THEORY OF HIGH-MODE PHENOMENA FOR STELLARATORS

It is shown that besides the ion orbit loss mechanism, which occurs in a region a - epsilon(t) rho(p) < r < a, the drift-orbit transport flu x driven by the collisionless helically trapped particles can also dri ve the poloidal (E) over right arrow x (B) over right arrow velocity i n a region r < a - epsilon(t) rho(p) in stellarators. Here, r(a) is th e minor (plasma) radius, epsilon(t) is the toroidal amplitude of the m agnetic field spectrum, (E) over right arrow((B) over right arrow) is the electric (magnetic) field, and rho(p) is the poloidal ion gyroradi us. The transport flux-driven (E) over right arrow x (B) over right ar row velocity can be triggered most efficiently by an increase of the i on temperature gradient. The theory is applied to the high-mode phenom enon observed in stellarators.