
Author(s):
R. Kanno, M. Nunami, S. Satake, H. Takamaru and M. Okamoto

Title:
Radial Thermal Diffusivity of Toroidal Plasma Affected by Resonant Magnetic Perturbations

Date of publication:
Apr. 01, 2012

Key words:
collisional transport, thermal diffusion, resonant magnetic perturbation, toroidal plasma, diffusion process, stochastic analysis, δ f simulation, Monte Carlo method

Abstract:
We investigate how the radial thermal diffusivity of an axisymmetric toroidal plasma is modified by effect of resonant magnetic perturbations (RMPs), using a drift kinetic simulation code for calculating the thermal diffusivity in the perturbed region. The perturbed region is assumed to be generated on and around the resonance surfaces, and is wedged in between the regular closed magnetic surfaces. It has been found that the radial thermal diffusivity χr in the perturbed region is represented as χr = χ(0) r {1 + c <¡ÂδBr¡Â^{2}>}. Here <¡ÂδBr¡Â2>^{1/2} is the strength of the RMPs in the radial directions, <¡¦> means the flux surface average defined by the unperturbed (i.e., original) magnetic field, χ(0) r is the neoclassical thermal diffusivity, and c is a positive coefficient. In this paper, dependence of the coefficient c on parameters of the toroidal plasma is studied in results given by the δ f simulation code solving the drift kinetic equation under an assumption of zero electric field. We find that the dependence of c is given as c ∝ ωb/νeff m in the low collisionality regime νeff < ωb, where νeff is the effective collision frequency, ωb is the bounce frequency and m is the particle mass. In case of νeff > ωb, the thermal diffusivity χr evaluated by the simulations becomes close to the neoclassical thermal diffusivity χ(0) r .
