Spiro Antiochos from the Naval Research Lab describes how
eclipses are valuable for research.
physicist Nancy Crooker a researcher from Boston University
For a few minutes
during a total solar eclipse, when the disk of the moon slides precisely
between our planet and the sun, we'll glimpse a sight seldom seen:
the sun's hot, churning atmosphere, called the corona. Unless light
from the sun is blocked, the corona is usually too dim for us to
see from earth. During an eclipse, we'll have a better view of the
lower corona than even space telescopes can provide.
To routinely view the sun's corona, space-based solar observatories,
such as SOHO (Solar Heliospheric Observatory), employ a kind of
artificial eclipse. The "eclipse" is generated from a
solid disk mounted in the observatory's detector. The disk blocks
light from the sun's surface, just as the moon blocks our view of
the sun during a solar eclipse. But the detectors on space observatories
can't view the part of the sun's atmosphere just above the surface,
the layer where violent solar storms gather their energy. Contained
by the sun's powerful magnetic fields, these storms brew until they
burst through in an exploding mass of charged gas that can rush
toward the earth at speeds of up to 1250 miles a second.
SOHO spacecraft. A still from a NASA animation.
These violent solar explosions
are called Coronal Mass Ejections, or CMEs. When CMEs are directed
toward the earth, turbulent shock waves of charged gas and their accompanying
magnetic fields can interfere with radio, television, and telephone
signals, damage satellites and disrupt satellite communications, and
build up voltages in electric power lines. High-energy particles from
these storms also contribute to the beautiful polar light shows known
as aurora borealis (in the northern hemisphere) and aurora australis
(in the southern hemisphere). The most violent solar storms can threaten
the safety of space-walking astronauts and generate huge geomagnetic
storms on the earth. A direct hit by a CME in 1989 knocked out power
to Quebec and produced significant damage in satellites orbiting the
earth. In 1977, a CME knocked out a communications satellite and silenced
pagers all over the world.