الفهرس 
Chapter 1 IntroductionOnly 14 pages are availabe for public view
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Abstract
The dynamics of plasmas, as inferred from both space observations and laboratory experiments almost universally reveal non-linear phenomena. This thesis concerns the exploration of both linear and nonlinear processes in various plasma environments, where the primary focus is on aspects of nonlinear wave propagation. The expansion of a multi-component plasma into a vacuum is a well-known problem in non-linear plasma dynamics. This process is not only a fundamental issue in plasma dynamics but also occurs in various plasma engineering applications. In Chapter 3, plasma expansion into vacuum is investigated assuming that half of the space is covered by a bi - ion plasma. Using model non-thermal electron distributions, the effect of highly energetic electrons on the non-linear evolution of the expanding ion front is explored. The parametric dependence on the charge to mass ratio and density ratio between the respective ion species is determined. In Chapter 4, I turn my attention to ultra-dense degenerate plasmas. For such a plasma, the so-called Fermi pressure plays an important role in the plasma behaviour. Using a multi-fluid model, the growth of perturbations resulting from an energetic ion beam streaming into an ultra-dense electron-ion plasma is examined. The dispersion relation for this system, assuming a relativistic Chandrasekhar one-dimensional equation of state, has been derived. from the dispersion relation, it can be seen that the plasma has three different modes, including the beam resonant mode which is found to be unstable. The dependence of the resulting instability on the ion beam density and velocity is determined. Building on this picture, an exact one-dimensional nonlinear model of a multicomponent plasma including quantum effects through the Fermi pressure is introduced in Chapters 5 and 6. Using Sagdeev’s pseudo-potential method, the relevant parameter space determining the allowable regions for arbitrary amplitude electrostatic pulses propagating into the plasma has been obtained. The presence of a negatively charged beam is shown to result in the coexistence of a positive and negative electrostatic potential polarity in this region. In Chapter 7, I continue with the theme of non-linear phenomena in the presence of negatively charged ions, although moving away from the ultra-dense plasmas. Specifically, I consider a slowly-varying modulated amplitude wave propagating into a plasma in the presence of negative ions. A multi-scale perturbation technique has been used to derive a nonlinear Schr¨odinger equation that models the wave envelope amplitude. The modulational instability condition for the wave envelope has been explored taking into account the effect of the negative - to - positive ion density and charge ratios. The role of negative ions in the plasma on the occurrence of nonlinear waves such as freak waves is discussed. The generation of freak waves from a slowly varying modulated amplitude of a sinusoidal wave is examined via numerical integration of the nonlinear Schrodinger equation. I conclude with the discussion in Chapter 8.