Observations at sub-auroral latitudes of airglow structures associated with STEVEs and SAR arcs

Typical optical observations at sub-auroral latitudes consist of stable auroral (SAR) red arcs. These arcs are the result of magnetosphere-ionosphere coupling at L-shell values ~3-4 and have been thoroughly studied. SAR arcs are narrow in latitude, last for several hours and extend thousands of kilometers in longitude. One of the main characteristics is that they are monochromatic, observed only in 630.0 nm. Their location coincides with the region where fast westward flows, i.e. SAPS/SAIDs, are observed. A newly discovered optical phenomenon named STEVE ( Strong Thermal Emission Velocity Enhancement) has been observed at similar latitudes. STEVEs are thinner than SAR arcs, their lifetimes are much shorter, and they are observed at multiple wavelengths. But they share some common characteristics: they are observed in the same region where fast westward plasma flows exist and satellite measurements at higher altitudes detect similar perturbations in electron temperature and ion density. Thus, while the community is still trying to identify the sources of STEVE, there are efforts trying to find if SAR arcs and STEVEs are related or not. In this work we use multiple sub-auroral all-sky imagers to investigate a bright arc that can be catalogued as a STEVE or a SAR arc. In addition to the optical data we use SWARM and DMSP satellite data from a wide longitude sector covering ~50 W to ~120 W to investigate how the electron temperature and ion density compare with the optical observations.