Ballooning limit of collisional drift waves driven by temperature gradients

Abstract

It is shown that in the ballooning limit collisional drift waves are unstable for temperature and density gradients of opposite signs, whereas they are stable if both gradients have the same sign. If shear damping persists (e.g. in cylindrical systems) both situations are stable. Instabilities are thus expected in such configurations as occur during the initial current rise in Tokamaks, possibly while fueling the system by cold neutral injection, and also in the case of a cold plasma mantle. The ballooning limit is consistent with the requirement on collisionality only in the Pfirsch-Schluter regime.