Auroras, sometimes called the northern and southern (polar) lights or aurorae, are natural light displays in the sky, usually observed at night, particularly in the polar regions. They typically occur in the ionosphere. They are also referred to as polar auroras, and are not seen in more southern and tropical parts of the world.
Auroras are the result of the emissions of photons in the Earth’s upper atmosphere, above 80 km (50 miles), from ionized nitrogen atoms regaining an electron, and oxygen and nitrogen atoms returning from an excited state to ground state. They are ionized or excited by the collision of solar wind particles being funneled down and accelerated along the Earth’s magnetic field lines; excitation energy is lost by the emission of a photon of light, or by collision with another atom or molecule:
- oxygen emissions – Green or brownish-red, depending on the amount of energy absorbed.
- nitrogen emissions – Blue or red. Blue if the atom regains an electron after it has been ionized. Red if returning to ground state from an excited state.
Auroras are common near the Poles. They are occasionally seen in temperate latitudes, when a magnetic storm temporarily expands the auroral oval. Large magnetic storms are most common during the peak of the eleven-year sunspot cycle or during the three years after that peak. (more)
I really love aurora borealis. Although I haven’t seen it directly, I know that aurora borealis are beautiful. Enjoy nice gallery of aurora borealis photographs!
Nice Aurora Borealis Photos
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