Modulation of Whistler Mode Waves by Ion-Scale Waves Observed in the Distant Magnetotail

Wave activities in tailward flows have been explored in the distant magnetotail at similar to 54 RE, where the coupling between whistler mode waves and ion-scale waves was observed. The whistler mode waves periodically appeared at each cycle of the ion-scale waves, and the electron distribution functions associated with the whistler mode waves showed enhancement in the direction parallel to background magnetic field. Wave analyses show that the field-aligned electron components act as the energy source of the whistler mode waves. The ion-scale waves are generated by the interaction of the hot ion beam with background ions. A likely candidate of the ion-scale wave is the kinetic Alfven wave, which can generate the enhanced field-aligned electron populations by the parallel electric field.