Analytical treatment of particle motion in circularly polarized slab-mode wave fields

TL;DR

This paper analytically investigates particle motion in circularly polarized slab-mode wave fields, showing no chaos occurs in single wave interactions but chaos can emerge with multiple waves, supported by simulations.

Contribution

It provides an exact analytic solution for particle motion in a single circularly polarized wave and explores how multiple waves induce chaotic trajectories.

Findings

No chaos in single wave interaction

Multiple waves can induce chaos

Analytic solutions validated by simulations

Abstract

Wave-particle interaction is a key process in particle diffusion in collisionless plasmas. We look into the interaction of single plasma waves with individual particles and discuss under which circumstances this is a chaotic process, leading to diffusion. We derive the equations of motion for a particle in the fields of a magnetostatic, circularly polarized, monochromatic wave and show that no chaotic particle motion can arise under such circumstances. A novel and exact analytic solution for the equations is presented. Additional plasma waves lead to a breakdown of the analytic solution and chaotic particle trajectories become possible. We demonstrate this effect by considering a linearly polarized, monochromatic wave, which can be seen as the superposition of two circularly polarized waves. Test particle simulations are provided to illustrate and expand our analytical considerations.