AbstractThe recalibrated FAST/TEAMS data is used to study the response of O⁺ and H⁺ outflow to energy inputs in the nightside aurora during the 24–25 September 1998 geomagnetic storm, the same storm studied by Strangeway et al. (2005), https://doi.org/10.1029/2004JA010829. In contrast to the cusp, the Poynting flux and electron precipitation energy input are not as well correlated on the nightside, so their effects on outflow can be differentiated. The O⁺ outflow shows a strong correlation with both the Alfvénic Poynting flux (r = 0.71) and the soft electron precipitation (r = 0.69), while the H⁺ outflow only correlates well with the electron number flux (r = 0.74). This indicates that the auroral H⁺ outflow is close to its limiting flux without additional wave acceleration, while the outflow for the heavier O⁺ ion is increased by additional wave acceleration.