Aurora Borealis, or the northern lights, is a phenomenon of shine in the night sky, which is caused by luminescence of nitrogen and oxygen in the atmosphere of the Earth ionized by charged particles of the solar wind, which are deflected by the magnetic field of the Earth to the areas near the northern pole.
Aurora Australis, or the southern lights, is a similar effect caused by the oppositely charged particles near the southern pole. Particles of opposite charge are attracted to opposite poles.
In modern English it is recommended not to capitalize the first letters in these terms and to write "aurora borealis" and "aurora australis".
Auroras are visible in the night time. In the areas close to the poles winter nights are long and may last 20 or more hours a day. In the latitudes higher than the polar circles nights may last several months in winter, up to half a year on the poles, and days may last up to half a year in summer.
With modern electronic equipment it is possible to detect auroras in the daytime, when they are not visible with the naked eye. Scientists established that auroras have similar intensity near the north and the south poles. This intensity increases and decreases simultaneously near both poles, depending on the intensity of the solar wind.
As the magnetic poles do not coincide with the geographical poles, and auroras appear around magnetic poles, the latitudes, at which auroras are visible, vary depending on the longitude. For instance, currently aurora borealis can be seen in Canada in latitudes much to the south from the latitudes, in which it can be seen in Russia.
The intensity of auroras depends on the intensity of the solar wind, which is the flow of charged particles, mainly protons and electrons, emitted by the Sun. This flow is not stable and changes depending on the activity of the Sun. Events such as coronal mass ejections (CME) may increase the intensity of the flow manifold, and when the ejection is directed to the Earth or very closely, the auroras are especially strong and can be seen in territories, where usually they are not observed. For instance, in 2012 due to a powerful CME aurora borealis was observed in Quebec and Ontario. And in extremely powerful CME directed to the Earth, which happened in 1859 and is called now the Carrington Event, aurora borealis was observed even in areas close to the equator, such as islands in the Caribbean Sea.
Astronomers observe auroras near the magnetic poles of other planets, which have magnetic field. But there is nobody on those planets to admire or worship them or to be scared of them.
The dominating color of the auroras on the Earth is green. Red and blue colors are also present. These colors are determined by quantum levels of excitation of electrons in atoms of nitrogen and oxygen. The lights in the sky may shift every second or may stay unchanged for hours.
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