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This paper studies one of the driving mechanisms of low mode number fluctuations at the tokamak plasma edge. It is shown that ion viscosity and heat conduction along the field lines are destabilising if the gradient of the parallel flow velocity exceeds certain thresholds, which are usually appreciably lower (by a factor of about 100) than that of the well-known ideal Kelvin-Helmholtz mode. The relationship between mode number and frequency is compatible with that of the Toi mode. Restricting the analysis to self-similar solutions, two of the instabilities are found to be self-stabilising when the rotation velocity is close to the respective instability thresholds. The turbulence slows down the rotation. In the third instability regime the unstable mode spins up the rotation and drives the plasma further into the unstable domain. An equilibrium bifurcation could be linked to this quasi-linear behaviour.

Additional information

Authors: ROGISTER A, Forschungszentrum Jülich GmbH, Institut für Plasmaphysik (DE);HASSELBERG G, Forschungszentrum Jülich GmbH, Institut für Plasmaphysik (DE);LI D, Academia Sinica, Institute of Plasma Physics, Hefei (CN);KHALIL M, Atomic Energy Authority, Nuclear Research Center, Cairo (EG)
Bibliographic Reference: Article: Plasma Physics and Controlled Fusion Vol. 34 (1992) No. 7, pp. 1265-1289
Record Number: 199211270 / Last updated on: 1994-11-29
Original language: en
Available languages: en