A team of physicists from the University of Iowa (USA) has identified a hitherto unknown type of aurora. It takes place when the diffuse aurora, a tiny glow that remains in the background after the most striking brightness of traditional auroras, darkens and suddenly reappears to offer us all its splendor in the night sky.
In March 2002, physicist David Knudsen noticed something extraordinary while observing the auroras in northern Canada. After filming the aurora, the matter stayed there. Almost two decades later, the video they recorded at that time has been studied intensively and it turns out that the auroral phenomenon they saw in 2002 had not been recorded before.
Physicists still don’t understand what caused this curious aurora or how often it occurs, but it is clear that we are now on the way to find out. It is unusual that this new and elusive type of aurora was observed in a video made 19 years ago by a physicist and that it has never been described in the scientific literature before.
The video, recorded on March 15, 2002 in Churchill, a city in northern Manitoba, Canada, on the west coast of Hudson Bay, was not seen by the eyes of the observers. Despite clear skies and a location reasonably close to Earth’s north geomagnetic pole, none saw it, but the camera did . It was sensitive enough to capture the diffuse auroral background and dimming events.
“A diffuse, pulsating ‘dimming’ glow, which then fills in for several seconds,” Knundsen wrote in his notes.
The researchers ‘christened’ the phenomenon “fuzzy auroral drafts.”
“I knew there was something there. I knew it was different and unique . I had some ideas on how to analyze it, but hadn’t done it yet. I gave it to Riley and he went much further by discovering his own way of analyzing the data and producing some meaningful conclusions, ”explains Allison Jaynes, co-author of the study published in the Journal of Geophysical Research.
The physics that trigger these auroras in the upper atmosphere and their connection to the Sun’s outbursts became understandable at least six decades ago but we continue to find many new and puzzling aspects, such as the narrow reddish-pink band nicknamed Steve, an atmospheric optical phenomenon that appears as a ribbon of purple and green light in the sky and which was named as such in late 2016 when seen in Alberta (Canada).
What specific process is behind the hiding and reappearance of parts of the diffuse aurora that are seen in the new variant? At the moment it is unknown; many unknowns remain to be solved.
Knudsen’s video is two hours long, during which they counted up to 22 “erasure events.” Although they cannot explain what causes them, by including them in the scientific literature, they can put aurora watchers in search of a new repeat of the phenomenon, hopefully allowing us to learn more about them.
Referencia: The Diffuse Auroral Eraser. R. N. Troyer, A. N. Jaynes, S. L. Jones, D. J. Knudsen, T. S. Trondsen. Journal of Geophysical Research: Space Physics (2021).DOI:https://doi.org/10.1029/2020JA028805
