Untitled DocumentAn 11-year cycle of solar tantrums expected to peak during the summer of 2000 has so far been weaker than anticipated, but forecasters cautioned that the worst could still be ahead -- way ahead.
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In 1996, near the solar minimum, the Sun is nearly featureless. By 1999, approaching maximum, it is dotted by sunspots and fiery hot gas trapped in magnetic loops.
SOURCE: ESA/NASA/SOHO/US Naval Research Laboratory
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Meanwhile, scientists operating space telescopes have been puzzled by unexpected gusts of solar radiation. But scientists are seizing the opportunity to use the orbiting observatories' science instruments to study the brief, mysterious waves of energy that have buffeted the crafts without warning.
In four cases this year, NASA's Chandra X-ray Observatory has automatically shut its instruments down to protect itself from space weather. But project scientists say that despite radiation levels that have at times exceeded expectations, both Chandra and the European Space Agency's XMM-Newton, another X-ray telescope now in space, are so far weathering the storms and functioning properly.
| Current Solar Cycle 
Graph shows past and predicted sunspot numbers. Click to enlarge
SOURCE: NOAA Animated Severe Storm
See a November 8 radiation storm. A coronal mass ejection to the right is followed by a proton barrage that overwhelms the camera on board the SOHO spacecraft. Source: NASA/SOHO Space Weather 101
All about solar energy and how it affects Earth Astronauts at risk?
NASA monitors the amount of radiation astronauts accumulate during several missions, and once they hit their limits they can't fly anymore. What that limit is depends on each crew member, and because of medical privacy it's never been publicly announced that an astronaut won't fly because of radiation concerns.
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Solar max
The Sun's anger fluctuates roughly on an 11-year cycle. During the peak of activity the Sun throws more tantrums than usual in the form of sunspots, flares and other ejections, spewing massive quantities of charged particles into space.
These events, which can bathe Earth in radiation a few moments later and also hurl charged particles at us for several days, threaten satellites and space travelers, high-frequency radio communications, power grids and even the navigation of birds.
People on the ground are not directly at risk, as Earth's magnetic field and atmosphere provide a blanket of protection.
But NOAA says an airline passenger can experience as much radiation as 10 chest X-rays on extended flights during strong radiation storms, though this figure is debated. Experts do agree, however, that anyone on a high-altitude jet or in space is exposed to more radiation than someone on the ground.
And astronauts on space walks can be exposed to potentially deadly amounts of radiation in a storm.
The latest peak, known as a solar maximum, was forecast back in 1999 to occur during 2000 and be of moderate intensity. Most space weather experts say we are in the midst of that peak right now.
But the height of activity is typically more like a plateau, explains Bill Murtagh, a space weather forecaster with NOAA's Space Environment Center in Boulder, Colorado. And the plateau can last for many, many months, with severe space weather coming at any time.
Next Page: History paints a stormy future
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