[P-EM12] Coupling Processes in the Atmosphere-Ionosphere System

[PEM12-P05] Aurora-like fragments at the poleward boundary of the auroral oval

*Katie Herlingshaw^1,2, Noora Partamies^1,2, Dan Whiter³, Dag Lorentzen^1,2 (1.University Centre in Svalbard, 2.Birkeland Centre for Space Science, 3.University of Southampton)

Keywords:ionosphere, aurora-like, optics

Aurora-like fragments are an exciting new ionospheric feature in the 557.7 nm emissions that have been recently discovered in 2021 above Svalbard in the High Arctic (78 geographic degrees North). The fragments cannot be considered aurora in the conventional sense as they are not created by particle precipitation and are not field-aligned. They are small in scale (km), short-lived (minutes) and often periodically occurring, where individual fragments show dynamic internal structuring. Their cause is currently a mystery, but an important one to solve as we believe they are visible manifestations of invisible instabilities that occur under strong electric fields.

We present fragment observations identified from one year of Svalbard all-sky camera data, where AI was used to identify periods that were cloud-free and contained aurora. Triangulation techniques were applied to the fragments, which allows an estimation of the emission altitude. High-resolution, narrow field cameras were used to study the fragment dynamics in detail and resulted in the new discovery of exclamation mark shaped fragments. Fragments were frequently observed close to auroral arcs, suggesting there could be coupling between aurora-like and auroral features. We discuss the conditions for fragment formation and suggest possible generation mechanisms.