Fig. 6

Simulation results of wave–particle interaction for a sample electron with the initial energy of 500 keV and the initial equatorial pitch angle of 60°. a Spatiotemporal profile of generation and propagation of multi-subpacket chorus wave amplitude and a trajectory (white line) of the sample electron. The adiabatic motion of the electron distorted by the wave–particle interaction over location A–B. b Variation of resonance velocity \( {\text{V}}_{\text{R}} \) (black line) with the trapping region (yellow region) formed around it. The blue line shows the variation of the electron velocity \( v_{\parallel } \). The trajectory of \( v_{\parallel } \) is clearly disturbed to follow the variation of \( V_{R} \) over location A–B, indicating the electron is entrapped and accelerated by the chorus wave during the interaction. c Energy variation of the sample electron resulting in energy increase of more than 60 keV. d Trajectory of the electron in the (θ −ζ) phase space draws closed region, indicating the electron falls into the trapping region generated by the chorus wave. The dot color is changed at the points where the electron starts to interact with a new subpacket and experiences a phase discontinuity