Red and green auroras may share electron-driven origins

On the night of May 10, 2024, a powerful solar storm swept across Earth, prompting researchers from Braunschweig Technical University, the Fraunhofer Institute for Surface Engineering and Thin Films, the University of Göttingen, and the Max Planck Institute for Solar System Research to venture outdoors in search of auroras. Experienced observer Sami K. Solanki from the Max Planck Institute recalled his own encounter, excited to capture the rare green auroras near Göttingen.

However, their photographs revealed something unexpected - a reddish glow emanating from above the green auroras, with bright rays connecting the two hues in a manner never documented before. This phenomenon, described by Bruce T. Tsurutani, the study's lead author and former NASA scientist, suggests that a shared mechanism may drive both red and green auroras.

The May 10 storm, one of the most intense magnetic storms in the space age, triggered bright rays extending from the red aurora down to the green. The mechanism behind red auroras has been the subject of extensive research, with theories offering various explanations. However, testing these hypotheses has been limited due to the difficulty of accessing the auroral region.

Green auroras, typically observed in polar regions, occur when fast-moving electrons from Earth's magnetosphere collide with oxygen atoms, causing them to glow green. The May 10 photographs now provide evidence supporting the idea that the same physical process may be responsible for both red and green auroras. Researchers are encouraging the public to contribute by sharing photographs of future auroras, using a short exposure time of no more than six seconds to capture the telltale rays.