Statistical properties of Charney-Hasegawa-Mima zonal flows

TL;DR

This paper analyzes the statistical properties of intermittent plasma transport events in zonal flows using the Charney-Hasegawa-Mima model, revealing how PDFs can be matched with analytical predictions and how distributions vary with flow dynamics.

Contribution

It provides a theoretical interpretation of PDFs in zonal flows within the CHM model, linking numerical results with analytical instanton predictions and characterizing distribution types.

Findings

PDFs match analytical instanton predictions after removing autocorrelations

Statistics relax to Gaussian distributions in many cases

Exponential PDFs occur in regions with strong nonlinear interactions

Abstract

A theoretical interpretation of numerically generated probability density functions (PDFs) of intermittent plasma transport events in unforced zonal flows is provided within the Charney-Hasegawa-Mima (CHM) model. The governing equation is solved numerically with various prescribed density gradients that are designed to produce different configurations of parallel and anti-parallel streams. Long-lasting vortices form whose flow is governed by the zonal streams. It is found that the numerically generated PDFs can be matched with analytical predictions of PDFs based on the instanton method by removing the autocorrelations from the time series. In many instances the statistics generated by the CHM dynamics relaxes to Gaussian distributions for both the electrostatic and vorticity perturbations, whereas in areas with strong nonlinear interactions it is found that the PDFs are exponentially distributed.