Finite beta destabilization of long-wavelength drift mode in tokamaks

Analysis based on integral equation formalism in the ballooning space indicates that in toroidal geometry, extremely long-wavelength modes with the ion finite Larmor radius parameter (k p)^2 <~ (10^-2) and mode frequency of the order of the ion transit frequency can be strongly destabilized by a finite beta (the ratio of plasma to magnetic pressure). In high beta regimes, a resultant mixing length thermal diffusivity is linearly proportional to beta.