What are the Colors of the Aurora?
Auroral displays appear in many colors with pale green and pink the most common. However, different shades of red, yellow, green, blue, and violet have all been observed. The brightest auroral color is generally a green light emitted by excited oxygen atoms. A red diffuse glow results from another oxygen atom transition. A purple color results from a transition in a Nitrogen molecular ion. The mixture of the major green, red and purple emissions may combine to give aurora a general 'whitish' appearance. The color variations are a product of the altitude of the storm, and the density and composition of the ions at that altitude. The folding effect results from the electric field induced on either side of the auroral curtain by the electrons.
Where do Auroras Occur?
The global distribution of auroral activity is an oval around the magnetic poles in both hemispheres. As the level of magnetic disturbance of the Earth's magnetic field increases, the oval of auroral activity expands equatorward. Known as 'Aurora borealis' in the north, auroras occur in the upper atmosphere of both poles and are occasionally visible from middle latitudes as a dark red glow near the poleward horizon.
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