It is shown that a pre-existing electron density ripple in a dense plasma can excite electron neutrino oscillations. For our purposes, we use the dispersion relation for neutrino oscillations and derive the Mathieu equation for the propagation of neutrino oscillations in the presence of a spatially oscillating electron density ripple. The Mathieu equation predicts instability of neutrino oscillations. The criterion under which instability occurs is presented. Analytical expressions for the neutrino oscillation frequency and the growth rate are obtained. The possible relevance of our investigation to non-thermal neutrino oscillations in dense plasma environments (e.g. the supernovae, the core of white dwarf stars etc.) is briefly mentioned.

The filamentation of the high-power laser beam is investigated by taking off axial contribution when relativistic nonlinearity is considered. The effect of filamentation of the laser beam is studied on the localization of the electron plasma wave (EPW) and on the stimulated Raman scattering (SRS). The semi-analytical solution of the nonlinearly coupled EPW equation in the presence of laser beam filaments has been found. It is observed that due to this nonlinear coupling between two waves, localization of EPW takes place. This localization of EPW affects the Eigen frequency and damping of plasma wave. The new enhanced damping of the plasma wave has been calculated and it is found that the SRS process gets suppressed due to the localization of plasma wave in laser beam filamentary structures. For typical laser beam and plasma parameters with wavelength λ (=1064 nm), power flux (=1018 W cm−2) and plasma density n/ncr (=0.2); the SRS back reflectivity is found to be suppressed by a factor of approximately 8%.

Through a simple one-dimensional collisionless plasma sheath model, behavior of the floating potential in an electronegative plasma sheath is studied. Specially, the floating potential behavior as a function of the plasma electronegativity for various negative ion temperatures has been studied. It has been observed that negative ion temperature strongly affects the variation of floating potential.

A problem of the stability of an inhomogeneous axisymmetric plasma jet in a parallel magnetic field is solved. The jet boundary becomes, under certain conditions, unstable relative to magnetosonic oscillations (Kelvin–Helmholtz instability) in the presence of a shear flow at the jet boundary. Because of its internal inhomogeneity the plasma jet has resonance surfaces, where conversion takes place between various modes of plasma magnetohydrodynamic (MHD) oscillations. Propagating in inhomogeneous plasma, fast magnetosonic waves drive the Alfven and slow magnetosonic (SMS) oscillations, tightly localized across the magnetic shells, on the resonance surfaces. MHD oscillation energy is absorbed in the neighbourhood of these resonance surfaces. The resonance surfaces disappear for the eigenmodes of SMS waves propagating in the jet waveguide. The stability of the plasma MHD flow is determined by competition between the mechanisms of shear flow instability on the boundary and wave energy dissipation because of resonant MHD-mode coupling. The problem is solved analytically, in the Wentzel, Kramers, Brillouin (WKB) approximation, for the plasma jet with a boundary in the form of a tangential discontinuity over the radial coordinate. The Kelvin–Helmholtz instability develops if plasma flow velocity in the jet exceeds the maximum Alfven speed at the boundary. The stability of the plasma jet with a smooth boundary layer is investigated numerically for the basic modes of MHD oscillations, to which the WKB approximation is inapplicable. A new 'unstable mode of MHD oscillations has been discovered which, unlike the Kelvin–Helmholtz instability, exists for any, however weak, plasma flow velocities.

It is shown that sheared/zonal flows (ZFs) can be nonlinearly excited by incoherent drift waves (DWs) in a strongly magnetized non-uniform plasma composed of electrons, positrons and ions. The dynamics of incoherent DWs in the presence of ZFs is governed by a wave-kinetic equation. The governing equation for ZFs in the presence of nonlinear forces (associated with nonlinear ion polarization and nonlinear ion-diamagnetic drifts) of the DWs is deduced by combining the Poisson equation, as well as the e-p-i continuity equations, together with appropriate plasma particle velocities in the DW and the ZF fields. Standard techniques are used to derive a nonlinear dispersion relation, which depicts two classes of the modulational instability of the DWs against the ZFs. Non-thermal ZFs can reduce the turbulent cross-field particle transport in non-uniform, strongly magnetized e-p-i plasmas.

On the basis of two magneto-fluid model for two time-scales, the evolution of double layer in the downward current region of the aurora is numerically simulated under the non-static limit case. The results show that localized drop in density owing to collapsed high-frequency field can lead to the formation of double layer. The amplitude of the double layer is the order of the electron temperature, and the ramp potential is up to 36 V localized to tens of Debye lengths, which is around 100–200 m. These are consistent with the measurements in both the ramp potential and thickness by the Fast Auroral SnapshoT satellite in the downward current region of the aurora.

