Sunspot Cluster Ejects Huge Radiation Storm
By Kelly Young - NewScientist.com - 22 January 2005
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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