On the diffusion of stochastic magnetic field lines in tokamak plasma M Negrea 1 , I Petrisor 1 and B Weyssow 2 1 Department of Physics, University of Craiova, Association Euratom-MEdC, Romania 13 A.I.Cuza Str, 200585 Craiova, Romania 2 Physique Statistique–Plasmas, Association Euratom-Etat Belge, Universite Libre de Bruxelles, Campus Plaine, Bd. du Triomphe, 1050 Bruxelles, Belgium The transport of magnetic field line due to a mean magnetic shear and an anisotropy in the magnetic fluctuation spectrum is fundamental for gaining a proper understanding of recent hot plasma experiments, which operate naturally in such conditions or are making use of external means (coils) to generate a magnetic stochasticity. The latter is a proven method to divert unclean plasma from the bulk in toroidal devices such as Tore-Supra or Textor. In relatively recent experiments in the DIII-D tokamak [1] have shown strong anomalous electron heat conduction even for low levels of electrostatic turbulence. The physical mechanism involved in the process can be the magnetic stochasticity [2]. It is indeed well known that magnetic stochasticity, even small, can be sufficiently widespread so as to destroy the transport barrier due to good nested magnetic surfaces of the confining geometry. As demonstrated in [3], the intensity of the magnetic fluctuations is not the only parameter that is important. The mean magnetic shear or the stochastic anisotropy also play a role as in the case of the self consistently generated poloidal flow, which is known to reduce the radial turbulent transport. This mechanism may be responsible for a rapid transition to an enhanced confinement, i.e. the celebrated H-mode regime. In our contribution the decorrelation trajectory method is applied to study the diffusion of magnetic field lines in a perturbed sheared slab stochastic anisotropic magnetic configuration. The isotropic sheared stochastic magnetic field lines diffusion analysis was presented in [4]. The running and asymptotic diffusion tensor components are calculated taking into account the influence of the anisotropy in the magnetic fluctuation spectrum (stochastic anisotropy) and the magnetic shear, using a semi- analytical method, namely the decorrelation trajectory method, which in contradistinction with the Corrsin approximation, handles the trapping effect of the turbulent field [5]. The study considers ranges for the anisotropy parameter, magnetic Kubo number and shear parameter and particularly, the trapping of the stochastic magnetic field lines is analysed. An asymptotic ‘poloidal’ velocity larger for stronger anisotropy is obtained for the wandering of the magnetic field lines for different values of the parameters [6]. References [1] Greenfeld C M et al 1997 Phys. Plasmas 4 1596 [2] Bickerton R J 1997 Plasma Phys. Control. Fusion 39 339 [3] DeRover M et al 1999 Phys. Plasmas 6 2443 [4] Negrea M, Petrisor I and Balescu R 2004 Phys. Rev. E 70 046409 [5] Vlad M, Spineanu F, Misguich J-H and Balescu R 1998 Phys. Rev. E 58 7359 [6] Negrea M, Petrisor I and Weyssow B 2007 Plasma Phys. Control. Fusion 49 1767 View publication stats View publication stats