A global model of mantle conductivity derived from 5 years of CHAMP, Orsted, and SAC-C magnetic data

We present a global 1-D conductivity model which is obtained by analysis of five years ( 2001 - 2005) of simultaneous magnetic data from the three satellites Orsted, CHAMP and SAC-C. After removal of core and crustal fields as predicted by a recent field model we used non-polar scalar and vector observations from the night-side sector, and interpret the field residuals in terms of a large-scale contribution from the magnetospheric ring current and its induced counterpart. We then derive transfer functions between internal ( induced) and external expansion coefficients of the magnetic potential and provide globally-averaged C-responses in the period range between 14 hours and 4 months. Since the satellite responses are probably influenced by induction in the oceans for periods shorter than a few days, we correct the data for this effect. Interpreting the corrected responses yields a 1-D conductivity model which is rather similar to models derived from ground-based data.