# 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:

- 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}

}