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Linear and nonlinear properties of obliquely propagating waves are studied in a degenerate dense cold magnetoplasma, comprising of Thomas–Fermi distributed electrons and ions as well as non-degenerate negatively charged dust particulates. By using the plane wave approximation, a linear dispersion relation for the dust-cyclotron (DC) and dust-acoustic (DA) waves is derived and analyzed numerically. For fully nonlinear waves, a Sagdeev pseudopotential theory is employed to derive an energy-balance equation and the soliton existence domain depending upon the dust concentration $(h)$ , obliqueness $(L_{z})$ , and Mach number $(M)$ . Numerical analysis reveals that the parameter $h$ enhances the domain for allowed Mach numbers, i.e., $M_{1} and therefore favoring the solitary excitations, where $M_{1}$ and $M_{2}$ are the lower and upper Mach numbers, respectively. In addition, the dust concentration significantly reduces the amplitude and the profile sharpness of the solitary pulses. Similarly, variations in the obliqueness parameter and the Mach numbers modify the wave characteristics. This paper is important for understanding the nonlinear properties of electrostatic excitations in degenerate dusty magnetoplasma, relevant to white dwarfs (WDs), namely $GD56,\,\,GD29-38,\,\,GD362$ , and $WD2115-560$ , being termed as the DUSTY DAZ WDs.

Linear and nonlinear coupling of drift and ion acoustic waves are studied in a nonuniform magnetized plasma comprising of Oxygen and Hydrogen ions with nonthermal distribution of electrons. It has been observed that different ratios of ion number densities and kappa and Cairns distributed electrons significantly modify the linear dispersion characteristics of coupled drift-ion acoustic waves. In the nonlinear regime, KdV (for pure drift waves) and KP (for coupled drift-ion acoustic waves) like equations have been derived to study the nonlinear evolution of drift solitary waves in one and two dimensions. The dependence of drift solitary structures on different ratios of ion number densities and nonthermal distribution of electrons has also been explored in detail. It has been found that the ratio of the diamagnetic drift velocity to the velocity of the nonlinear structure determines the existence regimes for the drift solitary waves. The present investigation may be beneficial to understand the formation of solitons in the ionospheric F-region.

We consider a low frequency plasma comprising of Kappa distributed electrons and Maxwellian ions embedded in an external magnetic field in toroidal ion-temperature-gradient driven modes. A set of nonlinear equations are derived in the presence of equilibrium density, temperature, and magnetic field gradients. In the nonlinear regime, solutions in the form of tripolar vortices are derived by using Braginskii’s transport equations. It has been observed that the scale lengths over which the nonlinear vortex structures form get modified in the presence of Kappa distributed electrons. In tokamak the present study is applicable where non-Maxwellian population has been observed in electron cyclotron heating experiments and resonant frequency heating.

The effect of nonthermal distributions of electrons on ion-temperature-gradient (ITG)-driven drift modes in the presence of tiny dust particles for bi-ion magneto plasmas is investigated. The dynamics of bi-ions and dust particles is considered for the study of low-frequency (less than the gyrofrequencies of dust and ions) ITG mode. A new dispersion relation is derived and analyzed numerically as well as analytically. Three different distributions for nonthermal electrons (Kappa, q, and Cairns distribution) are used. It is found that the presence of nonthermal electrons in bi-ion dusty magnetoplasma reduces the growth rate of the ITG instability. These results should be useful for laboratory and space plasmas where nonthermal electrons and dust is always present.

Linear and nonlinear characteristics of electrostatic waves in a multicomponent magnetoplasma comprising of Boltzmann distributed electrons, Cairn’s distributed hot electrons, and cold dynamic ions are studied. It is found that the effect of superthermal electrons, ion-neutral collisions, and ion shear flow modifies the propagation of ion-acoustic and drift waves. The growth rate of the ion shear flow instability varies with the addition of Cairn’s distributed hot electrons. It is also investigated that the behavior of different type of vortices changes with the inclusion of superthermal hot electrons. The relevance of this investigation in space plasmas such as in auroral region and geomagnetic tail is also pointed out.

