Evolution of Electron Distributions in Electrostatic ionCyclotron Waves With Associated Parallel ElectricField and Analysis of Resulting Instabilities

Electrostatic ion cyclotron wave (EIC)can induce anormalous resistivity and parallel electric field. In this paper, evolution of distributions of electrons is analyzed.The results show that the distribution can be divided in two groups-trapped part andrun-away part. Two-stream instability can flatten the distribution of the run-away electrons, resulting in a distribution with a long and flat tail. Such kind of distribution is instable to anormalous cyclotron resonance is certain velocity space, resulting in thermalization and pitch-angle scattering of the electrons, therefore the losses of parallel velocity of the electrons. As a result of development of such instability, a bump-on-tail distribution can be established, and a new instability develops and results in flattenning of the bump-on-tail. This instability can ramp the parallel velocity around a critical value. After that, although small part of electrons can be accelerated further, but very slowly, at same time be thermalized.Finally, the results of this paper are compared with the observation results of the wave fields and precipitating electrons, and general consistency is showed.