A simplified model to estimate nonlinear turbulent transport by linear dynamics in plasma turbulence.

A simplified model to estimate nonlinear turbulent transport only by linear calculations is proposed, where the turbulent heat diffusivity in tokamak ion temperature gradient(ITG) driven turbulence is reproduced for a wide parameter range including near- and far-marginal ITG stability. The optimal nonlinear functional relation(NFR) between the turbulent diffusivity, the turbulence intensity [Formula: see text], and the zonal-flow intensity [Formula: see text] is determined by means of mathematical optimization methods. Then, an extended modeling for [Formula: see text] and [Formula: see text] to incorporate the turbulence suppression effects and the temperature gradient dependence is carried out.