| Summary: | The existence of a Fisk-type heliospheric magnetic field (HMF) is one of the most debated
questions in cosmic-ray modulation. Recently, Burger and Hitge [2004] developed a divergence-free
Fisk-Parker hybrid magnetic field model to demonstrate the behaviour of cosmic rays in
the heliosphere due to such a field. This approach has been refined and the properties of the
consequent field are investigated. It is found that randomly directed magnetic field diffusion
in and above the photosphere significantly influences the solar magnetic field both at the solar
poles and near the polar coronal hole boundary. The solar cycle dependence of this field is
investigated, a study which is of particular importance for studies of the long-term behaviour
of cosmic rays, such as those undertaken at the SANAE base in Antarctica. The amplitudes of
the 26-day recurrent cosmic-ray variations are modelled as function of both latitudinal gradient
and heliolatitude and are found to agree qualitatively and in some cases quantitatively with
the observational results reported by Zhang 119971 and Paizis et al. 119991. Although magnetic
field data do not clearly indicate the existence of the Fisk field [see, e.g., Fursyth et al., 20021,
this study supports the existence of a Fisk-type HMF. === Thesis (M.Sc. (Physics))--North-West University, Potchefstroom Campus, 2006.
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