New ion wave path in the energy cascade

We present the results of kinetic numerical simulations that demonstrate the existence of a novel branchof electrostatic nonlinear waves driven by particle trapping processes. These waves have an acoustic-typedispersion with phase speed comparable to the ion thermal speed and would thus be heavily Landaudamped in the linear regime. At variance with the ion-acoustic waves, this novel electrostatic branch canexist at a small but finite amplitude even for low values of the electron to ion temperature ratio. Our resultsprovide a new interpretation of observations in space plasmas, where a significant level of electrostaticactivity is observed in the high frequency region of the solar-wind turbulent spectra.