow ing IAGA recommendations, in this work we present a candidate model for the IGRF-13, for which we have used the available Swarm satellite and geomagnetic observatory ground data for the last year. In order to provide the IGRF-13 candidate, we have extrapolated the Gauss coefcients of the main feld and its secular variation to January 1st, 2020. In addition, we have generated a Defnitive Geomagnetic Reference Field model for 2015.0 using the same model ling approach, but focussed on a 1-year time window of data centred on 2015.0. To jointly model both satellite and ground data, we have followed the classical protocols and data flters applied in geomagnetic feld modelling. Novelty arrives from the application of bootstrap analysis to solve issues related to the inhomogeneity of the spatial and temporal data distributions. This new approach allows the estimation of not only the Gauss coefcients, but also their uncertainties.
© The Author(s) 2020. The authors are grateful to the Spanish research project PGC2018-099103-A-I00 of the Spanish Ministry of Science, Innovation and Universities. We would like to thank the editors of this special issue and two anonymous reviewers for their use ful comments. We are also grateful to the task force team of the Working Group V of IAGA for promoting and evaluating the IGRF-13 candidates. We also thank ESA for providing the Swarm Level-1b data. This work has used geomagnetic observatory data and we thank all the research institutions and observatories that provide these data, most of them supported by the INTERMAGNET network. Finally, a special dedication to all the people who are sufering the present pandemic situation, and in particular to all of them working for us while we rest at home. This work has been funded by the project PGC2018-099103-A-I00 entitled “Candidato Español para Campo Geomagnético de Referencia Internacional 2020” under the umbrella of the programme “I+D de Generación de Conocimiento” of the Spanish Ministry of Science, Innovation and Universities.