Item

Abstract

Satel1ite 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 0rsted 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 spherical1y gridded data yields the final degree 14-65 spherical harmonic expansion of the total intensity anomaly at the mean satel1ite 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. INDEX TERMS: 1545 Geomagnetic and Paleomagnetism: Spatial variations (all harmonics and anomalies); 1594 Geomagnetic and Paleomagnetism: Instruments and techniques; 1532 Geomagnetic and Paleomagnetism: Reference fields (regional, global); 2778 Magnetospheric Physics: Ring current potsdam.de/champ for details). Our analysis of scalar data from the first 14 months of the mission provides strong evidence in favor of a relatively weak lithospheric field. The lithospheric magnetic anomaly map exhibits remarkable similarity to the combined Magsat/POGO map of Arkani-Hamed et al. [1994].