Toroidal coupling in the kinetic response to edge magnetic perturbations

The magnetic topology of the stochastic edge of a helical reversed-field pinch, with helicity m/n, shows to be deeply influenced by higher harmonics (m +/- 1)/n, with the same n, due to toroidal coupling. As a consequence, by measuring kinetic quantities in a particular theta, phi location, one can incur in substantial errors or mis-interpretations of the kinetic plasma response: only a full 3D coverage of theta, phi angles can reveal the real topology of the plasma. This can be a caveat for MP application in tokamaks, because it shows that toroidal and poloidal sidebands, though smaller than the base mode by a factor similar to epsilon = a/R, can have a sizable effect on the kinetic response of the edge plasma, and thus on related issues (for example, ELM stabilization and suppression).