The relation between transpolar potential and reconnection rates during sudden enhancement of solar wind dynamic pressure: OpenGGCM-CTIM results

This study investigates how solar wind energy is deposited into the magnetosphere-ionosphere system during sudden enhancements of solar wind dynamic pressure (Psw), using the coupled Open Geospace General Circulation Model-Coupled Ionosphere Thermosphere Model (OpenGGCM-CTIM) 3-D global magnetosphere-ionosphere-thermosphere model. We simulate three unique events of solar wind pressure enhancements that occurred during negative, near-zero, and positive interplanetary magnetic field (IMF) Bz. Then, we examine the behavior of the dayside and nightside reconnection rates and quantify their respective contributions to cross polar cap potential (CPCP), a proxy of ionospheric plasma convection strength. The modeled CPCP increases after a Psw enhancement in all three cases, which agrees well with observations from the Defense Meteorological Satellite Program spacecraft and predictions from the assimilative mapping of ionospheric electrodynamics technique. In the OpenGGCM-CTIM model, dayside reconnection increases within 9-13min of the pressure impact, while nightside reconnection intensifies about 13-25min after the pressure increase. As the strong Psw compresses the dayside magnetosheath and, subsequently, the magnetotail, their magnetic fields intensify and activate stronger antiparallel reconnection on the dayside magnetopause first and near the central plasma sheet second. For southward IMF, dayside reconnection contributes to the CPCP enhancement 2-4 times more than nightside reconnection. For northward IMF, the dayside contribution weakens, and nightside reconnection contributes more to the CPCP enhancement. We find that high-latitude magnetopause reconnection during northward IMF produces sunward ionospheric plasma convection, which decreases the typical dawn-to-dusk ionosphere electric field. This results in a weaker dayside reconnection contribution to the CPCP during northward IMF.