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Title: Zakharov simulations of Langmuir turbulence: Effects on the ion-acoustic waves in incoherent scattering

Abstract

This paper presents a numerical study of the effect of Langmuir turbulence on incoherent scatter spectra. The Langmuir turbulence is driven by low energy beams of electrons in the Earth's upper ionosphere above 300 km. The nonlinear coupling between Langmuir waves and ion-acoustic waves is governed by the Zakharov system of equations. The model is enhanced with stochastic forcing in order to estimate by how much over the thermal level the spectrum seen by an incoherent scatter radar will be enhanced. This also allows us to directly compare the modeled spectra to the observed spectra collected by the incoherent scattering technique, as well as to statistically investigate the signature of the modeled spectra through an exploratory data analysis. Results for different beam energies are presented, covering the regimes of weak as well as strong turbulence. The incoherent scatter spectra signature is discussed in light of these regimes. It is shown that incoherent scatter radar observations of enhanced ion-acoustic and/or Langmuir waves compared to thermal level can provide good estimates of the beam parameters and of the type of turbulent regime. The cascade regime leads to strongly asymmetric spectra with enhancements over a limited range of wave numbers. The cavitation regimemore » leads to marginally asymmetric spectra, with enhancement over a wide range of wave numbers, and features a central peak for a limited range of wave numbers. Finally, it is shown that the Langmuir turbulence should be preferentially observed for scattering wavelengths large compared to the Debye length.« less

Authors:
;  [1];  [2]
  1. Physics Department, University of Oslo, N-0316 Oslo (Norway)
  2. (France)
Publication Date:
OSTI Identifier:
20860452
Resource Type:
Journal Article
Resource Relation:
Journal Name: Physics of Plasmas; Journal Volume: 13; Journal Issue: 12; Other Information: DOI: 10.1063/1.2402145; (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; ASYMMETRY; BEAM-PLASMA SYSTEMS; COMPARATIVE EVALUATIONS; COUPLING; DATA ANALYSIS; DEBYE LENGTH; ELECTRON BEAMS; ELECTRONS; INCOHERENT SCATTERING; ION ACOUSTIC WAVES; IONOSPHERE; IONS; NONLINEAR PROBLEMS; NUMERICAL ANALYSIS; PLASMA; PLASMA SIMULATION; STOCHASTIC PROCESSES; TURBULENCE; VISIBLE RADIATION

Citation Formats

Guio, P., Forme, F., and CETP, University of Versailles, F-78140 Velizy. Zakharov simulations of Langmuir turbulence: Effects on the ion-acoustic waves in incoherent scattering. United States: N. p., 2006. Web. doi:10.1063/1.2402145.
Guio, P., Forme, F., & CETP, University of Versailles, F-78140 Velizy. Zakharov simulations of Langmuir turbulence: Effects on the ion-acoustic waves in incoherent scattering. United States. doi:10.1063/1.2402145.
Guio, P., Forme, F., and CETP, University of Versailles, F-78140 Velizy. Fri . "Zakharov simulations of Langmuir turbulence: Effects on the ion-acoustic waves in incoherent scattering". United States. doi:10.1063/1.2402145.
@article{osti_20860452,
title = {Zakharov simulations of Langmuir turbulence: Effects on the ion-acoustic waves in incoherent scattering},
author = {Guio, P. and Forme, F. and CETP, University of Versailles, F-78140 Velizy},
abstractNote = {This paper presents a numerical study of the effect of Langmuir turbulence on incoherent scatter spectra. The Langmuir turbulence is driven by low energy beams of electrons in the Earth's upper ionosphere above 300 km. The nonlinear coupling between Langmuir waves and ion-acoustic waves is governed by the Zakharov system of equations. The model is enhanced with stochastic forcing in order to estimate by how much over the thermal level the spectrum seen by an incoherent scatter radar will be enhanced. This also allows us to directly compare the modeled spectra to the observed spectra collected by the incoherent scattering technique, as well as to statistically investigate the signature of the modeled spectra through an exploratory data analysis. Results for different beam energies are presented, covering the regimes of weak as well as strong turbulence. The incoherent scatter spectra signature is discussed in light of these regimes. It is shown that incoherent scatter radar observations of enhanced ion-acoustic and/or Langmuir waves compared to thermal level can provide good estimates of the beam parameters and of the type of turbulent regime. The cascade regime leads to strongly asymmetric spectra with enhancements over a limited range of wave numbers. The cavitation regime leads to marginally asymmetric spectra, with enhancement over a wide range of wave numbers, and features a central peak for a limited range of wave numbers. Finally, it is shown that the Langmuir turbulence should be preferentially observed for scattering wavelengths large compared to the Debye length.},
doi = {10.1063/1.2402145},
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}
}