Aurora FactsTHE AURORA has a curtain-like shape, and the altitude of its lower edge is sixty or seventy miles, about ten times higher than a jet aircraft flies.
AURORAS OCCUR along ring-shaped regions around the north and south geomagnetic poles. Fairbanks, Alaska, is a good place for aurora watching because it is under this region in the north. where people see aurora borealis, or northern lights: the southern aurora is aurora australis.
LIKE A NEON SIGN, auroral light is produced by a high-vacuum electrical discharge. It is powered by interactions between the sun and earth. The light is glow from atoms and molecules in the earth's upper atmosphere.
THE SUN IS a ball of gases that is so hot its outermost part blows away as the solar wind. Consisting of charged particles. this tenuous gas travels to earth in about three days. Because the earth's magnetic field prevents the solar wind from penetrating our atmosphere, its solar particles stream around our planet, encasing earth and its magnetic field within a comet-shaped cavity called the magnetosphere.
THE SOLAR WIND powers the gigantic electrical discharge process, causing the magnetosphere to behave as a generator that produces up to ten million megawatts of electrical power.
THE UPPER ATMOSPHERE contains, at the lower edge of the aurora, a thin and partly ionized layer called the ionosphere. Reflected by the ionosphere, radiowaves can propagate great distances by bouncing between it and the ground.
AURORAL DISPLAYS INDICATE that the ionosphere and our protective atmosphere are being energized by the electric power generated in the magnetosphere. As these electrical currents are discharged in the ionosphere. many phenomena are produced including the visible emissions we recognize as the aurora and magnetic storms.