Stochasticity of Phase Trajectory of a Charged Particle in a Plasma Wave

Stochastic behavior of charged particles in finite amplitude plasma waves is studied by means of particle simulations under the condition that the perturbation scheme breaks down. The improved expression of resonances for the case of a large perturbation is introduced. Then the growing process of the stochastic region is examined and accordingly the width of the stochastic region is discussed. As a result, the origin of inapplicability of the perturbation scheme to this case is clarified. The validity of Chirikov's criterion is also ascertained. Discussions on the effects of higher order resonances are also presented.