Once in a while I post pictures from a favorite book of mine called "Astronomy, 365 days". It was given to me as a Christmas gift last year and I love the fact that it displays astronomy pictures for each day of the year.
For the 4th of November the picture in the book depicts a fish-eye view of a colourful auroral corona near Quebec, Canada. The reds and green are absolutely vivid and create an abstract painting in the night sky.
The Auroras, or also called the Northern Lights are spectacular light shows that can be observed in the nights sky near to polar regions. They are most frequent around the equinoxes; that means from March to April and September to October. In northern latitudes, the effect is known as the aurora borealis, named after the Roman goddess of dawn, Aurora, and the Greek name for north wind, Boreas, by Pierre Gassendi in 1621. The auroras, both surrounding the north magnetic pole (aurora borealis) and south magnetic pole (aurora australis) occur when highly charged electrons from the solar wind interact with elements in the earth's atmosphere.
As the electrons enter the earth's upper atmosphere, they will encounter atoms of oxygen and nitrogen at altitudes from 20 to 200 miles above the earth's surface. The color of the aurora depends on which atom is struck, and the altitude of the meeting.
* Green - oxygen, up to 150 miles in altitude
* Red - oxygen, above 150 miles in altitude
* Blue - nitrogen, up to 60 miles in altitude
* Purple/violet - nitrogen, above 60 miles in altitude
Although I live in the north, I have yet to experience the magic of Northern Lights. The only Aurora I was familiar with as a child was oddly enough a ship. Or rather a Russian cruiser that became a symbol for the Russian Revolution, as it was taught to us in school in the former communist bloc. On the 7th of November 1917 (25th October 1917 in Julian calendar), the refusal of an order for the Aurora to take to sea sparked the October Revolution. At 9.45 p.m. on that date, a blank shot from her forecastle gun signaled the start of the assault on the Winter Palace, which was to be the last episode of the revolution.