REVISITED NEOCLASSICAL TRANSPORT-THEORY FOR STEEP, COLLISIONAL PLASMAEDGE PROFILES

It is shown that existing neoclassical theories in the high collisiona lity regime are inadequate to describe the edge plasma, where the grad ient length scales are of the order of (only) a few centimeters (the ' 'edge'' is defined here in relation to the neutrals ionization depth). Gyrostresses indeed modify considerably the continuity, energy, and p arallel momentum equations if, as is usually the case, LAMBDA1 = nu(i) (qR)2/OMEGA(i)L(psi)r is not negligible compared to unity (L(psi)=L(N ), L(T), L(V), where, e.g., L(N) is the density length scale). Particl e transport, moreover, is no longer automatically ambipolar: the radia l electric field -delV is actually determined by the ambipolarity cons traint. Another parameter also usually erroneously considered to be sm aller than unity is LAMBDA2 = (m(e)/m(i))1/2 (qRnu(i)/c(i))2. The theo ry presented here encompasses the more general conditions, where LAMBD A1 approximately 1, LAMBDA2 approximately 1.