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The Basics of Auroras
Auroras can be found at both the northern and southern poles. The northern variety is called the Aurora Borealis, and the southern variety is called the Aurora Astralis. Obviously, the Northern Lights can only be seen in the Northern Hemisphere while the Southern Lights can only be seen in Southern Hemisphere.
They are displays of light typically found in the night sky and occur in the ionosphere. When a person is closer to the magnetic north pole, there is a greater possibility of viewing the Aurora Borealis. Auroras usually give off a green hue, but sometimes they have a reddish tint. Also, auroras have been spotted on other planets, such as Jupiter and Saturn.
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The Causes of Auroras
Massive amounts of electrons are emitted from the Sun and carried on the solar wind. The aurora is produced when these electrons, attracted by the magnetism at the Earth's poles, slams into the atmosphere. When the electrons collide with the oxygen and nitrogen atoms, the atoms are ionized, and this ionization causes the atoms to become excited and emit photons of light.
Different auroral colors are produced depending on the kind of atom involved with the collision. Oxygen generally produces shades of colors ranging from green to brown, and nitrogen produces shades of red or blue. Auroras are more often seen during the intense phase of the Sun's cycles, such as during coronal mass ejections. These increase the solar winds that are responsible for the creation of the auroras. Auroras can appear as either a faint glow in the sky or as curtains which slowly change shape.
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The Mechanics of Auroras
As mentioned, the solar winds are responsible for the auroras. The way in which they produce this effect is that the solar winds consist of ionized gas, otherwise known as plasma. Plasma conducts electricity, and when a electrical conductor is placed within a magnetic field, such as the magnetosphere, the electricity flows across the magnetic field. The amount of electricity is great enough to then extract energy from the flow of the solar winds.
The entirety of how auroras take their shape have yet to be completely determined. Both Jupiter and Saturn have much stronger magnetic fields at their poles, and auroras have been observed on these planets. Auroras have also been observed on Uranus and Neptune. The combination of the solar winds and strong magnetic fields at the poles are most obviously responsible for the appearances of auroras, yet exactly what causes them to take the shape that they do is not completely understood. Nevertheless, understanding the mechanics of the Aurora Borealis does not subtract in any way the enjoyment of this natural beauty.
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picture credit: http://www.sxc.hu/photo/1174630%20(Dave Dyet)