Figure 3: Diffusion rates.

Bounce-averaged pitch angle (〈D_αα〉, (a,d)), momentum (〈D_pp〉, (b,e)) and cross (〈D_αp〉, (c,f)) diffusion rates (in unit of s⁻¹) for resonant interactions between chorus (left) or MS (right) wave with electrons. Diffusion rates cover an entire region of pitch angles 0°–90° for chorus but a limited region 30°–60° for MS waves. Combination of chorus and MS waves leads to efficient acceleration of electrons between 2 and 3.6 MeV at medium pitch angles 30°–60° and high pitch angles up to 90°, yielding the resultant butterfly distribution on a timescale comparable to 10 h.