Re: How do the Northern Lights work and what are they made of?

Dear Anna,

Thank you for your question. You are lucky to live in Alaska, 
where you can see the Northern Lights! 

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 they move, they give off light.
For instance, when you see a green aurora, you are seeing atoms of oxygen
giving off the green light at a wavelength of 558 nanometers.

Where can you see aurorae?  (note aurorae is the plural of 
aurora)  Generally, the aurorae are seen in a ring around
the earth lying between about 10 and 20 degrees from the 
magnetic poles.  The location of the magnetic poles
on Earth change with time because of molten magnetic material 
(iron) inside the Earth moves around with time.  Right now, 
the north magnetic pole is now located in Canada, about 11 degrees 
from the rotation axis of the Earth.
This is why a compass needle doesn't point exactly
north!

When the sunspots become most active, 
aurorae can  be seen closer to the equator (but I've never 
seen them in Arizona...).  Sunspots activity and solar flares, 
which can be thought of as magnetic storms, become more 
numerous every 11 years on the Sun.  Thus, the aurorae should
also become more numerous every 11 years.  The next solar 
"maximum" should be happening between 1999 and 2002, so we are already
seeing
an increase in solar activity now.  Have you seen any aurorae yet?

These dramatic effects are called the aurora borealis if seen
at extreme northern latitudes, and aurora australis at extreme southern
latitudes. 

Susan Stolovy