Role of collective effects in dominance of scattering off thermal ions over Langmuir wave decay: Analysis, simulations, and space applications

摘要: Langmuir waves driven to high levels by beam instabilities are subject nonlinear processes, including the closely related processes of scattering off thermal ions (STI) and a decay process in which ion response is organized into product acoustic wave. Calculations growth rates predict that should always dominate STI, creating two paradoxes. The first three independent computer simulation studies show STI proceeding, with no evidence for at all. second observations space type III solar radio bursts Earth’s foreshock, simulations were intended model, proceeding but STI. Resolutions these paradoxes follow from realization cannot proceed when its rate exceeds minimum frequency participating waves, since required collective be maintained respond appropriately, significant number e-foldings wave periods must contained time available. It shown application “collective” “time scale” constraints explains why does not them, as well proceeds specific simulations. This appears demonstration important understanding phenomena. Furthermore, applying observations, it predicted (and STI) sources speed regions foreshock range levels, possible role alone slightly higher levels. Deeper slower beams weaker become ineffective. Suggestions given future testing constraint an explanation usually much than