What Causes The Northern Lights? (Aurora Borealis)
By FizziksGuy, 08/23/2013
The aurora borealis or northern lights is one of the most spectacular natural displays on the planet. Theories about its origins have been debated for centuries and common misconceptions persist that the aurora is the sun's rays scattered off ice crystals in the high atmosphere. In truth, the light is created more than 100km above Earth's surface as high speed electrons and protons ejected from the sun in a solar flare or coronal mass ejection collide with air molecules in the upper atmosphere. The charged particles from the sun excite air molecules which then de-excite by emitting light. The display is most common around the north and south poles because the Earth's magnetic field deflects the solar wind from the equator to the poles. Here the magnetic field dips towards the Earth's surface, channeling the charged particles into the atmosphere.
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