Salah Kamel El-Labany

The characteristics of nonlinear and supernonlinear Alfvén waves propagating in a multicomponent plasma composed of a double spectral electron distribution and positive and negative ions were investigated. The Sagdeev technique was employed, and an energy equation was derived. Our findings show that the proposed system reveals the existence of a double-layer solution, periodic, supersoliton, and superperiodic waves. The phase portrait and potential analysis related to these waves were investigated to study the main features of existing waves. It was also found that decreasing the electron temperature helps the superperiodic structure to be excited in our plasma model. Our results help interpret the nonlinear and supernonlinear features of the recorded Alfvén waves propagating in the ionosphere D-region.

The propagation features of dust acoustic waves in a three-component plasma system composed of regularized Kappa distributed electrons, Maxwellian ions, and dust grains carrying positive charges are investigated. The reductive perturbation technique is employed to derive the KdV equation. A generalized expression for the polarization force is derived and the effect of the polarization force is taken into consideration as well. The bifurcation analysis is used, and the solitary wave solution was investigated. The critical value of the superthermal spectral index κ is introduced at which the solitonic structure turns up from rarefactive to compressive. It is found that in the range 0<κ2.23. In addition, it is found that by increasing the value of cutoff parameter α, the polarization strength increases too. All the obtained results are helpful to investigate the characteristics of the nonlinear wave propagating in the mesosphere region.

First of all, we would like to thank the commenting authors1 for their interest in our article.2

According to the observations that detected significant ionospheric escape from Venus, a test charge approach is suggested to explain the ionic loss caused by the solar wind (SW) interaction with the Venusian upper ionosphere. The proposed plasma system consists of two positive planetary ions (H ⁺ and O ⁺) with isothermal electrons and streaming SW protons, with Maxwellian electrons. The electrostatic Debye screening and wakefield potentials caused by a moving test charge as well as the modified dielectric constant of the ion-acoustic waves (IAWs) created in the model are derived. The normalized Debye potential is found to decrease exponentially with the axial distance. Whereas the amplitude of the wakefield potential is amplified with the altitudes and decreases with increasing the density of either planetary oxygen or the SW protons but it is enhanced by SW electrons number density. However, the wakefield amplitude is not affected by the SW protons velocity or their temperatures because the SW protons velocity is fast compared with the velocity of the plasma system. Thus, the properties of the ions escaping are affected by the velocity variations within a certain range called the velocity scale window. The obtained results are found to be in a good agreement with the observed data.

Motivated by the recent Magnetospheric Multiscale (MMS) observations of oblique electron acoustic waves, we addressed the generation mechanism of the observed waves by utilizing the reductive perturbation technique. A nonlinear Zakharov-Kuznetsov (ZK) equation is derived for a collisionless, magnetised plasma composed of cool inertial background electrons, cool inertial electron beam, hot inertialess suprathermal electrons; represented by a κ-distribution, and stationary ions. Moreover, the instability growth rate is derived by using the small-k perturbation expansion method. Our findings revealed that the structure of the electrostatic wave profile is significantly influenced by the external magnetic field, the unperturbed hot, cool, and electron beam densities, the obliquity angle, and the rate of superthermality. Such parameters also have an effect on the instability growth rate. This study clarifies the characteristics of the oblique electron solitary waves that may be responsible for changing the electron and ion distribution functions, which alter the magnetic reconnection process. Moreover, the increase of the growth rate with the plasma parameters could be a source of anomalous resistivity that enhances the rate of magnetic reconnection.

A three-dimensional (3D) modulational instability (MI) of dust acoustic waves (DAWs) in a three-component magnetized dusty plasma system consisting of a negatively charged fluid, inertialess generalized ( r , q ) distributed electrons and Boltzmann distributed ions, is investigated. The basic system of the nonlinear hydrodynamic equations is reduced to a 3D nonlinear Schrödinger equation (NLS) which is valid for small but finite amplitude DAWs using a reductive perturbation technique. The domain of the stability and instability regions is investigated that is strongly affected by the spectral parameters of the generalized ( r , q ) distribution and the electron-to-ion temperature ratio ( T _e / T _i ). The existence domains for observing the first-and second-order solutions of the dust acoustic rogue waves (DARWs) are determined and the basic features (viz the width and amplitude) for the first-order solution are found to be significantly dependent on the system physical parameters changes such as T _e / T _i , number density ratio [ n _{e 0} /( n _{d 0} z _{d 0} )] and the dust cyclotron frequency ( ω _cd ) as well as the spectral indexes r and q . A comparison between the first-and second-order DARW amplitudes is presented. Moreover, another comparison between the first-order DARW amplitudes obtained by generalized ( r , q ) distributed electrons and those corresponds to Maxwellian is provided. Finally, implication of our consequences in specific plasma situations are briefly discussed.

Propagation properties of weakly nonlinear ion acoustic waves are investigated in a plasma at the Venusian ionosphere. The plasma model consists of two positive cold ions (oxygen O ⁺ and hydrogen H ⁺ ), as well as isothermal electrons. The basic set of fluid equations is reduced to Zakharov-Kuznetsov (ZK) equation and linear inhomogeneous ZK-type equation (LIZKT) equation. The renormalization method is adopted to obtain solitary solutions of both equations. The effects of plasma parameters and higher-order correction on the nature of the solitary waves are investigated. It is found that the wave phase velocity is supersonic, which is in agreement with the observations. Furthermore, the higher-order correction enlarges the soliton amplitude, which is suitable for describing the solitary waves when the wave amplitude grows.

A reductive perturbation technique (multiple scales) is applied to a weakly relativistic warm unmagnetized adiabatic plasma system consisting of inertial ions fluid and nonextensively distributed electrons. A nonlinear Schrödinger-type (NST) equation for finite wave number at the second order is derived. Using the reductive perturbation technique we derived the corresponding Korteweg-de Vries (K-dV) equation. For small wavenumber limit the K-dV equation is transformed into NST equation. It is found that the coefficient of the NST equation obtained from the K-dV equation agree with the corresponding coefficients of NST equation obtained by the multiple scales. Moreover we investigated the effect of the physical parameters of the system namely temperature ratio of the ion temperature T_i to electron temperature T_e, the relativistic factor u_0/C as well as the nonextensive parameter (q) of the distribution on the stability/instability of the system. It is found that these parameters affect strongly on the stability/instability regions. Finally, the validity of our results in astrophysical plasma is briefly discussed.