Abstract
AbstractDetailed mapping of the Earth's magnetic field brings key constraints on the composition, dynamics, and history of the crust. Satellite and near‐surface measurements detect different length scales and are complementary. Here, we build a model, selecting and processing magnetic field measurements from the German CHAMP and ESA Swarm satellites, which we merge with near‐surface scalar anomaly data. We follow a regional approach for modeling the magnetic field measurements and next transform the series of regional models into a unique set of spherical harmonic (SH) Gauss coefficients. This produces the first global model to SH degree 1050 derived by inversion of all available measurements. The new model agrees with previous satellite‐based models at large wavelengths and fits the CHAMP and Swarm satellite data down to expected noise levels. Further assessment in the geographical and spectral domains shows the model to be stable when downward continued to the Earth's surface.
Highlights
The magnetic field produced by the Earth's lithosphere arises because of lateral contrasts between magnetized rocks (e.g., Purucker & Clark, 2011)
We build a model, selecting and processing magnetic field measurements from the German CHAMP and European Spatial Agency (ESA) Swarm satellites, which we merge with near-surface scalar anomaly data
Consistent models derived from measurements at satellite altitudes, using the German CHAMP (Reigber et al, 2002) and ESA Swarm (Friis-Christensen et al, 2006) satellites, have a spatial horizontal resolution limited to 250 km (Olsen et al, 2017)
Summary
The magnetic field produced by the Earth's lithosphere arises because of lateral contrasts between magnetized rocks (e.g., Purucker & Clark, 2011). No global inversion combining all available near-surface gridded data and satellite direct measurements have yet been performed to best take advantage of the data and build a fully consistent joint model We carry such a joint inversion, using CHAMP and Swarm measurements combined with the WDMAM-2 anomaly grid to build a model of the Earth's lithospheric magnetic vector field with a 40-km horizontal spatial resolution. The method involves an iterative piecewise approach using the Revised Spherical Cap Harmonic functions (R-SCHA, Thébault, 2006) to allow independent regional data analyses, build regional models and combine them into a global SH model This makes it possible to best take advantage of all available measurements at reduced and manageable numerical costs.
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