GRTTM distribution functions of non-thermal electron energies versus positions with a colour coded M(μ₀) corresponding to the current density j = 6 A m^-2 in the VAL C atmosphere at time t = 0.3 s after the beam injection into the loop at its apex. Top: primary footpoint, bottom: secondary footpoint, left: M^FF, right: M^SU. The solid lines indicate the instantaneous energy deposits corresponding to ℱ₀/2 = 2.5 × 10⁹ erg cm^-2 s^-1, the dotted horizontal lines the bottom boundary of the magnetic mirror and the blue ellipses labelled L and H denote tails in the particle distribution function. Only the vicinity of the footpoints are displayed.