STEVE Community Workshop: Expanding our Understanding on the Physics of Extreme Forcing in the Subauroral Region; Fairbanks, Alaska; Spring 2025

The project seeks funds to organize a workshop that would discuss a relatively new upper atmospheric phenomenon referred to as STEVE (Strong Thermal Emission Velocity Enhancements). This manifests in the form of a spectacular optical display in the night skies at lower latitudes than the usual auroral regions. It appears as a distinct mauve ribbon that extends to a broad longitudinal region and is confined in latitude.

This intriguing feature has aroused the curiosity of several scientists resulting in preliminary studies providing new insights into its characteristics. However, detailed work on its formation, drivers with the magnetosphere-ionosphere-thermosphere (MIT) system is required to solve this mysterious phenomenon. To enable brainstorming discussions, this proposal will provide funds for the third STEVE workshop.

Such efforts offer a forum for Geospace scientists to come together, present their recent STEVE-related observations and theoretical work. This provides an excellent opportunity to plan for future experiments, and research activities that will advance scientific knowledge about STEVE, its occurrence and formation mechanisms. It brings professional, citizens/amateurs together, thus enhancing collaborations and initiation of new partnerships.

Recent observations have demonstrated that STEVE spans approximately 400 – 800 nm wavelength regions. It is accompanied by extremely narrow and fast-moving plasma flows channels (~10 km/s) within a region of high electron temperatures in the range of 104 K. These features are indicative of intense subauroral drifts (SAIDs).

Several investigations have indicated that particle precipitation does not appear to play a role in the STEVE occurrence, which is one of the major differences from auroral emissions. The mechanisms behind the highly structured optical emissions associated with STEVE events often referred to as “Picket Fence,” is a topic of significant debate. While early studies suggest a possible link to particle precipitation, the picket fence spectrum remains partially unexplained and stands out from the typical auroral emissions due to the absence of enhanced emission lines.

This has prompted the scientific community to explore alternative generation mechanisms, including parallel electric fields. All these recent scientific advances, which shed light on STEVE, the picket fence, and their possible sources, would not have been possible without the contributions from citizen scientists, who accidentally discovered this phenomenon during their auroral chase.

Some photographs taken by amateurs have played a crucial role in determining the altitude of the STEVE and Picket Fence emissions. The third STEVE workshop plans to discuss the role of chemistry in STEVE formation, association with substorms, relationship with SAR arcs and impact on technological structures.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.