MINIMUM ENSTROPHY STATE IN THE TOKAMAK SCRAPE-OFF LAYER

A theory is presented on turbulence and transport in the scrape-off la yer of a tokamak. It is argued that there is a dual cascade of energy (to long wavelengths) and enstrophy (to short wavelengths), driving an equilibrium in which enstrophy is minimized for a fixed energy. For a toroidally-limited tokamak scrape-off layer, this flow takes the form V(r) = V(a)e(-lambda(r-a)theta). The electrostatic-potential profile and the electron-temperature profile follow directly from V(r). Thus, the thermal transport problem is solved without the need for intermedi ate transport coefficients. The two parameters lambda and V(a) are det ermined from a combination of energy balance and dimensional analysis.