Effective heat conduction in a configuration with nonoverlapped magnetic islands

The effective radial heat conduction κeff in a plasma configuration with nonoverlapped magnetic island chains is assessed by applying an ''optimal path'' method. This approach implies that heat is transported predominantly along paths rendering the minimum temperature variation and is related to the principle of minimum entropy production. Paths combined of up to three radial sections and two segments aligned along magnetic field lines are considered. It is demonstrated that the enhancement of κeff over the level of perpendicular heat conduction κperpendicular arising due to flows along magnetic field lines is controlled only by the Chirikov parameter and by the value 4br2κparallel/κperpendicular, where br is the relative amplitude of the radial field resonant harmonic and κparallel is the parallel heat conduction