Self-consistent formation of electron kappa distribution: 2. Further numerical investigation

Abstract

In the preceding article (Yoon et al., 2006) the basic physics behind the generation of suprathermal electrons (the kappa distribution) by means of self-consistent processes is elucidated. In this followup paper, further numerical investigation of the electron kappa formation is carried out. In particular, the underlying input physical parameters which include the plasma parameter g = 1/(n) over cap lambda(3)(D), the electron beam-to-background density ratio, (n) over cap (b)/(n) over cap, the electron-to-ion temperature ratio, T-e/T-i, and the ratio of average beam speed to electron thermal speed, V-0/v(Te), are systematically varied. It is shown that the electron suprathermal tail formation takes place over a wide range of physical parameters. It is also found that the formation of suprathermal tail appears to exhibit critical behavior in that there is a threshold beam energy below which no suprathermal population is formed, but when the energy threshold is crossed, the tail generation is greatly facilitated.