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Sunspot Cluster Ejects Huge Radiation Storm
2005 01 22

By Kelly Young |

The Sun spewed forth a massive amount of radiation this week, causing brilliant auroras and a radio blackout.

Since 14 January alone, it has unleashed at least 17 medium and five large solar flares from a single sunspot cluster. Forecasters at the US National Oceanic and Atmospheric Administration (NOAA) expect medium to high solar activity to continue until 23 January.

"Having so many big flares from one particular region of the Sun is quite something," says Bernhard Fleck, project scientist for the Solar and Heliospheric Observatory satellite.

The X-rays produced by the flares did not rise to the level of the notorious solar storms of October and November 2003, but in terms of high-energy protons, this is the largest radiation storm since October 1989.

Magnetic fields
Solar flares occur when energy stored in magnetic fields above sunspots is suddenly released. In this case, the offending sunspot grew into a cluster eight times the diameter of Jupiter in about five days.

Solar activity typically follows an 11-year cycle. Scientists estimate that the Sun experienced its last peak in 2000. "Often the biggest events are in the falling part of the solar cycle," Fleck told New Scientist. "So this is actually not that surprising."

Effects of the solar storms were seen on Earth. Auroras produced by the increased solar activity were spotted over northern parts of Europe and North America and above New Zealand on 18 and 19 January. NOAA also received reports of communication blackouts.

Evasive action
Two major US airlines rerouted planes away from the polar areas to avoid additional radiation, said Bill Murtagh, a space weather forecaster for NOAA. Instruments on two of NOAA's satellites, SOHO and the Advanced Composition Explorer, were blinded by radiation contamination for several hours, and there are unconfirmed reports of problems on other satellites.

The eruptions also required evasive action aboard the International Space Station. The two-man crew, Leroy Chiao and Salizhan Sharipov, ducked for cover inside the bulkier Russian side of the station when their orbit took them through the worst of the storm. High doses of radiation can cause health problems: astronauts are more prone to cataracts later in life, for example.

The astronauts plan to conduct a 5.5-hour spacewalk outside the station's protective walls on 26 January. They will install a new work platform, a small robotic experiment and other science equipment.

NOAA officials say that the sunspot region that caused the solar storms should rotate to the far side of the Sun by 22 January, so the astronauts should not be in danger of increased radiation exposure during their excursion.

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