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We studied the propagation of small-amplitude dust ion acoustic (DIA) solitary waves in four-component relativistic plasma comprised of nonthermal electrons, mobile positively charged ions, positron beam and negatively charged massive dust particles. By using the reductive perturbation method, the Korteweg–de-Vries (KdV) nonlinear wave equation is derived numerically. In this work, we have elucidated the role of energetic positron beam in the relativistic plasma and analyzed the existence region for ion-acoustic (IA) solitary wave formation. It is found that for certain plasma parameters, the propagation of both compressive and rarefactive solitary waves is possible. Here, the injecting streaming positron beam in plasma gives rise to the increase in the phase velocity (Mach number) and reaches up to the hypersonic regime of flow velocity. It is observed that the initial increase in relativistic factor of positron beam , as well as temperature ratio of the positron beam to electrons decrease the characteristic features (the amplitude) of the compressive solitary wave potential profiles. On the other hand, on increasing dust grain charge , positron beam concentration ratio as well as nonthermal electrons concentration result in enhancement of the amplitudes of IA solitary wave potential profiles. The findings of this work can be more helpful in understanding the Earth's upper atmosphere (Aurora region of the ionosphere) as well as the space plasmas. [ABSTRACT FROM AUTHOR]

The dust–ion–acoustic (DIA) solitary wave (SW) propagation in a magnetized dusty plasma consisting of mobile positive and heavy negative ions, nonthermal electrons and positrons is presented. By using reductive perturbation technique, three dimensional Zakharov–Kuznetsov (Z–K) equation is derived and the solution is obtained by using the tan-hyperbolic method. Here, the dust grain charging process by plasma constituents is represented by the equation following orbital motion limited (OML) theory. The characteristics features of solitary wave amplitudes arising due to different plasma parameters such as ions mass ratio, nonthermal parameters of electrons and positrons, temperature ratio of electrons and positrons, ions density ratio, and dust density ratio are analyzed. In this analysis, the influence of nonthermal electrons on solitary wave amplitude variation is observed as more significant than that of nonthermal positrons. The findings of this work can be helpful in understanding D, E, and F regions of the Earth's ionosphere, its mesosphere region, solar photosphere, and Titan's ionosphere. [ABSTRACT FROM AUTHOR]

The sheath formation in a weakly magnetized collisionless electronegative plasma consisting of electrons and negative and positive ions has been numerically investigated using the hydrodynamic equations. The electrons and negative ions are assumed to follow the Boltzmann relation. A sheath formation criterion has been analytically derived. This paper focuses on studying the sheath structure by varying the electronegativity. It has been observed that the presence of negative ions has a substantial effect on the sheath structure. The observations made in the present work have profound significance on processing plasmas, specifically in the semiconductor industry as well as in fusion studies. [ABSTRACT FROM AUTHOR]