Non-perturbative models of intermittency in edge turbulence

TL;DR

This paper develops a non-perturbative theoretical model for the probability distribution function tails of blob density in plasma edge turbulence, confirming non-Gaussian features and analyzing the effects of spatial scales and blob speed.

Contribution

It introduces a simplified, non-perturbative model for PDF tails in plasma edge turbulence, aligning with experimental observations and exploring scale and velocity effects.

Findings

PDF tails are strongly non-Gaussian.

Increasing cross-sectional scale length increases transport.

Increasing blob speed decreases the PDF.

Abstract

A theory of the probability distribution function (PDF) tails of the blob density in plasma edge turbulence is provided. A simplified model of the fast convective radial transport is used. The theoretically predicted PDF tails corroborate earlier measurements of edge transport, further confirming the strongly non-Gaussian feature of edge transport. It is found that increasing the cross sectional spatial scale length ($L_x$ and $L_y$) of the blob results in larger transport whereas increasing the toroidal scale length ($L_z$) decreases the PDF. The results imply that the PDF decreases for larger blob speed $v_b$.