Magnetic island width change by turbulence spreading in electrostatic gyrokinetic simulation *

Magnetic island is attributed to flattening of temperature profile inside the island and steepening outside. Considering profile gradient as a driving source, it is anticipated that turbulence is quite strong outside the island and barely grows inside. In that regard, magnetic island can be an ideal setup for studying physics of turbulence spreading.

In this research we characterize the behavior of turbulence spreading on a fixed magnetic island using electrostatic gyrokinetic simulation GENE (Gyrokinetic Electromagnetic Numerical Experiment). Effects of the turbulence spreading on the temperature profile near the island boundary and resultant change of the magnetic island width are presented. Parameteric scanning is carried out over amplitude of externally given magnetic perturbation and radial position of the island. Furthermore, subsequent changes in particle and heat transports are examined for each parameter.