Origin of Lagrangian Intermittency in Drift-Wave Turbulence

TL;DR

This paper investigates the Lagrangian velocity statistics in drift-wave turbulence, revealing exponential acceleration tails at high adiabaticity and algebraic tails at low adiabaticity, linked to vortex dynamics.

Contribution

It demonstrates the robustness of exponential acceleration tails in drift-wave turbulence and connects tail shapes to adiabaticity and vortex-like behaviors.

Findings

Exponential tails dominate at high adiabaticity, independent of Reynolds number.

Algebraic tails appear at low adiabaticity, indicating vortex influence.

A causal link exists between acceleration PDF shape and autocorrelation of acceleration norm.

Abstract

The Lagrangian velocity statistics of dissipative drift-wave turbulence are investigated. For large values of the adiabaticity (or small collisionality), the probability density function of the Lagrangian acceleration shows exponential tails, as opposed to the stretched exponential or algebraic tails, generally observed for the highly intermittent acceleration of Navier-Stokes turbulence. This exponential distribution is shown to be a robust feature independent of the Reynolds number. For small adiabaticity, algebraic tails are observed, suggesting the strong influence of point-vortex-like dynamics on the acceleration. A causal connection is found between the shape of the probability density function and the autocorrelation of the norm of the acceleration.