Northern lights – in pictures

The northern lights, or aurora borealis, dance across the sky in Ozark, Arkansas, US Photograph: AP

The photographer, Brian Emfinger, a storm chaser, said these were only the second northern lights in a decade he had seen this far south Photograph: Brian Emfinger/AP

The lights are caused by charged particles spewed out by the sun striking the upper atmosphere Photograph: Brian Emfinger/AP

The northern lights over West Grand Traverse Bay near Traverse City, Michigan Photograph: Jan-Michael Stump/AP

A 27 September picture of the northern lights over Hines, Minnesota Photograph: Justin Dernier/Corbis