Finite beta destabilization of long-wavelength drift mode in tokamaks

Analysis based on integral equation formalism in the ballooning space indic ates that in toroidal geometry, extremely long-wavelength modes with the io n finite Larmor radius parameter (k (perpendicular to) rho)(2) less than or similar to O(10(-2)) and mode frequency of the order of the ion transit fr equency can be strongly destabilized by a finite beta (the ratio of plasma to magnetic pressure). In high beta regimes, a resultant mixing length ther mal diffusivity is linearly proportional to beta.