Quantum Effects on Low Frequency Waves in Dense Plasmas

Abstract

The low frequency electrostatic and electromagnetic waves in dense plasmas are studied using the quantum hydrodynamic formulation. Several linear and nonlinear waves in uniform as well as nonuniform plasmas are investigated taking into account the quantum diffraction and quantum statistical effects. In an inhomogenous plasma, the drift type wave can appear which doesn’t require electron temperature to be non‐zero for its existence and the electron quantum effects contribute to the wave dispersion at very short length scales. The effect of stationary dust is also discussed. It is also found that the drift wave of ultracold dense plasma can couple with Alfven wave and the linear dispersion relation is analogous to the classical plasma case. But physically, both the dispersion relations are very different. The dispersion relations are analyzed numerically for particular cases of ultracold dense plasma. In a homogenous quantum plasmas, the linear waves are studied for electron‐ion as well as stationary dust case. It is found that the quantum ion‐acoustic wave frequency in the presence of background dust increases with electron quantum effects and dust concentration. In a magnetized electron‐ion plasma, the wave frequency increases with electron number density and magnetic field. The linearly coupled electrostatic and Alfven waves are also investigated and the role of electron fermionic pressure in the wave dynamics of dense quantum plasmas is pointed out. A comparison of fermionic pressure with the quantum pressure due to Bohm potential term is presented. The limit of ultracold dense plasma is discussed in the light of this comparison. The wave dispersion properties for static as well as dynamic ions are elaborated. In the nonlinear regime, it is found that the dust concentration in unmagnetized plasma increases the amplitude and width of dust ion‐acoustic soliton whereas the increase in quantum diffraction parameter reduces the width of the soliton, but doesn’t affect its amplitude. For, magnetized electron‐ion quantum plasma, the quantum diffraction effects are found to increase the amplitude as well as width of the solitons. The increase in magnetic field shrinks the soliton keeping the amplitude constant. The results presented in this thesis are supported by numerical analysis and illustrations. The relevance of the study with the dense astrophysical and laboratory plasmas is also pointed out.

Keywords: Dense quantum plasmas, low frequency waves, quantum effects, solitons, etc.