Schematic view of the spectral evolution with distance of ${\widehat{E}}_{\pm }$ in the fast Alfvénic stream. (i) ${\widehat{E}}_{-}$ does not evolve with distance and has a Kolmogorov scaling at all wave numbers. (ii) ${\widehat{E}}_{+}$ has a 1/k scaling at large scales where energy decays as 1/R. (iii) At small scales, ${\widehat{E}}_{+}$ has a Kolmogorov slope and the energy decays as 1/R². (iv) The break dividing the two branches shifts toward larger scales as R^−3/2. Starting with the first two properties, which are drawn in black, and using phenomenological arguments, one can obtain the other properties, which are drawn in grey.