Merging of zonal flows in gyrofluid resistive drift-wave turbulence

TL;DR

This paper investigates the nonlinear dynamics of zonal flows in gyrofluid resistive drift-wave turbulence, focusing on flow merging, energy transfer mechanisms, and the potential for phase transition behavior.

Contribution

It introduces a comprehensive analysis of zonal flow merging using a gyrofluid model with finite Larmor radius effects, highlighting the role of Reynolds stress transfer over viscous dissipation.

Findings

Reynolds stress transfer drives zonal flow merging

Finite Larmor radius effects are crucial for accurate modeling

Evidence of hysteresis suggests a phase transition in zonal flows

Abstract

Non-linear dynamics of zonal flows is investigated in the context of the gyrofluid modified Hasegawa-Wakatani model. Merging of zonal flows and the chaotic developement of the initial zonal flow pattern is explored. Conservation equations for zonal flow momentum and energy with consistent finite Larmor radius (FLR) effects are derived and used for a quantitative analysis of zonal flow mergers in numerical simulations. The nonlinear local Reynolds stress transfer as opposed to (hyper)viscous dissipation is found to be the main cause of merging. The applicability of the concept of a phase transition in the strict thermodynamical sense is discussed in context of zonal flow transition hysteresis.