The evolution and propagation characteristics of ion-acoustic (IA) shocklets are examined in an unmagnetized collisionless plasma, comprised of warm ions and non-Maxwellian (Kappa/Cairns) electrons. Solving the fluid equations and using the frameworks of diagonalized-matrix/changing variable techniques, a nonlinear set of two characteristic wave equations is obtained, which admits dispersionless/dissipationless evolution of IA shocklets. Numerical analyses have also confirmed the excitation/deformation of IA shocklets and the wave overtaking/breaking effects at time τ > 0 for nonlinear coupling of potential field. It is found that superthermal (Kappa distributed) electrons can enhance the overtaking/breaking of IA perturbations in comparison with nonthermal Cairns distributed electrons that lead to less steepened potential field to stabilize IA excitations against the nonlinear steepening. Finite ion temperature has significant impact on the wave coupling to lead the profiles of IA shocklets ahead. This study is important to understand the physical mechanism for excitation and deformation of IA shocklets relevant to the F-region of Ionosphere.

Theoretical investigation of electrostatic ion acoustic periodic (cnoidal) waves and solitons with warm ions is presented with electrons that are assumed to follow the double spectral index distribution function. The double spectral index distribution imitates effectively the distributions that have often been seen in space plasmas. Using the standard reductive perturbation technique, the Korteweg-de Vries (KdV) equation is derived which describes the nonlinear periodic waves with appropriate boundary conditions. By using planar dynamical system to this KdV equation, the existence of solitary wave solutions and periodic wave solutions are found. It is shown that changing the electron population in regions of low and high phase space density regions alter the propagation characteristics of nonlinear ion acoustic periodic and solitary structures. Comparison of non-Maxwellian distribution functions with Maxwellian distribution is also made. The importance of the present work with regard to space plasmas is also pointed out.

Dust acoustic (DA) waves evolving into shocklets are investigated in the comet Halley plasma system relaxing to Maxwellian, Kappa, and Cairns distributions. Here, dynamics of dust is described by the fully nonlinear continuity and momentum equations. A set of two characteristic wave nonlinear equations is obtained and numerically solved to examine the DA solitary pulse that develops into oscillatory shocklets with the course of time such as at time τ = 0 , symmetric solitary pulses are formed, which develop into oscillatory shocklets. It has been observed that the variation in superthermality strongly affects the profiles of nonlinear DA structures in terms of negative potential, dust velocity, and density.

In the present investigation, we have studied the linear and nonlinear propagation of electrostatic waves in a dense magnetoplasma with trapped electrons. Using the small amplitude approximation, formation of solitary structures has been studied both for fully and partially degenerate plasmas. The theoretical results obtained have been analyzed numerically for the parameters typically found in white dwarfs. The present work may be beneficial to understand the propagation of solitary structures with weak transverse perturbation with special reference to white dwarf asteroseismology.

Using Boltzmann-Vlasov kinetic model for nonthermal distributed electron-positron-ion plasma of our Earth’s magnetosphere and the solar wind streaming plasma can drive ion-acoustic waves unstable. It is found that the growth rate increases with the decrease of spectral index and increases with the streaming velocity of the solar wind. The numerical results are also presented by choosing some suitable parameters of magnetospheric plasma.

The effect of nonthermal electrons on ion-temperature-gradient (ITG) driven modes is investigated in the presence of variable dust charge and ion shear flow. The dust charge fluctuating expression is obtained in the presence of kappa distributed electrons. A dispersion relation is derived and analyzed numerically by choosing space plasma parameters of Jupiter/Saturn magnetospheres. It is found that the presence of nonthermal electrons population reduces the growth rate of ITG mode driven instability. The effects of ion temperature, electron density and magnetic field variation on the growth rate of ITG instability are presented numerically. It is also pointed out that the present results will be useful to understand the ITG driven modes with variable dust charge and kappa distributed electrons, present in most of the space plasma environments.

Electron temperature gradient (ETG) driven solitons are investigated having gradients in equilibrium electron temperature and equilibrium number density and with electron shear flow. In a linear regime, using model equations, a linear dispersion relation has been analysed analytically as well as numerically. ηe and electron to ion temperature ratio effects, real frequency, and growth rate of ETG instability are determined. In the nonlinear regime, the Korteweg--de Vries equation for the ETG mode has been derived and analysed numerically which shows that it admits solitary wave solutions. It can also be noted that soliton amplitude is sensitive to ηe, the magnetic field, and the temperature ratio. This work may be helpful for low frequency electrostatic modes in nonuniform electron-ion plasma having gradients in density and electron temperature and also in tokamak plasma.

