A harmonic spline magnetic main field model for Southern Africa combining ground and satellite data to describe the evolution of the South Atlantic Anomaly in this region between 2005 and 2010

CHAMP satellite and relatively densely spaced ground-based data measured over southern Africa between 2005 and 2010 are combined in a new regional, harmonic spline based, core field model. This new SACFM-2 model is compared to the regional SARM model, which is based only on satellite data, and the global CHAOS-6 model. The results agree well in the vertical (Z) component, with somewhat larger differences in the horizontal components. The Z component and total intensity F are used to investigate the evolution of the South Atlantic Anomaly in this region. The computed maps of main field of the Z component and total intensity F show a steady decrease in the field over the years during the study period, indicating the evolution of the South Atlantic Anomaly over southern Africa and suggesting an increase in the area of this feature.