REYNOLDS STRESS OF LOCALIZED TOROIDAL MODES

An investigation of the two-dimensional (2-D) toroidal eigenmode problem reveals the possibility of a new consistent 2-D structure, the dissipative ballooning mode of the second kind (BM-II). In contrast to the conventional ballooning mode, the new mode is poloidally localized at pi/2 (or-pi/2), and possesses significant radial asymmetry. The radial asymmetry in turn, allows the dissipative BM-II to generate considerably larger Reynolds stress as compared to the standard slab drift-type modes. It is also shown that a wide class of localized dissipative toroidal modes are likely to be of the dissipative BM-II nature, suggesting that at the tokamak edge, the fluctuation generated Reynolds stress (a possible source of poloidal flow) can be significant. (C) 1995 American Institute of Physics.