On the mass dependence of transverse ion acceleration by broad-band extremely low frequency waves

Recent data from the Fast Auroral Snapshot Explorer (FAST) and other satellites indicate that broad-band extremely low frequency (BBELF) waves account for most of the transverse ion acceleration in the aurora. These waves tend to accelerate ions of different masses to approximately the same energy. We have shown previously that a downward parallel electric field is necessary in order to explain this result in terms of a cyclotron resonant acceleration process. In this paper we use triangular electric field distributions to investigate how strong and how extensive a field is necessary to equalize the energization of ions of different mass.