Aurora puts on stunning display

Posted: Tuesday, November 06, 2001

Monday evening's northern lights towering columns of pink, red, green and white may be just one of the striking displays in the night sky this winter.

Sunspots, which provide the energy that lights the lights, come in 11-year cycles. This is a peak of one of those cycles, which means an active time for the aurora borealis, said Michael Orelove, a volunteer with Juneau's Marie Drake Planetarium.

"That means two things: There will be more and stronger aurora, and the aurora will extend further south than it normally does," he said. "It normally makes an oval shape around the earth in the high northern latitudes."

Monday's display, which at times filled three-quarters of Juneau's sky, was a particularly large one that was spotted as far south as the San Francisco Bay area. Residents of New Zealand probably were getting the same visual light show.

"When there are northern lights, there are southern lights, which are the exact mirror image," Orelove said.

The northern lights are linked to sunspots - dark, cool areas on the surface of the sun accompanied by increased geomagnetic disturbances, according to scientists. Charged electrons and protons fly through space and are pulled to the most northern and southern latitudes by the Earth's magnetic forces.

They strike gas particles in the upper atmosphere, generating the aurora. The color depends on how hard the gas particles are being struck. Displays take place as low as 40 miles above the Earth's surface, but usually begin about 68 miles up and extend hundreds of miles into space.

They concentrate in two bands roughly centered above the Arctic Circle in the north and above the Antarctic Circle in the south. The southern display is known as aurora australis, Orelove said.

The Marie Drake Planetarium, in the building between Juneau-Douglas High School and Harborview Elementary School, is presenting two shows this week on the aurora australis. Volunteers will show slides and videos, some from NASA and others produced by observatories, Orelove said. Tonight's show, from 7-7:30 p.m., is intended for kids 4 and 5 years old. Wednesday's show for adults and families is scheduled for 7-8 p.m. The shows are free, but donations are accepted.

In Alaska and other northern latitudes, the greatest occurrence of aurora displays is in the spring and fall months. Residents of Fairbanks see the aurora borealis an average of 240 nights a year, prompting the University of Alaska Fairbanks to issue daily aurora forecasts each winter. The forecasts can be reached on the Internet at www.gi.alaska.edu\cgi-bin\predict.cgi.

Ann Chandonnet can be reached at achandonnet@juneauempire.com.





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