Chaos and Nonlinear Dynamics Due Wave Particle Interaction

We studies chaos and nonlinear dynamics of single-particle orbit in the presence of an electrostatic wave excited in the magnetosphere. Using surface of section technique we traced the motion of a bouncing test particle under paraxial approximation. For low wave amplitudes, particle trajectories are regular and bounded. As we increase the amplitude the trajectories show chaotic behavior. These calculations are performed for a wide range of initial energies, typical of those in radiation belt. We also studies role of nonlinearity at Landau resonance. Diffusion coefficients were calculated based on the unperturbed trajectories of the particle. We will extend these calculations to study particle diffusion in the presence of chaos.