Scale-free vortex cascade emerging from random forcing in a strongly coupled system

TL;DR

This study reveals a universal scale-free vortex cascade in a strongly coupled system under random forcing, linking turbulence and self-organized criticality through experimental and simulation data.

Contribution

It demonstrates the emergence of a scale-free vortex cascade in a strongly coupled system, unifying turbulence and SOC phenomena via experimental and model comparisons.

Findings

Scale-free vortex cascade observed in experiments and models.

Universal non-Gaussian PDFs of fluctuations identified.

Cascade features consistent across different systems and conditions.

Abstract

The notions of self-organised criticality (SOC) and turbulence are traditionally considered to be applicable to disjoint classes of phenomena. Nevertheless, scale-free burst statistics is a feature shared by turbulent as well as self-organised critical dynamics. It has also been suggested that another shared feature is universal non-gaussian probability density functions (PDFs) of global fluctuations. Here, we elucidate the unifying aspects through analysis of data from a laboratory dusty plasma monolayer. We compare analysis of experimental data with simulations of a two-dimensional (2D) many-body system, of 2D fluid turbulence, and a 2D SOC model, all subject to random forcing at small scales. The scale-free vortex cascade is apparent from structure functions as well as spatio-temporal avalanche analysis, the latter giving similar results for the experimental and all model systems studied. The experiment exhibits global fluctuation statistics consistent with a non-gaussian universal PDF, but the model systems yield this result only in a restricted range of forcing conditions.