An aurora borealis in the Canadian sky
Swirling northern lights
The aurora borealis over Wapusk National Park in Manitoba, Canada
Yellow-green northern lights over trees
Aurora borealis at dusk
The aurora borealis at night
The aurora borealis at night
The aurora borealis in Churchill, Canada
Aurora borealis above the Mackenzie River in the Northwest Territories, Canada
The aurora borealis above evergreens in the Canadian night sky
Aurora borealis in Canadian sky
The northern lights above Manitoba, Canada
Northern lights over trees
North Pole aurora
Northern lights over snow
Northern lights
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Aurora Borealis, Churchill, Canada
An aurora borealis glows brightly over Churchill, Canada. Auroras occur when charged particles outside the Earth's atmosphere collide with atoms in the upper atmosphere. The result: a glowing display of curtains, arcs, and bands in the sky. The phenomenon is called aurora borealis or northern...
Photograph by Norbert Rosing

Patterns in Nature: Auroras

See aurora pattern photos, from National Geographic.