Effects of electron temperature gradient on the c/ omega pe instability in tokamaks

Summary form only given. The electromagnetic instability predicted (see Hirose et al., 1990) in the tokamak magnetic geometry is characterized by the following features: (a) nonadiabatic electron response; (b) ballooning nature in the sense that the instability is operative only in toroidal geometry with magnetic curvature; and (c) large growth rates peaking at k_{perpendicular to} approximately= omega _pe/c. The instability is operative at beta well below the ballooning critical limit-that is, it should prevail in almost all tokamaks. In Hirose et al. (1990), the electron temperature gradient eta _e was not incorporated. A finite eta _e is intuitively expected to be further destabilizing because of the ballooning nature. Results of local analysis with a finite eta _e indeed indicate that the growth rate increases with eta _e, and also the unstable domains in k_{perpendicular to} and epsilon _n=L_n/R broaden. An expression giving the nonlocal mode equation for the scalar potential is presented.