Stochastic magnetic field and enhanced transport

Abstract Using the differential effective medium approach, the diffusivity, χ e , of a weakly collisional plasma confined by a magnetic configuration close to the stochastic threshold is estimated. With a good approximation, one gets χ e ∼ χ ⊥ ƒ , where χ ⊥ is the diffusivity in the KAM region with undestroyed magnetic surfaces and ƒ the fraction of these regions.