H. G. Abdelwahed

Envelope ion-acoustic solitary waves in a plasma with positive-negative ions and nonthermal electrons

Modulation instability of ion-acoustic waves is investigated in a plasma composed of positive and negative ions as well as nonthermal electrons. For this purpose, a linear dispersion relation and a nonlinear Schrodinger equation are derived. The latter admits localized envelope solitary wave solutions of bright-(pulses) and dark-(holes, voids) type. The envelope soliton depends on the intrinsic plasma parameters. It is found that modulation instability of ion-acoustic waves is significantly affected by the presence of nonthermal electrons. The present model is used to investigate the solitary excitations in the (H+,O2−) and (H+,H−) plasmas, where they are presented in the D-region and F-region of the Earth’s ionosphere. The findings of this investigation should be useful in understanding the stable electrostatic wave packet acceleration mechanisms in positive-negative ion plasmas, and also enhance our knowledge on the occurrence of instability associated to the propagation of the envelope ion-acoustic sol...

Dust Acoustic Solitary Waves in Saturn F-ring's Region

Effect of hot and cold dust charge on the propagation of dust-acoustic waves (DAWs) in unmagnetized plasma having electrons, singly charged ions, hot and cold dust grains has been investigated. The reductive perturbation method is employed to reduce the basic set of fluid equations to the Kortewege-de Vries (KdV) equation. At the critical hot dusty plasma density Nh0, the KdV equation is not appropriate for describing the system. Hence, a set of stretched coordinates is considered to derive the modified KdV equation. It is found that the presence of hot and cold dust charge grains not only significantly modifies the basic properties of solitary structure, but also changes the polarity of the solitary profiles. In the vicinity of the critical hot dusty plasma density Nh0, neither KdV nor mKdV equation is appropriate for describing the DAWs. Therefore, a further modified KdV (fmKdV) equation is derived, which admits both soliton and double layer solutions.

Improved Speed and Shape of Ion-Acoustic Waves in a Warm Plasma

The basic set of fluid equations can be reduced to the nonlinear Kortewege-de Vries (KdV) and nonlinear Schrodinger (NLS) equations. The rational solutions for the two equations has been obtained. The exact amplitude of the nonlinear ion-acoustic solitary wave can be obtained directly without resorting to any successive approximation techniques by a direct analysis of the given field equations. The Sagdeevs potential is obtained in terms of ion acoustic velocity by simply solving an algebraic equation. The soliton and double layer solutions are obtained as a small amplitude approximation. A comparison between the exact soliton solution and that obtained from the reductive perturbation theory are also discussed.

Dust acoustic shock waves in two temperatures charged dusty grains

The reductive perturbation method has been used to derive the Korteweg–de Vries–Burger equation and modified Korteweg–de Vries–Burger for dust acoustic shock waves in a homogeneous unmagnetized plasma having electrons, singly charged ions, hot and cold dust species with Boltzmann distributions for electrons and ions in the presence of the cold (hot) dust viscosity coefficients. The behavior of the shock waves in the dusty plasma has been investigated.

On the rogue wave propagation in ion pair superthermal plasma

Effects of superthermal electron on the features of nonlinear acoustic waves in unmagnetized collisionless ion pair plasma with superthermal electrons have been examined. The system equations are reduced in the form of the nonlinear Schrodinger equation. The rogue wave characteristics dependences on the ionic density ratio (ν = n–0/n+0), ionic mass ratio (Q = m+/m−), and superthermality index (κ) are investigated. It is worth mentioning that the results present in this work could be applicable in the Earths ionosphere plasmas.

Compressive and rarefactive dressed solitons in plasma with nonthermal electrons and positrons

The study of dressed solitary ion waves in a collisionless unmagnetized plasma composed warm fluid of ion, nonthermal distributed positrons and electrons are discussed. Concerning nonlinear ion acoustic waves, a reductive perturbation method is applied to obtain the KdV equation in terms of first order potential. Our results exemplify that, if soliton amplitude enlarged, the shape of the wave sidetrack from KdV equation. In order to improve the soliton shape, the perturbed KdV equation is suggest. In particular, the effects of nonthermal positrons and ionic temperature on the electrostatic dressed rarefactive and compressive soliton structures are discussed.

Effect of Higher-Order Corrections on the Propagation of Nonlinear Dust-Acoustic Solitary Waves in Mesospheric Dusty Plasmas

The contribution of the higher-order correction to nonlinear dust-acoustic waves are studied using the reductive perturbation method in an unmagnetized collisionless mesospheric dusty plasma. A Korteweg - de Vries (KdV) equation that contains the lowest-order nonlinearity and dispersion is derived from the lowest order of perturbation, and a linear inhomogeneous (KdV-type) equation that accounts for the higher-order nonlinearity and dispersion is obtained. A stationary solution is achived via renormalization method

Higher-order corrections to broadband electrostatic shock noise in auroral zone

Nonlinear shock wave structures in collisionless unmagnetized viscous plasma comprised of fluid of cold electron and nonisothermal hot electrons obeying superthermal electron distribution and ions in stationary state are examined. For nonlinear electron acoustic shock waves, a reductive perturbation method was applied to deduce the Burger equation in terms of first order potential. When the shock wave amplitude was enlarged, the steepness and the velocity of the wave sidetrack from Burger equation. We have to resume our calculations to obtain the Burger-type equation with higher order dissipation. The collective solution for the resulting equations has been given by the renormalization method. The effects of spectral index κ, the ratio of the initial equilibrium density of cold electron to hot electrons β, and the kinematic viscosity coefficient η on the broadband electrostatic shock noise in aurora are also argued.

Effect of nonthermality of electrons on the speed and shape of ion-acoustic solitary waves in a warm plasma

Nonlinear ion-acoustic solitary waves in a warm collisionless plasma with nonthermal electrons are investigated by a direct analysis of the field equations. The Sagdeev’s potential is obtained in terms of ion acoustic speed by simply solving an algebraic equation. It is found that the amplitude and width of the ion-acoustic solitons as well as the parametric regime where the solitons can exist are sensitive to the population of energetic non-thermal electrons. The soliton and double layer solutions are obtained as a small amplitude approximation.

The Effect of Higher-Order Corrections on the Propagation of Nonlinear Dust-Acoustic Solitary Waves in a Dusty Plasma with Nonthermal Ions Distribution

Propagation of nonlinear dust-acoustic (DA) waves in a unmagnetized collisionless mesospheric dusty plasma containing positively and negatively charged dust grains and nonthermal ion distributions are investigated. For nonlinear DA waves, a reductive perturbation method is employed to obtain a Korteweg-de Vries (KdV) equation for the first-order potential. As it is well-known, KdV equations contain the lowest-order nonlinearity and dispersion, and consequently can be adopted for only small amplitudes. As the wave amplitude increases, the width and velocity of a soliton can not be described within the framework of KdV equations. So, we extend our analysis and take higher-order nonlinear and dispersion terms into account to clarify the essential effects of higher-order corrections. Moreover, in order to study the effects of higher-order nonlinearity and dispersion on the output solution, we address an appropriate technique, namely the renormalization method.