Journal
EARTH PLANETS AND SPACE
Volume 62, Issue 10, Pages 753-763Publisher
TERRA SCIENTIFIC PUBL CO
DOI: 10.5047/eps.2010.05.004
Keywords
Magnetic field; main field; secular variation; modeling; IGRF; temporal extrapolation; core field acceleration
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Funding
- German Aerospace Center (DLR)
- Federal Ministry of Education and Research (BMBF)
- CNES
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We submit three candidate models following the call for IGRF-11. We apply a simple modeling approach in spherical harmonics based on a quadratic Taylor expansion for the internal field time variations. We use the D-st magnetic index as a proxy for the external field variations. In order to compensate for the limitations incurred by such a conventional approach, we focus on the optimal selection of satellite data in space and time. We also show that some a priori knowledge about the core field state helps us to avoid the pitfall encountered in the case of rapid changes of core field accelerations. Indeed, various acceleration events of relevance for the IGRF 11th occurred between 2003 and 2010, one of them being a geomagnetic jerk. They could entail disagreements between IGRF candidate models for the secular variation (SV) if data prior to 2008 are used. Our SV and main field (MF) candidate models have a root mean square uncertainty less than 6 nT/yr and 8 nT, respectively, with respect to the modeled magnetic field contributions. These values correspond to the intrinsic error associated with truncating SV and MF models to spherical harmonic degree 8 and 13, respectively, as requested for IGRF models.
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