Planet Earth

Planet Earth, a Great Magnet

Earth itself is a gigantic magnet. The solar wind confines Earth's magnetic field to a comet-shaped cavity known as the magnetosphere. As the solar wind flows past the magnetosphere, it acts like a cosmic generator, producing millions of amps of electric current. Some of this electric current flows into Earth's upper atmosphere which can light up like a neon tube to create the mysterious and beautiful aurora. (Illustration courtesy of the High Altitude Observatory/NCAR)

The First Major Discovery of the Space Age

The Van Allen Radiation Belts were the first scientific discovery of the Space Age. In 1958, Geiger counters aboard the U.S. satellites Explorers 1 and 3 detected energetic charged particles trapped in the magnetosphere fairly close to Earth called the Van Allen Radiation Belts -- two doughnut shaped belts that surround Earth. (Photograph of William Pickering, James Van Allen, and Werner von Braun display the first U.S. satellite, Explorer 1 courtesy of U. of Iowa)

Auroras: Billboards for Electric Space

People living in the arctic or antarctic regions can witness the aurora -- beautiful shimmering curtains of light appearing in the night sky. Auroras are like giant advertisements for the existence of Electric Space -- the world's largest neon-like billboards. (Photo courtesy of David Fritts © 1995)

The aurora takes its name from the Roman goddess of dawn, but its cause has nothing to do with the Sun's light. Earth's magnetotail deflects solar wind toward Earth's polar regions. An aurora is produced when the energetic charged particles comprising the solar wind collide with neutral gas molecules in the upper atmosphere. The electrical discharge occurs about 70 miles above Earth's surface.

Seeing Auroras from Space

Auroras can also be photographed by Space Shuttle astronauts and by artificial satellites. The photograph on the left was taken by NASA's Discovery astronauts in 1991. (Photo courtesy of NASA.) Satellites that orbit thousands of miles above Earth's surface can provide a global view of the aurora.

The photograph at right shows that the light of the aurora forms an oval shape high above and surrounding Earth's magnetic poles. (Photo courtesy of Louis A. Frank/ U. of Iowa)

Upper Atmosphere Weather: Electrified Winds

The uppermost part of Earth's atmosphere, the ionosphere, consists of a medium able to conduct electricity. The ionosphere is created when ultraviolet rays from the Sun and high-energy particles from the magnetosphere collide with and ionize some of the atoms in Earth's upper atmosphere.

The ionosphere provides a path for electric current generated in the magnetosphere. This artist's conception of Earth's ionosphere shows the activity going on in this dynamic region. (Illustration courtesy of the Space Physics Division/NASA)

Electrical Damage

The charged particles in the solar wind, magnetosphere, and ionosphere carry large scale electric currents. When these currents change near Earth, destruction of electrical equipment on the ground can result.

In March, 1989, a magnetic storm caused a blackout of the Hydro-Quebec power system in Canada, plunging virtually all of Quebec province into darkness. This satellite image of the March 1989 magnetic storm shows both the northern and southern auroral ovals in ultraviolet wavelengths. (Photo courtesy of Louis A. Frank/U. of Iowa)

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