Evaluation of candidate geomagnetic field models for IGRF-12

Research areas:
  • Erwan Thébault
  • Christopher C. Finlay
  • Patrick Alken
  • Ciaran D. Beggan
  • Elizabeth Canet
  • Arnaud Chulliat
  • Benoit Langlais
  • Vincent Lesur
  • Frank J. Lowes
  • Chandrasekharan Manoj
  • Martin Rother
  • Reyko Schachtschneider
Earth Planets Space
The 12th revision of the International Geomagnetic
Reference Field (IGRF) was issued in December 2014 by the
International Association of Geomagnetism and Aeronomy (IAGA) Division
V Working Group V-MOD
(http://www.ngdc.noaa.gov/IAGA/vmod/igrf.html). This revision
comprises new spherical harmonic main field models for epochs 2010.0
(DGRF-2010) and 2015.0 (IGRF-2015) and predictive linear secular
variation for the interval 2015.0-2020.0 (SV-2010-2015). The models
were derived from weighted averages of candidate models submitted by
ten international teams. Teams were led by the British Geological
Survey (UK), DTU Space (Denmark), ISTerre (France), IZMIRAN (Russia),
(France), LPG Nantes (France), and ETH Zurich (Switzerland). Each
candidate model was carefully evaluated and compared to all other
models and a mean model using well-defined statistical criteria in the
spectral domain and maps in the physical space. These analyses were
made to pinpoint both troublesome coefficients and the geographical
regions where the candidate models most significantly differ. Some
models showed clear deviation from other candidate models. However, a
majority of the task force members appointed by IAGA thought that the
differences were not sufficient to exclude models that were well
documented and based on different techniques. The task force thus
voted for and applied an iterative robust estimation scheme in
space. In this paper, we report on the evaluations of the candidate
models and provide details of the algorithm that was used to derive
the IGRF-12 product.