Bonn 2000 – wissenschaftliches Programm

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P: Plasmaphysik

P 22: Theorie (Poster)

P 22.1: Poster

Donnerstag, 6. April 2000, 17:00–19:30, Aula

Comparison of transport properties between field line and particle models in stochastic magnetic fields — •M. Eberhard and K.H. Spatschek — Universität Düsseldorf

Transport properties in a perturbed magnetic field are calculated based on an exact symplectic method of integration [1,2]. The field changes from the integrable case to a mixed phase space system with islands and stochastic layers for different strengths of the perturbation. The dynamics in this system are investigated and exhibit different transport regimes. It is possible to calculate space dependent diffusion coefficients by adding parallel and perpendicular collisions. Without a parallel dynamic the field line motion is calculated, with parallel dynamics the particle motion. It is thus possible to compare both with each other and independent analytical models. Apart from the quasi linear limit and the model of Rechester and Rosenbluth [3] a new transport regime is discovered, during the formation of island chains and before the islands start to overlap. Although field lines show no transport in this regime, the particle transport is increased. Since islands are existent in nearly all experimental devices, this might be an important point to consider.

[1] H. Yoshida, Construction of higher order symplectic integrators, Phys. Lett. A 150 (1990) 262–268

[2] E. Forest and R. D. Ruth, Fourth-order symplectic integration, Physica D 43 (1990) 105–117

[3] A. B. Rechester and M. N. Rosenbluth, Electron heat transport in a tokamak with destroyed magnetic surfaces, Phys. Rev. Lett. 40 (1978) 38–41