A peculiar whitish and gray spot that occasionally appears next to the northern lights is no longer a mystery. A team of researchers from the University of Calgary has managed to explain this phenomenon for the first time, revealing new complexities in the largest natural spectacle of the night sky, according to a study published in Nature Communications.
“You see this dynamic green aurora, you see some of the red aurora in the background and, suddenly, you see this structured emission – almost like a patch – of gray or white tones connected to the aurora,” describes Dr. Emma Spanswick, lead author of the study and associate professor in the Department of Physics and Astronomy. “So any scientist’s first response is, ‘Well, what is that?'” Spanswick says.
Although this phenomenon had already been mentioned in previous scientific publications, according to a statement from the University of Calgary, No one had been able to explain its origin. Current research reveals that this is “undoubtedly a heat source” and suggests that the northern lights are more complex than previously thought.
STEVE vs. the white spot: two unique phenomena
The discovery bears similarities to another rare atmospheric phenomenon recently described and known as STEVE (Strong Thermal Emission Velocity Enhancement), a long, glowing ribbon of purple light. However, there is a crucial difference: while STEVE appears separated from the aurora as a large band crossing the sky, this new emission is practically embedded in it – and can span sizes of tens to hundreds of kilometers – making it more difficult to distinguish.
The chemical secrets of the polar atmosphere
Although it appears to share the same type of continuous emission as STEVE, it is still not entirely clear what chemical rearrangements cause it. The authors consider that the atmosphere warms locally in the area of the spot, which would trigger the reactions that generate white light.
The key to unraveling the mystery came from high-resolution sensors such as those of the Transition Region Explorer (TREx) project, promoted by the University of Calgary and financed in part by the Canadian Foundation for Innovation, the Government of Alberta and the Canadian Space Agency. These new cameras, along with the popularization of digital photography, have allowed specialists and amateurs to capture real-color images of the night sky and discover details that were previously difficult to perceive.
“Everyone has realized the advance of digital photography. Now your phone can take photos of the aurora,” explains Spanswick.
The polar sky continues to reveal its secrets thanks to technological advances, and this enigmatic whitish spot reminds us that Arctic nights hold wonders beyond the iconic green curtains of the auroras, in an atmospheric spectacle that never ceases to surprise us.
Edited by Felipe Espinosa Wang with information from the University of Calgary, Nature Communications, Science Alert and The Debrief.
