Interactive Ion-Neutral Dynamics in the Low Latitude Evening Ionosphere

Neutral winds in the ionosphere drive global electrodynamic phenomena which alter theupper-atmosphere so significantly that they can affect the orbit of satellites andground-to-spacecraft communications. Understanding these winds and what drives them is centralto prediction and risk management associated with such a dynamic upper atmosphere. This studyexamined the relationship between accelerations acting on neutral winds in the ionosphere and theformation of a vertical shear of those winds in low latitudes (between ±30 magnetic) and earlyevening local times (16-22 LT). Accelerations were calculated using variables output by thethermosphere ionosphere electrodynamics general circulation model (TIEGCM) under differentsolar activity and night-time ionization conditions and visualized both spatially and temporally. Ingeneral, with acceleration values averaged along magnetic latitudes between ±30 degrees(inclusive) and only considering medium solar activity conditions, we found that the ionosphereexhibits distinct layering defined by the dominant accelerations in each layer. We also found hintsthat during different night-time ionization levels, ion drag acceleration tends to remain constantwhile ion and neutral velocities change to conserve the difference between them. When consideringspecific latitudes and solar conditions, previously unreported structures appear which involveinteractions between the ion drag and viscous forces.