Solar Wind Makes Waves; Killer Electrons Go Surfing?

"Killer" electrons capable of wreaking havoc on orbiting spacecraft may "surf" magnetic waves driven by the solar wind, according to a team of space scientists.

The team from Boston University and the National Oceanic and Atmospheric Administration (NOAA) combined observations from NASA and NOAA spacecraft to identify a phenomenon that explains how the solar wind makes waves in Earths magnetic field (magnetosphere). Ordinary electrons orbiting the Earth in the Van Allen radiation belts may boogyboard the waves, accelerating to near the speed of light, with energies 300-500 times greater than the electrons in a television screen.

The solar wind is a stream of electrically charged particles blown constantly from the Sun. The magnetosphere is a cavity formed when the solar wind encounters the Earths magnetic field. When the solar wind density is high and comes up against the magnetosphere, the magnetosphere gets compressed. When the wind density is low, the magnetosphere expands. The researchers discovered that the solar wind contains periodic structures of high and low density, driving a periodic "breathing" action of the magnetosphere and the global generation of magnetic waves.

It's known that if the frequency of these waves matches the frequency of the electrons in their motion in the Van Allen belt, the electrons can be accelerated, significantly boosting their energies. The process is similar to a boogyboarder catching a wave. Some electrons "ride the wave" and gain so much energy that they can then damage expensive spacecraft.

"If we can confirm this as a significant mechanism for making the waves that accelerate killer electrons, then scientists using data from satellites like Wind could develop advance warning for spacecraft operators that their spacecraft may be in danger of excessive and damaging radiation exposure," said Dr. Barbara Giles, project scientist for the Polar spacecraft at Goddard.

For the complete article on solar wind, go to: http://www.gsfc.nasa.gov/topstory/2003/0904magwaves.html