Top and third panels: total (green), perpendicular (red), slab (blue) and summation of perpendicular and slab, that is perpendicular plus slab (black) turbulence energy corresponding to the energy in forward propagating modes (A1/B1), the energy in backward propagating modes (A2/B2), the fluctuating magnetic energy (A3/B3), and the fluctuating kinetic energy (A4/B4) for the slow and fast solar wind as a function of the angle between the mean solar wind speed and the mean magnetic field (θ_UB). Second and fourth panels: ratio between the 2D and slab variances of energy in forward propagating modes (a1/b1) and backward propagating modes (a2/b2), the fluctuating magnetic energy (a3/b3), and the fluctuating kinetic energy (a4/b4) as a function of θ_UB. (a) Slow solar wind. (b) Fast solar wind.