Transcript: Auroras are caused when high energy particles from the solar wind crash into the atmosphere of the Earth near its poles. They’re called the northern and southern lights respectively or the Aurora Borealis and the Aurora Australis. The solar wind takes several days to reach us from the Sun. When those particles reach the edge of the magnetosphere they are channeled along magnetic field lines and accelerated. These interactions can build up voltages up to a hundred thousand volts or greater. When the reach the upper atmosphere they have enormous energy and they can excite molecules of oxygen, ozone, and nitrogen producing strong emission. That’s why the gas in the upper atmosphere glows, and it leads to the delicate patterns and curtains of light that are familiar for the aurora. Because the excitation of the atmosphere happens near the poles, the auroras are normally only seen above the Arctic Circle. There is always several days warning of a spectacular aurora because of the time it takes the solar wind to reach the Earth. During extreme periods of solar activity these interactions can spread such that the aurora can be seen even from continental United States.