From: jim.speirs@canrem.com (Jim Speirs)
To: dannys@iis.ee.ethz.ch (Danny Schwendener)
Subject: Northern Lights



Article #R80.
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Northern Lights
Ben Kruser
The Leader, February 1992.


Aurora Borealis, the Northern Lights, has been the subject of
speculation, myth, and scientific study throughout history. 
Indigenous people in Canada and the northern U.S. had many
legends to explain the lights.  One legend says the souls of
departed friends were lighting torches to guide those who
followed.  Another describes a great hole in the sky through
which souls pass from this world to the next.  Many stories tell
of spirits with light bands on heads and waist playing a lively
game of football with a walrus skull.

Although auroras were common occurrences to northern peoples, the
occasional aurora seen in central and southern Europe created
panic.  Greek and Roman philosophers believed the sky was opening
and spewing forth flame and smoke.  In early times, people
detected major fires by the light reflected from the evening
clouds.  When an aurora made an uncommon appearance in southern
latitudes, troops rushed to neighbouring cities to help with what
appeared to be a major conflagration 

In the middle ages, Europeans went from hysteria to
hallucination.  They saw vast armies of angels clashing in the
sky, and tens of thousands of peasants across Europe joined
pilgrimages in hopes of saving the world from approaching
Armageddon.

Science also had its opinions about the aurora.  Some scientists
speculated that the force of ice and glaciers produced flame,
while others thought that vast ice belts reflected the sun's
light into the evening sky.  Active research began in the 17th
century when Pierre Gassendi, a mathematician and philosopher,
named the lights after Aurora, the Romans' rosy-fingered Goddess
of Dawn, whose job was to usher in the rising sun.

Carl Stonner, a Norwegian physicist, was the first to solve the
question of the aurora's length.  He took pictures of two widely
separated points and used triangulation to calculate auroral
span. Auroras usually start around 105 km above the earth and
stretch to altitudes over 485 km.

Another question researchers addressed was where auroras occur
most often.  After compiling records of auroral activity from
northern expeditions and other accounts, Elias Loomis, a Yale
professor, developed a map of the arctic showing auroras
frequency.  It has since been updated by more sophisticated
means, such as satellites.  We know that people living on
latitude 65 degrees N can expect to average 243 nights of
northern lights a year.  Most Canadians live in an area of 50 to
100 auroras per year

But what is an aurora?  What causes the Northern Lights?  Using a
prism, Norwegian scientists discovered auroral light was
discontinuous;  that is, it did not have ail the colours of the
rainbow.  The only colours produced in an aurora are deep violet,
green-yellow, and red.

When atoms become electrically charged, they emit energy that
produces radio waves, x-rays, and visible light waves.  Air
consists of nitrogenand oxygen atoms.  When nitrogen atoms become 
electrically charged, they emit violet and red colour waves.
Charged oxygen atoms produce green yellow light.

Scientists studying the sun discovered that sun spots produce
solar flares, which shoot streams of highly charged electrons
into space.  As charged particles reach earth, they are drawn
into the planet's magnetic field, which is heavily concentrated
in northern latitudes.  (That's why we have a 'magnetic north"
and "true north" compass readying.) The collision of forces
causes a geomagnetic storm, which we witness as an aurora. 

The principle that lights up our sky is the same that commonly
lights neon signs.  Electricity charges a gas, which emits energy
as coloured light.  We also make an "aurora" when we turn on a
colour television.  The only difference is that a real aurora is
more interesting to watch.

It's important for Canadians to continue studying the aurora. 
Auroral activity can interfere with the radio and satellite
operations that form vital communications links in northern
communities.  And, because auroras consist of an electric current
of about one million amps, in intense northern geomagnetic
storms, an aurora can induce electric current along lengthy
conductors such as oil pipelines, power tines, and telephone 
cables.  The result: transformer malfunction and power outages.

Despite some of the technical headaches auroras can cause, most
of us see them as one of nature's wonders.  And some popular
myths persist.  For example, some people believe you can control
the behaviour of an aurora by whistling.  The better the whistle,
the more the aurora will change and even dance to you.  Others    
                                            believe you can
control the aurora by spitting at it, but I
don't recommend telling this one to a
group of small boys.

There's still disagreement about whether the aurora makes a
noise.  While some researchers claim no evidence that the lights
produce a sound, there are those who believe they can hear the
lights crackling.  While science and philosophers argue over this
point and others, I am happy to believe that the aurora is
friends from days gone by calling me out to enjoy the northern
lights and, maybe, a lively game of walrus skull football.