Radiation Belts Around Earth Adversly Affecting Satellites

December 07, 1998

Much of the energetic electron activity in Earth's radiation belts, once thought to be generated by the sun and solar wind, actually is accelerated to light-speed by Earth's own magnetic shell, creating periodic havoc with satellites.

Daniel Baker, director of the University of Colorado at Boulder's Laboratory for Atmospheric and Space Physics, said new findings indicate that electrons in the Van Allen radiation belts circling Earth are energized to speeds much higher than researchers had thought. The Van Allen belts are two main zones in Earth's magnetosphere where charged particles are confined by the planet's magnetic fields.

"We used to think that the Van Allen Belts slowly waxed and waned and were not particularly dynamic," he said. "But these belts have now been shown to be powerful, energetic particle accelerators, generating excitement and awe in the scientific community."

Named for physicist James Van Allen who discovered them in 1958, the belts consist of two doughnut-shaped regions containing electrons and protons centered thousands of miles above Earth's surface.

Speeding particles in the near-Earth environment from the sun, solar wind and Earth's magnetosphere -- commonly known as "killer electrons" -- have had a dramatic effect on human technological systems, said Baker. "This includes many of the satellites that are up there now and future spacecraft like the space station, which have the potential to be severely impaired electronically by light-speed electrons."

Baker presented his latest findings at the fall meeting of the American Geophysical Union held Dec. 6 to Dec. 10 in San Francisco.

A paper authored by Baker and colleagues in the Oct. 6 issue of Eos, a publication of AGU, indicate an intense flux of electrons from Earth's magnetosphere likely played an important role in the failure of the Galaxy 4 spacecraft last May. The event led to a temporary loss of pager service to 45 million customers.

Activity in the two known Van Allen radiation belts grew so intense in May 1998 that a new belt was created, said Baker. The activity was detected by several NASA spacecraft, including NASA's WIND, SAMPEX and Polar satellites, all part of the multi-agency International Solar and Terrestrial Physics Program.

"We have gotten a much clearer picture of cosmic particle acceleration in the Van Allen Belts from these satellites," said Baker, an investigator on the Polar and WIND experiments. "New observations indicate very rapid changes in these belts on timescales of months, weeks, days, hours and even seconds."

The new findings that killer electrons can be accelerated inside the Van Allen belts may help scientists better protect satellites by powering them down or using back-up systems during electronic storms. "This knowledge will help us better prepare for the next solar maximum period when the sun is most active, expected in late 2000 or early 2001," said Baker.

Scientists plan to coordinate observations from more than a dozen spacecraft, which may allow them to produce "space weather" maps of particle acceleration that could be potentially damaging to satellites. "In many ways, every spacecraft will act as a high-energy detector," said Baker.

In addition, CU-Boulder recently was selected to design, build, operate and control a NASA satellite that will study the response of Earth's Van Allen radiation belts to the powerful solar wind. The $12.8 million satellite project, known as the Inner Magnetosphere Explorer, or IMEX, is being directed by Professor John Wygant of the University of Minnesota in Minneapolis.

Co-Investigators include Baker and LASP Associate Researcher Xinlin Li. CU-Boulder is expected to receive about half of the funding for the project.

IMEX will study the energetic charged particles -- primarily protons and electrons -- comprising Earth's radiation zones. In 1996, Baker's research indicated the operational failure of a Canadian communications satellite. Anik E1, appeared to be linked to severe space weather.

University of Colorado at Boulder

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