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Last fall, the sun unleashed a series of powerful storms. The fiercest of the bunch turned out to be one of the strongest solar flares (eruptions of energy from the sun) ever recorded. And even though the sun is about 150 million kilometers (93 million miles) away, these flares spelled danger for Earth.

Why did our gaseous star turn so ferocious? Scientists blame a group of sunspots (cooler areas of the sun that have intense magnetism). When a sunspot flares, a cloud of radiation (a form of high-energy waves or particles) erupts into space. That's not all. Energized particles, called protons and electrons, carrying some of the sun's magnetism also explode.

"The recent eruptions headed straight for us, like a freight train traveling about 5 million miles per hour," says John Kohl, a solar physicist at the Harvard-Smithsonian Center for Astrophysics. "The radiation produced effects similar to those resulting from chest X-rays," explains Kohl. Too much radiation can kill or damage cells. "Without the full protection of Earth's atmosphere (a protective layer of gases), astronauts and airplane pilots had to take special precautions," adds Kohl. Astronauts holed up in a protected section of the International Space Station. And some pilots flew lower than usual so Earth's atmosphere could shield passengers from the incoming radiation.

The solar storms weren't all bad, though. The flurry of high-energy particles and magnetism triggered auroras (colored lights in the sky, usually seen near Earth's poles) for sky watchers as far south as Texas (see diagram, right).


1 Solar wind (a stream of charged particles and magnetism) blows from the sun toward Earth.

2 Earth's magnetic field usually deflects most of the charged particles. It traps the rest.

3 Charged particles and magnetism carried from the sun collide with Earth's magnetism. This causes electrons to speed down Earth's magnetic field lines toward the poles.

4 There, the night sky lights up with auroras when electrons strike oxygen and nitrogen gas in Earth's upper atmosphere.


NIGHT LIGHTS: Auroras may appear to be low in the sky, but they actually occur more than 60 kilometers (40 miles) overhead.

FIRED UP: When a solar flare (bright spot, below) erupts on the sun, it can take days for the charged particles to reach Earth.
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Title Annotation:Physical/Solar System
Author:Janes, Patty
Publication:Science World
Date:Jan 12, 2004
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