Comments on profile consistency

It is argued that transport models with sufficiently small central (relative to edge) thermal conductivity, so as to allow sawteeth at the highest q, can easily explain ‘profile consistency’ in tokamaks. This includes the observed increase in temperature profile peakedness T(0)/⟨T⟩ with increasing q and the relatively small variation of the peakedness with variation in heating profile. In fact, it is proven that if q(0) = 1 and the Spitzer relation between current and temperature profiles holds, then the peakedness is bounded by q 2/3 ≲ T(0)/⟨T⟩ ≲ q. A distinction is made between the central sawtooth mechanism which ‘tops’ the profiles and possible q dependent edge mechanisms which ‘shrink’ profiles. The latter are not precluded from contributing to profile consistency and may be required to understand confinement time scaling.