Light glows on the horizon, dies out, and then comes back to life arching over the sky.  These extraordinary light rays are followed by more arches embedded with small waves and curls of light.  Within only a few minutes the Aurora illuminates the sky.  The sky is filled with this curtain of light that flickers overhead.  The colors of the aurora blend together and weave into each other capturing the sky.  At the same time rays of light shoot down from space -- a sign that greater action is yet to come.  The aurora keeps on disappearing and reappearing providing a great fireworks display.  Directly over head the center of the aurora -- the corona -- seems to spread its rays in all directions, calling one and all to witness this breathtaking phenomena.
 
 

    Such a magnificent event as the aurora cannot be without its set of legends, myths, and superstitions explaining its occurrence.  Two of the many beliefs follow.

    The Inuits of Hudson Bay believed the sky was a dome with holes.  They believed on the other side of the dome were the heavens.  The spirits of the dead were to go out of the earth through the holes and enter the heavens.  To guide the these spirits into the heaves torches ( auroras ) guided them.

    During the middle ages the belief was that soldiers who gave their life in battle were allowed to fight forever in the skies.  The auroras were these dead soldiers fighting.  The following painting is one explaining this belief.

   To understand why auroras occur we must start our journey on the sun.  To be more specific we must start in the suns atmosphere, which is also known as the corona.  The corona's temperature is several millions of degrees in Celsius.  Collisions are so violent at this temperature that hydrogen atoms disintegrate forming plasma -- which is a gas made up of electrons and protons.    The plasma is also called solar wind. The solar wind escapes from the sun's atmosphere through a  hole in the sun's magnetic field and makes its way towards the Earth.  This journey takes anywhere from 2-5 days.  Sunspots are a sign of solar activity and therefore the amount of sunspots corresponds to the amount of plasma that escapes the suns atmosphere as the graph below indicates.

    The above picture is a drawing of the magnetic field lines (magnetosphere) of the earth.  The upper layer of the Earths atmosphere is the ionosphere which is a layer that conducts electricity or charged particles like plasma.  The solar wind becomes trapped in the magnetic field of the earth, and travels as current.  These the charged particles that make up the solar wind are accelerated  down the magnetic field lines till they hit the gases in the Earth's atmosphere.  The collisions that occur give of energy  that we see as colored light.

    The weaker particles get trapped in the weaker part of the magnetosphere and can be seen closer to the poles. The stronger particles get trapped in the stronger part of the magnetosphere and can be seen closer to the equator.
 
 

Internal Brightness Coefficient (IBC)	Description	Recommended Exposure (in sec)
0	Sub visual; can be detected with photography.	----------
1	Weak; intensity is like that of the Milky Way	20-30
2	Comparable to moonlit cirrus clouds.	10
3	Quite Strong; Comparable to moonlit cumulus clouds	1-2
4	Strong; rare at mid latitudes	.25

 
 
 

Type	Color
A	Green with top fringes red.
B	Green with red bases.
C	Green
D	Red
E	same as type B
F	Blue or Purple

        The auroras in the northern hemisphere are called The Northern Lights or Aurora Borealis.  The auroras in the southern hemisphere are called The Southern Lights or the Aurora Australis.  When auroras occur The Northern Lights and The Southern Lights have symmetrical patterns.

    The colors given off by the aurora depend on the gas in the atmosphere.  Every gas has its own distinct color.  Oxygen gives of green and red color.  Nitrogen gives of red color.