Aurora Borealis, Arctic Circle, 2002

A leggy evergreen looms over a stretch of Arctic boreal forest as light from the aurora borealis paints the night sky emerald green.

These natural fireworks shows, also called the northern lights, occur when solar wind—electrically charged particles blasted from the sun—collides with atoms in the upper atmosphere over the Earth's magnetic poles.

(Photo shot on assignment for, but not published in, "Boreal: The Great Northern Forest," June 2002, National Geographic magazine)