The linear and nonlinear properties of ion-acoustic rogons and associated modulational instability (MI) are studied in an unmagnetized dense electron-ion plasma, containing degenerate trapped/untrapped electrons and classical adiabatic ions. Solving the quantum hydrodynamic equations by using the standard multiscale reductive perturbation technique, a nonlinear Schrodinger equation is derived, which admits potential envelopes to be stable (unstable) against the perturbations for PQ 0 ). Here, P and Q are the dispersion and nonlinearity coefficients, respectively. It is numerically shown that for the vanishing ionic temperature ratio ( σ = 0 ) , the parametric regime at perturbation wavelengths λ ≥ 2.5 λ eff ( λ ≤ 2.5 λ eff ) is always modulationally stable (unstable); here, λeff is the effective screening length. Moreover, the finite ionic temperature ( T i ≤ 10 eV ) restores the modulational stability at relatively short wavelengths by confining MI within the perturbation range 4.5 λ eff ≤ λ ≤ 1.3 λ eff . The parameter Θ ( = T e / 2 2 μ ) shows the impact of the untrapped electrons which not only enhances (reduces) the angular frequency (group speed) of the envelope but also piles up the wave crests (energy) to produce the MI. Furthermore, due to degenerate trapped electrons, the instability domain gets widened in the limit PQ > 0 and leads to the onset of MI and unstable excitations. The study has important results for understanding the mechanism of MI and unstable modes in the context of astrophysical environments (white dwarfs, neutron stars, etc.,) and high density experiments.

Employing Vlasov-Poisson model for nonthermal distributed permeating plasma consisting of electron-positron-ion plasma of our earth’s magnetosphere and the solar wind plasma with some fixed streaming velocity, can drive ion-acoustic waves unstable. The growth rates are computed with respect to the variation in spectral index of the kappa or generalized Lorentzian distribution and streaming velocity of the solar wind. It is found that the growth rate increases with the decrease of spectral index and increases with the streaming velocity of the solar wind. The numerical results are also presented by choosing some suitable parameters.

The effect of two negative ions on the Landau damping and stellar solar wind driven instability is analyzed using kinetic theory for the Lorentzian plasmas. It is investigated that the dispersion relations, damping rates and instability growths are appreciably modified in the presence of Generalized Lorentzian or kappa distributed function and additional negative ion in our plasma system. A quantitative measurement of the threshold value of the streaming velocity is also determined to estimate the condition of the growing instability.

Properties of fully nonlinear electron-acoustic solitary waves in an unmagnetized and collisionless electron-positron-ion plasma containing cold dynamical electrons, superthermal electrons and positrons obeying Cairns’ distribution have been analyzed in the stationary background of massive positive ions. A linear dispersion relation has been derived, from which it is found that even in the absence of superthermal electrons, the superthermal positron component can provide the restoring force to the cold inertial electrons to excite electron-acoustic waves. Moreover, superthermal electron and positron populations seem to enhance the electron acoustic wave phase speed. For nonlinear analysis, Korteweg-de Vries equation is obtained using the reductive perturbation technique. It is found that in the presence of positron both hump and dip type solitons appear to excite. The present work may be employed to explore and to understand the formation of electron acoustic soliton structures in the space and laboratory plasmas with nonthermal electrons and positrons.

Linear and nonlinear properties of coupled modes in a magnetized quantum plasma in the presence of electron Fermi pressure are studied in a nonuniform magnetoplasma composed of electrons, ions, and extremely massive and negatively charged immobile dust grains. Stationary solutions of the nonlinear equations that govern the dynamics of coupled modes are presented. It is found that electrostatic dipolar vortex structure can form in such a plasma. The dipolar structures in dense plasmas are observed to be formed on a much shorter scalelength by comparison with their classical counterparts. It is found that the increasing Fermi temperature shortens the scalelength over which the nonlinear coherent structures are formed. The relevance of the present investigation with regard to the dense astrophysical plasmas is also pointed out.

