Theoretical Studies On Drift Wave Instability In Fluid Models

In this dissertation,we study theoretically the drift waves and instabilities in non-uniform plasma using either the two-fluid(separate electron ion equations)or the extended MHD(center of mass)presentations.Two-fluid and finite Larmor radius effects can modify wave propagation,instability growth rates and relaxation physics of macroscopic phenomena for high temperature(fusion or space)as well as low temperature(quantum)plasmas.We usually apply two approaches,a two-fluid and anextended MHD approach to study dynamics of plasma including both macroscopic and microscopic physics.In two-fluid model,the dominant effects of separated fluids are retained in diamagnetic drift due to electrons and polarization drift due to ions.Whereas in the extended-MHD model,the dominant order of these effects are captured in generalized Ohm's law and gyro-viscous stress tensor.First,local dispersion relations for resistive drift mode in a nonuniform magnetized plasma are derived for thermal and non-thermal distribution of electrons.The coupled mode equations are obtained by using two-fluid plasma model with thermal as well as non-thermal(Cairns and kappa)distribution for electrons.It has been found that increasing values of ?(which estimate population of non-thermal electrons)for Cairn distribution are able to stabilize the mode.Furthermore,increasing the values of K(which is spectral index)for the kappa distribution has destabilizing effects on the mode.Second,gyro-viscosity effecton the linear electromagnetic(EM)resistive drift wave instability is analyzed by using an extended MHD model.The conventional resistive drift-Alfven mode is recovered in the cold ion regime.Third,new local dispersion relations for quantum drift modes in a magnetized dense plasma are derived,considering the effects of exchange and correlation for electrons.The newly found quantum drift mode(QDM)exists only under low temperature conditions.In addition,comparative study on the stability of resistive-drift-Alfven(RDA)mode has been performed with two different mathematical formulations,the extended MHD model and the two-fluid plasma model.A local dispersion relation for RDA mode with cold ions and hot electrons is derived.Our results validate thatthe two-fluid approach is comparable to the extended MHD for modeling the RDA mode.However,the two-fluid effects is more in two-fluid formulation as compared to that in extended MHD often include an additional term associated with ion polarization drift.Finally,the overlapping regime of drift wave andinterchange instabilities is analyzed by using anextended MHD model.At moderate plasma ? and Lundquist number S,the mode retains its drift wave character.For very small value of k?,the mode becomes resistive interchange.