Modeling the lithospheric magnetic field over France by means of revised spherical cap harmonic analysis (R‐SCHA)

Abstract

[1] We have recently proposed the revised spherical cap harmonic analysis (R-SCHA) modeling technique. The new mathematical functions represent faithfully the spatial variations of potential fields in a restricted area. In this paper, we tackle the inverse problem and outline the efficiency of the new basis functions with respect to real magnetic data. Processing simultaneously repeat stations, observatory, aeromagnetic, and CHAMP satellite data provides our first vector lithospheric field model over France, which extends from surface to 500 km of altitude. The magnetic field is represented with a minimum horizontal spatial representation of 40 km at the mean Earth radius. The magnetic lithospheric map consistency is confirmed with a comparison to known geological features. The model variation with altitude also suggests that the major French magnetic anomaly, the Paris basin anomaly, is produced by a deep-rooted geological structure. These results demonstrate the superiority of regional modeling over global modeling for delineating small-scale details in the lithospheric field. In view of forthcoming satellite missions, like Swarm, the revised spherical cap harmonic analysis method will help to accurately represent the lithospheric field for more detailed geological interpretations.

The Magnetic Field of the Earth’s Lithosphere

“…An example of its application is the merging of vector and scalar repeat station, observatory, aeromagnetic and satellite data for modelling the lithospheric fields of France (Fig. 7) and Germany to 30 km resolution (Thébault et al 2006b;Korte and Thébault 2007). Even though this is not the primary aim of the technique, a lithospheric field model using CHAMP satellite data was derived by stitching together independent regional models (Thébault 2006).…”

Geomagnetic Observations for Main Field Studies: From Ground to Space

“…Repeat station data are used to calculate regional models of the magnetic field, using modelling techniques such as Spherical Cap Harmonic Analysis (SCHA) (Haines 1985;Korte and Haak 2000; or the Revised Spherical Cap Harmonic Analysis R-SCH (Thébault et al 2004) used by Thébault et al (2006) and Korte and Thébault (2007). Together with geomagnetic observatory and satellite data, repeat station data are sometimes used in global main field models, such as C 3 FM which covers the years 1980 to 2000 (Wardinski and Holme 2006).…”

Crustal Magnetic Fields of Terrestrial Planets

“…A revised SCHA was proposed recently (Thébault et al 2006a), addressing the problem of altitude and multi-level data compatibility. This was used to merge ground and satellite data (Thébault et al 2006b). A specific formalism was recently developed to process ground data only (Thébault 2008).…”