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The sun gives off high-energy charged particles (also called ions) that
travel out into space at speeds of 320 to 704 kilometres per
second. A cloud of such particles is called a plasma. The stream
of plasma coming from the sun is known as the solar wind. As the solar
wind interacts with the fringes of the earth's magnetic field, some of
the particles are trapped by it and they follow the lines of magnetic force
down into the ionosphere, the section of the earth's atmosphere that extends
from about 60 to 100 kilometers above the earth's surface. When the particles
strike the gases in the ionosphere they start to glow, producing the spectacle
that we know as the auroras, northern and southern. The variety of colors:
red, green, blue and violet that appear in the sky corresponds to the different
gases in the ionosphere. |
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