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Title: Oblique modulation of electrostatic modes and envelope excitations in pair-ion and electron-positron plasmas

Abstract

The nonlinear amplitude modulation of electrostatic waves propagating in a collisionless two-component plasma consisting of negative and positive species of equal mass and absolute charge is investigated. Pair-ion (e.g., fullerene) and electron-positron (e-p) plasmas (neglecting recombination) are covered by this description. Amplitude perturbation oblique to the direction of propagation of the wave has been considered. Two distinct linear electrostatic modes exist, namely an acoustic lower mode and Langmuir-type optic-type upper one. The behavior of each of these modes is examined from the modulational stability point of view. The stability criteria are investigated, depending on the electrostatic carrier wave number, the angle {theta} between the modulation and propagation directions, and the positron-to-electron temperature ratio {sigma}. The analysis shows that modulated electrostatic wavepackets associated to the lower (acoustic) mode are unstable, for small values of carrier wave number k (i.e., for large wavelength {lambda}) and for finite (small) values of the angle {theta} (yet stable for higher {theta}), while those related to the upper (optic-like) mode are stable for large values of the angle {theta} only, in the same limit, yet nearly for all values of {sigma}. These results are of relevance in astrophysical contexts (e.g., in pulsar environments), where e-p plasmasmore » are encountered, or in pair fullerene-ion plasmas, in laboratory.« less

Authors:
; ;  [1];  [2];  [3]
  1. Azarbaijan University of Tarbiat Moallem, Faculty of Science, Department of Physics, 51745-406, Tabriz (Iran, Islamic Republic of)
  2. (Germany) and Universiteit Gent, Sterrenkundig Observatorium, Krijgslaan 281, B-9000 Gent (Belgium)
  3. (Germany)
Publication Date:
OSTI Identifier:
20860434
Resource Type:
Journal Article
Resource Relation:
Journal Name: Physics of Plasmas; Journal Volume: 13; Journal Issue: 12; Other Information: DOI: 10.1063/1.2405328; (c) 2006 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY; AMPLITUDES; DISTURBANCES; ELECTRON TEMPERATURE; ELECTRONS; EXCITATION; FULLERENES; ION ACOUSTIC WAVES; ION TEMPERATURE; IONS; MODULATION; NONLINEAR PROBLEMS; PLASMA; PLASMA INSTABILITY; POSITRONS; PULSARS; RADIATION TRANSPORT; STABILITY; WAVE PACKETS

