By Fatma Younis
Photos taken by stargazers during a powerful solar storm in May 2024 have helped scientists unravel the mechanism behind mysterious red glows seen above green auroras.
Unusual images captured during historic storm
On 10 May 2024, Earth experienced its second most intense magnetic storm since 1958 after being struck by a powerful solar eruption. Observers at middle latitudes captured images showing a reddish glow with bright vertical rays extending downward from the red emission to the green aurora below.
The continuous rays physically connecting the high-altitude red glow to the green aurora provided a crucial detail that had not been reported in scientific literature, said Bruce Tsurutani, author of a study published in Annales Geophysicae.
Same process at higher altitude
Researchers compared the images with solar wind data and disturbances in Earth's magnetic field. They found that the same physical process that creates common green auroras operates at even higher altitudes for red auroras. Green lights are produced when fast electrons collide with oxygen atoms at 85 to 130 km altitude. For red auroras, electrons strike sparse oxygen particles at 200 to 800 km, producing a red glow before descending to trigger the green display.
Scientists suspect there may be several distinct types of red aurora. They are calling for more photos taken with exposures of six seconds or less so that streaks appear and stars remain as reference points.
Even as the Sun moves away from the peak of its 11-year activity cycle, strong eruptions can still occur and produce bright auroras in the coming months to years. "Anyone who takes photos of the aurora with a smartphone or camera can contribute to their study," said Yasuhito Narita, a study author from the Technical University of Braunschweig.
