Particle-In-Cell simulation of electrostatic waves in the ionosphere

In the upper atmosphere (ionosphere), plasma with two electron populations is very common. The cold electrons (T-e similar to 1 eV) usually originate in the ionosphere, while the hot electrons (T-e similar to 100 eV) come from the magnetosphere. In addition to these two electron populations, there may be a beam of electrons streaming along the magnetic field lines. These electrons are responsible for exciting various electrostatic wave modes. In this article, we provide a systematic insight in the evolution of the system, based on the beam energy. With an increase in beam velocity, the beam temporarily recovers a portion of its initial energy as well as a higher saturation energy. The wave energy is lost significantly before saturation and after linear growth at a relatively modest beam velocity. In addition, the low beam velocity generates BGK electron holes in the phase space, which are missing at higher beam velocities. We also present the analysis of the condition of sustained electron holes in the phasespace.