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Solar Flare Produces Fabulous Fall Auroras

Posted on: Tuesday, 25 November 2003, 06:00 CST

ANCHORAGE (AP) -- A solar flare erupting from an enormous sunspot hit Earth last week with the second-biggest geomagnetic storm ever measured, said scientists at the Geophysical Institute at the University of Alaska Fairbanks.

It produced fabulous red and green auroras seen throughout the Northern Hemisphere, especially in Europe.

"The material that was ejected from that (sunspot) just happened to come at the Earth in a way that caused the most possible disruption," said research professor Dirk Lummerzheim. "You could say we were extremely lucky, or extremely unlucky, depending in your point of view."

A much larger storm in 1989 triggered a power outage in Quebec, and a storm last month damaged two Japanese satellites. Lummerzheim said there were no reports of damage during Thursday's event.

The charged particles streaming from the sun originated in the same sunspot that produced a huge flare and triggered auroras in October, Lummerzheim said.

The spot passed from view for a few weeks during the sun's 27-day rotation and re-emerged somewhat smaller. Another flare has erupted from the same spot and sent more particles toward Earth.

The institute had forecast maximum auroras for all of Alaska on Saturday. Even with the cloudy and snowy weather over much of the state, Alaskans should not despair of completely missing the display, Lummerzheim said. A friend out feeding his dogs reported that the clouds seemed brighter on Thursday night.

"He said it was like somebody turned on a light," Lummerzheim said.

What is an Aurora?

An auroral display in the Northern Hemisphere is called the aurora borealis, or the northern lights; in the Southern Hemisphere it is called the aurora australis.

Auroras are the most visible effect of the sun's activity on the earth's atmosphere. The beautiful and often eerie curtains of light in the night time sky have been observed by people for millennia. An aurora is an optical phenomenon.

The origin of the aurora is 93 million miles (149 million km) from Earth at the Sun. Energetic particles from the Sun are carried out into space along with the ever present hot solar wind. This wind sweeps supersonically toward Earth through interplanetary space at speeds ranging from 300 to over 1000 km per second, carrying with it the solar magnetic field.

Aurora seen in Wallacestone, Scotland. Image credit: Dr Russell Cockman (russell.cockman@blueyonder.co.uk)

This aurora was seen in Bopfingen, Ostalbkreis, Germany. Image credit: Gerhard Kupfer (gku.cku.1118@t-online.de)

This aurora was photographed in Menominee, Michigan, USA. Image credit: Duane Clausen (duaneclausen@cybrzn.com)

The solar wind distorts the Earth's magnetic field to create the comet-shaped , plasma-filled magnetosphere. The terrestrial magnetic shield acts as a barrier, protecting the Earth from energetic particles and radiation in the hot solar wind. Most of these energetic particles are deflected around the Earth by the magnetosphere, but some get trapped.

Electrons trapped in the Earth's magnetic field (the magnetic mirror effect) are accelerated along the magnetic field toward the polar regions and then strike the atmosphere to form the aurora. Auroras are most intense at times of intense magnetic storms caused by sunspot activity.

The distribution of auroral intensity with altitude shows a pronounced maximum near 100 km above the Earth. Auroras may occasionally be observed within 40° or less of the equator.

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On the Net:

Aurora information

The Solar and Heliospheric Observatory

http://www.spaceweather.com

More science, space, and technology from RedNova

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