Ion-temperature-gradient-driven modes in neoclassical regime

Abstract

A reduced set of neoclassical fluid equations, consisting of the parallel ion flow velocity ulI , the generalized potential F, the ion pressure p, and the parallel ion heat flow qll , is derived. The resultant equations are the extension of reduced fluid equations derived from Braginskii equations with the high collisionality to the equations relevant to a fusion plasma with low to intermediate collisionality. The linear Q mode dynamics is reinvestigated by using the resultant model equations. The effects of the perpendicular compressibility in the ion pressure response, the parallel heat flow, and the neoclassical viscosity are analyzed both analytically and numerically. It is stressed that the closure condition of neoclassical viscosity changes the sign of energy dissipation and seriously affects the stability of vi modes.

Nonlinear simulation of tearing mode based on 4-field RMHD model

“…However, this is not our case, since we have > 0 and the polarization current weakly affects the saturation of the magnetic island. In any case, the extension of the model equation is necessary to incorporate whole neoclassical transport effects [13]. Our final goal is to verify the statistical theory, which suggests turbulence excitation of NTM, and which is possible through several routes [14].…”

A reduced MHD model for ITG-NTM interplay

“…In fact the finite Larmor radius contribution to the generalised vorticity ω = ∆ ⊥ (φ − p i ) is always a challenge for the energy balance. This problem can be solved by increasing the complexity of the model and introducing an equation on the perpendicular current 43 , or avoided by neglecting the ion pressure or at least taking the limit of vanishing Larmor radius 41 (Ω i τ A ) −1 → 0 which allows to neglect p i in the expression of ω (recall the renormalisation of the pressure). In this limit we obtain δ E Larmor = 0.…”