The equilibrium and stability of a long–thin axisymmetric magnetic mirror with a nearly axis-encircling energetic ion component is presented. A local sufficient condition valid for arbitrary azimuthal mode number (m) is derived and numerically evaluated. The results indicate that the ion beam component is highly stabilizing in regions where the beam density is increasing outwards and destabilizing where it is decreasing outwards. The results also show the existence of a persistent coupling of the beam particles to the magnetohydrodynamic interchange mode for large m. This result disagrees with previous work which showid a decoupling of orbits and mode perturbations for large m. This disagreement is attributable to the special periodic nature of the nearly axis-encircling orbits in long and thin configurations and indicates that aperiodic or stochastic orbits whose gyrocentres have a minimum spread would be more effective in providing stabilization.
RF stabilization of high-density plasma in an axisymmetric mirror I: Identification and stabilization of flute mode