A study of cosmic ray anisotropies in the heliosphere / Godfrey Sibusiso Nkosi

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dc.contributor.author Nkosi, Godfrey Sibusiso
dc.date.accessioned 2009-03-16T14:34:39Z
dc.date.available 2009-03-16T14:34:39Z
dc.date.issued 2006
dc.identifier.uri http://hdl.handle.net/10394/1627
dc.description Thesis (M.Sc. (Physics))--North-West University, Potchefstroom Campus, 2007.
dc.description.abstract The three-dimensional (3D) steady-state electron modulation model of Ferreira (2002), based on Parker (1965) transport equation, is used to study the modulation of the 7 MeV galactic and Jovian electron anisotropies in the inner heliosphere. The Jovian electrons are produced in Jupiter's magnetosphere which is situated at ~ 5 AU in the ecliptic plane. The propagation of these particles is mainly described by the diffusion tensor applicable for the inner heliosphere. Some of the elements of the diffusion tensor are revisited in order to establish what contribution they make to the three-dimensional anisotropy vector and its components in the inner heliosphere. The 'drift' term is neglected since the focus of this study is on low-energy electrons. The effects on the electron anisotropy of different scenarios when changing the solar wind speed from minimum to maximum activity is illustrated. The effects on both the galactic and Jovian electron anisotropy of changing the polar perpendicular coefficient, in particular, are illustrated. It is shown that the computed Jovian electron anisotropy dominates the galactic anisotropy close to the Jovian electron source at ~5 AU, as expected, testifying to the validity of the3D-model. For the latitudinal anisotropy, the polar perpendicular diffusion plays a dominant role for Jovian electrons close to the source, with the polar gradient becoming the dominant factor away from the electron source. Of all three anisotropy components, the azimuthal anisotropy is dominant in the equatorial plane close to the source. It is found that there is a large azimuthal gradient close to the source because the low-energy electrons tend to follow the heliospheric magnetic field more closely than higher energy particles. The transition of the solar wind speed from minimum to intermediate to maximum solar activity condition was used to illustrate the modulation of the magnitude of the 7 MeV total anisotropy vector along the Ulysses trajectory. It was found that during the two encounters with the planet a maximum anisotropy of 38% was computed but with different anisotropy-timepeaks as the approach to Jupiter was different.
dc.publisher North-West University
dc.subject Cosmic rays en
dc.subject Galactic electrons en
dc.subject Jovian electrons en
dc.subject Heliospheric modulation en
dc.subject Solar wind en
dc.subject Solar activity en
dc.subject Transport processes en
dc.subject Perpendicular diffusion en
dc.subject Cosmic ray anisotropy en
dc.title A study of cosmic ray anisotropies in the heliosphere / Godfrey Sibusiso Nkosi en
dc.type Thesis en
dc.description.thesistype Masters

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    This collection contains the original digitized versions of research conducted at the North-West University (Potchefstroom Campus)

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