Effect Of Superthermal Electrons Research Articles

Nonlinear ion acoustic rogue waves in a superthermal electron–positron–ion plasma

In this paper, the nonlinear ion acoustic rogue waves (IARWs) are investigated in an unmagnetized, collisionless plasma which consist of positive ions, superthermal electrons and positrons, respectively. A nonlinear Schrodinger equation (NLSE) of IAW packets has been obtained by using the reductive perturbation technique. Furthermore, the effects of superthermal electrons and positrons on the nonlinear dispersion relation, the group velocity and the modulational instability of nonlinear ion acoustic wave (IAW) packets have been studied in detail. At the same time, the characteristics of first- and second-order IARW also have been discussed. It seems that there is some significant influence of superthermal electrons and positrons on the nonlinear ion acoustic waves. Meanwhile, it is also found that the first- and second-order IARW consisting of Peregrine breathers can be excited by using the modulational instability in this system.

Dust-Ion-Acoustic Solitary and Shock Structures in Multi-Ion Plasmas with Super-Thermal Electrons

Abstract The propagation of dust-ion-acoustic (DIA) solitary and shock waves in multi-ion (MI) unmagnetised and magnetised plasmas have been studied theoretically. The plasma system contains positively and negatively charged inertial ions, opposite polarity dusts, and high energetic super-thermal electrons. The fluid equations in the system are reduced to a Korteweg-de Vries (K-dV) and Korteweg-de Vries Burger (K-dVB) equations in the limit of small amplitude perturbation. The effect of super-thermal electrons, the opposite polarity of ions, and dusts in the solitary and shock waves are presented graphically and numerically. Present investigations will help to astrophysical and laboratory plasmas.

Ion-Acoustic Vortices in Two-Electron-Temperature Magnetoplasma with Cairn’s Distributed Electrons and in the Presence of Ion Shear Flow

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.

Effect of superthermal electrons on the characteristics of dust acoustic solitary waves in a magnetized hot dusty plasma with dust charge fluctuation

A nonlinear dust acoustic solitary wave (DASW) in a magnetized dusty plasma with superthermal electrons is studied analytically. In this model hot electrons are described by the kappa distribution function, but ions are taken to be Maxwellian and plasma pressure and dust-natural collisions have been taken into account. Using the reductive perturbation method the Zakharov–Kuznetsov equation is derived and effect of electrons’ hotness on the amplitude and width of soliton in dusty plasma is investigated. With decreasing energy of the hot electrons in the system, κ > 100, results coincide with the results of the dusty plasma system containing Maxwellian electrons. In this model anisotropy is caused by an external magnetic field while inhomogeneity is generated by ion density gradient in the plasma. The initial density decreases exponentially in the space along one direction. The amplitude of DASW is mainly affected by density inhomogenity rather than the electrons’ energy. With increasing energy of the system, the width of DASW increases significantly. Applying the effect of pressure in the model only rarefactive DASW may be generated in the dusty plasma.

Effects of superthermal electrons and negatively (positively) charged dust grains on dust-ion acoustic wave modulation

The modulational instability of dust-ion acoustic (DIA) waves is studied in an unmagnetized dusty plasma comprising arbitrarily charged dust particles, adiabatic fluid ions, and electrons satisfying a kappa (κ) distribution. By using the multiple space and time scales perturbation, a nonlinear Schrodinger (NLS) equation is derived, and then the existence along with the stability of wave packets are discussed in the parameter space of two oppositely charged dust and ion temperature over a range of values of electron superthermality. It is found that the transition from stable dark solitons to unstable bright ones shifts to the smaller wavelength regions in a way that depends on the increase of superthermality index κ. In this case, a narrower range (in spatial extension) of the envelope solitons is observed. It is also found that the instability growth rate reduces, due to the electron superthemality. Furthermore, positive dust concentration enhances the instability region, whereas more populations of negative dust grains may control or suppress one.