Properties of fully nonlinear ion-acoustic solitary waves in an unmagnetized and collisionless pair-ion (PI) plasma containing superthermal electrons obeying Cairns distribution have been analyzed. A linear biquadratic dispersion relation has been derived, which yields the fast (supersonic) and slow (subsonic) modes in a pair-ion-electron plasma with nonthermal electrons. For nonlinear analysis, Korteweg-de Vries equation is obtained using the reductive perturbation technique. It is found that in case of slow mode, both electrostatic hump and dip type structures are formed depending on the temperature difference between positively and negatively charged ions, whereas, only dip type solitary structures have been observed for fast mode. The present work may be employed to explore and to understand the formation of solitary structures in the space (especially, the Earth’s ionosphere where two distinct pair ion species (H ±) are present) and laboratory produced pair-ion plasmas with nonthermal electrons.

Nonlinear equations governing the dynamics of finite amplitude drift-acoustic-waves are derived by taking into account sheared ion flow perpendicular to the ambient magnetic field in a quantum magnetoplasma comprised of electrons, positrons, and ions. It is shown that stationary solution of the nonlinear equations can be represented in the form of a counter-rotating vortex for a particular choice of the equilibrium profile. The counter rotating vortices are, however, observed to form on very short scales i.e., of the order of ion Larmor radius ρi in quantum plasmas. It is observed that the scalelengths over which these structures form get modified in the presence of quantum statistical and Bohm potential terms as well as the positron concentration. The relevance of the present investigation with regard to dense astrophysical environments is also pointed out.

We have investigated some linear as well as nonlinear properties of ion-acoustic wave (IAW) propagation in a non-uniform two-electron-temperature magnetoplasma in the presence of ion-sheared flows. In the linear limit, new dispersion relation has been derived and analyzed in some interesting limiting cases. It is shown that ion-sheared flow can drive the IAW unstable under a certain limit.Whereas, in the nonlinear case, dipolar and vortex street type solutions can appear. It is observed that by choosing some typical parameters of Earth's auroral region, the scalelength of the nonlinear structures are significantly modified. The present investigation might be very useful to explain various types of nonlinear structure formation which has been observed in space environments where two-electron-temperature plasma exist.

The formation and propagation of shocks and solitons are investigated in an unmagnetized, ultradense plasma containing degenerate Fermi gas of electrons and positrons, and classical ion gas by employing Thomas-Fermi model. For this purpose, a deformed Korteweg-de Vries-Berger (dKdVB) equation is derived using the reductive perturbative technique for cold, adiabatic, and isothermal ions. Localized analytical solutions of dKdVB equation in planar geometry are obtained for dispersion as well as dissipation dominant cases. For nonplanar (cylindrical and spherical) geometry, time varying numerical shock wave solution of dKdVB equation is found. Its dispersion dominant case leading to the soliton solution is also discussed. The effect of ion temperature, positron concentration and dissipation is found significant on these nonlinear structures. The relevance of the results to the systems of scientific interest is pointed out.

The propagation characteristics of magnetoacoustic shock waves are investigated in an electron-ion dense magnetoplasma that accounts for spin − 1 2 electrons and geometrical effects within the framework of a two-fluid quantum magnetohydrodynamic model. For this purpose, we have employed the reductive perturbation technique and derived small-amplitude planar Korteweg de Vries Burgers (KdVB) and cylindrical KdVB equations. Numerically, cylindrical KdVB equations are analyzed by choosing the plasma parameters consistent with compact astrophysical systems. It is observed that the density, magnetic field, and viscosity are the parameters that ascertain significant modifications in the structure and propagation of magnetoacoustic shock waves. The amplitude of the shock wave becomes larger in the case of cylindrical geometry and propagates faster than that of planar shock waves. Furthermore, the results are compared with analytical solutions in the limit of earlier times to show an excellent agreement of the res...

