Coherent electric structures: Vlasov-Ampere simulations and observational consequences

Coherent electrostatic structures, like bipolar electric pulses (also called electrostatic solitary waves) or Langmuir waves, are frequently observed in many astrophysical plasma of the Earth environment (plasma sheet boundary layer, Earth bow shock, auroral regions etc.) or in the solar wind. They are thought to play a crucial role in the energy transfer from small to large scale and to reconnection processes. Numerous simulations have studied their emergence and evolution. Most of them are based on the development of two stream instabilities. Another mechanism is investigated here: the plasma is excited by a localized, time dependent modulation of the electron distribution function (heating of the electrons). The investigation is performed through a 1D Vlasov-Ampere code, in open boundary conditions. We explore the response of the plasma to several heating conditions, mass ratio and density gradient. We find that the heating leads to the development of an extended turbulent domain. We also show that the history of the electrostatic solitary waves (ESW) strongly depends on the presence of a density gradient and the mass ratio between species. If the positive charged neutralizing background is composed of heavy ions, the ESW turns back to the entrance domain when a density gradient is included. From the observational point of view, this means that the electric field shows a polarity reversal with time.