A southern African secular variation model derived from satellite data

Time variations of the geomagnetic field can be classified into two main categories of internal and external origin with respect to the surface of the Earth. It has been found that the variations that take place on longer time scales are commonly known as secular variation and are of internal origin. The authors study the time variations of the geomagnetic field on longer time scales over southern Africa region applying two regional geomagnetic field modelling techniques, namely, Polynomial Surface Modelling and Spherical Cap Harmonic Analysis to CHAMP satellite observations recorded between 2001 and 2005. They evaluate the performance of the developed model using two global models IGRF-10 and CHAOS with the help of ground-based data.The results identify the occurrence of rapid secular variation fluctuations in all components of the magnetic field vector in 2003 and 2004. These small scale features of the time variations of the geomagnetic field are not detectable by the global models. This book invites also those readers who are interested in operating geomagnetic instruments for data collection and in geomagnetic data processing.