published_or_final_version / Physics / Doctoral / Doctor of Philosophy

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The interaction of an anisotropic (in velocity space) ion beam with an isotropic background hydrogen plasma is theoretically investigated. The length and time scales are such that both the ions and electrons are magnetized. Using linear theory, the electrostatic dispersion relation is derived, and solved fully, using no approximations. It is shown that the anisotropy can significantly enhance the instability growth rates as compared to the isotropic case. The importance of ion magnetization is illustrated. Comparisons are made with unmagnetized plasma results. The modulational instability of an arbitrarily-large-amplitude electron cyclotron wave along the external magnetic field is investigated, taking into account the relativistic electron quiver velocity and the relativistic ponderomotive force. Three types of plasma slow responses, the forced-Raman, quasistatic and forced-quasistatic, are considered and a parameter study of the instability growth rates is carried out. / Thesis (M.Sc.)-University of Durban-Westville, 1989.

The behaviour of the crossfield current-driven ion acoustic instability in a plasma containing two ion species is theoretically examined. In our model the electrons are assumed to be hot and the ions cold, i.e. Tₑ »Tᵢ (~ 0), where both ion species are given the same temperature. The length and time scales are such that the electrons are magnetized and the ions unmagnetized. The linearised Vlasov equation is used to set up a dispersion relation for electrostatic waves for Maxwellian equilibrium velocity distributions of the electrons and ions. For the ion acoustic wave, a study is made of the dependence of the critical electron drift velocity (Vͨₒ) required to excite an instability on several parameters. The parameters include light ion fraction, heavy to light ion mass ratio, magnetic field strength and the propagation angle. In general the maximum value of Vͨₒ is found to be smaller than that for an unmagnetized plasma. Approximate analytic solutions of the dispersion relation are used to make comparisons with solutions from the full dispersion relation. The effect of drifts due to inhomogeneities in external magnetic field, perpendicular electron temperature and electron density on the growth rate of the ion acoustic instability are investigated in the ion rest frame. Finally, in a reference frame in which the electrons are stationary, both ion species are given external drifts. The effects of the ion drift velocities (both equal and unequal), electron to ion temperature ratio, light ion fraction, and heavy to light ion mass ratio on the growth rate of the ion acoustic instability are then studied. / Thesis (M.Sc.)-University of Durban-Westville, 1987.

No description available.

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