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B. Coppi, G. Penn, L. E. Sugiyama
Massachusetts Institute of Technology, Cambridge MA, United States of America
Abstract. Results of the investigation of two basic problems involving the
rotation of magnetically confined plasmas are presented. In the toroidal
direction, significant plasma rotation has been produced in plasmas subject to
ion cyclotron RF heating, in the absence of any evident direct angular
momentum source. The theoretical model proposes the excitation of two classes
of intrinsic magnetosonic whistler-like modes. The first, ``contained'' modes,
has toroidal momentum in the same direction as that of the plasma current and
is radially localized in the outer region of the plasma column, r > 0.4a.
The other class is nonlocal and convects radially outwards, carrying the
angular momentum in the counter-current direction to particles near the edge
of the plasma column that are then scattered out of the plasma. Thus, rotation
of the central part of the plasma column can be induced, with a velocity
radial profile that is consistent with the anomalous transport of angular
momentum resulting from the additional excitation of velocity-gradient-driven
modes. The question of poloidal rotation and the evolution of poloidal flows
in a torus is also examined. Results from the numerical simulation of MHD and
two-fluid plasmas shows that compressional and other effects are important in
the plasma response to rotation and provide an effective mechanism for damping
poloidal flows in a torus on relatively fast time scales. The two-fluid
response to rotation can be different than in MHD, due to differences in the
symmetries of the equations, but they experience similar break-up of the
poloidal rotation.
IAEA 2001
