Inverted profile for the gradient of the angular momentum, using ℓ = 1 to 20 modes (upper panel) and only ℓ = 8 modes (lower panel). The continuous line shows the actual gradient, whereas the blue crosses indicate inversion results and associated 1σ error bars. For the sake of clarity, the horizontal error bars (obtained from the averaging kernels) have been omitted in the lower panel. (Colour online.)