Neutral Winds in the Nighttime Auroral E‐Region From Ionization Gauges on the VortEx Sounding Rockets

Abstract

Neutral winds are a crucial parameter for studying and understanding the dynamics of Earth's Mesosphere‐Lower Thermosphere (MLT). The NASA Vorticity Experiment (VortEx) sounding rocket mission conducted two nighttime campaigns from Andøya Space Center, with low‐apogee instrumented payloads (∼150 km) launched within 2 min of high‐apogee TMA wind‐tracer payloads. The first campaign (VortEx‐1) took place on 23 March 2023 while the second campaign (VortEx‐2) was conducted on 10 November 2024. In addition to Langmuir/electric probes, the instrumented payloads included commercial off‐the‐shelf (COTS) hot‐filament ionization gauges (IGs): an axial‐mounted gauge to monitor neutral density and temperature, and a side‐mounted gauge to measure horizontal neutral wind. On a rotating payload, a side‐mounted gauge observes a perturbation caused by the neutral wind in addition to the generally ram‐directed flow. The in situ neutral wind measurements presented here from the VortEx‐1 and VortEx‐2 missions show wind magnitudes and shear consistent with concurrent electrodynamic conditions and are cross‐validated with independent chemical tracer‐derived winds and multistatic meteor radar horizontally resolved wind fields, typically to within 10 m/s. The results presented in this work validate in situ neutral wind measurements using low‐cost COTS ionization gauges, enabling rocket launches at any time of day, supporting new sounding‐rocket investigations that require neutral wind measurements in the MLT.