“…Up to now, two physical mechanisms that can affect the interchange stability have been reported: ͑1͒ the rf-generated equilibrium ponderomotive force 1-6 and ͑2͒ the process of nonlinear sideband wave coupling. 7,8 Hereafter, we use the abbreviations ''EPM,'' ''SBC,'' and ''SBW'' in order to denote the ''equilibrium pondermotive force,'' ''sideband wave coupling,'' and ''sideband wave,'' respectively, throughout the paper.…”