Heat flux effect in ηi-mode driven solitary and shock waves in electron-positron-ion plasma

The specific role of ion heat flux on the characteristics of the linear and nonlinear ion temperature gradient (ηi) driven mode in inhomogeneous electron-positron-ion plasma is presented. Inhomogeneity in density, temperature, and the magnetic field is considered. A modified linear dispersion relation is obtained, and its different limiting cases are when ηi 2/3, ωD(gradient in magnetic field) = 0 and β(density ratio of plasma species) = 1 are discussed. Furthermore, an expression for the anomalous transport coefficient of the present model is obtained. Nonlinear structure solutions in the form of solitons and shocks show that mode dynamics enhance in the presence of ion heat flux in electron-positron-ion plasma. The present study is essential in energy confinement devices such as tokamak because the heat flux observed experimentally in tokamak plasma is much higher than those described by collisions. Further, it could be helpful to understand the nonlinear electrostatic excitations in the interstellar medium.

Cylindrical and Spherical Nucleus-Acoustic Solitary and Shock Waves in Degenerate Electron-Nucleus Plasmas

The basic characteristics of cylindrical as well as spherical solitary and shock waves in degenerate electron-nucleus plasmas are theoretically investigated. The electron species is assumed to be cold, ultra-relativistically degenerate, negatively charged gas, whereas the nucleus species is considered a cold, non-degenerate, positively charged, viscous fluid. The reductive perturbation technique is utilized in order to reduce the basic equations (governing the degenerate electron-nucleus plasmas under consideration) to the modified Korteweg-de Vries and Burgers equations. The latter are numerically solved and analyzed to detect the basic characteristics of solitary and shock waves in such electron-nucleus plasmas. The nonlinear nucleus-acoustic waves are found to be propagated in the form of solitary as well as shock waves in such degenerate electron-nucleus plasmas. Their basic properties as well as their time evolution are significantly modified by the effects of cylindrical as well as spherical geometries. The results of this study is expected to be applicable not only to astrophysical compact objects, but also to ultra-cold dense plasmas produced in laboratory.

Role of entropy in η i -mode driven nonlinear structures obtained by homotopy perturbation method in electron–positron–ion plasma

We present an analysis of the effect of entropy on ion temperature gradient η i -mode driven solitary and shock waves in electron–positron–ion plasma having density and temperature inhomogeneities. Linear and nonlinear analysis having solutions in form of solitons and shocks shows that entropy influence changes the drift mode instability. Different limiting cases when (i) temperature fluctuations due to E × B only (η i ≫ 2/3), (ii) in the absence of entropy and (iii) neglecting positron effect (β = 1) are discussed. The homotophy perturbation method (HPM) is applied on the derived Korteweg–de-Vries (KdV) and KdV–Burger equations under small time approximation. It is found that both results, those obtained analytically and by the HPM technique, strongly agree with each other. These investigations may be useful to study low frequency electrostatic modes in magnetized electron–positron–ion plasma. For illustration, the model has been applied to the nonlinear electrostatic excitations in interstellar medium and tokamak plasma.

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

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.