Magnetic Fields

This computer animation illustrates the Earth's space storm shield in action. The solar wind, a thin, high-velocity electrified gas, or plasma, blows constantly from the Sun at an average speed of 250 miles per second (400 kilometers/sec). It is represented as a stream of yellow particles flowing from the Sun. The solar wind impacts the Earth's magnetic field, represented by the blue lines. As the solar wind flows past the Earth's magnetic field, it generates enormous electric currents that heat Earth's space storm shield — a layer in the Earth's electrically charged outer atmosphere (ionosphere) — causing the shield to eject electrically charged oxygen atoms (oxygen ions) into space. The expelled oxygen ions are represented by the green particle streams. The ejected oxygen ions gain tremendous speed as they leave the atmosphere, become trapped by the Earth's magnetic field and ultimately encircle the Earth, where they form a billion-degree plasma cloud around the planet, represented by the red cloud. The blue doughnut shape represents the high-speed flow of these particles around the Earth. The red 'ring of fire' around the Earth's polar regions represents the contribution of the particles to the aurora (the northern and southern lights).

See http://www.gsfc.nasa.gov/topstory/20020509imagessu.html