Effect of superthermal electrons on dust-acoustic Gardner solitons in nonplanar geometry

The properties of nonplanar (cylindrical and spherical) dust-acoustic solitary waves (DASWs) in an unmagnetized, collisionless three-component dusty plasma, whose constituents are negatively charged cold dust fluid, superthermal/non-Maxwellian electrons (represented by kappa distribution) and Boltzmann distributed ions, are investigated by deriving the modified Gardner (MG) equation. The well-known reductive perturbation method is employed to derive the MG equation. The basic features of nonplanar DA Gardner solitons (GSs) are discussed. It is seen that the properties of nonplanar DAGSs (positive and negative) significantly differ as the value of spectral index κ changes.

Effect of superthermal electrons on dust-acoustic shock waves in coupled dusty plasmas

AbstractNonlinear dust-acoustic (DA) shock waves in coupled dusty plasmas with negative dust grains and kappa-distributed electrons are discussed. Using a generalized hydrodynamic model, the dispersion relation and the Korteweg–de Vries-Burger (KdVB) equation for low-frequency DA modes in a strongly coupled dusty plasma are derived. The dependence of shock waves on various plasma parameters is then explored. A solitonic profile may be converted into a shock structure when correlation among dust particles becomes stronger. The amplitude as well as the steepness of shock waves increases with increasing the value of the spectral index k.

Obliquely propagating electron acoustic solitons in a magnetized plasma with superthermal electrons

The problem of small amplitude electron acoustic solitary waves is discussed using the reductive perturbation theory in magnetized plasmas consisting of cold electrons, hot electrons obeying superthermal distribution and stationary ions. The effects of superthermal electrons, the population ratio of hot to cool electrons and also the magnetic field on the behavior of plasma are investigated. The results show that only rarefactive solitary waves propagated in this plasma and the presence of superthermal electrons reduces the soliton amplitude and its width.

Magneto-modulational instability in Kappa distributed plasmas with self-generated magnetic fields

The behavior of magnetic fields generated by high-frequency transverse plasmons in Kappa distributed plasmas can be described by generalized Zakharov equations, which have considered the nonlinear wave-wave, wave-particle interactions in the kinetic regime and the effects of superthermal electrons. Modulational instability of the spontaneous magnetic fields is investigated on the basis of the equations. The effect of the superthermal electrons on the modulational instability is discussed and a comparison with previous results is presented. It is shown that the characteristic scale and maximum growth rate of the magnetic fields depend on the energy density of transverse plasmons and the superthermal index κ.

Cylindrical ion-acoustic solitary waves in electronegative plasmas with superthermal electrons

By using the standard reductive perturbation technique, a three-dimensional cylindrical Kadomtsev-Petviashvili equation (CKPE), which governs the dynamics of ion acoustic solitary waves (IASWs), is derived for small but finite amplitude ion-acoustic waves in cylindrical geometry in a collisionless unmagnetized plasma with kappa distributed electrons, thermal positrons, and cold ions. The generalized expansion method is used to solve analytically the CKPE. The existence regions of localized pulses are investigated. It is found that the solution of the CKPE supports only compressive solitary waves. Furthermore, the effects of superthermal electrons, the ratio of the electron temperature to positron temperature, the ratio of the positron density to electron density and direction cosine of the wave propagation on the profiles of the amplitudes, and widths of the solitary structures are examined numerically. It is shown these parameters play a vital role in the formation of ion acoustic solitary waves.

Electron-acoustic solitary structures in two-electron-temperature plasma with superthermal electrons

The propagation of nonlinear electron- acoustic waves (EAWs) in an unmagnetized collision- less plasma system consisting of a cold electron fluid, superthermal hot electrons and stationary ions is investigated. A reductive perturbation method is employed to obtain a modified Korteweg-de Vries (mKdV) equa- tion for the first-order potential. The small amplitude electron-acoustic solitary wave, e.g., soliton and dou- ble layer (DL) solutions are presented, and the effects of superthermal electrons on the nature of the solitons are also discussed. But the results shows that the weak stationary EA DLs cannot be supported by the present model.

