An examination of magnetosphere-ionosphere-thermosphere coupling during STEVE

The recent discovery that the mysterious optical feature Strong Thermal Emission Velocity Enhancement (STEVE), an east-west aligned and latitudinally narrow purple arc, might be a manifestation of Sub-Auroral Ion Drift (SAID) clearly shows the existence of new modes of energy transfer in the sub-auroral region and major gaps in our understanding of Magnetosphere-Ionosphere-Thermosphere (M-I-T) coupling. Our current understanding of STEVE is based on a limited set of observations and it is typically associated with “extreme” SAIDs with ionospheric speeds typically exceeding 4-5 km/s. It is further hypothesized that the photochemical reaction between Nitric Oxide (NO) and atomic oxygen (O) drives STEVE’s continuum emissions. In this study, we analyze an extended interval of strong geomagnetic driving when multiple observations of STEVE were made in all-sky imagers distributed across the North American sector. We will compare these STEVE observations with the simultaneous and collocated Sub-Auroral Polarization Streams (SAPS) and SAID flows observed by SuperDARN radars, and Field-Aligned Currents (FACs) determined by the AMPERE project. We will estimate the amount of energy deposited (Poynting flux) into the ionosphere during the STEVE events using SAPS/SAID electric fields and FACs. Finally, we will use NO volume emission rates derived from Thermosphere Ionosphere Mesosphere Energetics and Dynamics (TIMED) Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) to examine the relation between Poynting flux and NO volume emission rates at sub-auroral latitudes during STEVE, and validate if NO plays a role in driving STEVE’s continuum emissions.