A theory of non-local linear drift wave transport

TL;DR

This paper develops a theoretical framework for non-local transport in turbulent tokamak plasmas using a fractional Fokker-Planck equation, revealing how small deviations from Maxwellian distributions can significantly increase transport levels.

Contribution

It introduces a novel theory of non-local drift wave transport based on fractional derivatives in the Fokker-Planck equation, providing new insights into plasma turbulence.

Findings

Small deviations from Maxwellian distribution increase growth rates.

Fractional derivatives significantly affect dispersion relations.

Enhanced transport levels are linked to non-Maxwellian features.

Abstract

Transport events in turbulent tokamak plasmas often exhibit non-local or non-diffusive action at a distance features that so far have eluded a conclusive theoretical description. In this paper a theory of non-local transport is investigated through a Fokker-Planck equation with fractional velocity derivatives. A dispersion relation for density gradient driven linear drift modes is derived including the effects of the fractional velocity derivative in the Fokker-Planck equation. It is found that a small deviation (a few percent) from the Maxwellian distribution function alters the dispersion relation such that the growth rates are substantially increased and thereby may cause enhanced levels of transport.