UP-DOWN ASYMMETRY OF GLOBAL DRIFT WAVES IN TOKAMAKS

The mode structure of global drift waves in tokamaks, which are not lo calized by magnetic shear and density inhomogeneity, is investigated i n the framework of fully two-dimensional problems. We obtain the analy tically explicit, two dimensional expressions for the electrostatic po tential of global drift waves, distinguishing between the weak and str ong regimes with respect to the strength of torodicity (the ratio of t he density scale length to the major radius). The former is found to h ave an up-down asymmetry of the phase function on the cross-section of the torus, while the latter has that of both the phase function and t he amplitude.