I saw them in central southern Ontario during a winter exercise when I was in the forces. I was the poor sap stuck monitoring the radio, and at a certain point a transmission vanished into a blast of crackles. I poked my head out of the tent to see if anyone else had noticed "trouble on net", and immediately saw the reason: the sky was full of white and green shimmers. It lasted about 45 minutes, and the exercise just stopped until it was over.