High-Frequency Flutelike Instabilities in Multicomponent Plasmas

Abstract

Plasma in a magnetic field $B$ is subject to unstable electrostatic gyroharmonic waves propagating across $B$ , if the distribution of $f_0$ of particle velocities $v_{\perp }\mathrm{(\perp \hspace{0.17em}}\mathrm{to}\hspace{0.17em}\mathrm{B})$ has a region where ${\mathrm{\partial f}}_0{\mathrm{/\partial v}}_{\perp }\text{\hspace{0.17em}>\hspace{0.17em}0}$ . Stability limits are found for $f_0$ representative of mirror‐confined plasmas having a “warm” Maxwellian species, an otherwise identical “hot” species with a region of positive ${\mathrm{\partial f}}_0{\mathrm{/\partial v}}_{\perp }$ , and a neutralizing background. The waves are stable if the ratio of mean energies of the warm to hot species exceeds 0.1, or if the ratio of densities does not fall in an unstable interval roughly characterized by ${\text{0.01\hspace{0.17em}≲\hspace{0.17em}N}}_W{\mathrm{/N}}_H\text{\hspace{0.17em}≲\hspace{0.17em}1}$ , with more precise criteria given by Eqs. (5) and (6). It is important for fusion experiments that the conditions necessary for stability are less restrictive than the sufficient condition: ${\mathrm{\partial f}}_0{\mathrm{/\partial v}}_{\perp }\text{\hspace{0.17em}<\hspace{0.17em}0}$ for all the species.