Zonostrophic instability driven by discrete particle noise

Abstract

The consequences of discrete particle noise for a system possessing a possibly unstable collective mode are discussed. It is argued that a zonostrophic instability (of homogeneous turbulence to the formation of zonal flows) occurs just below the threshold for linear instability. The scenario provides a new interpretation of the random forcing that is ubiquitously invoked in stochastic models such as the second-order cumulant expansion (CE2) or stochastic structural instability theory (SSST); neither intrinsic turbulence nor coupling to extrinsic turbulence is required. A representative calculation of the zonostrophic neutral curve is made for a simple two-field model of toroidal ion-temperature-gradient-driven modes. To the extent that the damping of zonal flows is controlled by the ion--ion collision rate, the point of zonostrophic instability is independent of that rate.

13 pages, 3 figures

References in corpus (3)

• Direct Statistical Simulation of Out-of-Equilibrium Jets
• Astrophysical Fluid Dynamics via Direct Statistical Simulation
• Zonal-flow dynamics from a phase-space perspective

Cited by in corpus (4)

• On Nonlocal Energy Transfer via Zonal Flow in the Dimits Shift
• Wave-kinetic approach to zonal-flow dynamics: recent advances
• Nonlinear saturation and oscillations of collisionless zonal flows
• Vertically Sheared Horizontal Flow-Forming Instability in Stratified Turbulence: Analytical Linear Stability Analysis of Statistical State Dynamics Equilibria