Edge harmonic oscillations produced by toroidal velocity shear

McCarthy, D. R.
June 2002
Physics of Plasmas;Jun2002, Vol. 9 Issue 6, p2451
Academic Journal
It is shown that, for a plasma with similar edge density and parallel velocity profiles to that of the Doublet III-D [Fusion Technol. 8, 441 (1985)] tokamak operating in the quiescent double barrier (QDB) regime, the system is unstable to the parallel velocity shear instability. By means of three-dimensional nonlinear simulations, it is found that this system produces turbulence that is radially localized in the vicinity of the parallel velocity gradient and has a toroidal structure. These results are similar to the edge harmonic oscillations (EHOs) that are observed during the QDB discharge. Previously, it was thought that the EHOs were due to a magnetic magnetohydrodynamic mode, yet such structures have not been observed in any one-fluid theoretical models. These results indicate that EHOs may be due to this instability, which can only be realized in a two fluid model.


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