The aurora australis, the southern equivalent of the aurora borealis, was photographed from the flight deck of Space Shuttle Discovery in 1991, while it orbited at 250 kilometers above the Earth. The aurora are spectacular displays of light in the Earth's upper atmosphere, visible from high latitudes. When the stream of charged particles emanating from the Sun (the solar wind) meets the Earth's magnetic field, it is swept down towards the poles. Here the charged particles strike gases in the Earth's upper atmosphere and cause them to flow in the same way that electrons passing through gases in a tube cause a neon sign to light up.