Twin spacecraft watch space weather

By Stephen Withers
Monday, 05 March 2007 08:32

Science - Space

The near-identical twin satellites that make up NASA's Solar Terrestrial Relations Observatory (STEREO) have yet to reach their final orbits but are already sending back data about solar storms that can affect Earth.

Violent disturbances on the Sun cause the eruption of plasma, known as coronal mass ejection (CME). The interaction of a CME with the solar wind generates radiation that can damage spacecraft electronics and cause cancer in inadequately shielded astronauts.

If that wasn't enough, magnetic fields in a CME interact with those of the Earth, and the resulting magnetic storms can damage electrical power grids.

More accurate forecasts of CME behaviour will allow satellite operators and the electric power industry to better avoid their effects. STEREO is expected to allow scientists to more accurately predict such storms' arrival on Earth. Currently, the accuracy is only plus or minus 12 hours, but STEREO may reduce that to three hours.

Although the STEREO observatories have yet to reach their final position, they have already monitored one CME as it travels outwards through the Solar System, surprising scientists with the way it changes shape en route. Images are available at NASA's web site.

Taken last December, the image clearly shows the loops in the region of the Sun that produced a series of intense flares.