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Welcome to Northern Lights by Cameron |
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| Auroras, sometimes called the northern and southern (polar) lights or aurorae (singular: aurora), are natural light displays in the sky, usually observed at night, particularly in the polar regions. They typically occur in the ionosphere. They are also referred to as polar auroras. 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.[1] | Aurorae are produced by the collision of charged particles from Earth's magnetosphere, mostly electrons but also protons and heavier particles, with atoms and molecules of Earth's upper atmosphere (at altitudes above 80 km (50 miles)). The particles have energies of 1 to 100 keV. They originate from the Sun and arrive at the vicinity of Earth in the relatively low-energy solar wind. |
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Aurorae seen near the magnetic pole may be high overhead, but from further away, they illuminate the northern horizon as a greenish glow or sometimes a faint red, as if the sun was rising from an unusual direction. The aurora borealis most often occurs from September to October and from March to April. The northern lights have had a number of names throughout history. The Cree people call this phenomenon the "Dance of the Spirits." |
| The aurora borealis is also called the northern
polar lights, as it is only visible in the sky
from the
Northern Hemisphere, the chance of visibility
increasing with proximity to the
north magnetic pole, which is currently in the
arctic islands of northern
Canada. When the trapped
magnetic field of the solar wind is favourably
oriented (principally southwards) it connects with
Earth's magnetic field, and solar particles enter
the magnetosphere and are swept to the magnetotail.
Further magnetic reconnection accelerates the
particles towards Earth.
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The collisions in the atmosphere electrically excite atoms and molecules in the upper atmosphere. The excitation energy can be lost by light emission or collisions. Most aurorae are green and red emissions from atomic oxygen. Molecular nitrogen and nitrogen ions produce some low level red and very high blue/violet aurorae. The light blue and green colors are produced by ionic nitrogen and the neutral nitrogen gives off the red and purple color with the rippled edges. Different gases interacting with the upper atmosphere will produce different colors, caused by the different compounds of oxygen and nitrogen. The level of solar wind activity from the Sun can also influence the color of the aurorae.
ALL of this info was found on Wikipedia .com |