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. / Thesis (M.Sc. (Physics))--North-West University, Potchefstroom Campus, 2007.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:nwu/oai:dspace.nwu.ac.za:10394/1627 |
| Date | January 2006 |
| Creators | Nkosi, Godfrey Sibusiso |
| Publisher | North-West University |
| Source Sets | South African National ETD Portal |
| Detected Language | English |
| Type | Thesis |
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