Strong Langmuir turbulence in Kappa distributed plasmas

Superthermal electrons are often observed in space and astrophysics and can be appropriate modeled by the family of Kappa distribution functions. Taking the nonlinear wave-wave, wave-particle interactions and the effect of superthermal electrons into account, the strong Langmuir turbulence is investigated in kinetic regime. The modified Zakharov equations are obtained for the case of no damping or driving terms. On the basis of these equations, dynamics of collapse have been studied by the means of the general virial theorem, and the collapse thresholds which are strong modified by superthermal index κe are given.

Influence of superthermal electrons on obliquely propagating ion-acoustic solitons in magnetized plasmas

The effect of superthermal electrons, modeled by a Lorentzian velocity distribution function, on the oblique propagation characteristics of linear and nonlinear ion-acoustic waves in an electron–ion plasma in the presence of a uniform external magnetic field is investigated. First, the linear dispersion relations of the fast and slow modes are obtained. It is shown that the superthermal electrons make both modes propagate with smaller phase velocities. Then, the Korteweg–de Vries equation describing the propagation of nonlinear slow and fast ion-acoustic waves is derived. It is shown that the presence of superthermal electrons has a significant influence on the nature of magnetized ion-acoustic solitons. That is, for a larger population of the superthermal electrons, the soliton velocity of both modes in the laboratory frame significantly decreases and the soliton are slimmer, and on approaching the Maxwellian limit, the width becomes maximum.

Effect of superthermal electrons on Alfvén wave propagation in the dusty plasmas of solar and stellar winds

The dispersive characteristics and absorption coefficient of Alfvén waves propagating parallel to the ambient magnetic field are discussed, taking into account the effects of both the charged dust particles present in the interplanetary medium and the superthermal character of the electron distribution function, using physical parameters relevant for solar and stellar winds. The solar wind electrons are described by an isotropic κ distribution and the protons are described by a Maxwellian. The results are valid for a frequency regime well above the dust‐plasma and dust‐cyclotron frequencies. However, the theoretical formulation is fully kinetic and the dust charge variation is taken into account. The charging process of the dust is assumed to be associated with the capture of electrons and ions by the dust particles during inelastic collisions with the plasma particles. The dispersion relation for parallel‐propagating Alfvén waves is numerically solved and the solutions are compared with particular situations where either the dust particles are absent or the electrons are described by a Maxwellian. It is shown that the presence of both the charged dust particles and the superthermal character of the electron distribution function sensibly modify the dispersion relation of low‐frequency and long‐wavelength Alfvén waves and significantly increase the absorption coefficient, strongly suggesting that both effects are equally important for a realistic description of the physical processes that occur in solar and stellar winds and that are influenced by the Alfvén waves, such as the energization of particles and the turbulent cascade of magnetic fluctuations.

Investigation of Mach probe geometry effects in weakly magnetized plasmas

Probe geometry dependence of Mach probe diagnostics in weakly magnetized plasmas has been investigated. In order to obtain sufficiently saturated ion currents, and also to experimentally obtain the angular sensitivity of differently shaped probes, the effect of superthermal electrons was measured. When using the theoretical expressions of angular distribution of the ion current as fitting functions, estimated Mach numbers largely depend on the geometry of the probe. However, by taking the ratio of upstream to downstream ion currents, the effect of magnetic field can be eliminated. Furthermore, considering the broadening of the ion collection angles, the deduced Mach numbers show good agreement regardless of the probes geometry, and do not contradict the spectroscopic results.

The Effect of Superthermal Electrons on Mach Probe Diagnostics

For the analysis of plasma flow velocity, the Mach probe is widely used. Depending on the existence of superthermal electrons particularly at energies higher than the probe biasing voltage, collected ion saturation current can be reduced. This phenomenon can cause considerable errors in flow velocity estimation. The effect of superthermal electrons has been investigated in the steady-state linear divertor plasma simulator MAP-II. The directional measurement of electron energy distribution function (EEDF) suggests the energy of superthermal electrons and their generation mechanisms. The directional dependence of superthermal electrons is clearly observed from the angular distribution of ion saturation current measured using the Mach probe and a directional Langmuir probe (DLP). The error in flow velocity estimation under the conditions of a weakly magnetized plasma (ap/ρi∼1) is calculated.