Direct comparison of transverse ion acceleration mechanisms in the auroralregion at solar minimum

Previous studies have shown that most ion conics in the auroral zone are as sociated with either broadband extremely low frequency (BBELF) or electroma gnetic ion cyclotron (EMIC) emissions. EMIC emissions, which are correlated with preferential acceleration of He+, are concentrated in the premidnight sector. BBELF emissions, which are found at all local times, are not assoc iated with preferential acceleration of any species. We present a case stud y of five auroral passes which include ion conics associated with EMIC and BBELF waves at different locations. Our data indicate that EMIC waves can b e locally important for accelerating outflowing He+ in the aurora. However, although this study's design exaggerates the contribution of EMIC waves to transverse ion acceleration, we find in each case that BBELF waves produce higher energy fluxes of upflowing ions. Therefore, events with BBELF emiss ions dominate the overall ion outflow.