Re: Thor 2 -Movie Discussion, News, Interviews, Pics till release 2013
They were surprised that the latest one wasn't an aurora-type phenomenon, so presumably the others were. I'd guess that the barrier between Earth and Asgard was weakest in that area of New Mexico for whatever reason, and they'd see lightshows when the Bifrost was being used to go elsewhere. Hence the fact that they saw one when it Loki was using it as a weapon.
The Old Mixer, chillin' in Connecticut.