On the development and evolution of nonlinear ion acoustic wave packets

Abstract. A simple model of ion fluctuations (ion acoustic and ion cyclotron fluctuations for example) driven by an electron current which leads to intermittent fluctuations when the linear growth rate exceeds the wave packet dispersion rate is analized. The normalized fluctuation amplitude eφ₀/T can be much larger than the mass ratio (m_e/m_i) level predicted by the conventional quasilinear theory or Manheimer's theory (see references in this document), and where φ₀ represents the amplitude of the main peak of the ion fluctuations. Although the ion motion is linear, intermittency is produced by the strong nonlinear electron response, which causes the electron momentum input to the ion fluctuations to be spatially localized. We treat the 1-D case because it is especially simple from an intuitive and analytical point of view, but it is readily apparent and one can put forward the conjecture that the effect occurs in a three dimensional magnetized plasma. The 1-D analysis, as shown in this manuscript will clearly help identify the subtle difference between turbulence as conventionally understood and intermittency as it occurs in space and laboratory plasmas.

Keywords. Meteorology and atmospheric dynamics (Turbulence) – Ionosphere (Wave-particles interactions) – Space plasma physics (Waves and instabilities)