Direct Observations of Whistler-Mode Chorus Modulation of 500eV EDI Electrons by MMS

We present here direct observations of chorus-wave modulated quasi field-aligned electrons using the Electron Drift Instrument (EDI) on board the Magnetospheric Multiscale mission. These events demonstrated fluctuations in the count rates of 500 eV electrons exhibiting the same spectral characteristics as simultaneously observed whistler-mode chorus waves using the on-board search coil magnetometer. As these observations were made by all four spacecraft in a tetrahedral formation, we can use the wave telescope method to verify wave-particle resonance. Additionally, we use the multiple look directions of EDI close to the alignment direction in combination with the sweep of the instrument as the spacecraft spins to generate both pitch angle and gyrophase plots of the fluctuating counts in the wave perturbation frame of reference. We identify periods of gyrophase bunching suggesting active wave-particle interactions. These periods of wave activity were additionally observed to be modulated by Pc5-frequency magnetic perturbations, some of which have been identified as mirror-mode structures. The spacecraft encountered these mirror-mode structures just inside of the duskside magnetopause.