RARE RED AURORAS: It's not easy for Earth's atmosphere to make red auroras. Even longtime Arctic photographers and tour guides rarely see them. Yet, on March 10th, there they were:

https://imgur.com/EVULaSh

Rayann Elzein sends this picture from Utsjoki in the Finnish Lapland. "The red auroras looked pale white to my unaided eye, but a quick exposure with my camera revealed their true color."

What's so tricky about red? The action, if you can call it that, takes place more than 150 km above Earth's surface. At that high altitude, oxygen atoms excited by solar wind slowly spit out red photons. Emphasis on slowly. The radiative lifetime of the transition is 110 seconds--an eternity at the quantum scale. The atoms must remain undisturbed that long to produce their red light.

Perhaps that's why red auroras often appear when conditions are quiet. "The solar wind speed last night was quite low and there was no expectation of a geomagnetic storm," says Elzein. Tonight is expected to be quiet as well. Red auroras, anyone?

[link to www.spaceweather.com (secure)]