The Auroras: A Qualitative View
The name Aurora comes from the Roman goddess of dawn.
Auroras: radiant emission from the upper atmosphere that
occurs in middle and high latitudes as luminous streamers, bands, etc.
caused when air molecules are excited by charged particles from the solar
- More particles are thrown out into the
solar wind causing the interaction between the earth's geomagnetic field
and the plasma itself.
- Occurs usually after unusual activity on
the surface of the sun. The precipitating particles collide with the
neutral atmosphere and lose their energy.
- Collisions from above
- One of many manifestations of an array
of phenomena which occur in the near earth environment as a result of
interaction between plasma from the solar wind and the earth's
- The frequencies of occurrences of
auroras in the zenith when plotted against geomagnetic coordinates and
local time form oval-shaped patterns.
- Auroral oval is bounded by the greater
of 70% frequency of occurrence.
- The auroral zone's center is at 67
- Aurora appear most frequently at the
- The Auroral Oval
- Color Types
A Bit of Folklore
As far back as the 17th century, there have been many accounts of auroral
sightings. Since no scientific advancements in the explanation of these
forms were made until the late 19th century by Birkeland, there, of
course, were spiritual interpretations.
- Eskimo folklore associates the aurora
with the spirits or souls of the deceased at play, using a walrus head
for a football.
- Finnish folklore attributes the aurora
to the fox. Revontuli, the modern Finnish word for aurora, means
fox-fire, and legend recounts that when Repu (fox) turns,
his fur flashes; he strikes fire with his tail but a fire of no heat.
Folklore says that Repu's fur can be used for light in a gunpowder cellar.
- In Middle-Age Europe, the lights were
thought to be the reflections of heavenly warriors who were given a
posthumous award of battling in the skies forever.
- A Siberian tribe called the
Chuvash thought of the aurora as a god. The name of their god
Suratan-Tura was the name for the aurora. This god was associated
with birth and helping women through agonies of childbirth. It was
believed that the sky gave birth during a bright aurora.
A Bright Moment in History
Many monumental events occurred involving the studies of the auroras, but
with the help of his colleagues, Kristian Birkeland of Norway proved why
Expanding upon the ideas of J.J. Thomson, Birkeland conducted experiments
using his terella apparatus. He projected electrons in an evacuated
chamber toward the terella, which was to imitate the earth. Birkeland
was able to see where the electrons impinged upon the sphere.
Birkeland's studies inspired many others such as Carl Stormer, who
computed the trajectories of charged particles in the dipole field.
Idea of what Birkeland saw (gif).