Two-component model of strong Langmuir turbulence: Scalings, spectra, and statistics of Langmuir waves
- Department of Astrophysical, Planetary, and Atmospheric Sciences, University of Colorado at Boulder, Boulder, CO (USA)
A two-component model of strong Langmuir turbulence is developed, in which intense coherent Langmuir wave packets nucleate from and collapse amid a sea of low-level background waves. Power balance between these two components determines the overall scalings of energy density and power dissipation in the turbulence, and of the rate of formation, number density, volume fraction, and characteristic nucleation time of collapsing wave packets. Recent insights into the structure and evolution of collapsing wave packets are employed to estimate the spectra and field statistics of the turbulence. Extensive calculations using the Zakharov equations in two and three dimensions demonstrate that the predictions of the model are in excellent agreement with numerical results for scalings, spectra, and the distribution of fields in the turbulence in isotropic systems; strong support is thus found for the nucleation model. The scaling behavior proves to be insensitive to the form of the damping of the waves at large wave numbers. Wave collapse is approximately inertial between the nucleation and dissipation scales, yielding power-law energy spectra and field distributions in this range. The existence of a fixed arrest scale manifests itself in exponentially decreasing energy and dissipation spectra at high wave numbers and exponentially decreasing field distributions at high field strengths. It is suggested that such an exponential decrease may explain the field distributions seen in recent beam--plasma experiments. Generalizations to turbulence driven anisotropically by beams or governed by equations other than the Zakharov equations are outlined. It is shown that a previously unrecognized scaling observed in beam-driven systems is correctly predicted by the generalized model.
- OSTI ID:
- 6104667
- Journal Information:
- Physics of Fluids B; (USA), Vol. 2:12; ISSN 0899-8221
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
GENERAL PHYSICS
PLASMA
TURBULENCE
PLASMA WAVES
STATISTICS
ANALYTICAL SOLUTION
ENERGY BALANCE
NUMERICAL SOLUTION
PLASMA SIMULATION
SCALING LAWS
THREE-DIMENSIONAL CALCULATIONS
TWO-DIMENSIONAL CALCULATIONS
WAVE PACKETS
MATHEMATICS
SIMULATION
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