Ionospheric Currents from CHAMP Magnetic Field Data — Comparison with Ground Based Measurements

Summary

One important contribution to the magnetic field measured at satellite height is due to the external current systems. Above the polar regions the scalar data sampled by the Overhauser Magnetometer on CHAMP are used to study the horizontal Ionospheric Hall Current system. A series of line currents, placed at high latitudes at a height of 110 km is fitted to the spatial variations of the residual magnetic field across these regions. The observed current distribution depends on the local time of the satellite track. At dawn/dusk orbits the Polar ElectroJets (PEJs) can be detected clearly in the northern and southern auroral regions. Its variation with time is evidently correlated with the AE activity index. For a period of six months the results obtained from CHAMP measurements are compared to the currents determined from ground based observations of the Scandinavian IMAGE magnetometer network. During periods of increased activity the two current estimates are in good agreement. At quiet times uncorrected lithospheric magnetic fields cause spurious current features in the satellite results.