Waves In Multi-species Plasma Research Articles

Nonlinear equation for Farley–Buneman waves in multispecies plasma

The nonlinear equation describing the Farley–Buneman (FB) waves in multispecies collisional plasmas is derived by employing the multiple-scale reduction analysis. It is shown that the presence of several ion species with different collisionalities and different ion masses removes the degeneracy of the nonlinear equation and generates the nonlinear terms resulting in wave steepening and wave breaking. This effect may be responsible for formation of one-dimensional coherent FB waves of a finite amplitude.

Dust-ion-acoustic supersolitons in dusty plasmas with nonthermal electrons

Supersolitons are a recent addition to the literature on large-amplitude solitary waves in multispecies plasmas. They are distinguished from the usual solitons by their associated electric field profiles which are inherently distinct from traditional bipolar structures. In this paper, dust-ion-acoustic modes in a dusty plasma with stationary negative dust, cold fluid protons, and nonthermal electrons are investigated through a Sagdeev pseudopotential approach to see where supersolitons fit between ranges of ordinary solitons and double layers, as supersolitons always have finite amplitudes. They therefore cannot be described by reductive perturbation treatments, which rely on a weak amplitude assumption. A systematic methodology and discussion is given to distinguish the existence domains in solitary wave speed and amplitude for the different solitons, supersolitons and double layers, in terms of compositional parameters for the plasma model under consideration.

The optimum shielding around a test charge in plasmas containing two negative ions

AbstractThis paper focuses on the progress in understanding the shielding around a test charge in the presence of ion-acoustic waves in multispecies plasmas, whose constituents are positive ions, two negative ions, and Boltzmann distributed electrons. By solving the linearized Vlasov equation with Poisson equation, the Debye–Hückel screening potential and wakefield (oscillatory) potential distribution around a test charge particle are derived. It is analytically found that both the Debye–Hückel potential and the wakefield potential are significantly modified due to the presence of two negative ions. The present results might be helpful to understand and to form new materials from plasmas containing two negative ions such as Xe+ − F− − SF−6 and Ar+ − F− − SF−6 plasmas, as well as to tackle extension of the test charge problem in multinegative ions' coagulation/agglomeration.

On nonlinear Alfvén-cyclotron waves in multi-species plasma

AbstractLarge-amplitude Alfvén waves are ubiquitous in space plasmas and a main component of magnetohydrodynamic (MHD) turbulence in the heliosphere. As pump waves, they are prone to parametric instability by which they can generate cyclotron and acoustic daughter waves. Here, we revisit a related process within the framework of the multi-fluid equations for a plasma consisting of many species. The nonlinear coupling of the Alfvén wave to acoustic waves is studied, and a set of compressive and coupled-wave equations for the transverse magnetic field and longitudinal electric field is derived for waves propagating along the mean-field direction. It turns out that slightly compressive Alfvén waves exert, through induced gyro-radius and kinetic-energy modulations, an electromotive force on the particles in association with a longitudinal electric field, which has a potential that is given by the gradient of the transverse kinetic energy of the particles gyrating about the mean field. This in turn drives electric fluctuations (sound and ion-acoustic waves) along the mean magnetic field, which can nonlinearly react back on the transverse magnetic field. Mutually coupled Alfvén-cyclotron--acoustic waves are thus excited, a nonlinear process that can drive a cascade of wave energy in the plasma, and may generate compressive microturbulence. These driven electric fluctuations might have consequences for the dissipation of an MHD turbulence and, thus, for the heating and acceleration of particles in the solar wind.

Oblique propagation of solitary electrostatic waves in multispecies plasmas

Analyses of the oblique propagation of large amplitude electrostatic waves, encountered in the literature, use as additional assumptions that the plasma response is quasi-neutral and that there is no more than one inertial fluid species, so that the result is either a second-order differential equation or a Sagdeev-type energy integral. A careful discussion shows that, as electrostatic modes require that plasma currents be weak, lest unwanted wave magnetic effects are generated, the nonlinear amplitudes, at significant obliquity, have to be small, or, for stronger nonlinearities, the obliquity must remain small. Within the frame of the multispecies model assumptions, the description always leads to a Sagdeev-type of integral, the derivation of which has been given in a general and compact notation, to avoid all possibility of algebraic oversights.

General Discussion of Nonlinear Electrostatic Modes in Multispecies Plasmas

Parallel propagation of nonlinear electrostatic waves in multispecies plasmas is described via a Sagdeev-type pseudo-potential or by Korteweg-de Vries and modified Korteweg-de Vries equations for weak nonlinearities, almost regardless of the assumptions about plasma compositions or pressure closures. We explore the reasons for that in some detail and show why this should be the case.

Structural aspects of solitons in dusty plasmas

We can model a dusty plasma as a multispecies plasma, neglecting density and momentum losses and gains for the plasma electrons and ions, provided the dust charging is slow and hence the grain charges can be treated as constant.It is well known that nonlinear waves in multispecies plasmas give rise to soliton structures. For electromagnetic waves propagating parallel to an ambient magnetic field a derivative nonlinear Schrödinger equation is obtained, while for perpendicular and oblique electrostatic and electromagnetic modes the situation is adequately described by a Korteweg–de Vries equation.The localized solutions of these equations are used to analyze the width and height of the structures for a monosized dusty plasma. In reality however, different dust sizes coexist, and this affects the modes on the linear level. The influence on the nonlinear description is examined, and possible astrophysical applications as planetary rings, cometary environments and a dusty interstellar medium are discussed.

Nonlinear theory of drift waves in multispecies plasma

The saturation level of drift waves in a multispecies plasma is estimated. The convection rate of each species across the plasma is calculated.