No abstract

Ion-beam-plasma interaction effects on electrostatic solitary wave propagation in ultradense relativistic quantum plasmas Elkamash, I. S., Kourakis, I., & Haas, F. (2017 Publisher rights ©2017 American Physical Society. This work is made available online in accordance with the publisher's policies. Please refer to any applicable terms of use of the publisher. General rightsCopyright for the publications made accessible via the Queen's University Belfast Research Portal is retained by the author(s) and / or other copyright owners and it is a condition of accessing these publications that users recognise and abide by the legal requirements associated with these rights. Understanding the transport properties of charged particle beams is not only important from a fundamental point of view, but also due to its relevance in a variety of applications. A theoretical model is established in this article, to model the interaction of a tenuous positively charged ion beam with an ultradense quantum electron-ion plasma, by employing a rigorous relativistic quantumhydrodynamic (fluid plasma) electrostatic model proposed in [M. McKerr et al, Phys. Rev. E, 90, 033112 (2014)]. A nonlinear analysis is carried out to elucidate the propagation characteristics and the existence conditions of large amplitude electrostatic solitary waves propagating in the plasma in the presence of the beam. Anticipating stationary profile excitations, a pseudo-mechanical energy balance formalism is adopted to reduce the fluid evolution equation to an ordinary differential equation. Exact solutions are thus obtained numerically, predicting localized excitations (pulses) for all of the plasma state variables, in response to an electrostatic potential disturbance. An ambipolar electric field form is also obtained. Thorough analysis of the reality conditions for all variables is undertaken, in order to determine the range of allowed values for the solitonic pulse speed and how it varies as a function of the beam characteristics (beam velocity, density).

Adopting a multi-fluid dynamical approach, the propagation of weakly nonlinear electrostatic solitary waves in a warm multi-ion dust plasma is investigated. In particular, a plasma is composed of positively and negatively charged ions and positively or negatively charged dust in the presence of superthermal electrons immersed in an external magnetic field. In the linear regime, two modes exist, namely, the slow and fast ion-acoustic modes. Employing the reductive perturbation technique, the governing equation of the nonlinear propagation for the electrostatic solitary pulse is derived. The polarity and structural characteristics (amplitude and width) of the localized electrostatic pulse in the plasma are thus analyzed for various values of relevant plasma configurations, namely, the degree of the superthermality (κ), the magnetic field strength Ωj, and the adiabatic ion thermal pressure coefficient σj. Our investigations should be useful to better understand the characteristics of the low-frequency electrostatic solitary wave that are ubiquitous in the laboratory and space plasmas, where a warm dusty multi-ion plasma with the energetic (suprathermal) electrons exists and an external magnetic field is included.

A one-dimensional multifluid hydrodynamic model has been adopted as basis for an investigation of the role of suprathermal electrons on the wave breaking amplitude limit for electrostatic excitations propagating in an electronegative plasma. A three-component plasma is considered, consisting of two inertial cold ion populations of opposite signs, evolving against a uniform background of (non-Maxwellian) electrons. A kappa-type (non-Maxwellian) distribution function is adopted for the electrons. By employing a traveling wave approximation, the first integral for the fluid-dynamical system has been derived, in the form of a pseudo-energy balance equation, and analyzed. The effect of intrinsic plasma parameters (namely the ion density ratio, the ion mass ratio, and the superthermal index of the nonthermal electrons) on the wave breaking amplitude limit is explored, by analyzing the phase space topology of the associated pseudopotential function. Our results are relevant to particle acceleration in Space environments and to recent experiments based on plasma-based accelerator schemes, where the simultaneous presence of negative ions and nonthermal electrons may be observed.

A relativistic quantum-hydrodynamic plasma model is proposed, to model the propagation of electrostatic waves in an ultradense quantum electron-ion plasma in the presence of an ion beam. A dispersion relation is derived for harmonic waves, and the stability of electrostatic wavepackets is investigated. Three types of waves are shown to exist, representing a modified electron plasma (Langmuir-type) mode, a low-frequency ion acoustic mode, and an ion-beam driven mode, respectively. Stability analysis reveals the occurrence of an imaginary frequency part in three regions. The dependence of the instability growth rate on the ion beam parameters (concentration and speed) has been investigated.

No abstract

No abstract

The dispersion properties of electrostatic waves propagating in ultrahigh density plasma are investigated, from first principles, in a one-dimensional geometry. A self-consistent multispecies plasma fluid model is employed as starting point, incorporating electron degeneracy and relativistic effects. The inertia of all plasma components is retained, for rigor. Exact expressions are obtained for the oscillation frequency, and the phase and group velocity of electrostatic waves is computed. Two branches are obtained, namely an acoustic low-frequency dispersion branch and an upper (optic-like) branch: these may be interpreted as ion-acoustic and electron-plasma (Langmuir) waves, respectively, as in classical plasmas, yet bearing an explicit correction in account of relativistic and electron degeneracy effects. The electron-plasma frequency is shown to reduce significantly at high values of the density, due to the relativistic effect. The result is compared with approximate models, wherein either electrons are considered inertialess (low-frequency ionic scale) or ions are considered to be stationary (Langmuir-wave limit).