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The present investigation deals with the study of higher-order nonlinearity and dispersion to electron-acoustic waves in an unmagnetized and collisionless plasma system incorporating immobile ions, cool adiabatic electrons and nonthermal-Tsallis distributed hot electrons. Employing proper stretched coordinates and Reductive Perturbation Method (RPM), dispersion relation and Korteweg de-Vries (KdV) equation have been derived to the lower-order potential. An inhomogeneous KdV-type equation emerges to the next higher order that accounts for fifth-order dispersion. This study focuses on revealing the dependency of the behaviour of dressed electron-acoustic waves on nonthermal parameter (β), hot-to-cool electron density ratio (α), hot-to-cool electron temperature ratio (θ), Mach number ( Δ M ) and nonextensive parameter (q). Only negative potential structures are reported for which the numerical results are interpreted in the form of two and three-dimensional profiles. The numerical results reflect the decrease in the amplitude of dressed solitary structures, thus obliging simulation of electron-acoustic solitary behaviour in the auroral regions and magnetosphere of Earth. [ABSTRACT FROM AUTHOR]

Distributions different from those predicted by equilibrium statistical mechanics are commonplace in a number of physical situations, such as plasmas and self-gravitating systems. The best strategy for probing these distributions and unavailing their origins consists in combining theoretical knowledge with experiments, involving both direct and indirect measurements, as those associated with dispersion relations. This paper addresses, in a quite general context, the signature of nonequilibrium distributions in dispersion relations. We consider the very general scenario of distributions corresponding to a superposition of equilibrium distributions, that are well-suited for systems exhibiting only local equilibrium, and discuss the general context of systems obeying the combination of the Schrödinger and Poisson equations, while allowing the Planck's constant to smoothly go to zero, yielding the classical kinetic regime. Examples of media where this approach is applicable are plasmas, gravitational systems, and optical molasses. We analyse in more depth the case of classical dispersion relations for a pair plasma. We also discuss a possible experimental setup, based on spectroscopic methods, to directly observe these classes of distributions. [ABSTRACT FROM AUTHOR]

Obliquely propagating electron acoustic shock waves in plasma with stationary ions, cold and superthermal hot electrons are investigated in magnetized plasma. Employing reductive perturbation method, Korteweg-de Vries-Burgers equation (KdVB) is derived in the small amplitude approximation limit. The analytical and numerical calculations of the KdVB equation show the variation of shock waves structure (amplitude, velocity, and width) with different plasma parameters. Particle density (α), superthermal parameter (κ), electron temperature ratio (휃), kinetic viscosity (η0), obliqueness (kz), and strength of magnetic field (ωc) significantly modify the properties of the shock waves structures. The present investigation is useful to understand dissipative structures observed in space or laboratory plasma where multielectrons population with superthermal electrons are prevalent. [ABSTRACT FROM AUTHOR]

Precipitation of calcium carbonate from water films generates fascinating calcite morphologies that have attracted scientific interest over past centuries. Nowadays, speleothems are no longer known only for their beauty but they are also recognized to be precious records of past climatic conditions, and research aims to unveil and understand the mechanisms responsible for their morphological evolution. In this paper, we focus on crenulations, a widely observed ripple-like instability of the the calcite-water interface that develops orthogonally to the film flow. We expand a previous work providing new insights about the chemical and physical mechanisms that drive the formation of crenulations. In particular, we demonstrate the marginal role played by carbon dioxide transport in generating crenulation patterns, which are indeed induced by the hydrodynamic response of the free surface of the water film. Furthermore, we investigate the role of different environmental parameters, such as temperature, concentration of dissolved ions and wall slope. We also assess the convective/absolute nature of the crenulation instability. Finally, the possibility of using crenulation wavelength as a proxy of past flows is briefly discussed from a theoretical point of view. [ABSTRACT FROM AUTHOR]

Shielding potential of a test charge is investigated in the presence of electron-acoustic waves in two species magnetoplasma, whose constituents are immobile ions and two-electron species with different temperatures. The obtained potential profile deviates from the standard potential due to the presence of magnetic field and hot electrons. The numerical analysis is done using the observational data of the Auroral region. [ABSTRACT FROM AUTHOR]

The linear and nonlinear properties of high-frequency electron-acoustic (EA) solitons are investigated in multi-component dissipative plasma with a cold beam electron fluid, the Schamel-kappa distributed hot trapped electrons, and stationary ions. The linear phase speed is found to be modified significantly due to variations in dissipative, superthermality, and beam speed parameters. The impact of dissipation (cold electron-to-neutrals collisions) and superthermality on the characteristics of electron acoustics waves (EAWs) is elaborated. The multiple scale expansion method is employed to derive time-varying Schamel equation for small-amplitude electrostatic potential disturbances, carrying dissipative processes as well. The variations in superthermality, and beam speed parameters have been found to strongly impact the profiles of dissipative solitons obtained through numerical time evolution of Schamel equation. The significance of the work lies in the fact that positive potential electron acoustic solitons are sustained, which correspond to holes (or humps) in the cold (hot) electron number density. As trapping is a nonlinear phenomenon, so its impact on these solitary dissipative structures have also been highlighted with suitable application parameters. This study should be beneficial for understanding nonlinear structures reported in the dayside auroral zone and other regions of the magnetosphere. [ABSTRACT FROM AUTHOR]

In a quasineutral plasma, electrons undergo collective oscillations, known as plasma oscillations, when perturbed locally. The oscillations propagate due to finite temperature effects. However, the wave can lose the phase coherence between constituting oscillators in an inhomogeneous plasma (phase mixing) because of the dependence of plasma oscillation frequency on plasma density. The longitudinal electric field associated with the wave may be used to accelerate electrons to high energies by exciting large amplitude wave. However when the maximum amplitude of the wave is reached that plasma can sustain, the wave breaks. The phenomena of wave breaking and phase mixing have applications in plasma heating and particle acceleration. For detailed experimental investigation of these phenomena a new device, inverse mirror plasma experimental device (IMPED), has been designed and fabricated. The detailed considerations taken before designing the device, so that different aspects of these phenomena can be studied in a controlled manner, are described. Specifications of different components of the IMPED machine and their flexibility aspects in upgrading, if necessary, are discussed. Initial results meeting the prerequisite condition of the plasma for such study, such as a quiescent, collisionless and uniform plasma, are presented. The machine produces δnnoise/n ⩽ 1%, Luniform ~ 120 cm at argon filling pressure of ~10−4 mbar and axial magnetic field of B = 1090 G. [ABSTRACT FROM PUBLISHER]