Impact of electric potential and magnetic drift on microtearing modes stability

Abstract

The stability of a microtearing mode (MTM) as a function of collisonality is investigated by means of linear reduced model and numerical simulations using the gyrokinetic code GKW. The study is focused on the role of the electric potential and the magnetic drift, which are potential candidates to explain the destabilization of MTM observed at low collisionality in some recent gyrokinetic simulations. In the simulations, the magnetic drift and electric potential are found destabilizing in the presence of a finite collisionality. This destabilizating role is captured in the analytical calculation, which further highlights the requirement for a finite collisionality.

Linear stability of the JET H-mode pedestal

“…Linear gyrokinetic simulations [34] show that the mode structure is peaked at the low field side mid-plane and rotates in the electron diamagnetic direction. An analytical linear calculation has been developed and compared with numerical simulations using the gyrokinetic code GKW and non realistic physical parameters [37]. Here, the same model has been compared with gyrokinetic simulations using the GENE code and JET H-mode pedestal experimental data.…”

“…Here, the same model has been compared with gyrokinetic simulations using the GENE code and JET H-mode pedestal experimental data. A detailed description of the kinetic model can be found in [37].…”

“…where σ(x) is the dimensionless "conductivity" (see [37]) and ρ = x/δ e is the radial coordinate. The details of the calculation can be found in Ref.…”

“…In Ref. [37], a reduced kinetic linear theoretical for MT is described, which is a derivation of a current sheet model by solving the Fokker-Planck and Maxwell equations and its evaluation inside the resistive layer is obtained from a system of two equations linking the vector potential and the electric potential. This system of equations has been solved numerically using an eigenvalue code, called Solve AP.…”

“…The purpose of this paper is, starting with the model developed in Ref. [37] to compare the theoretical linear growth rate calculated by an eigenvalue code, called Solve AP, with gyrokinetic simulations using the GENE code [5,39] and the JET 82585 experimental data (see Ref. [7]) and to understand the effect of the physical parameters on MT destabilization.…”