Collisionless ballooning modes in a toroidal two-ion-component plasma

Abstract

A toroidal two-fluid model allowing for arbitrary magnetic field curvature is used to describe a contaminated plasma consisting of two ion species. A higher-order ballooning mode is identified in the high- and low-α regimes, and coexists with the ordinary ballooning mode in the medium-α regime (α=ballooning parameter). In the low-α regime the temperature-gradient-driven ηi mode is present. The impurities are, in general, found to be stabilizing—lowering the growth rate and narrowing the instability regime. Comparisons are made with ideal magnetohydrodynamics (MHD) and with a semilocal approximation of the eigenfunction, which are found to give a higher growth rate.