Similar lights in the Australian desert appear related to inversion layers refracting headlights over the horizon (http://www.abc.net.au/science/news/stories/s818193.htm)
Do you have any thoughts on the white flashes? They were the scary part. Everything was perfectly daytime for a split second, and there was no fading of the light like with lightning. It was immediately all white then immediately dark again. It creeps me out thinking about it.
The light on the horizon seemed 50 miles away, but the flash was right on us, extremely bright, and blanketed everything evenly.