As residents of the far north watched a dazzling auroral light display in late September, NASA's Polar space weather satellite made the first measurements to show that solar activity causing the aurora directly affects Earth's outer atmosphere. The Polar observations were reported on at the American Geophysical Union's annual West Coast conference in San Francisco, Calif., on Dec. 8.
"These observations will help us understand how space storms develop," said Dr. Jim Spann, a scientist at NASA's Marshall Space Flight Center Space Sciences Laboratory in Huntsville, Ala. Spann is a co-investigator on the Ultraviolet Imager, one of the instruments aboard the Polar spacecraft that measured the affects of the bubble of plasma -- electrified gas -- that collided with Earth's atmosphere in September.
Ultimately, scientists want to forecast these storms, which can disrupt satellite communications, electric power grid operations and pipeline operations. A major storm blacked out the Canadian and American Northeast in 1989.
"This is the first time we've been able to observe the Sun hurling these roiling bubbles of plasma, see the storm hit Earth's upper atmosphere, and measure the effects of low-energy oxygen and other gases being blown into space," Spann said.
The Sun ejected the mass of hot, ionized gas on Sept. 22, 1998. At its peak from Sept. 24-25, the storm pumped about 200 gigawatts of energy into Earth's atmosphere, causing oxygen and other gases to gush from the atmosphere into space.
"Normal values for auroral substorms are on the gigawatt levels -- emitting enough energy to run a large city for several days," Spann said. "So, 200 gigawatts is a tremendous amount of energy."
As Polar flew through this fountain of ionized gas, scientists confirmed that the flow of ions was caused when a storm from the Sun smacked into the Earth's atmosphere.
The Polar Ultraviolet Imager used unique filters to take pictures of the aurora, a ghostly light show that is sometimes visible at night, especially near Earth's polar regions. The Ultraviolet Imager can even observe the aurora during daylight. The brightness of these images can be translated directly into how much energy is being pumped into the ionosphere, the ionized top layer of Earth's atmosphere.
While the Ultraviolet Imager measured this explosion of auroral brightness, another Polar spacecraft instrument, the Thermal Ion Dynamics Experiment, measured the significant increase in oxygen and hydrogen ions blown from Earth's atmosphere. The Thermal Ion Dynamics Experiment principal investigator is Dr. Thomas E. Moore of NASA's Goddard Space Flight in Greenbelt, Md., who was formerly the chief of the Space Plasma Physics Branch at the Marshall Center. Dr. Moore and Dr. Spann discussed the Polar observations in an American Geophysical Union conference session, "Thirty Years of Ionospheric Outflow: Causes and Consequences."
The Polar satellite is one of several geoscience spacecraft launched by NASA and other nations in a coordinated effort to study space weather -- geomagnetic substorms and other events -- in Earth's space environment.
Note to Editors: For more information on the Polar spacecraft, please visit the Marshall Center's Space Sciences Laboratory Web site at: http://www.science.nasa.gov
For more information or to arrange interviews, contact Tim Tyson with Marshall's
Media Relations Office at (256) 544-0994 or (256) 544-0034. For an electronic
version of this release or more information, visit Marshall's News Center Web
site at:
http://www.msfc.nasa.gov/news
A related joint NASA Headquarters/Goddard Space Flight Center news release on
the Polar results can be viewed at:
ftp://pao.gsfc.nasa.gov/pub/pao/releases/1998/98-213.htm