· Auroras occur around Earth's north (aurora
borealis) and south (aurora australis) geomagnetic poles
in regions known as auroral ovals.
· The aurora is higher in the atmosphere than the
highest jet plane flies. The lowest fringes are at least
40 miles above the Earth, while the uppermost reaches
of the aurora extend 600 miles above the Earth. The space
shuttle flies near 190 miles altitude.
· Auroras occur because Earth's magnetic field
interacts with the solar wind, a tenuous mix of charged
particles blowing away from the sun. This wind from the
sun sweeps by Earth in the interplanetary magnetic field
which is produced by the sun.
· Auroral light is similar to light from color
television. In the picture tube, a beam of electrons controlled
by electric and magnetic fields strikes the screen, making
it glow in different colors, according to the type of
chemicals (phosphors) that coat the screen. Auroral light
is the from the air glowing as charged particles, particularly
electrons, rain down along the Earth's magnetic field
lines. The color of the aurora depends on the type of
atom or molecule struck by the charged particles.
· Auroral displays vary from night to night and
during a single night. Usually, if sun-earth conditions
produce an auroral substorm, a diffuse patch of glowing
sky will be seen first, followed by a discrete arc that
brightens, perhaps a thousand-fold in a minute. As an
arc moves toward the equator, new ones may form on its
Appearing within arcs are upward-reaching striations aligned
with the magnetic field, giving the impression of curtains
of light. Ripples and curls dance along the arc curtains
and pulsating patches of light may appear in the morning