What causes an aurora? Basically the Sun sends out hot plasma and charged particles into space, deadly radiation to human life, this is called the Solar wind. When the Solar wind gets to Earth, the Earth's Magnetosphere forces the Solar wind harmlessly around us and out into space. Some of the Solar wind however gets through and is trapped in the Magnetosphere and the Earth's upper atmosphere where it's charged particles collide with the oxygen and nitrogen particles of our atmosphere, the spent energy of the collision is turned into light energy, the greens and the reds we see are called the Auroras. They come and go before you know it. The closer you are to the poles the brighter they are but in high solar activity the Northern lights have been spotted as far south as Southern California. Look to the North in the Northern Hemisphere or South in the Southern Hemisphere on any particular night, if there has been heavy Solar activity chances are during the spring and fall seasons you'll see them, they spread out from the west to east. I just happened to be taking a picture of earthshine on the Moon and noticed they were starting to form, only lasted for a few hours, got a few pics and hope to get more through the spring.
A couple of updates for you. Kaguya the Japanese Lunar Orbiter has released more HD images of the Moon as well as some HD movies. Also, and I have discussed this previously here, the complete lunar photographic record, that is the original filght films from the Apollo project are being duplicated with high resolution scans and are releasing new scans on a daily basis here.
The above image is the hires scan of the week for the Apollo scan project, it is an image of the Apollo 17 landing site taken in 1972, this scan was released March 4th. The Kaguya image, ( top lunar image) was also of the Apollo 17 landing site, taken November 19/2007 released March 6th.
I would like to leave you now with one of my Aurora images as an animated gif.