The life-cycle of drift-wave turbulence driven by small scale instability

TL;DR

This paper presents a theoretical and numerical study of how zonal flows interact with drift-wave turbulence driven by small-scale instabilities, leading to a self-regulating saturation process in plasma systems.

Contribution

It introduces a novel model describing the feedback loop between zonal flows and drift-wave turbulence, explaining the saturation mechanism without damping large-scale modes.

Findings

Zonal flows are generated via a secondary modulational instability.

The energy injection into small scales is suppressed by zonal flows.

The system reaches a stationary state with saturated zonal flows.

Abstract

We demonstrate theoretically and numerically the zonal-flow/drift-wave feedback mechanism for the LH transition in an idealised model of plasma turbulence driven by a small scale instability. Zonal flows are generated by a secondary modulational instability of the modes which are directly driven by the primary instability. The zonal flows then suppress the small scales thereby arresting the energy injection into the system, a process which can be described using nonlocal wave turbulence theory. Finally, the arrest of the energy input results in saturation of the zonal flows at a level which can be estimated from the theory and the system reaches stationarity without damping of the large scales.