ANCHORAGE - The Internet is opening up a world of information to astronomy buffs and scientists who are using satellite data to get a good look at the northern lights.
The National Oceanic and Atmospheric Administration has four polar-orbiting satellites carrying detectors that count charged particles moving toward Earth. Internet users are also using NASA's Polar Satellite, which takes pictures of the aurora's ultraviolet light.
Amateur astronomers say the data on the Internet is taking the guesswork out of one of nature's wonders. The information is letting them know when it makes sense to bundle up, venture out in freezing temperatures and drive to remote locations free of light to view the aurora borealis.
Richard Pellessier of Anchorage said before he began using the Web, he bundled up more often to drive beyond the city lights, only to be disappointed.
"I've been using the Internet products, especially the downloaded satellite pictures and measurements, for about two years now," he said. "I just want to know if it is going to make sense to go out tonight or not."
The NOAA satellites download information to a tracking station at Gilmore Creek northeast of Fairbanks as often as every 105 minutes. The information is sent by satellite to a NOAA computer facility in suburban Washington, D.C., and from there to NOAA's Space Environment Center in Boulder, Colo.
David Evans, a scientist at the Boulder center, said the whole process takes about 45 minutes. Downloaded images of the aurora ovals on the North and South poles show up on the Web about once every hour.
Evans said downloading the information began four years ago and the Web site has become increasingly popular. Between 2,000 and 4,000 Internet users access the SEC's Web site daily, and that number increases to more than 10,000 users a day when solar storms are predicted.
The aurora borealis is caused by solar disturbances that produce the electrically charged particles that move toward earth at 900,000 miles an hour. The larger the solar disturbance, the more likely an awesome display.
"These particles are energized then and slam into the atmosphere and collide," said Charles Deehr, professor emeritus of physics at the University of Alaska Fairbanks. "Then light is given off just like a neon sign."
It takes about three days for the charged particles to reach Earth's magnetic field where they are directed around rings on the North and South poles.
The color of the aurora depends on the type of molecule struck by the charged particles and at what atmospheric level. Oxygen about 60 miles up produces a green color, the most common in the aurora. Higher-level oxygen produces the rare all-red auroras. Ionized nitrogen produces blue light and neutral nitrogen glows purplish-red at the edges of the aurora.
Deehr uses the Web satellite information to make daily forecasts used by media outlets in Alaska communities with frequent northern light displays.
The satellite information is particularly useful in predicting where the aurora can best be viewed, Deehr said. Large solar disturbances will show up as far south as Anchorage and sometimes into Southeast Alaska. Smaller solar storms rarely can be seen south of Fort Yukon, notheast of Fairbanks, he said.
Deehr plugs the information available on the Web into a model that describes what happens as the energy thrown off in the solar disturbance moves through space to Earth.
"If it hits the earth on our model, we can say OK, we will have this disturbance at such and such a time," he said. "We can tell within about plus or minus nine hours of when the disturbance will occur on Earth."
For Web sites on auroras, look for the Hot Links section on the front page of juneauempire.com.