NASA mission reveals what causes northern lights to dance

[img_assist|nid=6770|title=Click on image to enlarge or download|desc=This artist’s rendition shows how a substorm might look from space. A substorm is a type of violent space weather event that releases solar energy previously trapped in the Earth’s magnetic field. Illustration courtesy of NASA.|link=popup|align=left|width=160|height=200]NASA scientists have identified what triggers the sudden brightening of the northern lights, a panel announced in a teleconference Thursday.