Effects of solar wind dynamic pressure on the ionospheric O⁺ fluence during the 31 August 2005 storm

The Multifluid-Lyon-Fedder-Mobarry (MFLFM) global simulation model incorporating an ionospheric cusp O⁺ outflow model based on an empirical relation between downward DC Poynting flux and O⁺ outflow flux regulated by the precipitating electron number flux (F_en) is used to simulate the 31 August 2005 storm. A baseline run incorporating the original solar wind data is contrasted against a case where the solar wind dynamic pressure (P_dyn) is artificially adjusted to see what effects this variable has on the O⁺ fluence generated in the model. Consistent with data, it is found that both the fluence and O⁺ outflow flux have a positive correlation with the solar wind dynamic pressure. Additionally, changes in P_dyn affect the downward Poynting flux only marginally and regulates both outflow flux and cusp outflow area via F _en. Increases in P_dyn lead to increased cusp electron precipitation, which has the physical effect of enhancing the upwelling O ⁺ population available for outflow.