The Astronomy Picture of the Day page has an interesting photograph ofa green and black aurora, plus an explanation of what causes the blackgaps between the green curtains: http://antwrp.gsfc.nasa.gov/apod/ap060329.html
The Astronomy Picture of the Day page has an interesting photograph ofa green and black aurora, plus an explanation of what causes the blackgaps between the green curtains: http://antwrp.gsfc.nasa.gov/apod/ap060329.html