It was totally blue,” says Wright, a veteran guide who has witnessed hundreds of geomagnetic storms. “I’ve never seen anything quite like it!” In Tromso, Norway, Daniel Drelciuc saw it, too–“a big blue mass next to the classic green aurora,” he says. In auroras, blue is a sign of nitrogen. Energetic particles striking ionized molecular nitrogen (N2+) at very high altitudes can produce a cold azure glow, most often seen during intense geomagnetic storms. Last night, however, geomagnetic activity was not intense.