Scaling laws found under the assumption that two-body collisions domin
ate can be effectively used to benchmark complex multi-dimensional cod
es dedicated to investigating tokamak edge plasmas. The applicability
of such scaling laws to the interpretation of experimental data, howev
er, is found to be restricted to the relatively low plasma densities (
<10(19) m(-3)) at which multistep processes, which break the two-body
collision approximation, are unimportant. (C) 1996 American Institute
of Physics.