Curvature-driven trapped-particle modes in tandem mirrors

The variational structure of the plasma linear response function is used to demonstrate the relation of magnetohydrodynamic (MHD) and trapped-particle instabilities. Although in most systems, where bending energy stabilizes ballooning modes, trapped-particle instabilities have a low growth rate, in tandem mirrors with thermal barriers the trapped-particle instability growth rate can approach that of MHD instabilities. In addition, the kinetic theory yields stabilizing effects due to the difference in electron and ion orbits and destabilizing effects due to the variation of the E-vector x B-vector drift along a field line. (author)