Fig. 3

Schematic diagram of generation process of subpackets in the equatorial region. Seed electrons generate a chorus wave subpacket (packet 1) by cyclotron resonance. The resonant seed electrons are modulated by packet 1 through the interaction. The frequency of packet 1 at the timing of releasing the seed electrons is transferred to packet 2 when the modulated seed electrons trigger packet 2. Since phase of each subpacket is randomized in the simulation, phase difference between packet 2 and the resonant seed electrons gyrophase \( {\text{Z}}_{2} \) is discontinuously changed to \( {\text{Z}}_{3} \) at the timing of being released by packet 2 and interacting with packet 3