Scale-to-scale transfer of kinetic energy, T (m, m′), in the statistically steady state. Note that the figure has logarithmic axes and two colorbars; the left one indicates values for m = 0 or m′ = 0 and the right one for m, m′ > 0. A positive value of T(m, m′) shows that kinetic energy is transferred from wave number m′ to wave number m. We use the regions indicated by gray lines and labeled with letters (a) to (e) to refer to specific regions of the plot in the text and show the different spatial contributions to T(m, m′) for those regions in Fig. 7.