Solar Wind

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A hot wind constantly buffets Earth and the other bodies of the solar system: the solar wind. It's a flow of electrically charged particles from the Sun. It blows steadily at a million miles an hour or more, with gusts of more than twice that.

When the solar wind hits Earth, it triggers some impressive effects. It creates beautiful aurorae -- the shimmering curtains of color known as the northern and southern lights. It warms the outer atmosphere. And it can disrupt radio broadcasts and electric power grids.

The source of the solar wind has remained something of a mystery -- scientists have had a hard time figuring out how the particles are blown into space.

But astronomers who've watched the Sun with a Japanese spacecraft say they've found the answer.

The Sun's surface temperature isn't the same all over -- there are hot spots and cool spots. Observations by the Hinode spacecraft show that the hotspots produce their own magnetic fields -- bright filaments that loop above the Sun.

Charged particles follow these lines of magnetic force into space. Where the magnetic fields of two bright spots intersect, it's like streams from two water hoses flowing together -- there's a spray of particles heading in different directions. Some of the particles flow out into space -- forming the solar wind.

More about the Sun tomorrow.

Script by Damond Benningfield, Copyright 2008

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