Oct. 13, 2020: Arctic photographer Rayann Elzein sees auroras all the time over Utsjoki, Finland. But the auroras he saw last night were different. “They were red,” he says. “Almost only red.”
“Rarely have I seen anything like this before,” says Elzein. “I double-checked the white balance on my camera to make sure nothing was wrong. But it was the same color temperature as on all my other northern lights pictures.”
“Later, we were treated to the usual swirls of green and even some pink nitrogen fringe,” he says. “When the green swirls calmed down, the red returned.”
Auroras are normally green–the verdant glow of oxygen atoms about 150 km above Earth’s surface. Rare red auroras are also caused by oxygen atoms, but at higher altitudes between 150 km and 500 km. At those heights, the temperature and density of the atmosphere favors atomic transitions that emit red photons. Indeed, Elzein’s photos show red stacked on top of green just as theory predicts.
For some reason, unknown to us, the solar wind on Oct. 12th excited oxygen at higher altitudes than usual, giving rare red auroras their chance to shine. Aurora alerts: SMS Text.