Theoretical and experimental results of local energy transport analysis in Tokamaks show that it is convenient to write the local thermal diffusivity as c = cBF, where cB µ T/B is the Bohm coefficient and F is a function of local non-dimensional parameters. T is either Te or Ti (we choose, when required, the electron temperature Te). The toroidal magnetic field B0 is the appropriate reference field, however one can replace B0 with the poloidal field BP by allowing an additional dependence of F on the safety factor q.