TERRAPUB Earth, Planets and Space

Earth Planets Space, Vol. 62 (No. 10), pp. 719-727, 2010

The CHAOS-3 geomagnetic field model and candidates for the 11th generation IGRF

Nils Olsen1, Mioara Mandea2, Terence J. Sabaka3, and Lars Tøffner-Clausen1

1DTU Space, Juliane Maries Vej 30, 2100 Copenhagen, Denmark
2Université Paris Diderot, IPG Paris, Géophysique spatiale et planétaire,Bâtiment Lamarck, 5 rue Thomas Mann, 75013 Paris, France
3Geodynamics Branch, NASA GSFC, Greenbelt/MD, USA

(Received February 2, 2010; Revised June 28, 2010; Accepted July 1, 2010; Online published December 31, 2010)

Abstract: As a part of the 11th generation IGRF defined by IAGA, we propose a candidate model for the DGRF 2005, a candidate model for IGRF 2010 and a candidate model for the mean secular variation between 2010 and 2015. These candidate models, the derivation of which is described in the following, are based on the latest model in the CHAOS model series, called "CHAOS-3". This model is derived from more than 10 years of satellite and ground observatory data. Maximum spherical harmonic degree of the static field is n = 60. The core field time changes are expressed by spherical harmonic expansion coefficients up to n = 20, described by order 6 splines (with 6-month knot spacing) spanning the time interval 1997.0-2010.0. The third time derivative of the squared magnetic field intensity is regularized at the core-mantle boundary. No spatial regularization is applied.
Key words: Geomagnetic reference model, IGRF/DGRF, spherical harmonic analysis.

Corresponding author E-mail: nio@space.dtu.dk

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