Northern Lights

has anyone actually seen the Aurora with their naked eyes. I haven't, I want to but I haven't....Yet!. I will discuss how the auroras actually happens, that is, the physics or astrophysics behind it.

The Northern Lights are aurorae, colored (usually red or green)
patterns seen as rays, arcs, or "curtains" in the sky that are produced
when particles from the solar wind  hit the upper atmosphere of the Earth. 

What actually happens is that high energy particles from the sun (mostly electrons)
collide with atoms in the upper atmosphere, causing
the atoms to be ionized (lose electrons).  The ionized atoms then
spiral along the Earth's magnetic field, and move toward the north
and south magnetic poles. 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

 As they move, they give off light of different wavelengths in nanometers (nm):

• Green--495–570 nm

• Red---620–750 nm

• Blue--450–475 nm

• Purple/Violet--380–450 nm

 Solar winds stream away from the sun at speeds of about 4.5 x 10^5 meters/second. When they reach the earth, some 40 hours after leaving the sun, they follow the lines of magnetic force generated by the earth's core and flow through the magnetosphere, a teardrop-shaped area of highly charged electrical and magnetic fields.
All of the magnetic and electrical forces react with one another in constantly shifting combinations. These shifts and flows can be seen as the auroras  moving along with the atmospheric currents that can reach 1 billion Watts. (In contrast, the circuit breakers in your home will disengage when current flow exceeds 3600 Watts.)
 Usually when there are a lot of sunspots, the lights are farther south,. Sunspot activity follows an 11-year cycle. The next peak will occur in 2011 and 2012,  so you can see the auroras outside the normal time.

Just for your understanding
solar winds are traveling at  4.5 x 10^5 meters/second is equal to 1 million miles per hour!
 1 billion(1,000,000,000,000 Watts) = 20,000,000 Amps at 50,000 Volts
3600Watts = 30Amps at 120 Volts (for your household!!!)


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