Minimum enstrophy state in the tokamak scrape-off layer

A theory is presented on turbulence and transport in the scrape-off layer 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 intermediate transport coefficients. The two parameters lambda and V a are determined from a combination of energy balance and dimensional analysis.