Study of Nonlinear Interactions in Dense Plasmas

Abstract

It is intended here in this thesis to study the nonlinear interactions evolved from the interaction of linear modes in dense plasmas like astrophysical objects, laser produced plasmas and semiconductor plasmas, etc. The dense plasma systems in focus contain electrons, ions and negatively charged dust grains. The constituent modes are electrostatic and electromagnetic in nature. In addition to the coupling mechanism, an electron beam is also considered as an energy source. A multi-fluid model consisting upon momentum balancing equation, equation of continuity, Poisson’s equation and set of Maxwell equations for quantum plasmas is used to diagnose the plasmas analytically. The thesis is composed of two-fold studies of nonlinear interactions based upon the published papers. Firstly, excitation of a beat wave generated by the parametric coupling of two modes of slightly different wavelengths is discussed. The linear analysis of the dispersive nature of the incident (pump) and scattered (sideband) is carried out. A derivation of the nonlinear dispersion expression is carried out due to the linear coupling of the pump and sideband in the assembly of a homogeneous dense dusty magneto-plasmas. This leads to the growth rate of the parametric instability of three waves. Secondly, the nonlinear growth of the parametric instability of electrostatic electron Langmuir wave, produced by the coupling of two waves with slightly different frequencies in semiconductor plasma is discussed. The linearity behaviour of an electrostatic pump (upper-hybrid wave) and electromagnetic sideband (O-mode) in semiconductor quantum plasma is studied. The second order convective term couples the fields of pair modes to derive the nonlinear beat frequency of the resultant perturbation leading to three waves parametric instability in semiconductor quantum plasma system. In both the cases the quantum mechanical effects arising due to degenerate pressure of Fermi gas, quantum tunneling effect, and exchange-correlation potential have been incorporated for the fermions. The instability is analyzed graphically for both cases on varying different parameters.