Factors Controlling O⁺ and H⁺ Outflow in the Cusp During a Geomagnetic Storm: FAST/TEAMS Observations

Abstract

Abstract Factors related to two sources of energy input to the ionosphere, the Poynting flux associated with both quasistatic fields ( S dc ) and Alfvénic fluctuations ( S ac ), and the soft electron precipitation, are investigated to evaluate their correlations with the O + and the H + outflows in the dayside cusp region by using recalibrated FAST/Time‐of‐Flight Energy, Angle, and Mass Spectrograph (TEAMS) data during the 24–25 September 1998 geomagnetic storm studied by Strangeway et al. (2005, https://doi.org/10.1029/2004JA010829 ). The Poynting flux and the soft electron precipitation are well correlated with ion outflow flux in the dayside cusp region. S dc shows the highest correlation with the O + outflows, while it is the electron number flux that correlates best with the H + outflows. The Alfvénic waves play an essential role in accelerating outflows. The averaged O + /H + flux ratio is 3.0 and is positively correlated to the Poynting flux, suggesting that the O + flux increases more strongly with the energy input.