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Title: Parallel and lower hybrid turbulence in low {beta} plasmas driven by strong parallel currents and the resulting parallel electron and perpendicular ion energization

Abstract

In plasmas with strong field aligned currents, the most unstable mode is not always at parallel propagation, but may be at intermediate and very oblique angles. 2D particle simulations are performed in order to examine the interaction between the plasma waves at various angles and the electron and ion distributions in low {beta} collisionless plasmas with strong electron drifts. The parallel Buneman instability is known to arise in this situation, but the simulations demonstrate that the very oblique lower hybrid (LH) waves, until recently considered unimportant, may actually play a role just as significant as the waves at parallel propagation. The LH waves are energized by a current-driven linear instability, which may be seen as the oblique limit of the Buneman or ion-acoustic instability. The simulations resolve strong LH turbulence, substantial perpendicular ion tail heating and parallel electron heating. The combined action of parallel and oblique modes results in more complete electron relaxation than may be produced by the parallel Buneman instability alone.

Authors:
;  [1]
  1. School of Physics, Sydney University, NSW 2006, Sydney (Australia)
Publication Date:
OSTI Identifier:
20960081
Resource Type:
Journal Article
Resource Relation:
Journal Name: Physics of Plasmas; Journal Volume: 14; Journal Issue: 1; Other Information: DOI: 10.1063/1.2409764; (c) 2007 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; COLLISIONLESS PLASMA; CURRENTS; ELECTROMAGNETIC RADIATION; ELECTRON DRIFT; ELECTRONS; ION ACOUSTIC WAVES; IONS; LOWER HYBRID CURRENT DRIVE; LOWER HYBRID HEATING; PLASMA BEAM INJECTION; PLASMA INSTABILITY; PLASMA SIMULATION; TURBULENCE

Citation Formats

McMillan, Ben F., and Cairns, Iver H.. Parallel and lower hybrid turbulence in low {beta} plasmas driven by strong parallel currents and the resulting parallel electron and perpendicular ion energization. United States: N. p., 2007. Web. doi:10.1063/1.2409764.
McMillan, Ben F., & Cairns, Iver H.. Parallel and lower hybrid turbulence in low {beta} plasmas driven by strong parallel currents and the resulting parallel electron and perpendicular ion energization. United States. doi:10.1063/1.2409764.
McMillan, Ben F., and Cairns, Iver H.. Mon . "Parallel and lower hybrid turbulence in low {beta} plasmas driven by strong parallel currents and the resulting parallel electron and perpendicular ion energization". United States. doi:10.1063/1.2409764.
@article{osti_20960081,
title = {Parallel and lower hybrid turbulence in low {beta} plasmas driven by strong parallel currents and the resulting parallel electron and perpendicular ion energization},
author = {McMillan, Ben F. and Cairns, Iver H.},
abstractNote = {In plasmas with strong field aligned currents, the most unstable mode is not always at parallel propagation, but may be at intermediate and very oblique angles. 2D particle simulations are performed in order to examine the interaction between the plasma waves at various angles and the electron and ion distributions in low {beta} collisionless plasmas with strong electron drifts. The parallel Buneman instability is known to arise in this situation, but the simulations demonstrate that the very oblique lower hybrid (LH) waves, until recently considered unimportant, may actually play a role just as significant as the waves at parallel propagation. The LH waves are energized by a current-driven linear instability, which may be seen as the oblique limit of the Buneman or ion-acoustic instability. The simulations resolve strong LH turbulence, substantial perpendicular ion tail heating and parallel electron heating. The combined action of parallel and oblique modes results in more complete electron relaxation than may be produced by the parallel Buneman instability alone.},
doi = {10.1063/1.2409764},
journal = {Physics of Plasmas},
number = 1,
volume = 14,
place = {United States},
year = {Mon Jan 15 00:00:00 EST 2007},
month = {Mon Jan 15 00:00:00 EST 2007}
}
  • Parallel currents are usually in the form of field-aligned electron drifts in collisionless plasmas. The field-aligned drifts often drive instabilities. For instance, Drake et al. [Science, 299, 873 (2003)] found growth of parallel propagating turbulence initially and strong levels of oblique lower hybrid (LH) waves at later times; substantial parallel electron acceleration was also found. We use collisionless linear theory and quasilinear simulations to study wave growth and parallel electron dynamics in similar systems. In low-{beta} plasmas with intense parallel currents and both with or without parallel E fields, LH waves are shown to grow even for electron distributions stablemore » to the parallel Buneman instability and to accelerate electrons parallel to B very rapidly. This instability may be seen as the oblique limit of the ion acoustic and Buneman instabilities. The quasilinear diffusion via LH waves may release almost all of the available drift energy, and produce stronger electron acceleration and heating than the parallel Buneman instability alone.« less
  • This work presents an experimental study of current-driven turbulence in a plasma undergoing magnetic reconnection in a low-beta, strong-guide-field regime. Electrostatic fluctuations are observed by small, high-bandwidth, and impedance-matched Langmuir probes. The observed modes, identified by their characteristic frequency and wavelength, include lower-hybrid fluctuations and high-frequency Trivelpiece-Gould modes. The observed waves are believed to arise from electrons energized by the reconnection process via direct bump-on-tail instability (Trivelpiece-Gould) or gradients in the fast electron population (lower-hybrid).
  • In 1981, Chang and Coppi [Geophys. Res. Lett. [bold 8], 1253 (1981)] suggested that lower-hybrid turbulence could be the prime candidate for the acceleration of ions and generation of ion conics'' in the high-latitude ionosphere and magnetosphere. Subsequently, Retterer, Chang, and Jasperse [J. Geophys. Res. [bold 91], 1609 (1986)] demonstrated that nonlinear wave interactions near the lower-hybrid frequency through modulational instability, such as the collapse of waves into soliton (caviton) turbulence could play a key role in the energization of both the ambient ions and electrons. Recent sounding rocket observations in the source region of the topside auroral ionosphere seemmore » to confirm the details of such predictions [Kintner [ital et] [ital al]., Phys. Rev. Lett. [bold 68], 2448 (1992); Arnoldy [ital et] [ital al]., Geophys. Res. Lett. [bold 19], 413 (1992)]. In this paper, the scenario of this interesting micro/meso scale, nonlinear wave--wave and wave--particle interaction plasma process in the auroral ionosphere/magnetosphere is briefly reviewed.« less
  • The physical mechanism of the synergy current driven by lower hybrid wave (LHW) and electron cyclotron wave (ECW) in tokamaks is investigated using theoretical analysis and simulation methods in the present paper. Research shows that the synergy relationship between the two waves in velocity space strongly depends on the frequency ω and parallel refractive index N{sub //} of ECW. For a given spectrum of LHW, the parameter range of ECW, in which the synergy current exists, can be predicted by theoretical analysis, and these results are consistent with the simulation results. It is shown that the synergy effect is mainlymore » caused by the electrons accelerated by both ECW and LHW, and the acceleration of these electrons requires that there is overlap of the resonance regions of the two waves in velocity space.« less
  • Nonlinear equations governing the dynamics of finite amplitude drift-ion acoustic-waves are derived by taking into account sheared ion flows parallel and perpendicular to the ambient magnetic field in a quantum magnetoplasma comprised of electrons and ions. It is shown that stationary solution of the nonlinear equations can be represented in the form of a tripolar vortex for specific profiles of the equilibrium sheared flows. The tripolar vortices are, however, observed to form on very short scales in dense quantum plasmas. The relevance of the present investigation with regard to dense astrophysical environments is also pointed out.