This was taken from the Allan Brooks Nature Center during a RASC Astronomy outreach last night. As the Aurora moved in, it appeared like a white fog, but when you took a long exposure picture, you could see the green aurora appear.
This series of images was taken between 11:00 pm and midnight. Exposures were 5 seconds each (F/3.5 ISO-400), every 15 seconds on a Nikon D5200 18-55 mm lens.