Abstract
The International Geomagnetic Reference Field (IGRF) is a model of the geomagnetic main field and its secular variation, produced every 5 years from candidate models proposed by a number of international research institutions. For this 12th generation IGRF, three candidate models were solicited: a main field model for the 2010.0 epoch, a main field model for the 2015.0 epoch, and the predicted secular variation for the five-year period 2015 to 2020. The National Geophysical Data Center (NGDC), part of the National Oceanic and Atmospheric Administration (NOAA), has produced three candidate models for consideration in IGRF-12. The 2010 main field candidate was produced from Challenging Minisatellite Payload (CHAMP) satellite data, while the 2015 main field and secular variation candidates were produced from Swarm and Ørsted satellite data. Careful data selection was performed to minimize the influence of magnetospheric and ionospheric fields. The secular variation predictions of our parent models, from which the candidate models were derived, have been validated against independent ground observatory data.
Highlights
The Earth’s geomagnetic field is generated by a variety of sources
The International Geomagnetic Reference Field (IGRF) is a standard representation of the Earth’s geomagnetic main field and its secular variation, which is the temporal change of the magnetic field on time scales of 1 year or more
Candidate models After the parent model was estimated from the satellite data, we truncated it to spherical harmonic degree 13 for the main field and degree 8 for the secular variation, as specified in the IGRF call
Summary
The primary source, known as the main field, is produced by the convection of liquid iron in the Earth’s outer core. The International Geomagnetic Reference Field (IGRF) is a standard representation of the Earth’s geomagnetic main field and its secular variation, which is the temporal change of the magnetic field on time scales of 1 year or more. The IGRF is produced by an international collaborative effort and is updated every 5 years. For this 12th generation IGRF, models were solicited from the international community for a retroactive update of the main field for 2010.0, a description of the main field for 2015.0, and the predicted secular variation of the main field for 2015.0 to 2020.0. Retroactive updates of the IGRF, such as the current call for 2010, are named as the Definitive
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