Ion Acoustic Instability in the Presence of Plasma Turbulence in the Solar Wind

The adiabatic theory of interaction between high and low frequency waves has been studied for the case of electron plasma oscillations and ion acoustic waves and the results are applied to the solar wind. The modified dispersion relation for ion acoustic waves has been derived, taking a Gaussian distribution for plasmons. Two limiting cases of the spectrum are studied. For a broad spectrum, the plasma turbulence has a destabilising effect by introducing a growth rate denoted by γ turbulence, which is positive for k₀ > (m_e/m_i)^1/2 λ_De⁻¹, k₀ being the central wave numger of the spectrum, λ_De the electron Debye length. Also, even for v_d(drift velocity between electrons and ions) < c_s, we arrive at unstable ion acoustic modes. For narrow spectrum, the plasma turbulence has a stabilising effect.