Evolution of loss cone α (red) and pitch angle θ (black) for a simplified CMT acceleration model (model 1) with constant loop top velocity v_LT(t). Shown are the results for three different starting pitch angles θ_i close to the critical initial pitch angle. One can see that both Fermi and Betatron accelerations are operating simultaneously, however, betatron acceleration is the overall dominating mechanism, causing θ to increase.