<text><span class="style10">he Sun and the Solar System (3 of 6)</span><span class="style7"></span><span class="style10">The solar wind and aurorae</span><span class="style7">The Sun is constantly sending out a stream of charged particles into space. This is known as the </span><span class="style26">solar wind</span><span class="style7">. The strength of the solar wind is not constant, but changes with the activity of the Sun. Near the peak of the sunspot cycle, the solar wind is at its strongest.The Earth has a strong magnetic field, which traps ionized particles from the solar wind in the upper atmosphere. These regions are the </span><span class="style26">Van Allen Zones</span><span class="style7">, two belts which extend from 1000 to 5000 km (620 to 3100 mi) and from 15 000 to 25 000 km (9300 to 15 500 mi) above the equator.The solar wind also interacts with the Earth's magnetic field to produce brilliant displays of light called </span><span class="style26">aurorae</span><span class="style7"> - the </span><span class="style26">aurora borealis</span><span class="style7"> (or `northern lights') in the northern hemisphere and the </span><span class="style26">aurora australis</span><span class="style7"> in the southern. Aurorae are formed by the charged particles in the solar wind interacting with gases in the Earth's atmosphere at a height of about 100 km (60 mi), causing them to emit visible light. This can be seen from the ground as an ever-changing pattern of white or multicolored lights. The charged particles are attracted towards the Earth's magnetic poles and aurorae are therefore best seen from high latitudes. The most spectacular displays occur about 24 hours after major solar-flare activity.</span></text>
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<text><span class="style10"> display of aurora, </span><span class="style7">which take many forms, including curtains, arcs, rays, bands, and fan-shaped coronas. The arc is the most stable form of aurora, and it can persist for hours without noticeable variation.</span></text>
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<text>ΓÇó STARS AND GALAXIESΓÇó THE INNER PLANETSΓÇó THE OUTER PLANETS</text>