What causes Northern Lights?

(Lansing State Journal, June 24, 1992)

Question submitted by:  Angie Lewis

Our sun is continually spewing positive ions (positively charged parts of atoms) into space due to the nuclear processes that keep it burning.

The flow of ions, which occurs in all directions, is called the Solar Wind and is actually a stream of protons, or hydrogen nuclei.  When the particles that make up this wind near the Earth, they tend to be funneled toward the Earth’s poles by Earth’s magnetic field.  When they reach our atmosphere, they are moving fast they knock electrons out of atoms in the upper atmosphere.

When those loose electrons are caught by another atom, light is emitted.  The color of light depends on the type of gas, or atoms, involved.  Each type of gas emits a characteristic color when it captures an electron.

Green is oxygen, red hydrogen, and blue nitrogen.

This light is what we see as the Northern Lights, or Aurora Borealis.  They are called Northern Lights because the poles of the Earth’s magnetic field are near the north and south poles.  Light seen around the south pole are called the Southern Lights or the Corona Borealis.

Sometimes, the flow of ions from the sun gets stronger, and the Northern Lights can reach closer to the equator then they might otherwise.  Last June and November had spectacular displays because the sun was in one of its active phases.  It was so intense that even people as far south as Texas and Tennessee saw the lights.  This activity cycle is a long one (about 11 years), so keep you eyes on the sky this summer.

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