题目：Competition of kinetic and reactive instabilities driven by ion beams in space plasmas

　　报告人：Y. Voitenko, Solar-Terrestrial Center of Excellence, BIRA-IASB, Brussels, Belgium

　　摘要：High-energy ion beams accelerated by shocks set up compensating (return) currents in the solar wind (e.g. upstream of the terrestrial bow shock), around supernova remnants, and in many other astrophysical environments. Plasma instabilities developing in such compensated-current systems are important for energy release and particles acceleration. I will discuss interplay between two classes of plasma instabilities in the compensated-currents systems: kinetic and reactive. Kinetic plasma instabilities critically depend on the local gradients of particles’ velocity distributions at resonant velocities. Reactive instabilities are sensitive to global characteristics of particles, such as the thermal and bulk velocities of the plasma species. A particular emphasis will be on the kinetic Alfvén instability driven directly by the beams, and reactive Alfvén instability driven by compensated currents. The reactive Alfvén instability seems to be more robust than the kinetic one and dominate in the well over-threshold regime. This instability is related to the recently discovered Bell instability. Applications to the terrestrial foreshocks and supernova remnants will be shortly discussed.

　　报告时间：2016年8月15日（星期一）10:00-11:00

　　报告地点：紫台办公大楼317 会议室

欢迎大家积极参加！

　　                                                 紫金山天文台学术委员会