Interactive Ion-Neutral Dynamics in the Low Latitude Evening Ionosphere

Abstract:

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