In this paper, we have investigated the perpendicularly propagating kinetic mode employing the Vasyliunas-Cairns (VC) distribution. We have obtained the linear dispersion relation for Bernstein waves for two electron species and explored it both analytically and numerically. We have shown that Bernstein waves with the Vasyliunas-Cairns distribution exhibit a significant departure from the results reported earlier with Maxwellian and dual kappa distributions especially in the long wavelength regime. We have found that the parameters Λc and Λh, that represent the nonthermal percentage of cold and hot electrons in Cairns distribution, play a unique and vital role in determining the behavior of Bernstein modes in the VC distribution which has no parallel in Maxwellian and dual kappa distribution functions. Our study may be beneficial to understand the propagation characteristics of Bernstein waves in space plasmas where departure from Maxwellian behavior has been divulged by many expeditions in space.

In this paper, we have investigated the head-on collision of quantum ion acoustic solitons with relativistically degenerate electrons by deriving a set of Korteweg–de Vries equations. Using the refined Poincare-Lighthill-Kuo method, we have derived the expressions for phase shifts of colliding solitons. It has been found that the system under consideration admits only compressive electrostatic solitary structures. The solitons have also been found to form only for the sub-acoustic velocities of the nonlinear structures. It has been observed that the soliton interaction happens over long spatial and temporal scales in the non-relativistic limit whereas the converse happens in the ultrarelativistic regime. It has been found that the phase shift of the solitons after interaction is more pronounced in the ultra-relativistic limit by comparison with its non-relativistic counterpart. It has also been found that the phase shift settles to a constant value in the nonrelativistic limit. Using the parameters that are customarily found in white dwarf stars, we have given an estimate of the spatial scales over which the nonlinear structures are expected to interact with each other both in the non-relativistic and in the ultra-relativistic regimes.

The previous works on whistler waves with electron temperature anisotropy narrated the dependence on plasma parameters, however, they did not explore the reasons behind the observed differences. A comparative analysis of the whistler waves with different electron distributions has not been made to date. This paper attempts to address both these issues in detail by making a detailed comparison of the dispersion relations and growth rates of whistler waves with electron temperature anisotropy for Maxwellian, Cairns, kappa and generalized (r, q) distributions by varying the key plasma parameters for the problem under consideration. It has been found that the growth rate of whistler instability is maximum for flat-topped distribution whereas it is minimum for the Maxwellian distribution. This work not only summarizes and complements the previous work done on the whistler waves with electron temperature anisotropy but also provides a general framework to understand the linear propagation of whistler waves with electron temperature anisotropy that is applicable in all regions of space plasmas where the satellite missions have indicated their presence.The previous works on whistler waves with electron temperature anisotropy narrated the dependence on plasma parameters, however, they did not explore the reasons behind the observed differences. A comparative analysis of the whistler waves with different electron distributions has not been made to date. This paper attempts to address both these issues in detail by making a detailed comparison of the dispersion relations and growth rates of whistler waves with electron temperature anisotropy for Maxwellian, Cairns, kappa and generalized (r, q) distributions by varying the key plasma parameters for the problem under consideration. It has been found that the growth rate of whistler instability is maximum for flat-topped distribution whereas it is minimum for the Maxwellian distribution. This work not only summarizes and complements the previous work done on the whistler waves with electron temperature anisotropy but also provides a general framework to understand the linear propagation of whistler waves with...

Nonlinear equations which govern the dynamics of low-frequency (ω ⪡ ωci, where ω is the perturbation frequency of the wave and ωci is the ion gyro-frequency), ion-temperature-gradient-driven modes in the presence of equilibrium density, temperature and magnetic field gradients are derived. New set of nonlinear equations are derived. In the nonlinear case, new types of solutions in the form of dipolar vortices and vortex streets are found to exist in dense quantum plasma. These structures are found to be formed on very short spatial scales.

Nonlinear structure formation in ion-temperature-gradient (ITG) driven waves is investigated in pair-ion plasma comprising ions and nonthermal electrons (kappa, Cairns). By using the transport equations of the Braginskii model, a new set of nonlinear equations are derived. A linear dispersion relation is obtained and discussed analytically as well as numerically. It is shown that the nonthermal population of electrons affects both the linear and nonlinear characteristics of the ITG mode in pair-ion plasma. This work will be useful in tokamaks and stellarators where non-Maxwellian population of electrons may exist due to resonant frequency heating, electron cyclotron heating, runaway electrons, etc.

