Kinetic stabilization of interchange modes in an axisymmetric mirror by large orbit radius thermal ions

A dispersion functional analysis that includes the full kinetic effects of large Larmor radius thermal ions is applied to the problem of stability of an axisymmetric mirror to finite azimuthal mode number (m) interchange modes. Vlasov theory is used to describe the ions, which are imbedded in a background of fluid electrons. The dispersion functional is solved numerically, both for a trial function displacement, where only the growth rate is determined, and the general case, where both the displacement and the growth rate are determined. In the trial function case, it is found that finite Larmor radius (FLR) effects are recovered, with a significant reduction in the growth rate when (ρi/L)2≳γMHD/Ωi. In a general case, the growth rate is reduced, but not so strongly as in the trial function case. It is shown heuristically that FLR effects may be recovered from the analysis and that these effects increase with the phase-space decorrelation time of the thermal ion distribution.