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This thesis re-examines the classic description of turbulent transport in terms of diffusion and suggests a new framework for theoretical analysis. The standard approach to turbulence in plasma presupposes that the size and characteristic frequency of fluctuations is much inferior to those of equilibrium. This hypothesis permits a study by forcing through a constant gradient of equilibrium. Our study favours forcing through a flux, thus lifting the constraint of separating according to scale.

We develop a 1D cellular model with self organized criticality (SOC). The local transport to the gradient threshold is linked to the condition of neighbouring sites. The system is forced through a source that is coherent in volume, the ionisation of neutrals. Experience shows that average transport can be described in terms of diffusion and convection, although local transport is of an altogether different nature. The instability of interchange is studied along open field lines connected to the wall. The 2D model of this instability threshold is used in both types of forcing, by gradient and by flux. .

Additional information

Authors: SARAZIN Y, CEA, CEN Cadarache, Saint-Paul-lez-Durance (FR)
Bibliographic Reference: Report: EUR-CEA-FC-1625 FR (1998) 198pp.
Availability: Available from Association Euratom-CEA, CEN Cadarache, 13108 Saint-Paul-lez-Durance (FR)
Record Number: 199810442 / Last updated on: 1998-05-05
Original language: fr
Available languages: fr