The shear flow in dust dynamics driven waves in combination with the dust-neutral drag is studied in a plasma comprising of ions, electrons, and dust. Non-thermal population of ions is considered, which has been observed by many satellite missions. It is found that the dissipative instability produced by dust sheared flow and dust-neutral drag gets modified by the presence of nonthermal ions. It is found that the dissipative instability enhances for the Cairns distribution, whereas the kappa distribution arrests the growth of this instability. In the nonlinear regime, the formation of vortices in the system is studied. It is found that the nonthermal population of ions significantly alters these structures in comparison with their Maxwellian counterpart. The results obtained in this paper may have relevance in the planetary magnetospheres where the dust particles are present and non-Maxwellian distribution of particles have been observed by Freja and Viking satellites.

The Rayleigh–Taylor instability is investigated in a nonuniform dense quantum magnetoplasma. For this purpose, a quantum hydrodynamical model is used for the electrons whereas the ions are assumed to be cold and classical. The dispersion relation for the Rayleigh–Taylor instability becomes modified with the quantum corrections associated with the Fermi pressure law and the quantum Bohm potential force. Numerically, it is found that the quantum speed and density gradient significantly modify the growth rate of RT instability. In a dense quantum magnetoplasma case, the linear growth rate of RT instability becomes significantly higher than its classical value and the modes are found to be highly localized. The present investigation should be useful in the studies of dense astrophysical magnetoplasmas as well as in laser-produced plasmas.

The implosion dynamics and fusion parameters of a high density D-T fibre plasma driven by Z-pinch with current stepping technique is investigated. Our numerical results demonstrate that a current-stepping technique reduces the minimum pinch radius, and as a result high density, high temperature plasma can be formed. Thus a staged pinch device with current-stepping technique can be used as an alternative approach to achieve fusion conditions with relatively small values of discharge current and with a long pulse duration.

Ion acoustic shock waves (IASW's) are studied in an unmagnetized plasma consisting of electrons, positrons and adiabatically hot positive ions. This is done by deriving the Kortweg–deVries–Burger (KdVB) equation under the small amplitude perturbation expansion method. The dissipation is introduced by taking into account the kinematic viscosity among the plasma constituents. It is found that the strength of ion acoustic shock wave is maximum for spherical, intermediate for cylindrical, and minimum for planar geometry. It is observed that the positron concentration, ratio of ion to electron temperature, and the plasma kinematic viscosity significantly modifies the shock structure. Finally, it is found that the temporal evolution of the non-planar IASW's is quite different by comparison with the planar geometry. The relevance of the present study with regard to the dense astrophysical environments is also pointed out.

Cylindrical and spherical ion-acoustic solitons in electron–positron–ion plasma have been investigated. The reductive perturbation method has been used to derive a modified Korteweg-de-Vries (mKdV) equation. The numerical solutions of the mKdV equation are presented for both geometries. We found that the amplitude and width of ion-acoustic solitons decrease with an increase in positron concentration. It is also shown that adiabatically hot ions play a destructive role in the formation of solitons in both geometries.

The dust acoustic solitary waves (DASWs) in the presence of hot adiabatic dust in cylindrical and spherical geometries are investigated in an unmagnetized dusty plasma. The modified Korteweg–de Vries (mKdV) has been derived by using the reductive perturbation technique. The numerical solutions of the mKdV equation have been presented in both the geometries for hot dust plasmas. It is found that the amplitude of the dust acoustic wave (DAW) increases with the increase of dust temperature in both the geometries. However, the hot dust has more effect on DASW in spherical geometry as compared to the cylindrical case. These results might be very useful to explain the salient features of multidimensional DAWs for space and laboratory plasmas.

