  It is shown that in the framework of the weak turbulence theory, the
autocorrelation and cascade timescales are always of the same order of
magnitude. This means that, contrary to the general belief, any model of
turbulence which implies a large number of collisions among wave packets for an
efficient energy cascade (such as the Iroshnikov-Kraichnan model) are not
compatible with the weak turbulence theory.
