Aurora Borealis is made when storms on the the sun form solar winds, or large
streams of charged particles streaming toward the earth.These streams could
have upward of ten million megawatts of electrical power. That is enough power
to light up Los Angeles. It generally takes about three days for these streams
of particles to reach the earth's upper atmosmere, or ionosphere. When these
charged particles hit the earth's atmosphere, they exite the atoms contained
in the atmosphere. These excited atoms have a higher energy state that usual
and so want to get back to a more normal energy state. The excited atoms give
off excess energy in the form of heat, or the case of the aurora borealis, light.
The trillions of excited atoms give off enough light so that we can see the
light from where we live on the ground, 43-200 miles above us. Below is a picture
of the sun giving off a solar flare: the source of it all!