Alpha transmitter signal reflection and triggered emissions

Russian Alpha radio navigation system (RSDN‐20) emits F1=11.9kHz signals into the magnetosphere which propagate as whistler‐mode waves. Observed by waveform continuous burst mode from EMFISIS on Van Allen Probes, a case is presented and featured with ducted propagation, multiple reflections and triggered emissions. Both risers and fallers appear in the triggered emissions. We use a ray‐tracing method to demonstrate ducted propagation, which has a similar wave normal angle near 150° as the observation. The arrival time of reflected signals is estimated using propagation analysis and compared with the observed signal arrival time. To test the non‐linear cyclotron resonance theory, the interaction region scale and the order of chirping rate in triggered emission are estimated. The estimated interaction region scale of MLAT=‐3° is smaller than the observed MLAT=‐6°. The discrepancy may be caused by the parallel propagation assumption and background field model.