First scalar magnetic anomaly map from CHAMP satellite data indicates weak lithospheric field

Abstract

Satellite magnetic anomaly maps derived by different techniques from Magsat/POGO data vary by more than a factor of 2 in the deduced strength of the lithospheric magnetic field. Here, we present a first anomaly map from new CHAMP scalar magnetic field data. After subtracting a recent Ørsted main and external field model, we remove remaining unmodeled large‐scale external contributions from 120° track segments by subtracting a best‐fitting uniform field. In order to preserve N/S trending features, the data are not filtered along‐track. Direct integration of the spherically gridded data yields the final degree 14–65 spherical harmonic expansion of the total intensity anomaly at the mean satellite altitude of 438 km. Apart from enhanced long wavelength features and a smoother general appearance, our initial map is strikingly similar to one of the lower strength Magsat/POGO maps.