Fig. 14

Trajectories of trapped resonant electrons. Acceleration of electrons through nonlinear trapping by a chorus wave with the wave normal angle parallel (a, c) and oblique (b, d) to the background magnetic field. In a, b, resonance velocities for \(n = 0, 1, 2\) resonances are plotted in dash-dot lines (\(\omega =0.5 \Omega _{\text{e}}\)) and dotted lines (\(\omega = 0.2 \Omega _{\text{e}}\)). Going through the resonances, colors of the trajectories changes from black to blue, red, and green, corresponding to \(n= 0, 1, 2\) resonances. The numbers next to the branches of the Green’s functions represent the n-th resonances