Neutral Wind Dynamics in High‐Latitude Regions During the 17 March 2013 Storm

Abstract

Neutral winds play a critical role in transporting mass, momentum, and energy throughout the upper atmosphere. During geomagnetic storms, momentum is transferred to the thermosphere primarily through ion–neutral collisions, along with other forces. This study investigates high‐latitude neutral wind dynamics during the 17 March 2013 storm using the Global Ionosphere Thermosphere Model. We analyze the five acceleration terms—pressure gradient, viscosity, ion drag, Coriolis, and advection—across altitudes, at selected locations, and statistically across defined high‐latitude regions. These regions are categorized based on electron energy flux into auroral oval, polar cap, and subauroral boundaries using the Feature Tracking Empirical Model of Auroral Precipitation (FTA). It was found that above 300 km, pressure gradient dominated across all regions, followed by viscosity. The latter was driven by vertical shear in horizontal winds and amplified by decreasing mass density. Below 300 km, acceleration profiles varied by region: advection dominated in the polar cap, while pressure gradient was the leading driver in subauroral region, and dominated alongside ion drag in the auroral oval. Temporally, ion drag was most pronounced during the early storm main phase, then declined as the storm progressed due to O/N ₂ depletion, which reduced TEC and consequently ion‐neutral collision frequency. Spatially, ion drag was strongest within the auroral oval and increased with enhanced electron energy flux. These results revealed an underestimated pathway in which pressure gradients and ion drag in E and F1 layers generate horizontal shear, driving a viscous acceleration response at higher altitudes.