CTTM time evolution of distribution functions of non-thermal electron energies versus positions with a colour coded M(μ₀) in the VAL C atmosphere. Left: M^FF, right: M^SU. From top to bottom: individual snapshots at t = 0.1,0.15,0.3 s after the beam injection into the loop at its apex. The solid lines indicate the instantaneous energy deposits corresponding to ℱ₀/2 = 2.5 × 10⁹ erg cm^-2 s^-1. The dotted horizontal lines indicate the bottom boundary of the magnetic mirror. Only the lower part of the loop and one footpoint are displayed.