Multi‐Point Observations of Modulated Whistler‐Mode Waves and Energetic Electron Precipitation

Abstract

AbstractIn this study, we present simultaneous multi‐point observations of whistler‐mode waves detected by RBSP‐B, associated with conjugate electron precipitation observed through enhanced BARREL X‐rays at L ∼ 6 from noon to dusk. Both long period modulation at periods of several to tens of minutes and short period modulation at about tens of seconds are observed in X‐ray measurements. Similar periodicities are also observed for whistler‐mode wave amplitude. We show that the correlation coefficient between whistler‐mode waves and electron precipitation is high in several regions, including plumes and plasma trough. Ultra‐low‐frequency waves (8–30 mHz), which have been suggested to play a potential role in precipitating electrons by modulating whistler‐mode wave intensity or loss cone size, show a weak correlation with whistler‐mode wave amplitudes and the X‐ray counts during the conjunction. We further evaluate whistler‐mode wave driven electron precipitation using a physics‐based technique. The time evolution of the modeled electron precipitation is found to be remarkably consistent with the modulation in the BARREL X‐ray counts both in plumes and plasma trough. By taking advantage of the high‐resolution wave data and close conjunction, we provide strong evidence that whistler‐mode waves are not only directly responsible for the longer modulation (several to tens of minutes), but also the shorter modulation (tens of seconds) of the electron precipitation.