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arXiv · 2505.03029

An Exact Turbulence Law For the Fluid Description of Fusion Edge Plasmas

Luisa Scarivaglione·Sergio Servidio
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Abstract

Understanding turbulence via simplified fluid models is crucial for optimizing magnetic confinement in tokamak devices. In this work, we propose a novel high-order turbulence law that describes the turbulent cascade at the edges of fusion plasmas, namely valid within the Scrape-off Layer (SOL), in the framework of the Braginskii fluid model. Using the Yaglom-Monin approach, we derive an exact relation characterizing density fluctuations in these strongly magnetized systems. We obtain a third-order von K\'arm\'an-Howarth equation in increment form for the case of electrostatic Braginskii model, applied to a decaying turbulence regime. The new Yaglom-Braginskii law is validated through direct numerical simulations within a reduced (two-dimensional) model. Our analysis reveals that the plasma dynamics obey the cross-scale balance, exhibiting a well-defined inertial range of turbulence. This third-order law can provide an accurate measure of the cascade rate of density fluctuations in the scrape-off layer of laboratory plasmas.

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Luisa Scarivaglione, Sergio Servidio. 2025-05-05. An Exact Turbulence Law For the Fluid Description of Fusion Edge Plasmas. https://arxiv.org/abs/2505.03029

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