Chaos-induced transport due to electrostatic-fluctuations in a toroidal plasma
Plasma transport produced by electrostatic fluctuations is studied using a test particle model in a toroidal geometry. A model wave spectrum is assumed which introduces a time dependence in the Hamiltonian description of particle motion in the strong magnetic field. This allows for the existence of chaotic particle motion which gives rise to transport processes. Another way of producing transport is by introducing a stochastic process inside the wave spectrum. The two possibilities are explored and it is shown that both cases give rise to diffusive transport. The presence of chaotic motion is corroborated by computing approximate Lyapunov exponents. Additionally the presence of zonal flow is considered which can give rise to a transport barrier by suppressing radial particle fluxes, in the cases that show chaotic transport. This effect gives support to the existence of chaotic motion as responsible for transport since it reproduces the behavior of the robust invariant torus resilience to chaos, acting as a transport barrier, observed in Hamiltonian models of chaos.