The response of the electron temperature profile shape to variations of the electron heating and density profiles is investigated in different confinement regimes. It is shown that the changes in rTe = -Te/(dTe/dr) exceed the measurement error if the shape of the electron heat diffusivity χe(r) is kept fixed. The observed constancy of rTe(r) in the outer half of the plasma is incompatible with such a fixed χe(r) shape, i.e., a Te profile constraining mechanism must be present. Local transport laws of the form χe varies as rTe-α with α ≳ 4 and χe ∝ (dTe/dr)α with α ⩾ 2 yield the experimental stiffness of the Te(r) shape but conflict with empirical χe scalings. These results support the model of a self-organizing and adjusting χe(r) causing Te profile invariance
Temperature dependence of the electron thermal conductivity coefficient inferred from neutral-beam injection