The Maintenance of Coherent Vortex Topology by Lagrangian Chaos in Drift-Rossby Wave Turbulence

This work introduces the "potential vorticity (PV) bucket brigade", a conceptual mechanism for explaining the resilience of coherent vortex structures in drift-Rossby wave turbulence, critical for understanding turbulent transport in magnetically confined fusion plasmas and geophysical flows. Drawing parallels with the PV staircase, we show how spatially inhomogeneous patterns of mixing can reinforce, rather than destroy non-zonal structures in the flow. We accomplish this through an exact stochastic Lagrangian representation of vorticity transport, together with a wave eigenmode near-integrability property which elucidates the relationship between coherent flow topology and fluid relabeling symmetries. For concreteness, we demonstrate these ideas in a transitional regime of gradient-driven drift wave turbulence modeled by the flux-balanced Hasegawa-Wakatani equations. However, the tools we develop here are model-agnostic and have potential relevance to fluid and plasma systems well beyond the model studied here.