| Summary: | 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 (~ 1 year and longer)
are commonly known as secular variation (SV) and are of internal origin. There is a
need to develop SV models using satellite data as the use of ground data is not always
possible with many limitations including the limited data points and lack of data over
ocean areas that are not easily accessible. Two regional geomagnetic field modelling
techniques namely polynomial surface modelling (PolyM) and Spherical Cap Harmonic
Analysis (SCHA) were applied to CHAMP satellite data recorded between 2001 and
2005 to investigate the use of satellite data to develop a geomagnetic SV model over
southern Africa. The restricted area of investigation is between 10° and 40° South in
latitude and between 10° and 40° East in longitude. The resulting regional models of
this investigation were validated against the two widely used global field models IGRF
10 and CHAOS using the available ground survey data obtained during the same period
over southern Africa. The results suggest that the regional field models can be derived
based entirely on satellite data. However, the regional SV models can be improved by
combining both high quality satellite and ground survey data, since they lack the high
quality of a global field model like CHAOS. === Thesis (M.Sc.)-University of KwaZulu-Natal, Westville, 2011.
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