A large eruption of solar material from the sun's southwest hemisphere punched through the solar corona on Saturday, giving sun watchers a bit of a thrill.
It was powerful enough that it could have caused disruptions of radio signals and satellite communications had it been directed at Earth. Instead it shot a streaming flurry of charged particles southward into space, doing no particular damage.
The event, known as a coronal mass ejection, was detected by an instrument aboard the Solar and Heliospheric Observatory, a NASA and European Space Agency spacecraft that orbits at a point that is always between the sun and Earth.
"Given the direction that the coronal mass ejection was moving, you could see as it was lifting off the sun that it was not heading for Earth," said David Hathaway, a solar physicist at NASA's Marshall Space Flight Center.
Ejections of this magnitude are becoming more and more common as the sun nears the peak of its 11-year activity cycle. The sun should reach its most active period sometime in mid to late 2000, Hathaway said. At that time, it will not be uncommon to measure a coronal mass ejection every day.
Saturday's solar burst was at the weak end of the most powerful category of solar radiation. It was designated an X-1 event, where C and M-class events are less powerful.
Based on the position and the trajectory of the ejection, the Space Environment Center predicted shortly after the event that the ejection would not affect Earth. The center, located in Boulder, Colo., is a division of the National Oceanic and Atmospheric Administration that monitors solar events and forecasts their affect on Earth.
"We look at the set of observations from spacecraft," said JoAnn Joselyn, a space weather forecaster at the Space Environment Center. "We also look at radio signatures to assess the activity. But we mostly rely on plain old experience to put that event into context," she said.
Besides the fact that the ejection was not headed for Earth, Joselyn said the radio emissions from Saturday's ejection were not particularly powerful.
"They were of a low level. The radio signatures from the event could have been 10 to 100 times greater before they got my attention," she said.
Solar physicists and forecasters expect several hundred X-class events to be measured during the next few years, which is typical for a solar maximum.
As it turned out, the forecasters were correct that the event would not disturb Earth's geomagnetic field. Given the speed that charged particles travel on their way to Earth, any affects would have been felt by Tuesday at the latest. No significant anomalies or disturbances were detected, Joselyn said.
One of the most visible signs of a geomagnetic storm is an increase in auroral activity above the poles. Residents of Fairbanks, Alaska, and Iqaluit, on Baffin Island in Canada contacted Wednesday said they had not seen an increase in aurora lights, although the short night and relative brightness of even the darkest part of night leaves less opportunity to observe the northern lights, they said.
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