Anomalous diffusion and exit time distribution of particle tracers in plasma turbulence model

Abstract

To explore the character of transport in a plasma turbulencemodel with avalanchetransport, the motion of tracer particles has been followed. Both the time evolution of the moments of the distribution function of the tracer particle radial positions, 〈|r(t)−r(0)| n 〉, and their finite scale Lyapunov number are used to determine the anomalous diffusion exponent, ν. The numerical results show that the transport mechanism is superdiffusive with an exponent ν close to 0.88±0.07. The distribution of the exit times of particles trapped into stochastic jets is also determined. These particles have the lowest separation rate at the low resonant surfaces.