Vlasov simulations of strong Langmuir turbulence
Abstract
Strong Langmuir turbulence describes the evolution of intense and coherent electric fields that couple to the ion background, in an unmagnetized plasma. It is of common interest in ionospheric physics and laboratory plasmas and may be of great relevance in space physics where electric fields are high (shocks, early stage of type III). Strong Langmuir turbulence has been intensively studied for more than three decades by using the Zakharov equations that couple the evolution of the enveloppe of the high frequency electric field and the plasma density. These have successfully described self-focusing and collapse of intense Langmuir fluctuations, as well as the formation of density cavitons. However, the fluid like approximation underlying the Zakharov equations breaks out when the electric field gets close to the electron thermal energy, what commonly happens at the end of the Langmuir collapse. In this case, a kinetic approach has to be considered for the study of the long time evolution of strong turbulence, including in particular the kinetic effects on heated particules and the ion fluid nonlinearities. We perform 1D and 2D Vlasov-Poisson simulations with periodic boundary conditions to investigate strong Langmuir turbulence in an unmagnetized plasma. We observe self-focusing of Langmuir waves and formation of cavitons. We also analyse the difference between 1D and 2D strong Langmuir turbulence. A special emphasis is given to electronic kinetic effects and proton dynamics to illustrate the discrepancies with the Zakharov model.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2009
- Bibcode:
- 2009AGUFMSH53A1304H
- Keywords:
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- 7815 SPACE PLASMA PHYSICS / Electrostatic structures;
- 7839 SPACE PLASMA PHYSICS / Nonlinear phenomena;
- 7863 SPACE PLASMA PHYSICS / Turbulence