We derive a generalized linear dispersion relation of waves in a strongly magnetized, compressible, homogeneous and isotropic quasi-neutral plasma. Starting from a two-fluid model, describing distinguishable electron and ion fluids, we obtain a six-order linear dispersion relation of magnetized waves that contains effects due to electron and ion inertia, finite plasma beta and angular dependence of phase speed. We investigate propagation characteristics of these magnetized waves in a regime where scale lengths are comparable with electron and ion inertial length scales. This regime corresponds essentially to the solar wind plasma, where length scales, comparable with ion cyclotron frequency, lead to dispersive effects. These scales in conjunction with linear waves present a great deal of challenges in understanding the high-frequency, small-scale dynamics of turbulent fluctuations in the solar wind plasma.

Dispersion relation for the low-frequency magnetic electron-drift vortex (MEDV) mode in an inhomogeneous dense quantum plasma has been derived. New class of purely growing instabilities are found to exist on a time scale of the order of ion plasma period. We found that the MEDV mode become unstable when the propagation direction is perpendicular to the equilibrium density gradients. We believe that the present investigation would be useful to understand the wave phenomena and in the study of magnetic field generation in laser-produced plasmas as well as in dense space plasmas, where quantum effects are expected to play a dominant role.

The frequency shift is obtained for an extraordinary electromagnetic wave propagating through plasma as function of an external magnetic field. A linear theory is used here to calculate the frequency shift, and the numerical results are given for typical laboratory fusion plasma. A limit case where the wave is propagating through rarefied plasma in the presence of some weak magnetic field is also studied. Estimation is given on the basis of some simplifying approximation for the frequency upshift of a type III radio bursts interacting with the Earth's magnetosphere.

Large-amplitude Alfvén waves are ubiquitous in space plasmas and a main component of magnetohydrodynamic (MHD) turbulence in the heliosphere. As pump waves, they are prone to parametric instability by which they can generate cyclotron and acoustic daughter waves. Here, we revisit a related process within the framework of the multi-fluid equations for a plasma consisting of many species. The nonlinear coupling of the Alfvén wave to acoustic waves is studied, and a set of compressive and coupled-wave equations for the transverse magnetic field and longitudinal electric field is derived for waves propagating along the mean-field direction. It turns out that slightly compressive Alfvén waves exert, through induced gyro-radius and kinetic-energy modulations, an electromotive force on the particles in association with a longitudinal electric field, which has a potential that is given by the gradient of the transverse kinetic energy of the particles gyrating about the mean field. This in turn drives electric fluctuations (sound and ion-acoustic waves) along the mean magnetic field, which can nonlinearly react back on the transverse magnetic field. Mutually coupled Alfvén-cyclotron--acoustic waves are thus excited, a nonlinear process that can drive a cascade of wave energy in the plasma, and may generate compressive microturbulence. These driven electric fluctuations might have consequences for the dissipation of an MHD turbulence and, thus, for the heating and acceleration of particles in the solar wind.

A suitable modification on the plasma production device makes the plasma column length changeable; the axially propagating wave strikes on the movable circular base of the cavity and the reflected wave is affected enough. A tightening on the azimouthally propagating wave makes the amplitude measurements precarious, and the previous experimental results for fixed cavity length are valid. A strong boundaries' influence on the instability's reinforcement makes clear the need to extend even more the thermonuclear reactor's dimensions. In the present paper, an extended research of plasma parameters has been carried out, a corresponding theoretical model is developed to explain the phenomena and the comparison to the simulated results has been confirmed.

Space-charge waves in a relativistic electron beam that completely fills a cylindrical metallic waveguide and is guided by an ion channel are analyzed numerically. Equilibrium consists of a uniform and rigid rotation without betatron oscillations. Using cold fluid equations a differential equation and boundary conditions are derived that constitute an eigenvalue problem. This eigenvalue problem is solved, numerically, with the finite difference scheme using shooting method. Dispersion characteristics and electrostatic potential structures of azimuthally symmetric and nonsymmetric space-charge waves are studied. Perfect agreement with analytical results at asymptotic limit of zero axial velocity is found. It was found that relativistic effects modify the dispersion characteristics of the space-charge waves considerably and can concentrate the electric field energy of the wave into a thin and small shell around the axis.