Exploratorium: Solar Eclipse: Sun-Earth Connection (Page 1 of 5)

Astrophysicist Spiro Antiochos from the Naval Research Lab describes how eclipses are valuable for research.

Space physicist Nancy Crooker a researcher from Boston University describes CMEs.

To learn more about auroras visit, The Exploratorium's Auroras: Paintings in the Sky.

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 Space Craft

The 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.