Electrostatic ion-temperature-gradient (ITG) driven drift waves are investigated by using Brangskii's model for the ions and Boltzmann distribution for the electrons in a dust-contaminated plasma with equilibrium density, temperature, and magnetic field gradients. Within the local approximation, we are able to recover the coupled ion-acoustic drift-waves in an inhomogeneous magnetic field and the Rudakov–Sagdeev (R–S) ITG instability in the presence of dust-charge fluctuations. It has been shown that the dust charging is always dissipative and the growth rate of various modes are damped. Furthermore, we also derive an expression for the anomalous ion-energy flux and transport coefficient in the presence of nonthermal fluctuations. The present investigation should be helpful in identifying the features of low-frequency turbulence and associated cross-field ion-energy transport in magnetically confined dust-contaminated tokamak plasmas.

The dynamics of a high density D-T fiber plasma driven by a multi cascade system (N multiple shells of finite thicknesses) has been investigated with a view to suppress Rayleigh–Taylor (R–T) instability. Our numerical results show that the plasma parameters of the D-T fiber sensitively depends upon the shell mass ratios and thicknesses. Large values of puff-thickness and mass-ratios provide stabilization against the R–T instability in the final stage of compression but adversely affect fusion conditions. Our analysis, however, suggests that optimum values of the puff-thicknesses and mass ratios are needed to achieve fusion parameters in a multi cascade liner staged Z-pinch devices. The relevance of our present investigation to ultra high magnetic fluxes, X-ray lasers as well as controlled thermonuclear fusion is also pointed out.

Nonlinear electrostatic and electromagnetic low frequency waves are studied in magnetized electron–positron–ion (EPI) plasmas. The effects of full nonlinearity and three dimensional ion motion have been taken into account. It is shown that both density dips and humps can coexist in EPI plasmas along with bell-shaped and kink-type solitons. The new results as well as several limiting cases for comparison with earlier work have been discussed, for the sake of completeness. Relevance of this work to space, astrophysical and laboratory plasmas is pointed out.

The implosion dynamics of a dense ?-pinch plasma driven by a double gas-puff z-pinch is re-examined in the presence of kinetic pressure. A modified snow-plow model has been used to describe the dynamics of such a staged pinch plasma. The inclusion of kinetic pressure introduces the usual plasma ?-term. Numerical results demonstrate that the thermonuclear fusion parameters can be achieved in a dense ?-pinch Deuterium-Tritium (D-T) fiber plasma for an optimum choice of density ratio of the test to driver gas at the interface position (?-parameter) of imploding z-pinch plasma and kinetic to magnetic pressure ratio (?-factor). Thus double gas-puff staged pinch device can be a more feasible approach to achieve fusion conditions with an enhanced stability.

A set of nonlinear equations governing the dynamics of low-frequency electrostatic waves in the presence of equilibrium density, temperature, magnetic field and electrostatic potential gradients has been derived. In the linear limit, it is shown that nonzero equilibrium ion-temperature-gradient and the presence of positrons modify the basic drift modes. On the other hand, in the nonlinear case, it is shown that under certain conditions possible stationary solutions of the same set of nonlinear equations are reduced in the form of various types of vortex patterns. The results of the present investigation should be useful to understand the wave phenomena in laboratory and astrophysical e-p-i plasmas.

A system of nonlinear equations which governs the dynamics of low-frequency (in comparison with the ion gyrofrequency) electrostatic waves in a nonuniform electron–positron–ion (e-p-i) magnetoplasma with sheared ion flows is presented. In the linear limit, a dispersion relation is obtained that admits new instabilities of drift-waves. It is found that ion-acoustic and electrostatic drift waves can become unstable due to ion sheared flow. Furthermore, the nonlinear interactions between these finite amplitude short-wavelength waves give rise to quadrupolar vortices. The relevance of the investigation to laboratory and astrophysical plasmas is pointed out.

The implosion dynamics and fusion parameters of a high density θ-pinch plasma driven by a multicascade liner Z-pinch is investigated. The imploding multicascade liner Z-pinch plasma traps an axial magnetic field, compressing it to several megagauss in an extremely short time. The fast changing magnetic flux then induces an azimuthal θ-current on the fiber surface, with a rise time an order of magnitude smaller than the applied Z-pinch current. Numerical simulation shows that for optimum choice of shell thickness of the multicascade liner system, high-densities and temperatures can be realized for fibers seeded with some high-Z impurities. At peak compression the fuel densities of the order of 1026/cm3 and temperature about 10 keV can be achieved on a time scale of the order of 0.5 ns, yielding the Lawson criterion parameter nτ ≥ 1014 s/cm3 for DT-plasma.

