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A Nonlinear Dynamics Characterization of The Scrape-off Layer Plasma Fluctuations

A stochastic differential equation for the plasma density dynamics is derived, consistent with the experimentally measured distribution and the theoretical quadratic nonlinearity. The plasma density is driven by a multiplicative Wiener process and evolves on the turbulence correlation time scale, while the linear growth is quadratically damped by the fluctuation level. The sensitivity of intermittency to the nonlinear dynamics is investigated by analyzing the Langevin representation of two intermittent distributions, showing the agreement between the quadratic nonlinearity and the gamma distribution.