Parallel mean free path in the foreshock derived from in situ ion intensity measurements. Panel a: dots give the intensity-time profiles observed by EPAM for different energy channels, shifted downwards to avoid overlap. The straight lines give a time-averaged increase in the time intervals T₁ = [0 h, 0.5 h] (blue) and T₂ = [0.5 h, 10.3 h] (green), and the values above each line give the slope. Panel b: the dotted lines give the derived from the slopes presented in (a) for T₁ (blue background) and T₂ (green background). The solid line gives the f(s) (see Eq. (7)) used in the PARADISE simulations.