Plots of time evolution of energy for particle orbit 2 (initial pitch angle 86.2°). Shown are the total kinetic energy (upper left panel), the parallel energy (upper right panel), the perpendicular energy (lower left panel), and the energy associated with the E × B-drift motion (lower right panel). Using the normalisation discussed in the text, the numbers on the x-axis can be interpreted as seconds and the numbers on the y-axis as electron volts.