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arXiv · 1611.08231

Zonostrophic instability driven by discrete particle noise

D. A. St-Onge·J. A. Krommes
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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.

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D. A. St-Onge, J. A. Krommes. 2016-11-24. Zonostrophic instability driven by discrete particle noise. https://doi.org/10.1063/1.4978786

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