S. A. El-Tantawy

Nonlinear ion-acoustic structures in dusty plasma with superthermal electrons and positrons

Nonlinear ion-acoustic structures are investigated in an unmagnetized, four-component plasma consisting of warm ions, superthermal electrons and positrons, as well as stationary charged dust impurities. The basic set of fluid equations is reduced to modified Korteweg-de Vries equation. The latter admits both solitary waves and double layers solutions. Numerical calculations indicate that these nonlinear structures cannot exist for all physical parameters. Therefore, the existence regions for both solitary and double layers excitations have been defined precisely. Furthermore, the effects of temperature ratios of ions-to-electrons and electrons-to-positrons, positrons and dust concentrations, as well as superthermal parameters on the profiles of the nonlinear structures are investigated. Also, the acceleration and deceleration of plasma species have been highlight. It is emphasized that the present investigation may be helpful in better understanding of nonlinear structures which propagate in astrophysical environments, such as in interstellar medium.

Ion-acoustic super rogue waves in ultracold neutral plasmas with nonthermal electrons

The ion-acoustic rogue waves in ultracold neutral plasmas consisting of ion fluid and nonthermal electrons are reported. A reductive perturbation method is used to obtain a nonlinear Schrodinger equation for describing the system and the modulation instability of the ion-acoustic wave is analyzed. The critical wave number kc, which indicates where the modulational instability sets in, has been determined. Moreover, the possible region for the ion-acoustic rogue waves to exist is defined precisely. The effects of the nonthermal parameter β and the ions effective temperature ratio σ∗ on the critical wave number kc are studied. It is found that there are two critical wave numbers in our plasma system. For low wave number, increasing β would lead to cringe kc until β approaches to its critical value βc, then further increase of β beyond βc would enhance the values of kc. For large wave numbers, the increase of β would lead to a decrease of kc. However, increasing σ∗ would lead to the reduction of kc for all v...

Fully nonlinear solitary waves in a dusty electronegative multispecies plasmas

The formation and dynamics of fully nonlinear ion-acoustic solitary waves, which accompany electronegative plasmas composed of positive ions, two-negative ions, isothermal electrons, as well as a fraction of stationary charged (positive or negative) dust impurities are investigated. By using the hydrodynamic and Poisson equations, an energy-integral equation involving a Sagdeev pseudo-potential is derived. Using the latter, we have defined precisely the existence regions of the electrostatic localized pulses. The critical total negative ions concentration αc and critical second-negative ion density ratio νc thresholds, which indicate where the solitary pulses set in, have been determined for various regimes. Numerical calculations reveal that only supersonic pulses can exist. The total negative ions concentration, the second-to-total negative ions density ratio, electrons-to-positive ions temperature ratio, dust impurities concentration, positive-to-negative mass ratio, and Mach number have been investiga...

Arbitrary amplitude ion-acoustic waves in a multicomponent plasma with superthermal species

Properties of fully nonlinear ion-acoustic waves in a multicomponent plasma consisting of warm positive ions, superthermal electrons, as well as positrons, and dust impurities have been investigated. By using the hydrodynamic model for ions and superthermal electron/positron distribution, a Sagdeev potential has been derived. Existence conditions for large amplitude solitary and shock waves are presented. In order to show that the characteristics of the solitary and shock waves are influenced by the plasma parameters, the relevant numerical analysis of the Sagdeev potential is presented. The nonlinear structures, as predicted here, may be associated with the electrostatic perturbations in interstellar medium.

Nonplanar solitons collision in ultracold neutral plasmas

Collisions between two nonplanar ion-acoustic solitons in strongly coupled ultracold neutral plasmas composed of ion fluid and non-Maxwellian (nonthermal or superthermal) electron distributions are investigated. The extended Poincare-Lighthill-Kuo method is used to obtain coupled nonplanar Kortweg-de Vries equations for describing the system. The nonplanar phase shifts after the interaction of the two solitons are calculated. It is found that the properties of the nonplanar colliding solitons and its corresponding phase shifts are different from those in the planar case. The polarity of the colliding solitons strongly depends on the type of the non-Maxwellian electron distributions. A critical nonthermality parameter βc is identified. For values of β ≤ βc solitons with double polarity exist, while this behavior cannot occur for superthermal plasmas. The phase shift for nonthermal plasmas increases below βc for a positive soliton, but it decreases for β > βc for a negative soliton. For superthermal plasmas...

The impact of positrons beam on the propagation of super freak waves in electron-positron-ion plasmas

In this work, we examine the nonlinear propagation of planar ion-acoustic freak waves in an unmagnetized plasma consisting of cold positive ions and superthermal electrons subjected to cold positrons beam. For this purpose, the reductive perturbation method is used to derive a nonlinear Schrodinger equation (NLSE) for the evolution of electrostatic potential wave. We determine the domain of the plasma parameters where the rogue waves exist. The effect of the positron beam on the modulational instability of the ion-acoustic rogue waves is discussed. It is found that the region of the modulational stability is enhanced with the increase of positron beam speed and positron population. Second as positrons beam increases the nonlinearities of the plasma system, large amplitude ion acoustic rogue waves are pointed out. The present results will be helpful in providing a good fit between the theoretical analysis and real applications in future laboratory plasma experiments.

Super rogue waves in ultracold neutral nonextensive plasmas

The generation of ion-acoustic rogue waves in ultracold neutral plasmas (UNPs) composed of ion fluids and nonextensive electron distribution is investigated. For this purpose, basic equations are reduced to a nonlinear Schrodinger equation (NLSE) using a reductive perturbation technique. The existence region for the rogue waves defined precisely in terms of the critical wavenumber threshold k c . It is found that increasing the nonextensive parameter q would lead to a decrease of k c until q approaches to its critical value q c , then further increase of q beyond q c enhances k c ; however, k c shrinks with the increase of the ions effective temperature ratio σ∗. The dependence of the first- and second-order rational solutions profile on the UNP parameters is numerically examined. It is noticed that near to the critical nonextensive parameter q c , the rogue wave amplitude becomes smaller, but it enhances whenever we stepped away from q c . However, the enhancement of the temperature ratio σ∗ and the wavenumber k reduces the envelope rogue wave amplitudes.