Here's something interesting regarding the "sound" the aurora makes . . .
Some people swear that they can occasionally hear sounds from aurora displays similar to what you've described. I read an article about an informal experiment that was done to determine how real these sounds were. A bunch of people were brought outside during a major aurora event -- half of them blindfolded and half of them not. Some of the people who weren't blindfolded reported hearing that hissing/cracking sound, but none of those who were blindfolded reported hearing anything.
Go figure, eh?
Maybe the people looking at the Northern Lights were hearing their brains cook ? Just kidding of course.