Nondiffusive suprathermal ion transport in simple magnetized toroidal plasmas

TL;DR

This study explores how suprathermal ions move in simple magnetized toroidal plasmas with electrostatic turbulence, revealing a range of behaviors from subdiffusion to superdiffusion influenced by ion energy and turbulence strength.

Contribution

It provides a detailed analysis of suprathermal ion transport mechanisms and characterizes the transition from ballistic to turbulent interaction phases in a simplified plasma system.

Findings

Ion dispersion exhibits subdiffusive to superdiffusive behavior.

The duration of the ballistic phase depends on ion energy.

Transport characteristics are influenced by turbulence amplitude.

Abstract

We investigate suprathermal ion dynamics in simple magnetized toroidal plasmas in the pres- ence of electrostatic turbulence driven by the ideal interchange instability. Turbulent fields from fluid simulations are used in the non-relativistic equation of ion motion to compute suprathermal tracer ion trajectories. Suprathermal ion dispersion starts with a brief ballistic phase, during which particles do not interact with the plasma, followed by a turbulence interaction phase. In this one simple system, we observe the entire spectrum of suprathermal ion dynamics, from subdiffusion to superdiffusion, depending on beam energy and turbulence amplitude. We estimate the duration of the ballistic phase and identify basic mechanisms during the interaction phase that determine the character of suprathermal ion dispersion upon the beam energy and turbulence fluctuation amplitude.