Effect of the curvature and the β parameter on the nonlinear dynamics of a drift tearing magnetic island

Magali Muraglia (1) , Olivier Agullo (1) , Masatoshi Yagi (2) , Sadruddin Benkadda (1) , Beyer Peter (1) , Xavier Garbet (3) , Sanae -I. Itoh (2) , Kimitaka Itoh (4) , Abhijit Sen (5)

1 PIIM - Physique des interactions ioniques et moléculaires
2 RIAM - Research Institute for Applied Mechanics [Fukuoka]
3 CEA/DSM/DRFC - Association EURATOM-CEA
4 NIFS - National Institute for Fusion Science
5 Institute for Plasma Research [Gandhinagar]

We present numerical simulation studies of 2D reduced MHD equations investigating the impact of the electronic β parameter and of curvature effects on the nonlinear evolution of drift tearing islands. We observe a bifurcation phenomenon that leads to an amplification of the pressure energy, the generation of E × B poloidal flow and a nonlinear diamagnetic drift that affects the rotation of the magnetic island. These dynamical modifications arise due to quasilinear effects that generate a zonal flow at the onset point of the bifurcation. Our simulations show that the transition point is influenced by the β parameter such that the pressure gradient through a curvature effect strongly stabilizes the transition. Regarding the modified rotation of the island, a model for the frequency is derived in order to study its origin and the effect of the β parameter. It appears that after the transition, an E × B poloidal flow as well as a nonlinear diamagnetic drift are generated due to an amplification of the stresses by pressure effects.

Mots clés: magnetic islands; interchange; turbulence; magnetized plasmas; MHD; simulation

Domaines: Physique des plasmas [physics.plasm-ph]

Magali Muraglia, Olivier Agullo, Masatoshi Yagi, Sadruddin Benkadda, Beyer Peter, et al.. Effect of the curvature and the β parameter on the nonlinear dynamics of a drift tearing magnetic island. Nuclear Fusion, 2009, 49, pp.055016. ⟨hal-00578079⟩