Whistler‐Mode Chorus Wave Duct Propagation Caused by Ultralow Frequency Wave: Event Analysis and Ray‐Tracing Simulation

Abstract This study presents observational evidence and ray‐tracing simulations demonstrating ultra‐low frequency (ULF) wave‐induced duct propagation of whistler‐mode waves. Cluster satellite observation reveals chorus propagating quasi‐parallelly at high latitudes and ULF waves. Chorus intensity enhancements correlate with refractive index increases driven by the ULF wave‐induced electron density and magnetic field variations. The theoretical maximum wave normal angle for duct propagation agrees with observed angles. The ray‐tracing calculations, using observation‐based duct models, reproduce ducted propagation, showing the consistent relation between frequencies and wave normal angles with the observation. These findings indicate that ULF waves create ducts guiding chorus waves to high latitudes and modulate chorus intensity in the time scale of the ULF wave period. This ULF wave ducting mechanism may explain chorus wave distribution and ULF wave‐modulated electron precipitation/aurora, providing new insights into wave‐particle interactions in radiation belts.