Line: Aurora borealis/Northern Lights

There was a request for an askii art northern lights posted here some time
ago.  Here is an attempt:
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Winter night's northern lights                             by: D. Rice 12/94
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A few comments on aurora and on the figure:

Aurora borealis and its southern counterpart, aurora australis, are phenomena
that occur only in the high latitudes, about 65 degrees North or South.  The
earth's atmosphere glows due to the impingement of energetic particles that
are trapped by the earth's magnetic field.  These particles circle the lines of
force until they hit the atmosphere where the field dips into the earth.  When
they hit the atmosphere, they cause the air to glow.

The glow is not terribly bright, in general.  Thus the glow is seen usually
under conditions of low ambient light from other sources.  This means that the
sightings are mostly in winter, because it is light all the time in the summer
at high latitudes.  Also, clouds, fog, or smoke will obscure aurora.  The moon
can overpower aurora in its region of the sky.  Because the atmosphere itself
is doing the glowing, the aurora is transparent--stars, planets, earth
satellites, and other luminous bodies can be seen through it.

Most auroras are diffuse greenish-white clouds.  These are not so interesting
because they resemble clouds lit by moonlight.  When the sun, the main source
of particles, is particularly energetic, the entire sky may be lit with aurora. 
a spectacular show happened in 1959, where aurora was seen as far south as
Mexico City.  When they are this extensive, they are generally red.

The most interesting auroras fall between these two extremes.  They appear to
be "curtains," bands or streamers that thread their way through the night sky. 
These curtains appear to have nearly vertical "folds" and the streamers extend
horizontally great distances--like some of Cristo's artwork.  There may be one
or many streamers.  If more that one, the streamers follow nearly parallel
tracks, locally speaking.

The color can vary from bluish to green to red within a "fold," with red on the
bottom or hem of the curtain.  The hem is usually more distinct than the top of
the curtain, which can be quite diffuse.

I based this work--with huge artistic license--on a photo by Vic Hessler of the
Geophysical Institute of the University of Alaska, Fairbanks.  The Geophysical
Institute has also put out a video on auroral phenomena; music was composed to
accompany it.  It is commonly said that auroras can be heard, by my ears never
did, despite 16+ years of trying.

The ASCII figure doesn't do justice to the phenomenon.  I tried to represent
the detailed nature of the "folds" by using only vertical ascii characters and
centered dots.  At a distance the ascii-aurora looks like "smoke."  I don't
know what to do about it, except to view it as light against a dark background,
as on a computer screen.  There are numerous other things one could do in
ascii.  I put this art on one computer screen of text, but it could be extended
from the horizon ahead overhead to the horizon behind.  These things really do
cover a sizeable part of the sky.  Also, animation could show the movement and
intensity variations of the streamers as a function of time.  The starry
background could move with the rotation of the earth, and maybe even twinkle a
bit.

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