Trapping, anomalous transport and quasi-coherent structures in magnetically confined plasmas

TL;DR

This paper investigates how particle trapping and eddying in electrostatic turbulence within magnetically confined plasmas lead to non-Gaussian statistics, quasi-coherent structures, and influence the growth of drift modes, contributing to inverse cascades and zonal flow generation.

Contribution

It reveals the role of particle trapping in producing non-standard statistics and nonlinear effects in plasma turbulence, and links trapping to inverse cascades and zonal flow formation.

Findings

Trapping causes non-Gaussian, memory, and coherence effects in particle trajectories.

Trapping influences the growth rate of drift modes based on turbulence statistics.

It provides a physical mechanism for inverse cascade and zonal flow generation in plasma turbulence.

Abstract

Strong electrostatic turbulence in magnetically confined plasmas is characterized by trapping or eddying of particle trajectories produced by the $E\times B$ stochastic drift. Trapping is shown to produce strong effects on test particles and on test modes. It determines non-standard statistics of trajectories: non-Gaussian distribution, memory effects and coherence. Trapped trajectories form quasi-coherent structure. Trajectory trapping has strong nonlinear effects on the test modes on turbulent plasmas. We determine the growth rate of drift modes as function of the statistical characteristics of the background turbulence. We show that trapping provides the physical mechanism for the inverse cascade observed in drift turbulence and for the zonal flow generation.