Nonlinear Dynamics in a Nonextensive Complex Plasma with Viscous Electron Fluids

Cylindrical and spherical dust-electron-acoustic(DEA) shock waves and double layers in an unmagnetized,collisionless,complex or dusty plasma system are carried out.The plasma system is assumed to be composed of inertial and viscous cold electron fluids,nonextensive distributed hot electrons,Maxwellian ions,and negatively charged stationary dust grains.The standard reductive perturbation technique is used to derive the nonlinear dynamical equations,that is,the nonplanar Burgers equation and the nonplanar further Burgers equation.They are also numerically analyzed to investigate the basic features of shock waves and double layers(DLs).It is observed that the roles of the viscous cold electron fluids,nonextensivity of hot electrons,and other plasma parameters in this investigation have significantly modified the basic features(such as,polarity,amplitude and width) of the nonplanar DEA shock waves and DLs.It is also observed that the strength of the shock is maximal for the spherical geometry,intermediate for cylindrical geometry,while it is minimal for the planar geometry.The findings of our results obtained from this theoretical investigation may be useful in understanding the nonlinear phenomena associated with the nonplanar DEA waves in both space and laboratory plasmas.     

Small amplitude double layers in an electronegative dusty plasma with q-distributed electrons

The small amplitude dust ion-acoustic double layers in a collisionless four-component unmagnetized dusty plasma system containing nonextensive electrons, inertial negative ions, Maxwellian positive ions, and negatively charged static dust grains are investigated theoretically. Using the pseudo-potential approach and reductive perturbation method, an energy integral equation for the system has been derived and its solution in the form of double layers is obtained. The results appear that the existence regime of the double layer is very sensitive to the plasma parameters, e.g., electron nonextensivity,negative-to-positive ion number density ratio etc. It has been observed that for the selected set of parameters, the system supports rarefactive,(compressive) double layers depending upon the degree of nonextensivity of electrons.     

Simulation study of the sheath region of a processing plasma with two-temperature electrons and charged nanoparticles

A four-fluid model is used to investigate the structure of a dusty plasma sheath with two species of electrons, i.e., cold and hot electrons. Numerical results show that, in the presence of hot electrons, regular fluctuations are developed in the spatial profiles of the sheath potential and number densities of the plasma and dust nanoparticles. The amplitude and spatial period of the fluctuations depend on the hot electron parameters. The sheath width shows a non-monotonic dependence on the temperature and number density of the hot electrons, as well as the density and Mach number of the nanoparticles.     

Small amplitude ion-acoustic double layers with cold electron beam and q-nonextensive electrons

Small amplitude ion-acoustic double layers in an unmagnetized and collisionless plasma consisting of cold positive ions, q-nonextensive electrons, and a cold electron beam are investigated. Small amplitude double layer solution is obtained by expanding the Sagdeev potential truncated method. The effects of entropic index q, speed and density of cold electron beam on double layer structures are discussed.     

Large amplitude ion-acoustic double layers in a plasma havingvariable-charge dust grain particles

The dust grain charging effect on large amplitude ion-acoustic double layers in a dusty plasma are investigated by the numerical calculation. The nonlinear structures of ion-acoustic double layers are examined, showing that the characteristics of the double layer sensitively depend on the dust charging effect, the influence of the ion temperature, the electrostatic potential, and the Mach number. The flow of the plasma current to the surface of dust particles increases the dust charge numbers. The effect of the ion temperature decreases the propagation speed of the ion-acoustic double layers and decreases the dust charge numbers. It is found that rarefactive double layers can propagate in this system. New findings of large amplitude ion-acoustic double layers with the dust charging effect and finite ion temperature in a dusty plasma are predicted     

Parametric study of cylindrical and spherical dust ion acoustic shock waves with two temperature electrons in dusty plasma relevant to Saturn's E ring

We have performed numerical analysis of the one-dimensional dynamics of the cylindrical/spherical dust ion acoustic shock waves in unmagnetized dusty plasma consisting of positive ions, immobile dust particles, and nonextensive distributed cold and hot electrons. A multiple-scale expansion method is used to derive Burgers Equation (BE) and modified Burgers equation (MBE) by including higher order nonlinearity. The basic characteristics of the shock waves have been analysed numerically and graphically for different physical parameters relevant to Saturn' E ring through 2D figures. The parametric dependence of dust ion acoustic shock waves on some plasma parameters nonextensive index, density, and temperature of cold and hot electrons, concentration of dust particles, thermal effects and kinematic viscosity of ions is explored. Furthermore, it is found that the nonplanar geometry effects have an important impact on the establishment of shock waves. The amplitude of the wave decreases faster as one departs away from the axis of the cylinder or centre of the sphere. Such decaying behaviour continues as time progresses. It is also found that an increasing dust concentration decreases the amplitude of the dust ion acoustic shock waves.     

