Impact of Solar Wind Dynamic Pressure on Polar Electrojets and Large- and Small-Scale Field-Aligned Currents

This study examines the impact of the solar wind dynamic pressure (Pd) on the peak current density and latitude of polar electrojets (PEJs), large-scale field-aligned currents (LSFACs), and small-scale FACs (SSFACs) in various local times, seasons, and hemispheres, using Swarm observations during 2014 to 2020. The different Pd effects with enhanced solar wind mass density (Nsw effect) or with enhanced solar wind velocity (Vsw effect) are differentiated. LSFACs and PEJs show pronounced hemispheric and seasonal differences around noontime, where summer variations are more pronounced than winter, due to higher solar EUV conductivity. Increased Pd typically enhances LSFACs, except at midnight when opposing effects from Nsw and Vsw exert on poleward-side FACs. The impact of Vsw on FACp surpasses that of Nsw mostly except for midnight. In contrast, the Nsw impacts on equatorward-side FACs and SSFACs are mostly stronger than the Vsw effect except for the noontime. PEJs strengthen with increasing Vsw effects more efficiently than with increasing Nsw effects. Additionally, a higher Pd shifts PEJs and SSFACs equatorward, with Vsw effects being more prominent than Nsw effects, except for midnight SSFACs.