11:30 AM - 11:45 AM
[PEM15-09] Observation of Fragmented Aurora-like Emissions and Picket Fence Structures on the Poleward Edge of the Auroral Oval
Keywords:Fragmented aurora-like emission, picket fence, aurora, all-sky cameras, Swarm satellite
We report on the observation of fragmented aurora-like emissions (FAEs) and picket fence structures using an all-sky color digital camera in Skibotn, Norway, on January 1, 2025. FAEs have previously been observed in Svalbard, a polar cap region (Dreyer et al., 2021; Whiter et al., 2021; Partamies et al., preprint to ANGEO, 2024; Herlingshaw et al., 2024), while picket fence structures have been observed in the subauroral zone (Nishimura et al., 2023; Gilles et al., 2020; Archer et al., 2019; MacDonald et al., 2018). However, this time we observed both phenomena in the auroral oval for the first time.
This event occurred during the early recovery phase of a magnetic storm that began in the afternoon of December 31, 2024. Since New Year’s Eve night, intense auroral activity persisted over northern Scandinavia. At approximately 17:30 UT on January 1, a substorm was triggered, with a maximum AE index of ~2000 nT. This substorm was accompanied by a very bright aurora breakup and strong cosmic noise absorption was recorded by the spectral riometer in Kilpisjärvi, Finland, indicating precipitation of high-energy electrons.
During the first 30 minutes after the onset, intense auroral activity and cosmic noise absorption were observed. Subsequently, red aurora (630.0 nm) with shear structures became dominant. In addition to these auroral emissions, FAEs appeared as small-scale, localized green emissions with several kilometers of spatial gaps. FAEs are known to lack field-aligned structures, suggesting that electromagnetic waves in the ionosphere play a key role in their formation (Dreyer et al., 2021; Whiter et al., 2021). However, in this study we observed FAEs that have field-aligned structures, implying that magnetospheric instabilities may influence the generation of FAEs.
Additionally, we also observed FAEs without field-aligned structures, similar to those documented in previous studies, as well as picket fence structures, which are typically associated with STEVE. In the presentation, we will discuss the similarities and differences between these structures and explore their possible generation mechanisms.
This event occurred during the early recovery phase of a magnetic storm that began in the afternoon of December 31, 2024. Since New Year’s Eve night, intense auroral activity persisted over northern Scandinavia. At approximately 17:30 UT on January 1, a substorm was triggered, with a maximum AE index of ~2000 nT. This substorm was accompanied by a very bright aurora breakup and strong cosmic noise absorption was recorded by the spectral riometer in Kilpisjärvi, Finland, indicating precipitation of high-energy electrons.
During the first 30 minutes after the onset, intense auroral activity and cosmic noise absorption were observed. Subsequently, red aurora (630.0 nm) with shear structures became dominant. In addition to these auroral emissions, FAEs appeared as small-scale, localized green emissions with several kilometers of spatial gaps. FAEs are known to lack field-aligned structures, suggesting that electromagnetic waves in the ionosphere play a key role in their formation (Dreyer et al., 2021; Whiter et al., 2021). However, in this study we observed FAEs that have field-aligned structures, implying that magnetospheric instabilities may influence the generation of FAEs.
Additionally, we also observed FAEs without field-aligned structures, similar to those documented in previous studies, as well as picket fence structures, which are typically associated with STEVE. In the presentation, we will discuss the similarities and differences between these structures and explore their possible generation mechanisms.