Interaction Of Ion-acoustic Waves Research Articles

Kinetic Theory of Ion Acoustic Waves Observed at Comet 67P/Churyumov–Gerasimenko

Abstract This work presents the resonance interaction of ion acoustic waves with the cometary plasma as observed at comet 67P/Churyumov–Gerasimenko. The plasma is comprised of cold, warm, and suprathermal electron populations and water ions such that the quasineutrality is satisfied. The cold electron population is found to play a dominant role in the damping of the waves, and its maximum Landau damping rate is observed when it is 2% of the total electron density in the system. It is determined that lowering the cold electron density supports the current-driven ion acoustic instability at a relatively lower drift speed of the warm and suprathermal electron species. In the absence of cold electrons, the wave phase speed does not change by populating the high-energy suprathermal electron species, therefore, the Landau damping rate of both warm and suprathermal electrons increases by increasing their respective densities. The growth rate of the current-driven ion acoustic instability decreases by elevating the concentration of suprathermal electrons in the case of drifting warm and stationary suprathermal electrons. In the case of stationary warm and drifting suprathermal electrons, the elevated density of suprathermal electron instead favors the instability.

Plasmon beam instability and plasmon Landau damping of ion acoustic waves

A new view is proposed on wave propagation in a plasma, where the resonant interaction of ion acoustic waves with quasiparticles (plasmons) is considered. The distribution of quasiparticles is used to describe broadband electron plasma turbulence. Resonant interactions occur when the phase velocity of the ion acoustic wave is nearly equal to the group velocity of the electron plasma waves (or plasmons) associated with the turbulent spectrum. It is shown that plasmon Landau damping can take place, and beam type instabilities are discussed.

Coherent nonlinear interaction of ion-acoustic waves

It is shown that free-streaming perturbations enhance the interaction of ion-acoustic waves considerably. The method used is a normal mode analysis, extended to second order in the wave amplitude. In a plasma with a high electron-ion temperature ratio a spectrum of ion-acoustic waves is unstable in the range of wavelengths of about 10 Debye lengths or more. The instability pumps energy into waves of still larger wavelength, i.e. into the direction of smaller k.