Large amplitude double layers in a four component dusty plasma with non-thermal ions

Dust acoustic double layers are studied in a four component dusty plasma. Positively and negatively charged mobile dust and Boltzmann distributed electrons are considered. The ion distribution is taken as nonthermal. The existence of compressive and rarefractive double layers is studied by pseudopotential approach. The effect of non-thermal ions on small amplitude and arbitrary amplitude double layers are also studied.     

Dust-acoustic solitary waves in an adiabatic hot dusty plasma

An adiabatic hot dusty plasma (containing non-inertial adiabatic electron and ion fluids, and negatively charged inertial adiabatic dust fluid) is considered. The basic properties of arbitrary amplitude dust-acoustic (DA) solitary waves, which exist in such an adiabatic hot dusty plasma, are explicitly examined by the pseudo-potential approach. To compare the basic properties (critical Mach number, amplitude and width) of the DA solitary waves observed in a dusty plasma containing adiabatic electron, ion and dust fluids with those observed in a dusty plasma containing isothermal electron and ion fluids and adiabatic dust fluid, it has been found that the adiabatic effect of inertia-less electron and ion fluids has significantly modified the basic properties of the DA solitary waves, and that on the basic properties of the DA solitary waves, the adiabatic effect of electron and ion fluids is much more significant than that of the dust fluid.     

Slow electron acoustic double layer (SEADL) structures in bi-ion plasma with trapped electrons

The properties of ion acoustic double layer (IADL) structures in bi-ion plasma with electron trapping are investigated by using the quasi-potential analysis. The κ-distributed trapped electrons number density expression is truncated to some finite order of the electrostatic potential. By utilizing the reductive perturbation method, a modified Schamel equation which describes the evolution of the slow electron acoustic double layer (SEADL) with the modified speed due to the presence of bi-ion species is investigated. The Sagdeev-like potential has been derived which accounts for the effect of the electron trapping and superthermality in a bi-ion plasma. It is found that the superthermality index, the trapping efficiency of electrons, and ion to electron temperature ratio are the inhibiting parameters for the amplitude of the slow electron acoustic double layers (SEADLs). However, the enhanced population of the cold ions is found to play a supportive role for the low frequency DLs in bi-ion plasmas. The illustrations have been presented with the help of the bi-ion plasma parameters in the Earth's ionosphere F-region.     

Ion Beam Driven Ion Cyclotron Double Layers

We present here a self consistent theory of small amplitude double layers associated with electrostatic ion cyclotron waves in a plasma containing hot electrons, cold ions and traversed by an ion beam. It has been shown that compressive type of double layers solution exists when θ_b (beam temperature) < α_b (beam concentration) < 1.     

Effect of nonextensivity on the characteristics of supersolitons in a two-temperature electron plasma

Ion-acoustic supersolitons are investigated in an unmagnetized two-temperature electron plasma comprising cold fluid ions, hot nonextensive electrons, and cool Maxwellian electrons by using the Sagdeev pseudopotential technique. Existence domain of positive polarity supersolitons in terms of Mach number is computed, which is found to exist for Mach numbers beyond the existence of positive double layers. The domain of existence of supersolitons diminishes with the decrease of the nonextensive parameter (q ). The amplitude and width of the supersolitons are dependent on the cool-to-hot electron temperature ratio (τ ), cool electron density (f ), and nonextensive parameter (q ). The increase of cool electron density increases the amplitude of the supersolitons. For fixed values of f , q _, and Mach numbers, the decrease of τ exhibits more distinct wiggles in the electric fields of supersolitons. The present work may be helpful for further study of supersolitons in the auroral plasma.     

Effect of cold electron emission on diffusion plasma parameters and the sheath structure in a double plasma device

It is observed experimentally that by injecting cold electrons in the discharge region of a double plasma device, the plasma parameters and sheath structure can be controlled in the other region, which is devoid of any electrical discharge. The main discharge region is separated from the region under investigation by a grounded mesh grid. Both cold and hot ionizing electrons are emitted from separate sets of filaments in the discharge region. With an increase in the cold electron emission current, the plasma parameters in the discharge region get changed, which in turn alter the plasma parameters in the other region. Two important effects caused by cold electrons in the diffusion region are the increase in the plasma density and decrease in the plasma potential. The increase in the plasma density and decrease in the sheath potential drop therefore cause the contraction of the sheath.     

