This photo shows green "curtains" of the aurora borealis (Northern Lights). The picture was taken in Alaska in April 2001.
Click on image for full size
Image courtesy of Jan Curtis.
The aurora is formed
when protons and electrons from the Sun travel along the Earth's magnetic field lines
. These particles from the Sun are very energetic. We are talking major-league energy, much more than the power of lightning: 20 million amps at 50,000 volts is channeled into the auroral oval. It's no wonder that the gases of the atmosphere light up like the gases of a streetlamp!
The aurora is also known as the northern and southern lights. From the ground, they can usually be seen where the northern and southern auroral ovals are on the Earth. The northern polar auroral oval usually spans Fairbanks, Alaska, Oslo, Norway, and the Northwest Territories. Sometimes, when the Sun is active, the northern auroral oval expands and the aurora can be seen much farther south.
The lights of the aurora come in different colors. Oxygen atoms give off green light and sometimes red. Nitrogen molecules glow red, blue, and purple.
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