Simulation of the collapse and dissipation of Langmuir wave packets
- Department of Astrophysical, Planetary, and Atmospheric Sciences, University of Colorado at Boulder, Boulder, Colorado 80309 (USA)
The collapse of isolated Langmuir wave packets is studied numerically in two dimensions using both particle-in-cell (PIC) simulations and by integrating the Zakharov partial differential equations (PDE's). The initial state consists of a localized Langmuir wave packet in an ion background that either is uniform or has a profile representative of the density wells in which wave packets form during strong plasma turbulence. Collapse thresholds are determined numerically and compared to analytical estimates. A model in which Langmuir damping is significantly stronger than Landau damping is constructed which, when included in the PDE simulations, yields good agreement with the collapse dynamics observed in PIC simulations for wave packets with initial wave energy densities small compared to the thermal level. For more intense initial Langmuir fields, collapse is arrested in PIC simulations at lower field strengths than in PDE simulations. Neither nonlinear saturation of the density perturbation nor fluid electron nonlinearities can account for the difference between simulation methods in this regime. However, at these wave levels inhomogeneous electron heating and coherent jets of transit-time accelerated electrons in phase space are observed, resulting in further enhancement of wave damping and the consequent reduction of fields in the PIC simulations.
- OSTI ID:
- 6310977
- Journal Information:
- Physics of Fluids B; (USA), Vol. 2:11; ISSN 0899-8221
- Country of Publication:
- United States
- Language:
- English
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INHOMOGENEOUS PLASMA
TURBULENCE
ACCELERATION
ANNIHILATION
BURNOUT
CORRELATIONS
ELECTRON TEMPERATURE
ELECTRONS
ENERGY LOSSES
LANDAU DAMPING
NONLINEAR PROBLEMS
NUMERICAL SOLUTION
PARTIAL DIFFERENTIAL EQUATIONS
PHASE SPACE
PLASMA SIMULATION
PLASMA WAVES
SIMULATION
THRESHOLD ENERGY
TWO-DIMENSIONAL CALCULATIONS
WAVE PACKETS
BASIC INTERACTIONS
DAMPING
DIFFERENTIAL EQUATIONS
ELECTROMAGNETIC INTERACTIONS
ELEMENTARY PARTICLES
ENERGY
EQUATIONS
FERMIONS
INTERACTIONS
LEPTONS
LOSSES
MATHEMATICAL SPACE
PLASMA
SPACE
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