Theoretical analysis of electron acoustic shock waves in magnetized superthermal plasma with electron beam

We have analysed the small-amplitude non-linear electron acoustic shock waves by taking into account the effects of electron beam in magnetized plasma. Satellite observations in different regions of the Earth's magnetosphere have shown that the electrostatic solitary waves are generally associated with electron or/and ion beams. The nonlinear Korteweg-de-Vries Burgers (KdVB) equation has been derived by considering the basic fluid equations and dissipation effects. The nonlinear coefficient of KdVB equation comes out to be negative. Only dip-shaped potential structures are reported here. For the parameters discussed in this paper, we did not find positive polarity shocks. This could be due to the restrictions on the plasma parameters since we are using the fixed densities of the cold, hot, and beam electrons as observed by the Viking satellite in the auroral region. In this paper, the importance of the cold electron to hot electron temperature in conjunction with the beam speed is pointed out. Increase in beam density, kinematic viscosity, and magnetic field results in increase in the amplitude while the increase in hot electron concentration and superthermality leads to decrease in potential. The numerical analysis is presented for the parameters corresponding to the observation of burst b event by Viking satellite in the dayside auroral zone of the earth's magnetosphere.     

Weak Ion Acoustic Double Layers in a Warm Plasma

The analytic solutions of the weak ion acoustic double layers in warm unmagnetized and magnetized plasma have been presented with the fluid equation for ions and an arbitrary equation of state for the hot electrons. It has been shown that double layers solutions exist for both magnetized and unmagnetized plasmas when two Boltzmann model for electrons are considered. The potential, the thickness and the velocity of such type of double layers have been calculated and compared with those for the cold plasma.     

Weak electron acoustic double layers in a multicomponent plasma

Formation of electron acoustic double layers in a magneto-plasma with two ion species is investigated. The existence of double layers propagating almost perpendicular to the magnetic field in a plasma with two distinct ion species and cold electron is discussed.     

Large Amplitude Dust Ion Acoustic Solitons and Double Layers in Dusty Plasmas with Ion Streaming and High-Energy Tail Electron Distribution

Large amplitude dust ion acoustic （DIA） solitons as well as double layers （DLs） are studied in a dusty plasma having a high-energy-tail electron distribution. The influence of electron deviation from the Maxwellian distribution and ion streaming on the existence domain of solitons is discussed in the （M, f） space using the pseudo-potential approach. It is found that in the presence of streaming ions and for a fixed f, solitons may appear for larger values of M. This means that in the presence of ion streaming, high values of the Mach number are needed to have soliton. The DIA solitary waves profile is highly sensitive to the ion streaming speed. Their amplitude is found to decrease with an increase of the ion streaming speed. In addition, we find that the ion streaming effect may lead to the appearance of double layers. The results of this axticle should be useful in understanding the basic nonlinear features of DIA waves propagating in space dusty plasmas, especially those including a relative motion between species, such as comet tails and solar wind streams, etc.     

Propagation properties of dust-electron-acoustic waves in weakly magnetized dusty nonthermal plasmas

The linear and nonlinear properties of dust-electron acoustic waves (DEAWs) propagating in magnetized, collisionless, dusty plasma system containing inertial cold electrons, Maxwellian hot electrons, nonthermal ions, and arbitrarily (positively or negatively) charged stationary dust are investigated. The reductive perturbation technique is employed to reduce the basic set of fluid equations to the modified Korteweg-de Vries equation or Ostrovsky's equation, which governs the dynamics of small amplitude DEAWs in a weakly magnetized dusty nonthermal plasma. The approximate analytical as well as numerical solutions reveal that the basic characteristics of DEA nonlinear structures are found to be significantly modified by the key plasma configuration parameters. It is found that the leading compressive or rarefactive solitary wave structure separates from a trailing wave packet during a considerable time under the influence of magnetic field-induced Lorentz force.     

Effect of Electron Velocity Distribution on the Heating of Core by Corona in a Spherical Pellet

When a spherical plasma pellet is irradiated symmetrically from all sides by high power laser beams, hot electrons are produced at the plasma resonance layer. They move in the inward radial direction causing a counter-streaming cold electron current flowing outwardly to maintain the charge neutrality. In general, the interaction between the hot electrons and the counter-streaming cold background electrons leads to broadening of the velocity distribution of the latter. For a given heat flux, the electron velocity distribution constrained by the requirements for not supporting beam plasma instabilities, predicts a minimum electron velocity in the plasma ablation zone. These considerations affect the efficiency of heat transfer from the hot corona to the cold core. The purpose of this paper is to study the dependence of core-corona coupling on the electron velocity distribution, laser wavelength and other plasma parameters in detail.     

Theory of weak ion acoustic double layers

We present a theory of small amplitude ion acoustic double layers in a homogeneous unmagnetized plasma. Using fluid equations for ions and a general equation of state for electrons, we show that such double layers exist when the free and reflected electron distributions are different from maxwellians.