Abstract
Ten months of data from ESA's Swarm mission, together with recent ground observatory monthly means, are used to update the
CHAOS series of geomagnetic field models with a focus on time-changes of the core field. As for previous CHAOS field models
quiet-time, night-side, data selection criteria are employed and the magnetic field data is used in the instrument frame with Euler
angles for the rotation to the North-East-Center (NEC) frame co-estimated. The new model spans more than 15 years between
1999 and 2014, with the internal field being time-dependent up to spherical harmonic degree 20 using a 6th order spline
representation with knot points spaced at 0.5 year intervals. The resulting field model is able to consistently fit data from six
independent low Earth orbit satellites: Oersted, CHAMP, SAC-C and the three Swarm satellites. As an example, we present
comparisons of the excellent model fit obtained to both the Swarm data and the CHAMP data. The new model also provides a
good description of observatory secular variation, capturing rapid field evolution events during the past decade. Maps of the core
surface field and its secular variation can already be extracted in the Swarm-era. We therefore conclude that Swarm data is
suitable for building high-resolution models of the large-scale internal field, and proceed to extract IGRF-12 candidate models for
the main field in epochs 2010 and 2015, as well as the predicted linear secular variarion for 2015-2020. The properties of these
IGRF candidate models are briefly presented.
Original language | English |
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Publication date | 2014 |
Number of pages | 1 |
Publication status | Published - 2014 |
Event | 2014 AGU Fall Meeting - San Francisco, CA, United States Duration: 15 Dec 2014 → 19 Dec 2014 |
Conference
Conference | 2014 AGU Fall Meeting |
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Country/Territory | United States |
City | San Francisco, CA |
Period | 15/12/2014 → 19/12/2014 |