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Nonlinear Plasma Theory

Non-Maxwellian ion velocity distributions in the ionospheric F-region

The nonlinear behavior of the collisionless current‐driven drift instability in shearless and sheared magnetic fields is studied by means of particle simulation. Electrostatic models with guiding center electrons and full dynamic ions are used in both two‐and‐one‐half and three dimensions. The electron current (J∥), in the direction parallel to the magnetic field but perpendicular to the density gradient in the x direction, is maintained throughout the simulation. Instability thresholds, growth rates, real frequency spectra, and mode structures observed in the simulation are in good agreement with theory. Saturation of the unstable modes occurs by a flattening of the electron distribution function in x‐v∥ space. The measured potential saturation levels and final distribution functions are consistent with a quasilinear plateau theory for both shearless and sheared magnetic field configurations.

Particle simulations of current driven drift waves in shearless and sheared magnetic fields

An energetic proton beam passing through a stationary ionized medium, excites ion-acoustic turbulence. The ion-acoustic instability saturates due to the non-linear indirect wave-particle scattering. The electric field associated with the ion-acoustic waves accelerates the plasma particles. Applicability of the results to cometary tails is discussed.

Plasma acceleration by ion-acoustic turbulence

Particle Simulations and Polar Spacecraft Observations of Solitary Waves in the Magnetosphere

The purpose of the present paper is to elucidate the general topic of wave-wave interaction in plasmas by discussing some basic questions entering the analysis of nonlinear interactions of waves. We consider coherent nonlinear wave-wave interaction for nonlinearly stable as well as (explosively) unstable situations. Effects of saturation (due to nonlinear phase shifts) and dissipation (with mutually different linear damping of waves) are included. Particular attention is paid to the dynamics of the phases of the waves. For the problem of external excitation of the nonlinear effects, e.g. the stimulated Brillouin and Raman scattering processes occurring in laser-plasma interaction, the influence of deviation from perfect coherency of the pump wave (the incident laser beam) is considered, including the effects of pump depletion during the nonlinear coupling process. The results of a numerical analysis of the problem of transition between a coherent wave state of interacting waves and a random phase situation are also described. Finally, we discuss the nonlinear excitation of a nonresonant beat-wave, which interacts strongly with the plasma particles. Such a process is of considerable interest in connection with the heating of a plasma. It can also be viewed as a mechanism responsible for the stimulated scattering of waves by electrons, i.e., for the stimulated Compton scattering, and for beat-wave heating of plasmas. In fact, the problem of the Landau-damped nonresonant beat-wave may be viewed as a link between the descriptions of wave-wave and wave-particle interactions.

Nonlinear Plasma Theory

Citations

Non-Maxwellian ion velocity distributions in the ionospheric F-region

Particle simulations of current driven drift waves in shearless and sheared magnetic fields

Plasma acceleration by ion-acoustic turbulence

Particle Simulations and Polar Spacecraft Observations of Solitary Waves in the Magnetosphere

Wave-wave interaction in plasmas

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