Citation Formats

Esfandyari-Kalejahi, A., Kourakis, I., Shukla, P. K., Ruhr-Universitaet Bochum, Fakultaet fuer Physik und Astronomie, Institut fuer Theoretische Physik IV, D-44780 Bochum, and Ruhr-Universitaet Bochum, Fakultaet fuer Physik und Astronomie, Institut fuer Theoretische Physik IV, D-44780 Bochum. Oblique modulation of electrostatic modes and envelope excitations in pair-ion and electron-positron plasmas. United States: N. p., 2006. Web. doi:10.1063/1.2405328.
Esfandyari-Kalejahi, A., Kourakis, I., Shukla, P. K., Ruhr-Universitaet Bochum, Fakultaet fuer Physik und Astronomie, Institut fuer Theoretische Physik IV, D-44780 Bochum, & Ruhr-Universitaet Bochum, Fakultaet fuer Physik und Astronomie, Institut fuer Theoretische Physik IV, D-44780 Bochum. Oblique modulation of electrostatic modes and envelope excitations in pair-ion and electron-positron plasmas. United States. doi:10.1063/1.2405328.
Esfandyari-Kalejahi, A., Kourakis, I., Shukla, P. K., Ruhr-Universitaet Bochum, Fakultaet fuer Physik und Astronomie, Institut fuer Theoretische Physik IV, D-44780 Bochum, and Ruhr-Universitaet Bochum, Fakultaet fuer Physik und Astronomie, Institut fuer Theoretische Physik IV, D-44780 Bochum. Fri . "Oblique modulation of electrostatic modes and envelope excitations in pair-ion and electron-positron plasmas". United States. doi:10.1063/1.2405328.
@article{osti_20860434,
title = {Oblique modulation of electrostatic modes and envelope excitations in pair-ion and electron-positron plasmas},
author = {Esfandyari-Kalejahi, A. and Kourakis, I. and Shukla, P. K. and Ruhr-Universitaet Bochum, Fakultaet fuer Physik und Astronomie, Institut fuer Theoretische Physik IV, D-44780 Bochum and Ruhr-Universitaet Bochum, Fakultaet fuer Physik und Astronomie, Institut fuer Theoretische Physik IV, D-44780 Bochum},
abstractNote = {The nonlinear amplitude modulation of electrostatic waves propagating in a collisionless two-component plasma consisting of negative and positive species of equal mass and absolute charge is investigated. Pair-ion (e.g., fullerene) and electron-positron (e-p) plasmas (neglecting recombination) are covered by this description. Amplitude perturbation oblique to the direction of propagation of the wave has been considered. Two distinct linear electrostatic modes exist, namely an acoustic lower mode and Langmuir-type optic-type upper one. The behavior of each of these modes is examined from the modulational stability point of view. The stability criteria are investigated, depending on the electrostatic carrier wave number, the angle {theta} between the modulation and propagation directions, and the positron-to-electron temperature ratio {sigma}. The analysis shows that modulated electrostatic wavepackets associated to the lower (acoustic) mode are unstable, for small values of carrier wave number k (i.e., for large wavelength {lambda}) and for finite (small) values of the angle {theta} (yet stable for higher {theta}), while those related to the upper (optic-like) mode are stable for large values of the angle {theta} only, in the same limit, yet nearly for all values of {sigma}. These results are of relevance in astrophysical contexts (e.g., in pulsar environments), where e-p plasmas are encountered, or in pair fullerene-ion plasmas, in laboratory.},
doi = {10.1063/1.2405328},
journal = {Physics of Plasmas},
number = 12,
volume = 13,
place = {United States},
year = {Fri Dec 15 00:00:00 EST 2006},
month = {Fri Dec 15 00:00:00 EST 2006}
}
  • A semirelativistic fluid model is employed to describe the nonlinear amplitude modulation of low-frequency (ionic scale) electrostatic waves in an unmagnetized electron-positron-ion plasma. Electrons and positrons are assumed to be degenerated and inertialess, whereas ions are warm and classical. A multiscale perturbation method is used to derive a nonlinear Schr√∂dinger equation for the envelope amplitude, based on which the occurrence of modulational instability is investigated in detail. Various types of localized ion acoustic excitations are shown to exist, in the form of either bright type envelope solitons (envelope pulses) or dark-type envelope solitons (voids, holes). The plasma configurational parameters (namely,more » the relativistic degeneracy parameter, the positron concentration, and the ionic temperature) are shown to affect the conditions for modulational instability significantly, in fact modifying the associated threshold as well as the instability growth rate. In particular, the relativistic degeneracy parameter leads to an enhancement of the modulational instability mechanism. Furthermore, the effect of different relevant plasma parameters on the characteristics (amplitude, width) of these envelope solitary structures is also presented in detail. Finally, the occurrence of extreme amplitude excitation (rogue waves) is also discussed briefly. Our results aim at elucidating the formation and dynamics of nonlinear electrostatic excitations in superdense astrophysical regimes.« less
  • A pair plasma consisting of two types of ions, possessing equal masses and opposite charges, is considered. The nonlinear propagation of modulated electrostatic wave packets is studied by employing a two-fluid plasma model. Considering propagation parallel to the external magnetic field, two distinct electrostatic modes are obtained, namely a quasiacoustic lower moddfe and a Langmuir-like, as optic-type upper one, in agreement with experimental observations and theoretical predictions. Considering small yet weakly nonlinear deviations from equilibrium, and adopting a multiple-scale technique, the basic set of model equations is reduced to a nonlinear Schroedinger equation for the slowly varying electric field perturbationmore » amplitude. The analysis reveals that the lower (acoustic) mode is stable and may propagate in the form of a dark-type envelope soliton (a void) modulating a carrier wave packet, while the upper linear mode is intrinsically unstable, and may favor the formation of bright-type envelope soliton (pulse) modulated wave packets. These results are relevant to recent observations of electrostatic waves in pair-ion (fullerene) plasmas, and also with respect to electron-positron plasma emission in pulsar magnetospheres.« less
  • The effect of oblique modulation on the amplitude dynamics of ion-acoustic wave propagating in a collisionless electron-positron-ion plasma is investigated. Using Krylov-Bogoliubov-Mitropolsky (KBM) perturbation method, a nonlinear Schroedinger (NLS) equation is derived which governs the evolution of obliquely modulated ion-acoustic envelope excitations. It is found that the presence of positron component significantly modifies the stability domains for small angles of propagation with the direction of modulation. The stationary solutions of NLS equation, i.e., bright and dark envelope solitons, become narrower as the concentration of positron component increases.
  • The linear and nonlinear propagation of ion-acoustic waves are investigated in a magnetized electron-positron-ion (e-p-i) plasma with nonthermal electrons. In the linear regime, the propagation of two possible modes and their evolution are studied via a dispersion relation. In the cases of parallel and perpendicular propagation, it is shown that these two possible modes are always stable. Then, the Korteweg-de Vries equation describing the dynamics of ion-acoustic solitary waves is derived from a weakly nonlinear analysis. The influence on the solitary wave characteristics of relevant physical parameters such as nonthermal electrons, magnetic field, obliqueness, positron concentration, and temperature ratio ismore » examined. It is observed that the increasing nonthermal electrons parameter makes the solitary structures much taller and narrower. Also, it is revealed that the magnetic field strength makes the solitary waves more spiky. The present investigation contributes to the physics of the nonlinear electrostatic ion-acoustic waves in space and laboratory e-p-i plasmas in which wave damping produces an electron tail.« less