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Title: Langmuir wave turbulence transition in a model of stimulated Raman scatter

Abstract

In a one-dimensional stationary slab model, it is found that once the stimulated Raman scatter (SRS) homogeneous growth rate, {gamma}{sub 0}, exceeds a threshold value, {gamma}{sub T}, there exists a local, finite amplitude instability, which leads to Langmuir wave turbulence (LWT). Given energetic enough initial conditions, this allows forward SRS, a linearly convective instability, to be nonlinearly self-sustaining for {gamma}{sub 0}>{gamma}{sub T}. Levels of forward scatter, much larger than predicted by the linear amplification of thermal fluctuations, are then accessible. The Stochastic quasilinear Markovian (SQM) model of SRS interacting with LWT predicts a jump in the value of <{epsilon}>, the mean energy injection rate from the laser to the plasma, across this threshold, while one-dimensional plasma slab simulations reveal large fluctuations in {epsilon}, and a smooth variation of <{epsilon}> with {gamma}{sub 0}. Away from {gamma}{sub T}, <{epsilon}> is well predicted by the SQM. If a background density ramp is imposed, LWT may lead to loss of SRS gradient stabilization for {gamma}{sub 0}<<{gamma}{sub T}.(c) 2000 American Institute of Physics.

Authors:
 [1]
  1. Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States)
Publication Date:
OSTI Identifier:
20216547
Resource Type:
Journal Article
Journal Name:
Physics of Plasmas
Additional Journal Information:
Journal Volume: 7; Journal Issue: 6; Other Information: PBD: Jun 2000; Journal ID: ISSN 1070-664X
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY; RAMAN EFFECT; TURBULENCE; LANGMUIR FREQUENCY; PLASMA WAVES; PLASMA INSTABILITY; MARKOV PROCESS; STOCHASTIC PROCESSES; CONVECTION; THEORETICAL DATA

Citation Formats

Rose, Harvey A. Langmuir wave turbulence transition in a model of stimulated Raman scatter. United States: N. p., 2000. Web. doi:10.1063/1.874098.
Rose, Harvey A. Langmuir wave turbulence transition in a model of stimulated Raman scatter. United States. doi:10.1063/1.874098.
Rose, Harvey A. Thu . "Langmuir wave turbulence transition in a model of stimulated Raman scatter". United States. doi:10.1063/1.874098.
@article{osti_20216547,
title = {Langmuir wave turbulence transition in a model of stimulated Raman scatter},
author = {Rose, Harvey A.},
abstractNote = {In a one-dimensional stationary slab model, it is found that once the stimulated Raman scatter (SRS) homogeneous growth rate, {gamma}{sub 0}, exceeds a threshold value, {gamma}{sub T}, there exists a local, finite amplitude instability, which leads to Langmuir wave turbulence (LWT). Given energetic enough initial conditions, this allows forward SRS, a linearly convective instability, to be nonlinearly self-sustaining for {gamma}{sub 0}>{gamma}{sub T}. Levels of forward scatter, much larger than predicted by the linear amplification of thermal fluctuations, are then accessible. The Stochastic quasilinear Markovian (SQM) model of SRS interacting with LWT predicts a jump in the value of <{epsilon}>, the mean energy injection rate from the laser to the plasma, across this threshold, while one-dimensional plasma slab simulations reveal large fluctuations in {epsilon}, and a smooth variation of <{epsilon}> with {gamma}{sub 0}. Away from {gamma}{sub T}, <{epsilon}> is well predicted by the SQM. If a background density ramp is imposed, LWT may lead to loss of SRS gradient stabilization for {gamma}{sub 0}<<{gamma}{sub T}.(c) 2000 American Institute of Physics.},
doi = {10.1063/1.874098},
journal = {Physics of Plasmas},
issn = {1070-664X},
number = 6,
volume = 7,
place = {United States},
year = {2000},
month = {6}
}