Ponderomotive effects in nonadiabatic regimes and in nonneutral plasmas

Ponderomotive phenomena arising from nonlinear effects of RF electric fields in plasmas have been studied extensively for the case of neutral plasmas. The first part of this dissertation is concerned with the ponderomotive force in nonneutral plasmas. In a neutral plasma, the balance between the ponderomotive force and the plasma pressure results in density cavities with a fractional density depression given by the ratio of RF field energy to plasma thermal energy. In the second part of this dissertation a new theory of the ponderomotive effect is presented that agrees with the conventional theory when the particle motion is adiabatic, but predicts both a reduced ponderomotive force and also cyclotron resonant heating for plasma frequencies near the cyclotron frequency. Although the analytical theory involves an expansion (to order E2) about the particle's unperturbed trjectory, exact numerical orbit calculations corroborate the theoretical results, even for localized fields strong enough to reflect incident particles. Finally, the theory is compared to experimental measurements of the ponderomotive effect and found to be in good agreement over a considerable range of parameters