Analytical and numerical results are presented for the slowing down of a pair of heavy test charge projectiles through a multicomponent, dust-contaminated plasma. The correlation and interference effects of two collinear and noncollinear projectiles on electrostatic potential and energy loss are studied for a Maxwellian distribution and a special class of physically reasonable size distributions. The energy loss behavior versus projectile velocity of noncollinear projectiles is also examined for various orientations. It is found that the energy loss for Maxwellian distribution (for large value of spectral index κ) is larger compared to that for generalized Lorentzian distribution. It is also observed that for smaller values of κ, the test charge projectile gains energy instead of losing. These results would be useful for the understanding of the energy loss mechanism, which might be responsible for the coagulation of dust particles in molecular clouds, in the ion-beam driven inertial confinement fusion scheme and in dust plasma crystal formation, etc.

Nonlinear equations which govern the dynamics of low-frequency (ω≪ωci), ion-temperature gradient modes in the presence of equilibrium density, temperature, magnetic field, and electrostatic potential gradients are derived. For some specific profiles of the equilibrium flow velocity, number density, temperature, and magnetic field, new type of solutions in the form of quadrupole vortices are found for a nondissipative plasma. The results can have relevance to the understanding of the salient features of anomalous ion thermal transport and coherent vortex structure formation in magnetically confined plasmas, such as in tokamaks.

Exact localized nonlinear dust kinetic Alfven waves are investigated by retaining the complete dust nonlinearity and by invoking small but finite-β effects in a collisionless plasma, whose constituents are electrons, ions and negatively charged dust grains. Sub-Alfvenic, as well as super-Alfvenic, solitary waves consisting of smooth density humps or dips are found to exist. Further, super-Alfvenic kink type solitons are also found to occur. The soliton amplitude depends upon various plasma parameters along with the soliton propagation speed. The results of the present investigation may be useful in the diagnostics of dust in magnetized plasmas and in understanding the formation of coherent soliton structures in space and laboratory plasmas.

The formation and propagation of fully nonlinear dust-acoustic (DA) waves and shocks are studied in a non-Maxwellian thermal dusty plasma which is composed of Maxwellian electrons and nonthermal energetic ions with a neutralizing background of negatively charged dust grains. For this purpose, we have solved dust dynamical equations along with quasineutrality equation by using a diagonalization matrix technique. A set of two characteristic wave equations is obtained, which admits both analytical and numerical solutions. Taylor expansion in the small-amplitude limit ( Φ ≪ 1 ) leads to nonlinear effective phase and shock speeds accounting for nonthermal energetic ions. It is numerically shown that DA pulses can be developed into DA shocklets involving the negative electrostatic potential, dust fluid velocity, and dust number density. These structures are significantly influenced by the ion-nonthermality, dust thermal correction, and temporal variations. However, the amplitudes of solitary and shock waves are...

Compressional Dust Alfvenic Shocks (CDAS) are investigated in an electron depleted dusty plasma with dust-ion collisional effects. The large amplitude CDAS are obtained after solving the coupled nonlinear equations numerically, while small amplitude CDAS are explored through the Kortweg-de Vries Burger equation. It is pointed out that the spatio-temporal scale lengths for the formation of CDAS are different than the compressional Alfvenic shocks in an electron-ion plasma. The amplitude variation of CDAS with different parameters is shown. The transition of oscillatory shocks to monotonic shocks is presented in 3-D plots with variation in collision frequency. The importance of the results to space plasma environments is also briefly discussed.

A theoretical model for a multicascade liner system is proposed with a view to reduce the growth rate of Rayleigh-Taylor (R-T) instability and to calculate the fusion parameters of a dense θ-pinch plasma. The dynamics of such plasma has been described using the modified snow-plow model for sinusoidal and t1/3 types of discharge current profiles. Numerical results demonstrate that the thermonuclear fusion parameters can be achieved for a dense θ-pinch deuterium-tritium (D-T) fiber plasma for an optimum choice of shell thickness. The relevance of this kind of study is possible use of gas-liner and staged pinches as an alternative source of thermonuclear fusion.