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The solar wind is not uniform. Although it is always directed away from
the Sun, it changes speed and carries with it magnetic
clouds, interacting regions
where high speed wind catches up with slow speed wind, and composition variations. The solar wind
speed is high (800 km/s) over coronal holes and
low (300 km/s) over streamers. These high and
low speed streams interact with each other and alternately pass by the Earth as the Sun
rotates. These wind speed variations buffet the Earth's magnetic field and can produce
storms in the Earth's magnetosphere.
The Ulysses spacecraft has now
completed one orbit through the solar system during which it passed over the Sun's south
and north poles. Its measurements of the solar wind speed, magnetic field strength and
direction, and composition have provided us with a new view of the solar wind.
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